test fixes

Reviewed-on: #114

.github/workflows/ci.yml

@@ -1,42 +1,39 @@
-on: [push]
-
 name: ci
+on: [push, pull_request]
 
 jobs:
   check:
-    name: Check
+    name: Check build
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-      - uses: actions-rs/cargo@v1
-        with:
-          command: check
-          args: --release
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - run: cargo check --release
 
-  msrv:
-    name: Check with MSRV
+  test:
+    name: Run Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          toolchain: 1.61.0
-          override: true
-          profile: minimal
-      - uses: actions-rs/cargo@v1
-        with:
-          command: check
-          args: --release
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - name: Install nextest
+        uses: taiki-e/install-action@nextest
+      - run: cargo nextest run --all-features
+      - run: cargo test --doc
+
+  msrv:
+    name: Check MSRV
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@1.81.0
+      - run: cargo check --release
 
   cross-check:
-    name: Check Cross
+    name: Check Cross-Compilation
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -44,70 +41,32 @@ jobs:
           - armv7-unknown-linux-gnueabihf
           - thumbv7em-none-eabihf
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
         with:
-          profile: minimal
-          toolchain: stable
-          target: ${{ matrix.target }}
-          override: true
-      - uses: actions-rs/cargo@v1
-        with:
-          use-cross: true
-          command: check
-          args: --release --target=${{ matrix.target }} --no-default-features
+          targets: "armv7-unknown-linux-gnueabihf, thumbv7em-none-eabihf"
+      - run: cargo check --release --target=${{matrix.target}} --no-default-features
 
   fmt:
-    name: Rustfmt
+    name: Check formatting
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-          override: true
-      - run: rustup component add rustfmt
-      - uses: actions-rs/cargo@v1
-        with:
-          command: fmt
-          args: --all -- --check
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - run: cargo fmt --all -- --check
 
-  check-doc:
+  docs:
     name: Check Documentation Build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          toolchain: nightly
-          override: true
-          profile: minimal
-      - uses: actions-rs/cargo@v1
-        with:
-          command: doc
-          args: --all-features
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@nightly
+      - run: RUSTDOCFLAGS="--cfg docsrs --generate-link-to-definition -Z unstable-options" cargo +nightly doc --all-features
 
   clippy:
     name: Clippy
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-      - run: rustup component add clippy
-      - uses: actions-rs/cargo@v1
-        with:
-          command: clippy
-          args: -- -D warnings
-
-  ci:
-      if: ${{ success() }}
-      # all new jobs must be added to this list
-      needs: [check, fmt, clippy]
-      runs-on: ubuntu-latest
-      steps:
-        - name: CI succeeded
-          run: exit 0
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - run: cargo clippy -- -D warnings

CHANGELOG.md

@@ -8,6 +8,280 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+- Bumped MSRV to 1.81.0
+- Bump `zerocopy` to v0.8.0
+- Bump `thiserror` to v2.0.0
+
+# [v0.12.0] 2024-09-10
+
+- Bumped MSRV to 1.70.0
+
+## Added
+
+- Added new `cfdp::tlv::TlvOwned` type which erases the lifetime and is clonable.
+- Dedicated `cfdp::tlv::TlvLvDataTooLarge` error struct for APIs where this is the only possible
+  API error.
+- Added File Data PDU API which expects the expected file data size and then exposes the unwritten
+  file data field as a mutable slice. This allows to read data from the virtual file system
+  API to the file data buffer without an intermediate buffer.
+- Generic `EofPdu::new` constructor.
+- Added generic sequence counter module.
+- Added `MsgToUserTlv::to_tlv` converter which reduced the type and converts
+  it to a generic `Tlv`.
+- Implemented `From<MsgToUserTlv> for Tlv` converter trait.
+- Added CFDP maximum file segment length calculator method `calculate_max_file_seg_len_for_max_packet_len_and_pdu_header`
+
+## Added and Changed
+
+- Added new `ReadableTlv` to avoid some boilerplate code and have a common abstraction implemented
+  for both `Tlv` and `TlvOwned` to read the raw TLV data field and its length.
+- Replaced `cfdp::tlv::TlvLvError` by `cfdp::tlv::TlvLvDataTooLarge` where applicable.
+
+## Fixed
+
+- Fixed an error in the EOF writer which wrote the fault location to the wrong buffer position.
+- cfdp `ConditionCode::CheckLimitReached` previous had the wrong numerical value of `0b1001` (9)
+  and now has the correct value of `0b1010` (10).
+
+## Changed
+
+- Minor documentation build updates.
+- Increased delegate version range to v0.13
+
+# [v0.11.2] 2024-05-19
+
+- Bumped MSRV to 1.68.2
+
+## Fixed
+
+- Removed `defmt::Format` impl for `MetadataPduCreator` which seems to be problematic.
+
+# [v0.11.1] 2024-04-22
+
+## Fixed
+
+- The default data length for for `SpHeader` constructors where the data field length is not
+  specified is now 0.
+- The `SpHeader::new_from_fields` is public now.
+
+## Added
+
+- `SpHeader::to_vec` method.
+
+# [v0.11.0] 2024-04-16
+
+## Changed
+
+- Moved `CCSDS_HEADER_LEN` constant to the crate root.
+
+## Added
+
+- Added `SpacePacketHeader` type alias for `SpHeader` type.
+
+# [v0.11.0-rc.2] 2024-04-04
+
+## Changed
+
+- Renamed `PacketId` and `PacketSequenceCtrl` `new` method to `new_checked` and former
+  `new_const` method to `new`.
+- Renamed `tc`, `tm`, `tc_unseg` and `tm_unseg` variants for `PacketId` and `SpHeader`
+  to `new_for_tc_checked`, `new_for_tm_checked`, `new_for_unseg_tc_checked` and
+  `new_for_unseg_tm_checked`.
+- `PusTmCreator` and `PusTcCreator` now expect a regular instance of `SpHeader` instead of
+  a mutable reference.
+
+## Added
+
+- `SpHeader::new_from_apid` and `SpHeader::new_from_apid_checked` constructor.
+- `#[inline]` attribute for a lot of small functions.
+
+# [v0.11.0-rc.1] 2024-04-03
+
+Major API changes for the time API. If you are using the time API, it is strongly recommended
+to check all the API changes in the **Changed** chapter.
+
+## Fixed
+
+- CUC timestamp was fixed to include leap second corrections because it is based on the TAI
+  time reference. The default CUC time object do not implement `CcsdsTimeProvider` anymore
+  because the trait methods require cached leap second information. This task is now performed
+  by the `cuc::CucTimeWithLeapSecs` which implements the trait.
+
+## Added
+
+- `From<$EcssEnum$TY> from $TY` for the ECSS enum type definitions.
+- Added basic support conversions to the `time` library. Introduce new `chrono` and `timelib`
+  feature gate.
+- Added `CcsdsTimeProvider::timelib_date_time`.
+- Optional support for `defmt` by adding optional `defmt::Format` derives for common types.
+
+## Changed
+
+- `PusTcCreator::new_simple` now expects a valid slice for the source data instead of an optional
+  slice. For telecommands without application data, `&[]` can be passed.
+- `PusTmSecondaryHeader` constructors now expects a valid slice for the time stamp instead of an
+  optional slice.
+- Renamed `CcsdsTimeProvider::date_time` to `CcsdsTimeProvider::chrono_date_time`
+- Renamed `CcsdsTimeCodes` to `CcsdsTimeCode`
+- Renamed `cds::TimeProvider` to `cds::CdsTime`
+- Renamed `cuc::TimeProviderCcsdsEpoch` to `cuc::CucTime`
+- `UnixTimestamp` renamed to `UnixTime`
+- `UnixTime` seconds are now private and can be retrieved using the `secs` member method.
+- `UnixTime::new` renamed to `UnixTime::new_checked`.
+- `UnixTime::secs` renamed to `UnixTime::as_secs`.
+- `UnixTime` now has a nanosecond subsecond precision. The `new` constructor now expects
+   nanoseconds as the second argument.
+- Added new `UnixTime::new_subsec_millis` and `UnixTime::new_subsec_millis_checked` API
+  to still allow creating a timestamp with only millisecond subsecond resolution.
+- `CcsdsTimeProvider` now has a new `subsec_nanos` method in addition to a default
+  implementation for the `subsec_millis` method.
+- `CcsdsTimeProvider::date_time` renamed to `CcsdsTimeProvider::chrono_date_time`.
+- Added `UnixTime::MIN`, `UnixTime::MAX` and `UnixTime::EPOCH`.
+- Added `UnixTime::timelib_date_time`.
+- Error handling for ECSS and time module is more granular now, with a new
+  `DateBeforeCcsdsEpochError` error and a `DateBeforeCcsdsEpoch` enum variant for both
+  `CdsError` and `CucError`.
+- `PusTmCreator` now has two lifetimes: One for the raw source data buffer and one for the
+  raw timestamp.
+- Time API `from_now*` API renamed to `now*`.
+
+## Removed
+
+- Legacy `PusTm` and `PusTc` objects.
+
+# [v0.11.0-rc.0] 2024-03-04
+
+## Added
+
+- `From<$TY>` for the `EcssEnum$TY` ECSS enum type definitions.
+- `Sub` implementation for `UnixTimestamp` to calculate the duration between two timestamps.
+
+## Changed
+
+- `CcsdsTimeProvider` `subsecond_millis` function now returns `u16` instead of `Option<u16>`.
+- `UnixTimestamp` `subsecond_millis` function now returns `u16` instead of `Option<u16>`.
+
+# [v0.10.0] 2024-02-17
+
+## Added
+
+- Added `value` and `to_vec` methods for the `UnsignedEnum` trait. The value is returned as
+  as `u64`. Renamed former `value` method on `GenericUnsignedByteField` to `value_typed`.
+- Added `value_const` const function for `UnsignedByteField` type.
+- Added `value_typed` const functions for `GenericUnsignedByteField` and `GenericEcssEnumWrapper`.
+
+# [v0.9.0] 2024-02-07
+
+## Added
+
+- `CcsdsPacket`, `PusPacket` and `GenericPusTmSecondaryHeader` implementation for
+  `PusTmZeroCopyWriter`.
+- Additional length checks for `PusTmZeroCopyWriter`.
+
+## Changed
+
+- `PusTmZeroCopyWriter`: Added additional timestamp length argument for `new` constructor.
+
+## Fixed
+
+- Typo: `PUC_TM_MIN_HEADER_LEN` -> `PUS_TM_MIN_HEADER_LEN`
+
+# [v0.8.1] 2024-02-05
+
+## Fixed
+
+- Added `pub` visibility for `PacketSequenceCtrl::const_new`.
+
+# [v0.8.0] 2024-02-05
+
+## Added
+
+- Added `len_written` and `to_vec` methods to the `TimeWriter` trait.
+
+# [v0.7.0] 2024-02-01
+
+# [v0.7.0-beta.4] 2024-01-23
+
+## Fixed
+
+- `MetadataPduCreator`: The serialization function shifted the closure requested information
+  to the wrong position (first reserved bit) inside the raw content field.
+
+# [v0.7.0-beta.3] 2023-12-06
+
+## Added
+
+- Add `WritablePduPacket` trait which is a common trait of all CFDP PDU implementations.
+- Add `CfdpPdu` trait which exposes fields and attributes common to all CFDP PDUs.
+- Add `GenericTlv` and `WritableTlv` trait as abstractions for the various TLV types.
+
+## Fixed
+
+- Set the direction field inside the PDU header field correctly explicitely for all CFDP PDU
+  packets.
+
+## Changed
+
+- Split up `FinishedPdu`into `FinishedPduCreator` and `FinishedPduReader` to expose specialized
+  APIs.
+- Split up `MetadataPdu`into `MetadataPduCreator` and `MetadataPduReader` to expose specialized
+  APIs.
+- Cleaned up CUC time implementation. Added `width` and `counter` getter methods.
+- Renamed `SerializablePusPacket` to `WritablePusPacket`.
+- Renamed `UnsignedPfc` to `PfcUnsigned` and `RealPfc` to `PfcReal`.
+- Renamed `WritablePduPacket.written_len` and `SerializablePusPacket.len_packed` to `len_written`.
+- Introduce custom implementation of `PartialEq` for `CommonPduConfig` which only compares the
+  values for the source entity ID, destination entity ID and transaction sequence number field to
+  allow those fields to have different widths.
+- Removed the `PusError::RawDataTooShort` variant which is already covered by
+  `PusError::ByteConversionError` variant.
+- Ranamed `TlvLvError::ByteConversionError` to `TlvLvError::ByteConversion`.
+- Renamed `PusError::IncorrectCrc` to `PusError::ChecksumFailure`.
+- Some more struct variant changes for error enumerations.
+
+## Removed
+
+- `PusError::NoRawData` variant.
+- `cfdp::LenInBytes` which was not used.
+
+# [v0.7.0-beta.2] 2023-09-26
+
+## Added
+
+- `PacketId` trait impls: `Ord`, `PartialOrd` and `Hash`
+- `SerializablePusPacket` trait: Add `to_vec` method with default implementation.
+
+# [v0.7.0-beta.1] 2023-08-28
+
+- Bump `zerocopy` dependency to v0.7.0
+
+## Changed
+
+- The `Tlv` and `Lv` API return `&[u8]` instead of `Option<&[u8]>`.
+- `ByteConversionError` error variants `ToSliceTooSmall` and `FromSliceTooSmall` are struct
+  variants now. `SizeMissmatch` was removed appropriately.
+- `UnsignedByteFieldError` error variants `ValueTooLargeForWidth` and `InvalidWidth` are struct
+  variants now.
+- `TimestampError` error variant `InvalidTimeCode` is struct variant now.
+
+## Added
+
+- Added `raw_data` API for `Tlv` and `Lv` to retrieve the whole `Lv`/`Tlv` slice if the object
+  was created from a raw bytestream.
+- Added `MsgToUserTlv` helper class which wraps a regular `Tlv` and adds some useful functionality.
+- `UnsignedByteField` and `GenericUnsignedByteField` `new` methods are `const` now.
+- `PduError` variants which contained a tuple variant with multiple fields were converted to a
+  struct variant.
+
+# Added
+
+- Added `pdu_datafield_len` getter function for `PduHeader`
+
+## Removed
+
+- `SizeMissmatch` because it is not required for the `ByteConversionError` error enumeration
+  anymore.
+
 # [v0.7.0-beta.0] 2023-08-16
 
 - Moved MSRV from v1.60 to v1.61.
@@ -60,7 +334,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   `PusTm` object.
 
 ## Changed
- 
+
 - The `EcssEnumeration` now requires the `UnsignedEnum` trait and only adds the `pfc` method to it.
 - Renamed `byte_width` usages to `size` (part of new `UnsignedEnum` trait)
 - Moved `ecss::CRC_CCITT_FALSE` CRC constant to the root module. This CRC type is not just used by

Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "spacepackets"
-version = "0.7.0-beta.0"
+version = "0.12.0"
 edition = "2021"
-rust-version = "1.61"
+rust-version = "1.81.0"
 authors = ["Robin Mueller <muellerr@irs.uni-stuttgart.de>"]
 description = "Generic implementations for various CCSDS and ECSS packet standards"
 homepage = "https://egit.irs.uni-stuttgart.de/rust/spacepackets"
@@ -13,16 +13,20 @@ categories = ["aerospace", "aerospace::space-protocols", "no-std", "hardware-sup
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-zerocopy = "0.6"
 crc = "3"
-delegate = ">=0.8, <0.11"
+delegate = ">=0.8, <=0.13"
+paste = "1"
+
+[dependencies.zerocopy]
+version = "0.8"
+features = ["derive"]
 
 [dependencies.thiserror]
-version = "1"
-optional = true
+version = "2"
+default-features = false
 
 [dependencies.num_enum]
-version = "0.6"
+version = ">0.5, <=0.7"
 default-features = false
 
 [dependencies.serde]
@@ -31,23 +35,35 @@ optional = true
 default-features = false
 features = ["derive"]
 
+[dependencies.time]
+version = "0.3"
+default-features = false
+optional = true
+
 [dependencies.chrono]
 version = "0.4"
 default-features = false
+optional = true
 
 [dependencies.num-traits]
 version = "0.2"
 default-features = false
 
-[dev-dependencies.postcard]
-version = "1"
+[dependencies.defmt]
+version = "0.3"
+optional = true
 
 [features]
 default = ["std"]
-std = ["chrono/std", "chrono/clock", "alloc", "thiserror"]
-serde = ["dep:serde", "chrono/serde"]
-alloc = ["postcard/alloc", "chrono/alloc"]
+std = ["alloc", "chrono/std", "chrono/clock", "thiserror/std"]
+serde = ["dep:serde", "chrono?/serde"]
+alloc = ["chrono?/alloc", "defmt?/alloc", "serde?/alloc"]
+timelib = ["dep:time"]
+
+[dev-dependencies]
+postcard = { version = "1", features = ["alloc"] }
+chrono = "0.4"
 
 [package.metadata.docs.rs]
 all-features = true
-rustdoc-args = ["--cfg", "doc_cfg"]
+rustdoc-args = ["--generate-link-to-definition"]

README.md

@@ -1,6 +1,7 @@
 [![Crates.io](https://img.shields.io/crates/v/spacepackets)](https://crates.io/crates/spacepackets)
 [![docs.rs](https://img.shields.io/docsrs/spacepackets)](https://docs.rs/spacepackets)
 [![ci](https://github.com/us-irs/spacepackets-rs/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/us-irs/spacepackets-rs/actions/workflows/ci.yml)
+[![coverage](https://shields.io/endpoint?url=https://absatsw.irs.uni-stuttgart.de/projects/spacepackets/coverage-rs/latest/coverage.json)](https://absatsw.irs.uni-stuttgart.de/projects/spacepackets/coverage-rs/latest/index.html)
 
 ECSS and CCSDS Spacepackets
 ======
@@ -28,10 +29,6 @@ Currently, this includes the following components:
 
 `spacepackets` supports various runtime environments and is also suitable for `no_std` environments.
 
-It also offers optional support for [`serde`](https://serde.rs/). This allows serializing and
-deserializing them with an appropriate `serde` provider like
-[`postcard`](https://github.com/jamesmunns/postcard).
-
 ## Default features
 
  - [`std`](https://doc.rust-lang.org/std/): Enables functionality relying on the standard library.
@@ -42,8 +39,35 @@ deserializing them with an appropriate `serde` provider like
 ## Optional Features
 
  - [`serde`](https://serde.rs/): Adds `serde` support for most types by adding `Serialize` and `Deserialize` `derive`s
+ - [`chrono`](https://crates.io/crates/chrono): Add basic support for the `chrono` time library.
+ - [`timelib`](https://crates.io/crates/time): Add basic support for the `time` time library.
+ - [`defmt`](https://defmt.ferrous-systems.com/): Add support for the `defmt` by adding the
+   [`defmt::Format`](https://defmt.ferrous-systems.com/format) derive on many types.
 
 # Examples
 
 You can check the [documentation](https://docs.rs/spacepackets) of individual modules for various
 usage examples.
+
+# Coverage
+
+Coverage was generated using [`grcov`](https://github.com/mozilla/grcov). If you have not done so
+already, install the `llvm-tools-preview`:
+
+```sh
+rustup component add llvm-tools-preview
+cargo install grcov --locked
+```
+
+After that, you can simply run `coverage.py` to test the project with coverage. You can optionally
+supply the `--open` flag to open the coverage report in your webbrowser.
+
+# Miri
+
+You can run the [`miri`](https://github.com/rust-lang/miri) tool on this library to check for
+undefined behaviour (UB). This library does not use use any `unsafe` code blocks, but `miri` could
+still catch UB from used libraries.
+
+```sh
+cargo +nightly miri nextest run --all-features
+```

automation/Dockerfile

@@ -6,10 +6,23 @@ RUN apt-get update
 RUN apt-get --yes upgrade
 # tzdata is a dependency, won't install otherwise
 ARG DEBIAN_FRONTEND=noninteractive
+RUN apt-get --yes install rsync curl
 
 # set CROSS_CONTAINER_IN_CONTAINER to inform `cross` that it is executed from within a container
 ENV CROSS_CONTAINER_IN_CONTAINER=true
 
 RUN rustup install nightly && \
     rustup target add thumbv7em-none-eabihf armv7-unknown-linux-gnueabihf && \
-    rustup component add rustfmt clippy
+    rustup component add rustfmt clippy llvm-tools-preview
+
+# Get grcov
+RUN curl -sSL https://github.com/mozilla/grcov/releases/download/v0.8.19/grcov-x86_64-unknown-linux-gnu.tar.bz2 | tar -xj --directory /usr/local/bin
+# Get nextest
+RUN curl -LsSf https://get.nexte.st/latest/linux | tar zxf - -C ${CARGO_HOME:-~/.cargo}/bin
+
+# SSH stuff to allow deployment to doc server
+RUN adduser --uid 114 jenkins
+
+# Add documentation server to known hosts
+RUN echo "|1|/LzCV4BuTmTb2wKnD146l9fTKgQ=|NJJtVjvWbtRt8OYqFgcYRnMQyVw= ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBNL8ssTonYtgiR/6RRlSIK9WU1ywOcJmxFTLcEblAwH7oifZzmYq3XRfwXrgfMpylEfMFYfCU8JRqtmi19xc21A=" >> /etc/ssh/ssh_known_hosts
+RUN echo "|1|CcBvBc3EG03G+XM5rqRHs6gK/Gg=|oGeJQ+1I8NGI2THIkJsW92DpTzs= ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBNL8ssTonYtgiR/6RRlSIK9WU1ywOcJmxFTLcEblAwH7oifZzmYq3XRfwXrgfMpylEfMFYfCU8JRqtmi19xc21A=" >> /etc/ssh/ssh_known_hosts

automation/Jenkinsfile

@@ -1,52 +1,81 @@
 pipeline {
 
-    agent {
-        dockerfile {
-            dir 'automation'
-            reuseNode true
-        }
+  agent {
+    dockerfile {
+      dir 'automation'
+      reuseNode true
+      args '--network host'
     }
+  }
 
-    stages {
-        stage('Clippy') {
-            steps {
-                sh 'cargo clippy'
-            }
-        }
-        stage('Docs') {
-            steps {
-                sh 'cargo +nightly doc --all-features'
-            }
-        }
-        stage('Rustfmt') {
-            steps {
-                sh 'cargo fmt --all --check'
-            }
-        }
-        stage('Test') {
-            steps {
-                sh 'cargo test --all-features'
-            }
-        }
-        stage('Check with all features') {
-            steps {
-                sh 'cargo check --all-features'
-            }
-        }
-        stage('Check with no features') {
-            steps {
-                sh 'cargo check --no-default-features'
-            }
-        }
-        stage('Check Cross Embedded Bare Metal') {
-            steps {
-                sh 'cargo check --target thumbv7em-none-eabihf --no-default-features'
-            }
-        }
-        stage('Check Cross Embedded Linux') {
-            steps {
-                sh 'cargo check --target armv7-unknown-linux-gnueabihf'
-            }
+  stages {
+    stage('Rust Toolchain Info') {
+      steps {
+        sh 'rustc --version'
+      }
+    }
+    stage('Clippy') {
+      steps {
+        sh 'cargo clippy'
+      }
+    }
+    stage('Docs') {
+        steps {
+          sh """
+            RUSTDOCFLAGS="--cfg docsrs --generate-link-to-definition -Z unstable-options" cargo +nightly doc --all-features
+          """
         }
     }
+    stage('Rustfmt') {
+        steps {
+          sh 'cargo fmt --all --check'
+        }
+    }
+    stage('Test') {
+      steps {
+        sh 'cargo nextest r --all-features'
+        sh 'cargo test --doc'
+      }
+    }
+    stage('Check with all features') {
+      steps {
+        sh 'cargo check --all-features'
+      }
+    }
+    stage('Check with no features') {
+      steps {
+        sh 'cargo check --no-default-features'
+      }
+    }
+    stage('Check Cross Embedded Bare Metal') {
+      steps {
+        sh 'cargo check --target thumbv7em-none-eabihf --no-default-features'
+      }
+    }
+    stage('Check Cross Embedded Linux') {
+      steps {
+        sh 'cargo check --target armv7-unknown-linux-gnueabihf'
+      }
+    }
+    stage('Run test with Coverage') {
+      when {
+        anyOf {
+          branch 'main';
+          branch pattern: 'cov-deployment*'
+        }
+      }
+      steps {
+        withEnv(['RUSTFLAGS=-Cinstrument-coverage', 'LLVM_PROFILE_FILE=target/coverage/%p-%m.profraw']) {
+          echo "Executing tests with coverage"
+          sh 'cargo clean'
+          sh 'cargo test --all-features'
+          sh 'grcov . -s . --binary-path ./target/debug -t html --branch --ignore-not-existing -o ./target/debug/coverage/'
+          sshagent(credentials: ['documentation-buildfix']) {
+            // Deploy to Apache webserver
+            sh 'rsync --mkpath -r --delete ./target/debug/coverage/ buildfix@documentation.irs.uni-stuttgart.de:/projects/spacepackets/coverage-rs/latest/'
+          }
+        }
+      }
+    }
+  }
 }

coverage.py

@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+import os
+import logging
+import argparse
+import webbrowser
+
+
+_LOGGER = logging.getLogger()
+
+
+def generate_cov_report(open_report: bool, format: str):
+    logging.basicConfig(level=logging.INFO)
+    os.environ["RUSTFLAGS"] = "-Cinstrument-coverage"
+    os.environ["LLVM_PROFILE_FILE"] = "target/coverage/%p-%m.profraw"
+    _LOGGER.info("Executing tests with coverage")
+    os.system("cargo test --all-features")
+
+    out_path = "./target/debug/coverage"
+    if format == "lcov":
+        out_path = "./target/debug/lcov.info"
+    os.system(
+        f"grcov . -s . --binary-path ./target/debug/ -t {format} --branch --ignore-not-existing "
+        f"-o {out_path}"
+    )
+    if format == "lcov":
+        os.system(
+            "genhtml -o ./target/debug/coverage/ --show-details --highlight --ignore-errors source "
+            "--legend ./target/debug/lcov.info"
+        )
+    if open_report:
+        coverage_report_path = os.path.abspath("./target/debug/coverage/index.html")
+        webbrowser.open_new_tab(coverage_report_path)
+    _LOGGER.info("Done")
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Generate coverage report and optionally open it in a browser"
+    )
+    parser.add_argument(
+        "--open", action="store_true", help="Open the coverage report in a browser"
+    )
+    parser.add_argument(
+        "--format",
+        choices=["html", "lcov"],
+        default="html",
+        help="Choose report format (html or lcov)",
+    )
+    args = parser.parse_args()
+    generate_cov_report(args.open, args.format)
+
+
+if __name__ == "__main__":
+    main()

docs.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+export RUSTDOCFLAGS="--cfg docsrs --generate-link-to-definition -Z unstable-options"
+cargo +nightly doc --all-features --open

release-checklist.md

@@ -4,15 +4,22 @@ Checklist for new releases
 # Pre-Release
 
 1. Make sure any new modules are documented sufficiently enough and check docs with
-   `cargo doc --all-features --open`.
+   `RUSTDOCFLAGS="--cfg docsrs --generate-link-to-definition -Z unstable-options" cargo +nightly doc --all-features --open`
+   or `cargo +nightly doc --all-features --config 'build.rustdocflags=["--cfg", "docsrs" --generate-link-to-definition"]' --open`
+   (was problematic on more recent nightly versions).
 2. Bump version specifier in `Cargo.toml`.
 3. Update `CHANGELOG.md`: Convert `unreleased` section into version section with date and add new
    `unreleased` section.
-4. Run `cargo test --all-features`.
+4. Run `cargo test --all-features` or `cargo nextest r --all-features` together with
+   `cargo test --doc`.
 5. Run `cargo fmt` and `cargo clippy`. Check `cargo msrv` against MSRV in `Cargo.toml`.
 6. Wait for CI/CD results for EGit and Github. These also check cross-compilation for bare-metal
    targets.
 
+# Release
+
+1. `cargo publish`
+
 # Post-Release
 
 1. Create a new release on `EGit` based on the release branch.

src/cfdp/lv.rs

@@ -1,24 +1,38 @@
 //! Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
-use crate::cfdp::TlvLvError;
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::ByteConversionError;
 use core::str::Utf8Error;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 #[cfg(feature = "std")]
 use std::string::String;
 
+use super::TlvLvDataTooLargeError;
+
 pub const MIN_LV_LEN: usize = 1;
 
 /// Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
 ///
+/// Please note that this class is zero-copy and does not generate a copy of the value data for
+/// both the regular [Self::new] constructor and the [Self::from_bytes] constructor.
+///
 /// # Lifetimes
 ///  * `data`: If the LV is generated from a raw bytestream, this will be the lifetime of
 ///    the raw bytestream. If the LV is generated from a raw slice or a similar data reference,
 ///    this will be the lifetime of that data reference.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct Lv<'data> {
-    data: Option<&'data [u8]>,
+    data: &'data [u8],
+    // If the LV was generated from a raw bytestream, this will contain the start of the
+    // full LV.
+    pub(crate) raw_data: Option<&'data [u8]>,
+}
+
+impl PartialEq for Lv<'_> {
+    fn eq(&self, other: &Self) -> bool {
+        self.data == other.data
+    }
 }
 
 pub(crate) fn generic_len_check_data_serialization(
@@ -27,10 +41,10 @@ pub(crate) fn generic_len_check_data_serialization(
     min_overhead: usize,
 ) -> Result<(), ByteConversionError> {
     if buf.len() < data_len + min_overhead {
-        return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+        return Err(ByteConversionError::ToSliceTooSmall {
             found: buf.len(),
             expected: data_len + min_overhead,
-        }));
+        });
     }
     Ok(())
 }
@@ -40,68 +54,88 @@ pub(crate) fn generic_len_check_deserialization(
     min_overhead: usize,
 ) -> Result<(), ByteConversionError> {
     if buf.len() < min_overhead {
-        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+        return Err(ByteConversionError::FromSliceTooSmall {
             found: buf.len(),
             expected: min_overhead,
-        }));
+        });
     }
     Ok(())
 }
 
 impl<'data> Lv<'data> {
-    pub fn new(data: &[u8]) -> Result<Lv, TlvLvError> {
+    #[inline]
+    pub fn new(data: &[u8]) -> Result<Lv, TlvLvDataTooLargeError> {
         if data.len() > u8::MAX as usize {
-            return Err(TlvLvError::DataTooLarge(data.len()));
+            return Err(TlvLvDataTooLargeError(data.len()));
         }
-        Ok(Lv { data: Some(data) })
+        Ok(Lv {
+            data,
+            raw_data: None,
+        })
     }
 
     /// Creates a LV with an empty value field.
+    #[inline]
     pub fn new_empty() -> Lv<'data> {
-        Lv { data: None }
+        Lv {
+            data: &[],
+            raw_data: None,
+        }
     }
 
     /// Helper function to build a string LV. This is especially useful for the file or directory
     /// path LVs
-    pub fn new_from_str(str_slice: &str) -> Result<Lv, TlvLvError> {
+    #[inline]
+    pub fn new_from_str(str_slice: &str) -> Result<Lv, TlvLvDataTooLargeError> {
         Self::new(str_slice.as_bytes())
     }
 
     /// Helper function to build a string LV. This is especially useful for the file or directory
     /// path LVs
     #[cfg(feature = "std")]
-    #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
-    pub fn new_from_string(string: &'data String) -> Result<Lv<'data>, TlvLvError> {
+    #[inline]
+    pub fn new_from_string(string: &'data String) -> Result<Lv<'data>, TlvLvDataTooLargeError> {
         Self::new(string.as_bytes())
     }
 
     /// Returns the length of the value part, not including the length byte.
+    #[inline]
     pub fn len_value(&self) -> usize {
-        if self.data.is_none() {
-            return 0;
-        }
-        self.data.unwrap().len()
+        self.data.len()
     }
 
     /// Returns the full raw length, including the length byte.
+    #[inline]
     pub fn len_full(&self) -> usize {
         self.len_value() + 1
     }
 
     /// Checks whether the value field is empty.
+    #[inline]
     pub fn is_empty(&self) -> bool {
-        self.data.is_none()
+        self.data.len() == 0
     }
 
-    pub fn value(&self) -> Option<&[u8]> {
+    #[inline]
+    pub fn value(&self) -> &[u8] {
         self.data
     }
 
+    /// If the LV was generated from a raw bytestream using [Self::from_bytes], the raw start
+    /// of the LV can be retrieved with this method.
+    #[inline]
+    pub fn raw_data(&self) -> Option<&[u8]> {
+        self.raw_data
+    }
+
     /// Convenience function to extract the value as a [str]. This is useful if the LV is
     /// known to contain a [str], for example being a file name.
+    #[inline]
     pub fn value_as_str(&self) -> Option<Result<&'data str, Utf8Error>> {
-        self.data?;
-        Some(core::str::from_utf8(self.data.unwrap()))
+        if self.is_empty() {
+            return None;
+        }
+        Some(core::str::from_utf8(self.data))
     }
 
     /// Writes the LV to a raw buffer. Please note that the first byte will contain the length
@@ -112,40 +146,42 @@ impl<'data> Lv<'data> {
     }
 
     /// Reads a LV  from a raw buffer.
+    #[inline]
     pub fn from_bytes(buf: &'data [u8]) -> Result<Lv<'data>, ByteConversionError> {
         generic_len_check_deserialization(buf, MIN_LV_LEN)?;
         Self::from_be_bytes_no_len_check(buf)
     }
 
     pub(crate) fn write_to_be_bytes_no_len_check(&self, buf: &mut [u8]) -> usize {
-        if self.data.is_none() {
+        if self.is_empty() {
             buf[0] = 0;
             return MIN_LV_LEN;
         }
-        let data = self.data.unwrap();
         // Length check in constructor ensures the length always has a valid value.
-        buf[0] = data.len() as u8;
-        buf[MIN_LV_LEN..data.len() + MIN_LV_LEN].copy_from_slice(data);
-        MIN_LV_LEN + data.len()
+        buf[0] = self.data.len() as u8;
+        buf[MIN_LV_LEN..self.data.len() + MIN_LV_LEN].copy_from_slice(self.data);
+        MIN_LV_LEN + self.data.len()
     }
 
+    #[inline]
     pub(crate) fn from_be_bytes_no_len_check(
         buf: &'data [u8],
     ) -> Result<Lv<'data>, ByteConversionError> {
         let value_len = buf[0] as usize;
         generic_len_check_deserialization(buf, value_len + MIN_LV_LEN)?;
-        let mut data = None;
-        if value_len > 0 {
-            data = Some(&buf[MIN_LV_LEN..MIN_LV_LEN + value_len])
-        }
-        Ok(Self { data })
+        Ok(Self {
+            data: &buf[MIN_LV_LEN..MIN_LV_LEN + value_len],
+            raw_data: Some(buf),
+        })
     }
 }
 
 #[cfg(test)]
 pub mod tests {
-    use crate::cfdp::lv::Lv;
-    use crate::cfdp::TlvLvError;
+    use alloc::string::ToString;
+
+    use super::*;
+
     use crate::ByteConversionError;
     use std::string::String;
 
@@ -155,8 +191,8 @@ pub mod tests {
         let lv_res = Lv::new(&lv_data);
         assert!(lv_res.is_ok());
         let lv = lv_res.unwrap();
-        assert!(lv.value().is_some());
-        let val = lv.value().unwrap();
+        assert!(!lv.value().is_empty());
+        let val = lv.value();
         assert_eq!(val[0], 1);
         assert_eq!(val[1], 2);
         assert_eq!(val[2], 3);
@@ -172,7 +208,6 @@ pub mod tests {
         assert_eq!(lv_empty.len_value(), 0);
         assert_eq!(lv_empty.len_full(), 1);
         assert!(lv_empty.is_empty());
-        assert_eq!(lv_empty.value(), None);
         let mut buf: [u8; 4] = [0xff; 4];
         let res = lv_empty.write_to_be_bytes(&mut buf);
         assert!(res.is_ok());
@@ -211,10 +246,11 @@ pub mod tests {
         assert!(lv.is_ok());
         let lv = lv.unwrap();
         assert!(!lv.is_empty());
-        assert!(lv.value().is_some());
         assert_eq!(lv.len_value(), 4);
         assert_eq!(lv.len_full(), 5);
-        let val = lv.value().unwrap();
+        assert!(lv.raw_data().is_some());
+        assert_eq!(lv.raw_data().unwrap(), buf);
+        let val = lv.value();
         assert_eq!(val[0], 1);
         assert_eq!(val[1], 2);
         assert_eq!(val[2], 3);
@@ -228,7 +264,6 @@ pub mod tests {
         assert!(lv_empty.is_ok());
         let lv_empty = lv_empty.unwrap();
         assert!(lv_empty.is_empty());
-        assert!(lv_empty.value().is_none());
     }
 
     #[test]
@@ -237,11 +272,11 @@ pub mod tests {
         let lv = Lv::new(&data_big);
         assert!(lv.is_err());
         let error = lv.unwrap_err();
-        if let TlvLvError::DataTooLarge(size) = error {
-            assert_eq!(size, u8::MAX as usize + 1);
-        } else {
-            panic!("invalid exception {:?}", error)
-        }
+        assert_eq!(error.0, u8::MAX as usize + 1);
+        assert_eq!(
+            error.to_string(),
+            "data with size 256 larger than allowed 255 bytes"
+        );
     }
 
     #[test]
@@ -252,9 +287,9 @@ pub mod tests {
         let res = lv.write_to_be_bytes(&mut buf);
         assert!(res.is_err());
         let error = res.unwrap_err();
-        if let ByteConversionError::ToSliceTooSmall(missmatch) = error {
-            assert_eq!(missmatch.expected, 5);
-            assert_eq!(missmatch.found, 3);
+        if let ByteConversionError::ToSliceTooSmall { found, expected } = error {
+            assert_eq!(expected, 5);
+            assert_eq!(found, 3);
         } else {
             panic!("invalid error {}", error);
         }
@@ -267,9 +302,9 @@ pub mod tests {
         let res = Lv::from_bytes(&buf);
         assert!(res.is_err());
         let error = res.unwrap_err();
-        if let ByteConversionError::FromSliceTooSmall(missmatch) = error {
-            assert_eq!(missmatch.found, 3);
-            assert_eq!(missmatch.expected, 5);
+        if let ByteConversionError::FromSliceTooSmall { found, expected } = error {
+            assert_eq!(found, 3);
+            assert_eq!(expected, 5);
         } else {
             panic!("invalid error {}", error);
         }
@@ -282,14 +317,14 @@ pub mod tests {
         let res = res.unwrap();
         assert_eq!(res, 8 + 1);
         assert_eq!(buf[0], 8);
-        assert_eq!(buf[1], 't' as u8);
-        assert_eq!(buf[2], 'e' as u8);
-        assert_eq!(buf[3], 's' as u8);
-        assert_eq!(buf[4], 't' as u8);
-        assert_eq!(buf[5], '.' as u8);
-        assert_eq!(buf[6], 'b' as u8);
-        assert_eq!(buf[7], 'i' as u8);
-        assert_eq!(buf[8], 'n' as u8);
+        assert_eq!(buf[1], b't');
+        assert_eq!(buf[2], b'e');
+        assert_eq!(buf[3], b's');
+        assert_eq!(buf[4], b't');
+        assert_eq!(buf[5], b'.');
+        assert_eq!(buf[6], b'b');
+        assert_eq!(buf[7], b'i');
+        assert_eq!(buf[8], b'n');
     }
     #[test]
     fn test_str_helper() {

src/cfdp/mod.rs

@@ -1,11 +1,8 @@
 //! Low-level CCSDS File Delivery Protocol (CFDP) support according to [CCSDS 727.0-B-5](https://public.ccsds.org/Pubs/727x0b5.pdf).
 use crate::ByteConversionError;
-use core::fmt::{Display, Formatter};
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
-#[cfg(feature = "std")]
-use std::error::Error;
 
 pub mod lv;
 pub mod pdu;
@@ -18,6 +15,7 @@ pub const CFDP_VERSION_2: u8 = 0b001;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum PduType {
     FileDirective = 0,
@@ -26,6 +24,7 @@ pub enum PduType {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum Direction {
     TowardsReceiver = 0,
@@ -34,6 +33,7 @@ pub enum Direction {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum TransmissionMode {
     Acknowledged = 0,
@@ -42,15 +42,35 @@ pub enum TransmissionMode {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum CrcFlag {
     NoCrc = 0,
     WithCrc = 1,
 }
 
+impl From<bool> for CrcFlag {
+    fn from(value: bool) -> Self {
+        if value {
+            return CrcFlag::WithCrc;
+        }
+        CrcFlag::NoCrc
+    }
+}
+
+impl From<CrcFlag> for bool {
+    fn from(value: CrcFlag) -> Self {
+        if value == CrcFlag::WithCrc {
+            return true;
+        }
+        false
+    }
+}
+
 /// Always 0 and ignored for File Directive PDUs (CCSDS 727.0-B-5 P.75)
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum SegmentMetadataFlag {
     NotPresent = 0,
@@ -60,6 +80,7 @@ pub enum SegmentMetadataFlag {
 /// Always 0 and ignored for File Directive PDUs (CCSDS 727.0-B-5 P.75)
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum SegmentationControl {
     NoRecordBoundaryPreservation = 0,
@@ -68,6 +89,7 @@ pub enum SegmentationControl {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum FaultHandlerCode {
     NoticeOfCancellation = 0b0001,
@@ -78,17 +100,7 @@ pub enum FaultHandlerCode {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-#[repr(u8)]
-pub enum LenInBytes {
-    ZeroOrNone = 0,
-    OneByte = 1,
-    TwoBytes = 2,
-    ThreeBytes = 4,
-    FourBytes = 8,
-}
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum ConditionCode {
     /// This is not an error condition for which a faulty handler override can be specified
@@ -101,7 +113,7 @@ pub enum ConditionCode {
     FileSizeError = 0b0110,
     NakLimitReached = 0b0111,
     InactivityDetected = 0b1000,
-    CheckLimitReached = 0b1001,
+    CheckLimitReached = 0b1010,
     UnsupportedChecksumType = 0b1011,
     /// Not an actual fault condition for which fault handler overrides can be specified
     SuspendRequestReceived = 0b1110,
@@ -111,6 +123,7 @@ pub enum ConditionCode {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum LargeFileFlag {
     /// 32 bit maximum file size and FSS size
@@ -119,10 +132,28 @@ pub enum LargeFileFlag {
     Large = 1,
 }
 
+/// Transaction status for the ACK PDU field according to chapter 5.2.4 of the CFDP standard.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
+pub enum TransactionStatus {
+    /// Transaction is not currently active and the CFDP implementation does not retain a
+    /// transaction history.
+    Undefined = 0b00,
+    Active = 0b01,
+    /// Transaction was active in the past and was terminated.
+    Terminated = 0b10,
+    /// The CFDP implementation does retain a tranaction history, and the transaction is not and
+    /// never was active at this entity.
+    Unrecognized = 0b11,
+}
+
 /// Checksum types according to the
 /// [SANA Checksum Types registry](https://sanaregistry.org/r/checksum_identifiers/)
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum ChecksumType {
     /// Modular legacy checksum
@@ -142,68 +173,96 @@ impl Default for ChecksumType {
 
 pub const NULL_CHECKSUM_U32: [u8; 4] = [0; 4];
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, thiserror::Error)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[error("data with size {0} larger than allowed {max} bytes", max = u8::MAX)]
+pub struct TlvLvDataTooLargeError(pub usize);
+
+/// First value: Found value. Second value: Expected value if there is one.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, thiserror::Error)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[error("invalid TLV type field, found {found}, expected {expected:?}")]
+pub struct InvalidTlvTypeFieldError {
+    found: u8,
+    expected: Option<u8>,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, thiserror::Error)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum TlvLvError {
-    DataTooLarge(usize),
-    ByteConversionError(ByteConversionError),
-    /// First value: Found value. Second value: Expected value if there is one.
-    InvalidTlvTypeField((u8, Option<u8>)),
-    /// Logically invalid value length detected. The value length may not exceed 255 bytes.
-    /// Depending on the concrete TLV type, the value length may also be logically invalid.
+    #[error("{0}")]
+    DataTooLarge(#[from] TlvLvDataTooLargeError),
+    #[error("byte conversion error: {0}")]
+    ByteConversion(#[from] ByteConversionError),
+    #[error("{0}")]
+    InvalidTlvTypeField(#[from] InvalidTlvTypeFieldError),
+    #[error("invalid value length {0}")]
     InvalidValueLength(usize),
     /// Only applies to filestore requests and responses. Second name was missing where one is
     /// expected.
+    #[error("second name missing for filestore request or response")]
     SecondNameMissing,
     /// Invalid action code for filestore requests or responses.
+    #[error("invalid action code {0}")]
     InvalidFilestoreActionCode(u8),
 }
 
-impl From<ByteConversionError> for TlvLvError {
-    fn from(value: ByteConversionError) -> Self {
-        Self::ByteConversionError(value)
-    }
-}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
 
-impl Display for TlvLvError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
-        match self {
-            TlvLvError::DataTooLarge(data_len) => {
-                write!(
-                    f,
-                    "data with size {} larger than allowed {} bytes",
-                    data_len,
-                    u8::MAX
-                )
-            }
-            TlvLvError::ByteConversionError(e) => {
-                write!(f, "{}", e)
-            }
-            TlvLvError::InvalidTlvTypeField((found, expected)) => {
-                write!(
-                    f,
-                    "invalid TLV type field, found {found}, possibly expected {expected:?}"
-                )
-            }
-            TlvLvError::InvalidValueLength(len) => {
-                write!(f, "invalid value length {len} detected")
-            }
-            TlvLvError::SecondNameMissing => {
-                write!(f, "second name missing for filestore request or response")
-            }
-            TlvLvError::InvalidFilestoreActionCode(raw) => {
-                write!(f, "invalid filestore action code with raw value {raw}")
-            }
-        }
+    #[test]
+    fn test_crc_from_bool() {
+        assert_eq!(CrcFlag::from(false), CrcFlag::NoCrc);
     }
-}
 
-#[cfg(feature = "std")]
-impl Error for TlvLvError {
-    fn source(&self) -> Option<&(dyn Error + 'static)> {
-        match self {
-            TlvLvError::ByteConversionError(e) => Some(e),
-            _ => None,
-        }
+    #[test]
+    fn test_crc_flag_to_bool() {
+        let is_true: bool = CrcFlag::WithCrc.into();
+        assert!(is_true);
+        let is_false: bool = CrcFlag::NoCrc.into();
+        assert!(!is_false);
+    }
+
+    #[test]
+    fn test_default_checksum_type() {
+        let checksum = ChecksumType::default();
+        assert_eq!(checksum, ChecksumType::NullChecksum);
+    }
+
+    #[test]
+    fn test_fault_handler_code_from_u8() {
+        let fault_handler_code_raw = FaultHandlerCode::NoticeOfSuspension as u8;
+        let fault_handler_code = FaultHandlerCode::try_from(fault_handler_code_raw).unwrap();
+        assert_eq!(fault_handler_code, FaultHandlerCode::NoticeOfSuspension);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_impl_pdu_type() {
+        generic_serde_test(PduType::FileData);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_impl_direction() {
+        generic_serde_test(Direction::TowardsReceiver);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_impl_transmission_mode() {
+        generic_serde_test(TransmissionMode::Unacknowledged);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_fault_handler_code() {
+        generic_serde_test(FaultHandlerCode::NoticeOfCancellation);
     }
 }

src/cfdp/pdu/ack.rs

@@ -0,0 +1,335 @@
+use crate::{
+    cfdp::{ConditionCode, CrcFlag, Direction, TransactionStatus},
+    ByteConversionError,
+};
+
+use super::{
+    add_pdu_crc, generic_length_checks_pdu_deserialization, CfdpPdu, FileDirectiveType, PduError,
+    PduHeader, WritablePduPacket,
+};
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+/// ACK PDU abstraction.
+///
+/// For more information, refer to CFDP chapter 5.2.4.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct AckPdu {
+    pdu_header: PduHeader,
+    directive_code_of_acked_pdu: FileDirectiveType,
+    condition_code: ConditionCode,
+    transaction_status: TransactionStatus,
+}
+
+impl AckPdu {
+    pub fn new(
+        mut pdu_header: PduHeader,
+        directive_code_of_acked_pdu: FileDirectiveType,
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) -> Result<Self, PduError> {
+        if directive_code_of_acked_pdu == FileDirectiveType::EofPdu {
+            pdu_header.pdu_conf.direction = Direction::TowardsSender;
+        } else if directive_code_of_acked_pdu == FileDirectiveType::FinishedPdu {
+            pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
+        } else {
+            return Err(PduError::InvalidDirectiveType {
+                found: directive_code_of_acked_pdu as u8,
+                expected: None,
+            });
+        }
+        // Force correct direction flag.
+        let mut ack_pdu = Self {
+            pdu_header,
+            directive_code_of_acked_pdu,
+            condition_code,
+            transaction_status,
+        };
+        ack_pdu.pdu_header.pdu_datafield_len = ack_pdu.calc_pdu_datafield_len() as u16;
+        Ok(ack_pdu)
+    }
+
+    pub fn new_for_eof_pdu(
+        pdu_header: PduHeader,
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) -> Self {
+        // Unwrap okay here, [new] can only fail on invalid directive codes.
+        Self::new(
+            pdu_header,
+            FileDirectiveType::EofPdu,
+            condition_code,
+            transaction_status,
+        )
+        .unwrap()
+    }
+
+    pub fn new_for_finished_pdu(
+        pdu_header: PduHeader,
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) -> Self {
+        // Unwrap okay here, [new] can only fail on invalid directive codes.
+        Self::new(
+            pdu_header,
+            FileDirectiveType::FinishedPdu,
+            condition_code,
+            transaction_status,
+        )
+        .unwrap()
+    }
+
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    pub fn directive_code_of_acked_pdu(&self) -> FileDirectiveType {
+        self.directive_code_of_acked_pdu
+    }
+
+    pub fn condition_code(&self) -> ConditionCode {
+        self.condition_code
+    }
+
+    pub fn transaction_status(&self) -> TransactionStatus {
+        self.transaction_status
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        if self.crc_flag() == CrcFlag::WithCrc {
+            return 5;
+        }
+        3
+    }
+
+    pub fn from_bytes(buf: &[u8]) -> Result<AckPdu, PduError> {
+        let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
+        let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
+        generic_length_checks_pdu_deserialization(buf, current_idx + 3, full_len_without_crc)?;
+        let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::AckPdu),
+            }
+        })?;
+        if directive_type != FileDirectiveType::AckPdu {
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::AckPdu,
+            });
+        }
+        current_idx += 1;
+        let acked_directive_type =
+            FileDirectiveType::try_from(buf[current_idx] >> 4).map_err(|_| {
+                PduError::InvalidDirectiveType {
+                    found: buf[current_idx],
+                    expected: None,
+                }
+            })?;
+        if acked_directive_type != FileDirectiveType::EofPdu
+            && acked_directive_type != FileDirectiveType::FinishedPdu
+        {
+            return Err(PduError::InvalidDirectiveType {
+                found: acked_directive_type as u8,
+                expected: None,
+            });
+        }
+        current_idx += 1;
+        let condition_code = ConditionCode::try_from((buf[current_idx] >> 4) & 0b1111)
+            .map_err(|_| PduError::InvalidConditionCode((buf[current_idx] >> 4) & 0b1111))?;
+        let transaction_status = TransactionStatus::try_from(buf[current_idx] & 0b11).unwrap();
+        Self::new(
+            pdu_header,
+            acked_directive_type,
+            condition_code,
+            transaction_status,
+        )
+    }
+}
+
+impl CfdpPdu for AckPdu {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::AckPdu)
+    }
+}
+
+impl WritablePduPacket for AckPdu {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::AckPdu as u8;
+        current_idx += 1;
+
+        buf[current_idx] = (self.directive_code_of_acked_pdu as u8) << 4;
+        if self.directive_code_of_acked_pdu == FileDirectiveType::FinishedPdu {
+            // This is the directive subtype code. It needs to be set to 0b0001 if the ACK PDU
+            // acknowledges a Finished PDU, and to 0b0000 otherwise.
+            buf[current_idx] |= 0b0001;
+        }
+        current_idx += 1;
+        buf[current_idx] = ((self.condition_code as u8) << 4) | (self.transaction_status as u8);
+        current_idx += 1;
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::cfdp::{
+        pdu::tests::{common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID},
+        LargeFileFlag, PduType, TransmissionMode,
+    };
+
+    use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
+
+    fn verify_state(ack_pdu: &AckPdu, expected_crc_flag: CrcFlag, expected_dir: Direction) {
+        assert_eq!(ack_pdu.condition_code(), ConditionCode::NoError);
+        assert_eq!(ack_pdu.transaction_status(), TransactionStatus::Active);
+
+        assert_eq!(ack_pdu.crc_flag(), expected_crc_flag);
+        assert_eq!(ack_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(ack_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            ack_pdu.file_directive_type(),
+            Some(FileDirectiveType::AckPdu)
+        );
+        assert_eq!(ack_pdu.transmission_mode(), TransmissionMode::Acknowledged);
+        assert_eq!(ack_pdu.direction(), expected_dir);
+        assert_eq!(ack_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(ack_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(ack_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
+    }
+
+    #[test]
+    fn test_basic() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new(
+            pdu_header,
+            FileDirectiveType::FinishedPdu,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        )
+        .expect("creating ACK PDU failed");
+        assert_eq!(
+            ack_pdu.directive_code_of_acked_pdu(),
+            FileDirectiveType::FinishedPdu
+        );
+        verify_state(&ack_pdu, CrcFlag::NoCrc, Direction::TowardsReceiver);
+    }
+
+    fn generic_serialization_test(
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_finished_pdu(pdu_header, condition_code, transaction_status);
+        let mut buf: [u8; 64] = [0; 64];
+        let res = ack_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(written, ack_pdu.len_written());
+        verify_raw_header(ack_pdu.pdu_header(), &buf);
+
+        assert_eq!(buf[7], FileDirectiveType::AckPdu as u8);
+        assert_eq!((buf[8] >> 4) & 0b1111, FileDirectiveType::FinishedPdu as u8);
+        assert_eq!(buf[8] & 0b1111, 0b0001);
+        assert_eq!(buf[9] >> 4 & 0b1111, condition_code as u8);
+        assert_eq!(buf[9] & 0b11, transaction_status as u8);
+        assert_eq!(written, 10);
+    }
+
+    #[test]
+    fn test_serialization_no_error() {
+        generic_serialization_test(ConditionCode::NoError, TransactionStatus::Active);
+    }
+
+    #[test]
+    fn test_serialization_fs_error() {
+        generic_serialization_test(ConditionCode::FileSizeError, TransactionStatus::Terminated);
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_finished_pdu(
+            pdu_header,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        );
+        let ack_vec = ack_pdu.to_vec().unwrap();
+        let ack_deserialized =
+            AckPdu::from_bytes(&ack_vec).expect("ACK PDU deserialization failed");
+        assert_eq!(ack_deserialized, ack_pdu);
+    }
+
+    #[test]
+    fn test_with_crc() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_finished_pdu(
+            pdu_header,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        );
+        let ack_vec = ack_pdu.to_vec().unwrap();
+        assert_eq!(ack_vec.len(), ack_pdu.len_written());
+        assert_eq!(ack_vec.len(), 12);
+        let ack_deserialized =
+            AckPdu::from_bytes(&ack_vec).expect("ACK PDU deserialization failed");
+        assert_eq!(ack_deserialized, ack_pdu);
+    }
+
+    #[test]
+    fn test_for_eof_pdu() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_eof_pdu(
+            pdu_header,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        );
+        assert_eq!(
+            ack_pdu.directive_code_of_acked_pdu(),
+            FileDirectiveType::EofPdu
+        );
+        verify_state(&ack_pdu, CrcFlag::WithCrc, Direction::TowardsSender);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_ack_pdu_serialization() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_eof_pdu(
+            pdu_header,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        );
+        generic_serde_test(ack_pdu);
+    }
+}

src/cfdp/pdu/eof.rs

@@ -2,17 +2,20 @@ use crate::cfdp::pdu::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
     FileDirectiveType, PduError, PduHeader,
 };
-use crate::cfdp::tlv::EntityIdTlv;
-use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::cfdp::tlv::{EntityIdTlv, WritableTlv};
+use crate::cfdp::{ConditionCode, CrcFlag, Direction, LargeFileFlag};
+use crate::ByteConversionError;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::{CfdpPdu, WritablePduPacket};
+
 /// Finished PDU abstraction.
 ///
 /// For more information, refer to CFDP chapter 5.2.2.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct EofPdu {
     pdu_header: PduHeader,
     condition_code: ConditionCode,
@@ -22,24 +25,38 @@ pub struct EofPdu {
 }
 
 impl EofPdu {
-    pub fn new_no_error(pdu_header: PduHeader, file_checksum: u32, file_size: u64) -> Self {
+    pub fn new(
+        mut pdu_header: PduHeader,
+        condition_code: ConditionCode,
+        file_checksum: u32,
+        file_size: u64,
+        fault_location: Option<EntityIdTlv>,
+    ) -> Self {
+        // Force correct direction flag.
+        pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
         let mut eof_pdu = Self {
             pdu_header,
-            condition_code: ConditionCode::NoError,
+            condition_code,
             file_checksum,
             file_size,
-            fault_location: None,
+            fault_location,
         };
         eof_pdu.pdu_header.pdu_datafield_len = eof_pdu.calc_pdu_datafield_len() as u16;
         eof_pdu
     }
 
-    pub fn pdu_header(&self) -> &PduHeader {
-        &self.pdu_header
+    pub fn new_no_error(pdu_header: PduHeader, file_checksum: u32, file_size: u64) -> Self {
+        Self::new(
+            pdu_header,
+            ConditionCode::NoError,
+            file_checksum,
+            file_size,
+            None,
+        )
     }
 
-    pub fn written_len(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
     }
 
     pub fn condition_code(&self) -> ConditionCode {
@@ -63,39 +80,12 @@ impl EofPdu {
         if let Some(fault_location) = self.fault_location {
             len += fault_location.len_full();
         }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            len += 2;
+        }
         len
     }
 
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        let expected_len = self.written_len();
-        if buf.len() < expected_len {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: expected_len,
-            })
-            .into());
-        }
-        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
-        buf[current_idx] = FileDirectiveType::EofPdu as u8;
-        current_idx += 1;
-        buf[current_idx] = (self.condition_code as u8) << 4;
-        current_idx += 1;
-        buf[current_idx..current_idx + 4].copy_from_slice(&self.file_checksum.to_be_bytes());
-        current_idx += 4;
-        current_idx += write_fss_field(
-            self.pdu_header.pdu_conf.file_flag,
-            self.file_size,
-            &mut buf[current_idx..],
-        )?;
-        if let Some(fault_location) = self.fault_location {
-            current_idx += fault_location.write_to_be_bytes(buf)?;
-        }
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
-            current_idx = add_pdu_crc(buf, current_idx);
-        }
-        Ok(current_idx)
-    }
-
     pub fn from_bytes(buf: &[u8]) -> Result<EofPdu, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
@@ -106,13 +96,16 @@ impl EofPdu {
         }
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::EofPdu))
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::EofPdu),
+            }
         })?;
         if directive_type != FileDirectiveType::EofPdu {
-            return Err(PduError::WrongDirectiveType((
-                directive_type,
-                FileDirectiveType::EofPdu,
-            )));
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::EofPdu,
+            });
         }
         current_idx += 1;
         let condition_code = ConditionCode::try_from((buf[current_idx] >> 4) & 0b1111)
@@ -138,22 +131,99 @@ impl EofPdu {
     }
 }
 
+impl CfdpPdu for EofPdu {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::EofPdu)
+    }
+}
+
+impl WritablePduPacket for EofPdu {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::EofPdu as u8;
+        current_idx += 1;
+        buf[current_idx] = (self.condition_code as u8) << 4;
+        current_idx += 1;
+        buf[current_idx..current_idx + 4].copy_from_slice(&self.file_checksum.to_be_bytes());
+        current_idx += 4;
+        current_idx += write_fss_field(
+            self.pdu_header.pdu_conf.file_flag,
+            self.file_size,
+            &mut buf[current_idx..],
+        )?;
+        if let Some(fault_location) = self.fault_location {
+            current_idx += fault_location.write_to_bytes(&mut buf[current_idx..])?;
+        }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
 #[cfg(test)]
 mod tests {
-    use crate::cfdp::pdu::eof::EofPdu;
-    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use super::*;
+    use crate::cfdp::pdu::tests::{
+        common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID,
+    };
     use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
-    use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
+    use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag, PduType, TransmissionMode};
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
+    use crate::util::{UnsignedByteFieldU16, UnsignedEnum};
+
+    fn verify_state_no_error_no_crc(eof_pdu: &EofPdu, file_flag: LargeFileFlag) {
+        verify_state(eof_pdu, CrcFlag::NoCrc, file_flag, ConditionCode::NoError);
+    }
+
+    fn verify_state(
+        eof_pdu: &EofPdu,
+        crc_flag: CrcFlag,
+        file_flag: LargeFileFlag,
+        cond_code: ConditionCode,
+    ) {
+        assert_eq!(eof_pdu.file_checksum(), 0x01020304);
+        assert_eq!(eof_pdu.file_size(), 12);
+        assert_eq!(eof_pdu.condition_code(), cond_code);
+
+        assert_eq!(eof_pdu.crc_flag(), crc_flag);
+        assert_eq!(eof_pdu.file_flag(), file_flag);
+        assert_eq!(eof_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            eof_pdu.file_directive_type(),
+            Some(FileDirectiveType::EofPdu)
+        );
+        assert_eq!(eof_pdu.transmission_mode(), TransmissionMode::Acknowledged);
+        assert_eq!(eof_pdu.direction(), Direction::TowardsReceiver);
+        assert_eq!(eof_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(eof_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(eof_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
+    }
 
     #[test]
     fn test_basic() {
         let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
         let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
         let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
-        assert_eq!(eof_pdu.written_len(), pdu_header.header_len() + 2 + 4 + 4);
-        assert_eq!(eof_pdu.file_checksum(), 0x01020304);
-        assert_eq!(eof_pdu.file_size(), 12);
-        assert_eq!(eof_pdu.condition_code(), ConditionCode::NoError);
+        assert_eq!(eof_pdu.len_written(), pdu_header.header_len() + 2 + 4 + 4);
+        verify_state_no_error_no_crc(&eof_pdu, LargeFileFlag::Normal);
     }
 
     #[test]
@@ -165,7 +235,7 @@ mod tests {
         let res = eof_pdu.write_to_bytes(&mut buf);
         assert!(res.is_ok());
         let written = res.unwrap();
-        assert_eq!(written, eof_pdu.written_len());
+        assert_eq!(written, eof_pdu.len_written());
         verify_raw_header(eof_pdu.pdu_header(), &buf);
         let mut current_idx = eof_pdu.pdu_header().header_len();
         buf[current_idx] = FileDirectiveType::EofPdu as u8;
@@ -196,11 +266,103 @@ mod tests {
         let mut buf: [u8; 64] = [0; 64];
         eof_pdu.write_to_bytes(&mut buf).unwrap();
         let eof_read_back = EofPdu::from_bytes(&buf);
-        if !eof_read_back.is_ok() {
-            let e = eof_read_back.unwrap_err();
+        if let Err(e) = eof_read_back {
             panic!("deserialization failed with: {e}")
         }
         let eof_read_back = eof_read_back.unwrap();
         assert_eq!(eof_read_back, eof_pdu);
     }
+
+    #[test]
+    fn test_write_to_vec() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        let mut buf: [u8; 64] = [0; 64];
+        let written = eof_pdu.write_to_bytes(&mut buf).unwrap();
+        let pdu_vec = eof_pdu.to_vec().unwrap();
+        assert_eq!(buf[0..written], pdu_vec);
+    }
+
+    #[test]
+    fn test_with_crc() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        let mut buf: [u8; 64] = [0; 64];
+        let written = eof_pdu.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(written, eof_pdu.len_written());
+        let eof_from_raw = EofPdu::from_bytes(&buf).expect("creating EOF PDU failed");
+        assert_eq!(eof_from_raw, eof_pdu);
+        buf[written - 1] -= 1;
+        let crc: u16 = ((buf[written - 2] as u16) << 8) as u16 | buf[written - 1] as u16;
+        let error = EofPdu::from_bytes(&buf).unwrap_err();
+        if let PduError::Checksum(e) = error {
+            assert_eq!(e, crc);
+        } else {
+            panic!("expected crc error");
+        }
+    }
+
+    #[test]
+    fn test_with_large_file_flag() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Large);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        verify_state_no_error_no_crc(&eof_pdu, LargeFileFlag::Large);
+        assert_eq!(eof_pdu.len_written(), pdu_header.header_len() + 2 + 8 + 4);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_eof_serde() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        generic_serde_test(eof_pdu);
+    }
+
+    fn generic_test_with_fault_location_and_error(crc: CrcFlag) {
+        let pdu_conf = common_pdu_conf(crc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new(
+            pdu_header,
+            ConditionCode::FileChecksumFailure,
+            0x01020304,
+            12,
+            Some(EntityIdTlv::new(UnsignedByteFieldU16::new(5).into())),
+        );
+        let mut expected_len = pdu_header.header_len() + 2 + 4 + 4 + 4;
+        if crc == CrcFlag::WithCrc {
+            expected_len += 2;
+        }
+        // Entity ID TLV increaes length by 4.
+        assert_eq!(eof_pdu.len_written(), expected_len);
+        verify_state(
+            &eof_pdu,
+            crc,
+            LargeFileFlag::Normal,
+            ConditionCode::FileChecksumFailure,
+        );
+        let eof_vec = eof_pdu.to_vec().unwrap();
+        let eof_read_back = EofPdu::from_bytes(&eof_vec);
+        if let Err(e) = eof_read_back {
+            panic!("deserialization failed with: {e}")
+        }
+        let eof_read_back = eof_read_back.unwrap();
+        assert_eq!(eof_read_back, eof_pdu);
+        assert!(eof_read_back.fault_location.is_some());
+        assert_eq!(eof_read_back.fault_location.unwrap().entity_id().value(), 5);
+        assert_eq!(eof_read_back.fault_location.unwrap().entity_id().size(), 2);
+    }
+
+    #[test]
+    fn test_with_fault_location_and_error() {
+        generic_test_with_fault_location_and_error(CrcFlag::NoCrc);
+    }
+
+    #[test]
+    fn test_with_fault_location_and_error_and_crc() {
+        generic_test_with_fault_location_and_error(CrcFlag::WithCrc);
+    }
 }

src/cfdp/pdu/file_data.rs

@@ -3,11 +3,13 @@ use crate::cfdp::pdu::{
     PduError, PduHeader,
 };
 use crate::cfdp::{CrcFlag, LargeFileFlag, PduType, SegmentMetadataFlag};
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::ByteConversionError;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::{CfdpPdu, FileDirectiveType, WritablePduPacket};
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[repr(u8)]
@@ -41,6 +43,14 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
         })
     }
 
+    pub fn record_continuation_state(&self) -> RecordContinuationState {
+        self.record_continuation_state
+    }
+
+    pub fn metadata(&self) -> Option<&'seg_meta [u8]> {
+        self.metadata
+    }
+
     pub fn written_len(&self) -> usize {
         // Map empty metadata to 0 and slice to its length.
         1 + self.metadata.map_or(0, |meta| meta.len())
@@ -48,10 +58,10 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
 
     pub(crate) fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         if buf.len() < self.written_len() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: self.written_len(),
-            }));
+            });
         }
         buf[0] = ((self.record_continuation_state as u8) << 6)
             | self.metadata.map_or(0, |meta| meta.len() as u8);
@@ -63,10 +73,10 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
 
     pub(crate) fn from_bytes(buf: &'seg_meta [u8]) -> Result<Self, ByteConversionError> {
         if buf.is_empty() {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: buf.len(),
                 expected: 2,
-            }));
+            });
         }
         let mut metadata = None;
         let seg_metadata_len = (buf[0] & 0b111111) as usize;
@@ -82,16 +92,67 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
     }
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+struct FdPduBase<'seg_meta> {
+    pdu_header: PduHeader,
+    #[cfg_attr(feature = "serde", serde(borrow))]
+    segment_metadata: Option<SegmentMetadata<'seg_meta>>,
+    offset: u64,
+}
+
+impl CfdpPdu for FdPduBase<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        None
+    }
+}
+
+impl FdPduBase<'_> {
+    fn calc_pdu_datafield_len(&self, file_data_len: u64) -> usize {
+        let mut len = core::mem::size_of::<u32>();
+        if self.pdu_header.pdu_conf.file_flag == LargeFileFlag::Large {
+            len += 4;
+        }
+        if self.segment_metadata.is_some() {
+            len += self.segment_metadata.as_ref().unwrap().written_len()
+        }
+        len += file_data_len as usize;
+        if self.crc_flag() == CrcFlag::WithCrc {
+            len += 2;
+        }
+        len
+    }
+
+    fn write_common_fields_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        if self.segment_metadata.is_some() {
+            current_idx += self
+                .segment_metadata
+                .as_ref()
+                .unwrap()
+                .write_to_bytes(&mut buf[current_idx..])?;
+        }
+        current_idx += write_fss_field(
+            self.pdu_header.common_pdu_conf().file_flag,
+            self.offset,
+            &mut buf[current_idx..],
+        )?;
+        Ok(current_idx)
+    }
+}
+
 /// File Data PDU abstraction.
 ///
 /// For more information, refer to CFDP chapter 5.3.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct FileDataPdu<'seg_meta, 'file_data> {
-    pdu_header: PduHeader,
     #[cfg_attr(feature = "serde", serde(borrow))]
-    segment_metadata: Option<SegmentMetadata<'seg_meta>>,
-    offset: u64,
+    common: FdPduBase<'seg_meta>,
     file_data: &'file_data [u8],
 }
 
@@ -124,77 +185,35 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
             pdu_header.seg_metadata_flag = SegmentMetadataFlag::Present;
         }
         let mut pdu = Self {
-            pdu_header,
-            segment_metadata,
-            offset,
+            common: FdPduBase {
+                pdu_header,
+                segment_metadata,
+                offset,
+            },
             file_data,
         };
-        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
+        pdu.common.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
         pdu
     }
 
     fn calc_pdu_datafield_len(&self) -> usize {
-        let mut len = core::mem::size_of::<u32>();
-        if self.pdu_header.pdu_conf.file_flag == LargeFileFlag::Large {
-            len += 4;
-        }
-        if self.segment_metadata.is_some() {
-            len += self.segment_metadata.as_ref().unwrap().written_len()
-        }
-        len += self.file_data.len();
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
-            len += 2;
-        }
-        len
+        self.common
+            .calc_pdu_datafield_len(self.file_data.len() as u64)
     }
-    pub fn written_len(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+
+    pub fn segment_metadata(&self) -> Option<&SegmentMetadata> {
+        self.common.segment_metadata.as_ref()
     }
 
     pub fn offset(&self) -> u64 {
-        self.offset
+        self.common.offset
     }
 
     pub fn file_data(&self) -> &'file_data [u8] {
         self.file_data
     }
 
-    pub fn segment_metadata(&self) -> Option<&SegmentMetadata> {
-        self.segment_metadata.as_ref()
-    }
-
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        if buf.len() < self.written_len() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: self.written_len(),
-            })
-            .into());
-        }
-        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
-        if self.segment_metadata.is_some() {
-            current_idx += self
-                .segment_metadata
-                .as_ref()
-                .unwrap()
-                .write_to_bytes(&mut buf[current_idx..])?;
-        }
-        current_idx += write_fss_field(
-            self.pdu_header.common_pdu_conf().file_flag,
-            self.offset,
-            &mut buf[current_idx..],
-        )?;
-        buf[current_idx..current_idx + self.file_data.len()].copy_from_slice(self.file_data);
-        current_idx += self.file_data.len();
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
-            current_idx = add_pdu_crc(buf, current_idx);
-        }
-        Ok(current_idx)
-    }
-
-    pub fn from_bytes<'longest: 'seg_meta + 'file_data>(
-        buf: &'longest [u8],
-    ) -> Result<Self, PduError> {
+    pub fn from_bytes<'buf: 'seg_meta + 'file_data>(buf: &'buf [u8]) -> Result<Self, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
         let min_expected_len = current_idx + core::mem::size_of::<u32>();
@@ -207,35 +226,226 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
         let (fss, offset) = read_fss_field(pdu_header.pdu_conf.file_flag, &buf[current_idx..]);
         current_idx += fss;
         if current_idx > full_len_without_crc {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: current_idx,
                 expected: full_len_without_crc,
-            })
+            }
             .into());
         }
         Ok(Self {
-            pdu_header,
-            segment_metadata,
-            offset,
+            common: FdPduBase {
+                pdu_header,
+                segment_metadata,
+                offset,
+            },
             file_data: &buf[current_idx..full_len_without_crc],
         })
     }
 }
+impl CfdpPdu for FileDataPdu<'_, '_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.common.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        None
+    }
+}
+
+impl WritablePduPacket for FileDataPdu<'_, '_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        if buf.len() < self.len_written() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: self.len_written(),
+            }
+            .into());
+        }
+
+        let mut current_idx = self.common.write_common_fields_to_bytes(buf)?;
+        buf[current_idx..current_idx + self.file_data.len()].copy_from_slice(self.file_data);
+        current_idx += self.file_data.len();
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.common.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+/// File Data PDU creator abstraction.
+///
+/// This special creator object allows to read into the file data buffer directly. This avoids
+/// the need of an additional buffer to create a file data PDU. This structure therefore
+/// does not implement the regular [WritablePduPacket] trait.
+///
+/// For more information, refer to CFDP chapter 5.3.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct FileDataPduCreatorWithReservedDatafield<'seg_meta> {
+    #[cfg_attr(feature = "serde", serde(borrow))]
+    common: FdPduBase<'seg_meta>,
+    file_data_len: u64,
+}
+
+impl<'seg_meta> FileDataPduCreatorWithReservedDatafield<'seg_meta> {
+    pub fn new_with_seg_metadata(
+        pdu_header: PduHeader,
+        segment_metadata: SegmentMetadata<'seg_meta>,
+        offset: u64,
+        file_data_len: u64,
+    ) -> Self {
+        Self::new_generic(pdu_header, Some(segment_metadata), offset, file_data_len)
+    }
+
+    pub fn new_no_seg_metadata(pdu_header: PduHeader, offset: u64, file_data_len: u64) -> Self {
+        Self::new_generic(pdu_header, None, offset, file_data_len)
+    }
+
+    pub fn new_generic(
+        mut pdu_header: PduHeader,
+        segment_metadata: Option<SegmentMetadata<'seg_meta>>,
+        offset: u64,
+        file_data_len: u64,
+    ) -> Self {
+        pdu_header.pdu_type = PduType::FileData;
+        if segment_metadata.is_some() {
+            pdu_header.seg_metadata_flag = SegmentMetadataFlag::Present;
+        }
+        let mut pdu = Self {
+            common: FdPduBase {
+                pdu_header,
+                segment_metadata,
+                offset,
+            },
+            file_data_len,
+        };
+        pdu.common.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
+        pdu
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        self.common.calc_pdu_datafield_len(self.file_data_len)
+    }
+
+    pub fn len_written(&self) -> usize {
+        self.common.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+
+    /// This function performs a partial write by writing all data except the file data
+    /// and the CRC.
+    ///
+    /// It returns a [FileDataPduCreatorWithUnwrittenData] which provides a mutable slice to
+    /// the reserved file data field. The user can read file data into this field directly and
+    /// then finish the PDU creation using the [FileDataPduCreatorWithUnwrittenData::finish] call.
+    pub fn write_to_bytes_partially<'buf>(
+        &self,
+        buf: &'buf mut [u8],
+    ) -> Result<FileDataPduCreatorWithUnwrittenData<'buf>, PduError> {
+        if buf.len() < self.len_written() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: self.len_written(),
+            }
+            .into());
+        }
+        let mut current_idx = self.common.write_common_fields_to_bytes(buf)?;
+        let file_data_offset = current_idx as u64;
+        current_idx += self.file_data_len as usize;
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx += 2;
+        }
+        Ok(FileDataPduCreatorWithUnwrittenData {
+            write_buf: &mut buf[0..current_idx],
+            file_data_offset,
+            file_data_len: self.file_data_len,
+            needs_crc: self.crc_flag() == CrcFlag::WithCrc,
+        })
+    }
+}
+
+impl CfdpPdu for FileDataPduCreatorWithReservedDatafield<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.common.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        None
+    }
+}
+
+/// This structure is created with [FileDataPduCreatorWithReservedDatafield::write_to_bytes_partially]
+/// and provides an API to read file data from the virtual filesystem into the file data PDU buffer
+/// directly.
+///
+/// This structure provides a mutable slice to the reserved file data field. The user can read
+/// file data into this field directly and then finish the PDU creation using the
+/// [FileDataPduCreatorWithUnwrittenData::finish] call.
+pub struct FileDataPduCreatorWithUnwrittenData<'buf> {
+    write_buf: &'buf mut [u8],
+    file_data_offset: u64,
+    file_data_len: u64,
+    needs_crc: bool,
+}
+
+impl FileDataPduCreatorWithUnwrittenData<'_> {
+    pub fn file_data_field_mut(&mut self) -> &mut [u8] {
+        &mut self.write_buf[self.file_data_offset as usize
+            ..self.file_data_offset as usize + self.file_data_len as usize]
+    }
+
+    /// This functio needs to be called to add a CRC to the file data PDU where applicable.
+    ///
+    /// It returns the full written size of the PDU.
+    pub fn finish(self) -> usize {
+        if self.needs_crc {
+            add_pdu_crc(
+                self.write_buf,
+                self.file_data_offset as usize + self.file_data_len as usize,
+            );
+        }
+        self.write_buf.len()
+    }
+}
+
+/// This function can be used to calculate the maximum allowed file segment size for
+/// a given maximum packet length and the segment metadata if there is any.
+pub fn calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(
+    pdu_header: &PduHeader,
+    max_packet_len: usize,
+    segment_metadata: Option<&SegmentMetadata>,
+) -> usize {
+    let mut subtract = pdu_header.header_len();
+    if segment_metadata.is_some() {
+        subtract += 1 + segment_metadata.as_ref().unwrap().metadata().unwrap().len();
+    }
+    if pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
+        subtract += 8;
+    } else {
+        subtract += 4;
+    }
+    if pdu_header.common_pdu_conf().crc_flag == CrcFlag::WithCrc {
+        subtract += 2;
+    }
+    max_packet_len.saturating_sub(subtract)
+}
 
 #[cfg(test)]
 mod tests {
-    use crate::cfdp::pdu::file_data::{FileDataPdu, RecordContinuationState, SegmentMetadata};
+    use super::*;
+    use crate::cfdp::pdu::tests::{TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID};
     use crate::cfdp::pdu::{CommonPduConfig, PduHeader};
-    use crate::cfdp::{SegmentMetadataFlag, SegmentationControl};
-    use crate::util::UbfU8;
+    use crate::cfdp::{Direction, SegmentMetadataFlag, SegmentationControl, TransmissionMode};
+    #[cfg(feature = "serde")]
+    use postcard::{from_bytes, to_allocvec};
 
     #[test]
     fn test_basic() {
-        let src_id = UbfU8::new(1);
-        let dest_id = UbfU8::new(2);
-        let transaction_seq_num = UbfU8::new(3);
         let common_conf =
-            CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_num).unwrap();
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
         let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
         let file_data: [u8; 4] = [1, 2, 3, 4];
         let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
@@ -243,18 +453,25 @@ mod tests {
         assert_eq!(fd_pdu.offset(), 10);
         assert!(fd_pdu.segment_metadata().is_none());
         assert_eq!(
-            fd_pdu.written_len(),
-            fd_pdu.pdu_header.header_len() + core::mem::size_of::<u32>() + 4
+            fd_pdu.len_written(),
+            fd_pdu.pdu_header().header_len() + core::mem::size_of::<u32>() + 4
         );
+
+        assert_eq!(fd_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(fd_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(fd_pdu.pdu_type(), PduType::FileData);
+        assert_eq!(fd_pdu.file_directive_type(), None);
+        assert_eq!(fd_pdu.transmission_mode(), TransmissionMode::Acknowledged);
+        assert_eq!(fd_pdu.direction(), Direction::TowardsReceiver);
+        assert_eq!(fd_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(fd_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(fd_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
     }
 
     #[test]
     fn test_serialization() {
-        let src_id = UbfU8::new(1);
-        let dest_id = UbfU8::new(2);
-        let transaction_seq_num = UbfU8::new(3);
         let common_conf =
-            CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_num).unwrap();
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
         let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
         let file_data: [u8; 4] = [1, 2, 3, 4];
         let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
@@ -264,11 +481,11 @@ mod tests {
         let written = res.unwrap();
         assert_eq!(
             written,
-            fd_pdu.pdu_header.header_len() + core::mem::size_of::<u32>() + 4
+            fd_pdu.pdu_header().header_len() + core::mem::size_of::<u32>() + 4
         );
-        let mut current_idx = fd_pdu.pdu_header.header_len();
+        let mut current_idx = fd_pdu.pdu_header().header_len();
         let file_size = u32::from_be_bytes(
-            buf[fd_pdu.pdu_header.header_len()..fd_pdu.pdu_header.header_len() + 4]
+            buf[fd_pdu.pdu_header().header_len()..fd_pdu.pdu_header().header_len() + 4]
                 .try_into()
                 .unwrap(),
         );
@@ -284,12 +501,22 @@ mod tests {
     }
 
     #[test]
-    fn test_deserialization() {
-        let src_id = UbfU8::new(1);
-        let dest_id = UbfU8::new(2);
-        let transaction_seq_num = UbfU8::new(3);
+    fn test_write_to_vec() {
         let common_conf =
-            CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_num).unwrap();
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
+        let mut buf: [u8; 64] = [0; 64];
+        let written = fd_pdu.write_to_bytes(&mut buf).unwrap();
+        let pdu_vec = fd_pdu.to_vec().unwrap();
+        assert_eq!(buf[0..written], pdu_vec);
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
         let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
         let file_data: [u8; 4] = [1, 2, 3, 4];
         let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
@@ -301,13 +528,33 @@ mod tests {
         assert_eq!(fd_pdu_read_back, fd_pdu);
     }
 
+    #[test]
+    fn test_with_crc() {
+        let mut common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        common_conf.crc_flag = true.into();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
+        let mut buf: [u8; 64] = [0; 64];
+        let written = fd_pdu.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(written, fd_pdu.len_written());
+        let finished_pdu_from_raw = FileDataPdu::from_bytes(&buf).unwrap();
+        assert_eq!(finished_pdu_from_raw, fd_pdu);
+        buf[written - 1] -= 1;
+        let crc: u16 = ((buf[written - 2] as u16) << 8) | buf[written - 1] as u16;
+        let error = FileDataPdu::from_bytes(&buf).unwrap_err();
+        if let PduError::Checksum(e) = error {
+            assert_eq!(e, crc);
+        } else {
+            panic!("expected crc error");
+        }
+    }
+
     #[test]
     fn test_with_seg_metadata_serialization() {
-        let src_id = UbfU8::new(1);
-        let dest_id = UbfU8::new(2);
-        let transaction_seq_num = UbfU8::new(3);
         let common_conf =
-            CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_num).unwrap();
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
         let pdu_header = PduHeader::new_for_file_data(
             common_conf,
             0,
@@ -323,8 +570,8 @@ mod tests {
         assert!(fd_pdu.segment_metadata().is_some());
         assert_eq!(*fd_pdu.segment_metadata().unwrap(), segment_meta);
         assert_eq!(
-            fd_pdu.written_len(),
-            fd_pdu.pdu_header.header_len()
+            fd_pdu.len_written(),
+            fd_pdu.pdu_header().header_len()
                 + 1
                 + seg_metadata.len()
                 + core::mem::size_of::<u32>()
@@ -334,7 +581,7 @@ mod tests {
         fd_pdu
             .write_to_bytes(&mut buf)
             .expect("writing FD PDU failed");
-        let mut current_idx = fd_pdu.pdu_header.header_len();
+        let mut current_idx = fd_pdu.pdu_header().header_len();
         assert_eq!(
             RecordContinuationState::try_from((buf[current_idx] >> 6) & 0b11).unwrap(),
             RecordContinuationState::StartAndEnd
@@ -363,16 +610,13 @@ mod tests {
         current_idx += 1;
         assert_eq!(buf[current_idx], 4);
         current_idx += 1;
-        assert_eq!(current_idx, fd_pdu.written_len());
+        assert_eq!(current_idx, fd_pdu.len_written());
     }
 
     #[test]
     fn test_with_seg_metadata_deserialization() {
-        let src_id = UbfU8::new(1);
-        let dest_id = UbfU8::new(2);
-        let transaction_seq_num = UbfU8::new(3);
         let common_conf =
-            CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_num).unwrap();
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
         let pdu_header = PduHeader::new_for_file_data(
             common_conf,
             0,
@@ -394,4 +638,177 @@ mod tests {
         let fd_pdu_read_back = fd_pdu_read_back.unwrap();
         assert_eq!(fd_pdu_read_back, fd_pdu);
     }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_serialization() {
+        let common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
+        let output = to_allocvec(&fd_pdu).unwrap();
+        let output_converted_back: FileDataPdu = from_bytes(&output).unwrap();
+        assert_eq!(output_converted_back, fd_pdu);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_serialization_with_seg_metadata() {
+        let common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        let pdu_header = PduHeader::new_for_file_data(
+            common_conf,
+            0,
+            SegmentMetadataFlag::Present,
+            SegmentationControl::WithRecordBoundaryPreservation,
+        );
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let seg_metadata: [u8; 4] = [4, 3, 2, 1];
+        let segment_meta =
+            SegmentMetadata::new(RecordContinuationState::StartAndEnd, Some(&seg_metadata))
+                .unwrap();
+        let fd_pdu = FileDataPdu::new_with_seg_metadata(pdu_header, segment_meta, 10, &file_data);
+        let output = to_allocvec(&fd_pdu).unwrap();
+        let output_converted_back: FileDataPdu = from_bytes(&output).unwrap();
+        assert_eq!(output_converted_back, fd_pdu);
+    }
+
+    #[test]
+    fn test_fd_pdu_creator_with_reserved_field_no_crc() {
+        let common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let test_str = "hello world!";
+        let fd_pdu = FileDataPduCreatorWithReservedDatafield::new_no_seg_metadata(
+            pdu_header,
+            10,
+            test_str.len() as u64,
+        );
+        let mut write_buf: [u8; 64] = [0; 64];
+        let mut pdu_unwritten = fd_pdu
+            .write_to_bytes_partially(&mut write_buf)
+            .expect("partial write failed");
+        pdu_unwritten
+            .file_data_field_mut()
+            .copy_from_slice(test_str.as_bytes());
+        pdu_unwritten.finish();
+
+        let pdu_reader = FileDataPdu::from_bytes(&write_buf).expect("reading file data PDU failed");
+        assert_eq!(
+            core::str::from_utf8(pdu_reader.file_data()).expect("reading utf8 string failed"),
+            "hello world!"
+        );
+    }
+
+    #[test]
+    fn test_fd_pdu_creator_with_reserved_field_with_crc() {
+        let mut common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        common_conf.crc_flag = true.into();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let test_str = "hello world!";
+        let fd_pdu = FileDataPduCreatorWithReservedDatafield::new_no_seg_metadata(
+            pdu_header,
+            10,
+            test_str.len() as u64,
+        );
+        let mut write_buf: [u8; 64] = [0; 64];
+        let mut pdu_unwritten = fd_pdu
+            .write_to_bytes_partially(&mut write_buf)
+            .expect("partial write failed");
+        pdu_unwritten
+            .file_data_field_mut()
+            .copy_from_slice(test_str.as_bytes());
+        pdu_unwritten.finish();
+
+        let pdu_reader = FileDataPdu::from_bytes(&write_buf).expect("reading file data PDU failed");
+        assert_eq!(
+            core::str::from_utf8(pdu_reader.file_data()).expect("reading utf8 string failed"),
+            "hello world!"
+        );
+    }
+
+    #[test]
+    fn test_fd_pdu_creator_with_reserved_field_with_crc_without_finish_fails() {
+        let mut common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        common_conf.crc_flag = true.into();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let test_str = "hello world!";
+        let fd_pdu = FileDataPduCreatorWithReservedDatafield::new_no_seg_metadata(
+            pdu_header,
+            10,
+            test_str.len() as u64,
+        );
+        let mut write_buf: [u8; 64] = [0; 64];
+        let mut pdu_unwritten = fd_pdu
+            .write_to_bytes_partially(&mut write_buf)
+            .expect("partial write failed");
+        pdu_unwritten
+            .file_data_field_mut()
+            .copy_from_slice(test_str.as_bytes());
+
+        let pdu_reader_error = FileDataPdu::from_bytes(&write_buf);
+        assert!(pdu_reader_error.is_err());
+        let error = pdu_reader_error.unwrap_err();
+        match error {
+            PduError::Checksum(_) => (),
+            _ => {
+                panic!("unexpected PDU error {}", error)
+            }
+        }
+    }
+
+    #[test]
+    fn test_max_file_seg_calculator_0() {
+        let pdu_header = PduHeader::new_for_file_data_default(CommonPduConfig::default(), 0);
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 64, None),
+            53
+        );
+    }
+
+    #[test]
+    fn test_max_file_seg_calculator_1() {
+        let common_conf = CommonPduConfig {
+            crc_flag: CrcFlag::WithCrc,
+            ..Default::default()
+        };
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 64, None),
+            51
+        );
+    }
+
+    #[test]
+    fn test_max_file_seg_calculator_2() {
+        let common_conf = CommonPduConfig {
+            file_flag: LargeFileFlag::Large,
+            ..Default::default()
+        };
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 64, None),
+            49
+        );
+    }
+
+    #[test]
+    fn test_max_file_seg_calculator_saturating_sub() {
+        let common_conf = CommonPduConfig {
+            file_flag: LargeFileFlag::Large,
+            ..Default::default()
+        };
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 15, None),
+            0
+        );
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 14, None),
+            0
+        );
+    }
 }

src/cfdp/pdu/finished.rs

@@ -1,15 +1,21 @@
 use crate::cfdp::pdu::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, FileDirectiveType, PduError, PduHeader,
 };
-use crate::cfdp::tlv::{EntityIdTlv, Tlv, TlvType, TlvTypeField};
-use crate::cfdp::{ConditionCode, CrcFlag, PduType, TlvLvError};
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::cfdp::tlv::{
+    EntityIdTlv, FilestoreResponseTlv, GenericTlv, Tlv, TlvType, TlvTypeField, WritableTlv,
+};
+use crate::cfdp::{ConditionCode, CrcFlag, Direction, PduType};
+use crate::ByteConversionError;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::tlv::ReadableTlv;
+use super::{CfdpPdu, InvalidTlvTypeFieldError, WritablePduPacket};
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum DeliveryCode {
     Complete = 0,
@@ -18,6 +24,7 @@ pub enum DeliveryCode {
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum FileStatus {
     DiscardDeliberately = 0b00,
@@ -30,17 +37,18 @@ pub enum FileStatus {
 ///
 /// For more information, refer to CFDP chapter 5.2.3.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct FinishedPdu<'fs_responses> {
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct FinishedPduCreator<'fs_responses> {
     pdu_header: PduHeader,
     condition_code: ConditionCode,
     delivery_code: DeliveryCode,
     file_status: FileStatus,
-    fs_responses: Option<&'fs_responses [u8]>,
+    fs_responses:
+        &'fs_responses [FilestoreResponseTlv<'fs_responses, 'fs_responses, 'fs_responses>],
     fault_location: Option<EntityIdTlv>,
 }
 
-impl<'fs_responses> FinishedPdu<'fs_responses> {
+impl<'fs_responses> FinishedPduCreator<'fs_responses> {
     /// Default finished PDU: No error (no fault location field) and no filestore responses.
     pub fn new_default(
         pdu_header: PduHeader,
@@ -52,7 +60,7 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
             ConditionCode::NoError,
             delivery_code,
             file_status,
-            None,
+            &[],
             None,
         )
     }
@@ -69,7 +77,7 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
             condition_code,
             delivery_code,
             file_status,
-            None,
+            &[],
             Some(fault_location),
         )
     }
@@ -79,10 +87,16 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         condition_code: ConditionCode,
         delivery_code: DeliveryCode,
         file_status: FileStatus,
-        fs_responses: Option<&'fs_responses [u8]>,
+        fs_responses: &'fs_responses [FilestoreResponseTlv<
+            'fs_responses,
+            'fs_responses,
+            'fs_responses,
+        >],
         fault_location: Option<EntityIdTlv>,
     ) -> Self {
         pdu_header.pdu_type = PduType::FileDirective;
+        // Enforce correct direction bit.
+        pdu_header.pdu_conf.direction = Direction::TowardsSender;
         let mut finished_pdu = Self {
             pdu_header,
             condition_code,
@@ -94,13 +108,6 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         finished_pdu.pdu_header.pdu_datafield_len = finished_pdu.calc_pdu_datafield_len() as u16;
         finished_pdu
     }
-    pub fn pdu_header(&self) -> &PduHeader {
-        &self.pdu_header
-    }
-
-    pub fn written_len(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
-    }
 
     pub fn condition_code(&self) -> ConditionCode {
         self.condition_code
@@ -114,7 +121,8 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         self.file_status
     }
 
-    pub fn filestore_responses(&self) -> Option<&'fs_responses [u8]> {
+    // If there are no filestore responses, an empty slice will be returned.
+    pub fn filestore_responses(&self) -> &[FilestoreResponseTlv<'_, '_, '_>] {
         self.fs_responses
     }
 
@@ -123,23 +131,38 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
     }
 
     fn calc_pdu_datafield_len(&self) -> usize {
-        let mut base_len = 2;
-        if let Some(fs_responses) = self.fs_responses {
-            base_len += fs_responses.len();
+        let mut datafield_len = 2;
+        for fs_response in self.fs_responses {
+            datafield_len += fs_response.len_full();
         }
         if let Some(fault_location) = self.fault_location {
-            base_len += fault_location.len_full();
+            datafield_len += fault_location.len_full();
         }
-        base_len
+        if self.crc_flag() == CrcFlag::WithCrc {
+            datafield_len += 2;
+        }
+        datafield_len
+    }
+}
+
+impl CfdpPdu for FinishedPduCreator<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
     }
 
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        let expected_len = self.written_len();
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::FinishedPdu)
+    }
+}
+
+impl WritablePduPacket for FinishedPduCreator<'_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
         if buf.len() < expected_len {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: expected_len,
-            })
+            }
             .into());
         }
 
@@ -150,33 +173,89 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
             | ((self.delivery_code as u8) << 2)
             | self.file_status as u8;
         current_idx += 1;
-        if let Some(fs_responses) = self.fs_responses {
-            buf[current_idx..current_idx + fs_responses.len()].copy_from_slice(fs_responses);
-            current_idx += fs_responses.len();
+        for fs_responses in self.fs_responses {
+            current_idx += fs_responses.write_to_bytes(&mut buf[current_idx..])?;
         }
         if let Some(fault_location) = self.fault_location {
-            current_idx += fault_location.write_to_be_bytes(&mut buf[current_idx..])?;
+            current_idx += fault_location.write_to_bytes(&mut buf[current_idx..])?;
         }
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+        if self.crc_flag() == CrcFlag::WithCrc {
             current_idx = add_pdu_crc(buf, current_idx);
         }
         Ok(current_idx)
     }
 
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+/// Helper structure to loop through all filestore responses of a read Finished PDU. It should be
+/// noted that iterators in Rust are not fallible, but the TLV creation can fail, for example if
+/// the raw TLV data is invalid for some reason. In that case, the iterator will yield [None]
+/// because there is no way to recover from this.
+///
+/// The user can accumulate the length of all TLVs yielded by the iterator and compare it against
+/// the full length of the options to check whether the iterator was able to parse all TLVs
+/// successfully.
+pub struct FilestoreResponseIterator<'buf> {
+    responses_buf: &'buf [u8],
+    current_idx: usize,
+}
+
+impl<'buf> Iterator for FilestoreResponseIterator<'buf> {
+    type Item = FilestoreResponseTlv<'buf, 'buf, 'buf>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current_idx == self.responses_buf.len() {
+            return None;
+        }
+        let tlv = FilestoreResponseTlv::from_bytes(&self.responses_buf[self.current_idx..]);
+        // There are not really fallible iterators so we can't continue here..
+        if tlv.is_err() {
+            return None;
+        }
+        let tlv = tlv.unwrap();
+        self.current_idx += tlv.len_full();
+        Some(tlv)
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct FinishedPduReader<'buf> {
+    pdu_header: PduHeader,
+    condition_code: ConditionCode,
+    delivery_code: DeliveryCode,
+    file_status: FileStatus,
+    fs_responses_raw: &'buf [u8],
+    fault_location: Option<EntityIdTlv>,
+}
+
+impl<'buf> FinishedPduReader<'buf> {
     /// Generates [Self] from a raw bytestream.
-    pub fn from_bytes(buf: &'fs_responses [u8]) -> Result<Self, PduError> {
+    pub fn new(buf: &'buf [u8]) -> Result<Self, PduError> {
+        Self::from_bytes(buf)
+    }
+
+    /// Generates [Self] from a raw bytestream.
+    pub fn from_bytes(buf: &'buf [u8]) -> Result<Self, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
         let min_expected_len = current_idx + 2;
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::FinishedPdu))
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::FinishedPdu),
+            }
         })?;
         if directive_type != FileDirectiveType::FinishedPdu {
-            return Err(PduError::WrongDirectiveType((
-                directive_type,
-                FileDirectiveType::FinishedPdu,
-            )));
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::FinishedPdu,
+            });
         }
         current_idx += 1;
         let condition_code = ConditionCode::try_from((buf[current_idx] >> 4) & 0b1111)
@@ -185,24 +264,51 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         let delivery_code = DeliveryCode::try_from((buf[current_idx] >> 2) & 0b1).unwrap();
         let file_status = FileStatus::try_from(buf[current_idx] & 0b11).unwrap();
         current_idx += 1;
-        let (fs_responses, fault_location) =
+        let (fs_responses_raw, fault_location) =
             Self::parse_tlv_fields(current_idx, full_len_without_crc, buf)?;
         Ok(Self {
             pdu_header,
             condition_code,
             delivery_code,
             file_status,
-            fs_responses,
+            fs_responses_raw,
             fault_location,
         })
     }
 
+    pub fn fs_responses_raw(&self) -> &[u8] {
+        self.fs_responses_raw
+    }
+
+    pub fn fs_responses_iter(&self) -> FilestoreResponseIterator<'_> {
+        FilestoreResponseIterator {
+            responses_buf: self.fs_responses_raw,
+            current_idx: 0,
+        }
+    }
+
+    pub fn condition_code(&self) -> ConditionCode {
+        self.condition_code
+    }
+
+    pub fn delivery_code(&self) -> DeliveryCode {
+        self.delivery_code
+    }
+
+    pub fn file_status(&self) -> FileStatus {
+        self.file_status
+    }
+
+    pub fn fault_location(&self) -> Option<EntityIdTlv> {
+        self.fault_location
+    }
+
     fn parse_tlv_fields(
         mut current_idx: usize,
         full_len_without_crc: usize,
-        buf: &'fs_responses [u8],
-    ) -> Result<(Option<&'fs_responses [u8]>, Option<EntityIdTlv>), PduError> {
-        let mut fs_responses = None;
+        buf: &[u8],
+    ) -> Result<(&[u8], Option<EntityIdTlv>), PduError> {
+        let mut fs_responses: &[u8] = &[];
         let mut fault_location = None;
         let start_of_fs_responses = current_idx;
         // There are leftover filestore response(s) and/or a fault location field.
@@ -213,12 +319,12 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
                     if tlv_type == TlvType::FilestoreResponse {
                         current_idx += next_tlv.len_full();
                         if current_idx == full_len_without_crc {
-                            fs_responses = Some(&buf[start_of_fs_responses..current_idx]);
+                            fs_responses = &buf[start_of_fs_responses..current_idx];
                         }
                     } else if tlv_type == TlvType::EntityId {
                         // At least one FS response is included.
-                        if current_idx > full_len_without_crc {
-                            fs_responses = Some(&buf[start_of_fs_responses..current_idx]);
+                        if current_idx > start_of_fs_responses {
+                            fs_responses = &buf[start_of_fs_responses..current_idx];
                         }
                         fault_location = Some(EntityIdTlv::from_bytes(&buf[current_idx..])?);
                         current_idx += fault_location.as_ref().unwrap().len_full();
@@ -226,14 +332,26 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
                         // last TLV, everything else would break the whole handling of the packet
                         // TLVs.
                         if current_idx != full_len_without_crc {
-                            return Err(PduError::FormatError);
+                            return Err(PduError::Format);
                         }
                     } else {
-                        return Err(TlvLvError::InvalidTlvTypeField((tlv_type as u8, None)).into());
+                        return Err(PduError::TlvLv(
+                            InvalidTlvTypeFieldError {
+                                found: tlv_type.into(),
+                                expected: Some(TlvType::FilestoreResponse.into()),
+                            }
+                            .into(),
+                        ));
                     }
                 }
                 TlvTypeField::Custom(raw) => {
-                    return Err(TlvLvError::InvalidTlvTypeField((raw, None)).into());
+                    return Err(PduError::TlvLv(
+                        InvalidTlvTypeFieldError {
+                            found: raw,
+                            expected: None,
+                        }
+                        .into(),
+                    ));
                 }
             }
         }
@@ -241,21 +359,55 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
     }
 }
 
+impl CfdpPdu for FinishedPduReader<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::FinishedPdu)
+    }
+}
+
+impl PartialEq<FinishedPduCreator<'_>> for FinishedPduReader<'_> {
+    fn eq(&self, other: &FinishedPduCreator<'_>) -> bool {
+        self.pdu_header == other.pdu_header
+            && self.condition_code == other.condition_code
+            && self.delivery_code == other.delivery_code
+            && self.file_status == other.file_status
+            && self.fault_location == other.fault_location
+            && self
+                .fs_responses_iter()
+                .zip(other.filestore_responses().iter())
+                .all(|(a, b)| a == *b)
+    }
+}
+
+impl PartialEq<FinishedPduReader<'_>> for FinishedPduCreator<'_> {
+    fn eq(&self, other: &FinishedPduReader<'_>) -> bool {
+        other.eq(self)
+    }
+}
+
 #[cfg(test)]
 mod tests {
-    use crate::cfdp::pdu::finished::{DeliveryCode, FileStatus, FinishedPdu};
-    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use super::*;
+    use crate::cfdp::lv::Lv;
+    use crate::cfdp::pdu::tests::{
+        common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID,
+    };
     use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
-    use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
+    use crate::cfdp::tlv::FilestoreResponseTlv;
+    use crate::cfdp::{ConditionCode, CrcFlag, Direction, LargeFileFlag, TransmissionMode};
 
     fn generic_finished_pdu(
         crc_flag: CrcFlag,
         fss: LargeFileFlag,
         delivery_code: DeliveryCode,
         file_status: FileStatus,
-    ) -> FinishedPdu<'static> {
+    ) -> FinishedPduCreator<'static> {
         let pdu_header = PduHeader::new_no_file_data(common_pdu_conf(crc_flag, fss), 0);
-        FinishedPdu::new_default(pdu_header, delivery_code, file_status)
+        FinishedPduCreator::new_default(pdu_header, delivery_code, file_status)
     }
 
     #[test]
@@ -267,11 +419,31 @@ mod tests {
             FileStatus::Retained,
         );
         assert_eq!(finished_pdu.condition_code(), ConditionCode::NoError);
+        assert_eq!(
+            finished_pdu.pdu_header().pdu_conf.direction,
+            Direction::TowardsSender
+        );
         assert_eq!(finished_pdu.delivery_code(), DeliveryCode::Complete);
         assert_eq!(finished_pdu.file_status(), FileStatus::Retained);
-        assert_eq!(finished_pdu.filestore_responses(), None);
+        assert_eq!(finished_pdu.filestore_responses(), &[]);
         assert_eq!(finished_pdu.fault_location(), None);
         assert_eq!(finished_pdu.pdu_header().pdu_datafield_len, 2);
+
+        assert_eq!(finished_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(finished_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(finished_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            finished_pdu.file_directive_type(),
+            Some(FileDirectiveType::FinishedPdu)
+        );
+        assert_eq!(
+            finished_pdu.transmission_mode(),
+            TransmissionMode::Acknowledged
+        );
+        assert_eq!(finished_pdu.direction(), Direction::TowardsSender);
+        assert_eq!(finished_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(finished_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(finished_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
     }
 
     fn generic_serialization_test_no_error(delivery_code: DeliveryCode, file_status: FileStatus) {
@@ -285,8 +457,13 @@ mod tests {
         let written = finished_pdu.write_to_bytes(&mut buf);
         assert!(written.is_ok());
         let written = written.unwrap();
-        assert_eq!(written, finished_pdu.written_len());
+        assert_eq!(written, 9);
+        assert_eq!(written, finished_pdu.len_written());
         assert_eq!(written, finished_pdu.pdu_header().header_len() + 2);
+        assert_eq!(
+            finished_pdu.pdu_header().pdu_conf.direction,
+            Direction::TowardsSender
+        );
         verify_raw_header(finished_pdu.pdu_header(), &buf);
         let mut current_idx = finished_pdu.pdu_header().header_len();
         assert_eq!(buf[current_idx], FileDirectiveType::FinishedPdu as u8);
@@ -318,6 +495,20 @@ mod tests {
         generic_serialization_test_no_error(DeliveryCode::Incomplete, FileStatus::Unreported);
     }
 
+    #[test]
+    fn test_write_to_vec() {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::NoCrc,
+            LargeFileFlag::Normal,
+            DeliveryCode::Complete,
+            FileStatus::Retained,
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let written = finished_pdu.write_to_bytes(&mut buf).unwrap();
+        let pdu_vec = finished_pdu.to_vec().unwrap();
+        assert_eq!(buf[0..written], pdu_vec);
+    }
+
     #[test]
     fn test_deserialization_simple() {
         let finished_pdu = generic_finished_pdu(
@@ -328,9 +519,169 @@ mod tests {
         );
         let mut buf: [u8; 64] = [0; 64];
         finished_pdu.write_to_bytes(&mut buf).unwrap();
-        let read_back = FinishedPdu::from_bytes(&buf);
+        let read_back = FinishedPduReader::from_bytes(&buf);
         assert!(read_back.is_ok());
         let read_back = read_back.unwrap();
         assert_eq!(finished_pdu, read_back);
+        // Use all getter functions here explicitely once.
+        assert_eq!(finished_pdu.pdu_header(), read_back.pdu_header());
+        assert_eq!(finished_pdu.condition_code(), read_back.condition_code());
+        assert_eq!(finished_pdu.fault_location(), read_back.fault_location());
+        assert_eq!(finished_pdu.file_status(), read_back.file_status());
+        assert_eq!(finished_pdu.delivery_code(), read_back.delivery_code());
+    }
+
+    #[test]
+    fn test_serialization_buf_too_small() {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::NoCrc,
+            LargeFileFlag::Normal,
+            DeliveryCode::Complete,
+            FileStatus::Retained,
+        );
+        let mut buf: [u8; 8] = [0; 8];
+        let error = finished_pdu.write_to_bytes(&mut buf);
+        assert!(error.is_err());
+        if let PduError::ByteConversion(ByteConversionError::ToSliceTooSmall { found, expected }) =
+            error.unwrap_err()
+        {
+            assert_eq!(found, 8);
+            assert_eq!(expected, 9);
+        } else {
+            panic!("expected to_slice_too_small error");
+        }
+    }
+
+    #[test]
+    fn test_with_crc() {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::WithCrc,
+            LargeFileFlag::Normal,
+            DeliveryCode::Complete,
+            FileStatus::Retained,
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let written = finished_pdu.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(written, finished_pdu.len_written());
+        let finished_pdu_from_raw = FinishedPduReader::new(&buf).unwrap();
+        assert_eq!(finished_pdu, finished_pdu_from_raw);
+        buf[written - 1] -= 1;
+        let crc: u16 = ((buf[written - 2] as u16) << 8) as u16 | buf[written - 1] as u16;
+        let error = FinishedPduReader::new(&buf).unwrap_err();
+        if let PduError::Checksum(e) = error {
+            assert_eq!(e, crc);
+        } else {
+            panic!("expected crc error");
+        }
+    }
+
+    #[test]
+    fn test_with_fault_location() {
+        let pdu_header =
+            PduHeader::new_no_file_data(common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal), 0);
+        let finished_pdu = FinishedPduCreator::new_with_error(
+            pdu_header,
+            ConditionCode::NakLimitReached,
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+            EntityIdTlv::new(TEST_DEST_ID.into()),
+        );
+        let finished_pdu_vec = finished_pdu.to_vec().unwrap();
+        assert_eq!(finished_pdu_vec.len(), 12);
+        assert_eq!(finished_pdu_vec[9], TlvType::EntityId.into());
+        assert_eq!(finished_pdu_vec[10], 1);
+        assert_eq!(finished_pdu_vec[11], TEST_DEST_ID.value_typed());
+        assert_eq!(
+            finished_pdu.fault_location().unwrap().entity_id(),
+            &TEST_DEST_ID.into()
+        );
+    }
+
+    #[test]
+    fn test_deserialization_with_fault_location() {
+        let pdu_header =
+            PduHeader::new_no_file_data(common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal), 0);
+        let entity_id_tlv = EntityIdTlv::new(TEST_DEST_ID.into());
+        let finished_pdu = FinishedPduCreator::new_with_error(
+            pdu_header,
+            ConditionCode::NakLimitReached,
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+            entity_id_tlv,
+        );
+        let finished_pdu_vec = finished_pdu.to_vec().unwrap();
+        let finished_pdu_deserialized = FinishedPduReader::from_bytes(&finished_pdu_vec).unwrap();
+        assert_eq!(finished_pdu, finished_pdu_deserialized);
+    }
+
+    #[test]
+    fn test_deserialization_with_fs_responses() {
+        let entity_id_tlv = EntityIdTlv::new(TEST_DEST_ID.into());
+        let first_name = "first.txt";
+        let first_name_lv = Lv::new_from_str(first_name).unwrap();
+        let fs_response_0 = FilestoreResponseTlv::new_no_filestore_message(
+            crate::cfdp::tlv::FilestoreActionCode::CreateFile,
+            0,
+            first_name_lv,
+            None,
+        )
+        .unwrap();
+        let fs_response_1 = FilestoreResponseTlv::new_no_filestore_message(
+            crate::cfdp::tlv::FilestoreActionCode::DeleteFile,
+            0,
+            first_name_lv,
+            None,
+        )
+        .unwrap();
+        let fs_responses = &[fs_response_0, fs_response_1];
+
+        let pdu_header =
+            PduHeader::new_no_file_data(common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal), 0);
+        let finished_pdu = FinishedPduCreator::new_generic(
+            pdu_header,
+            ConditionCode::NakLimitReached,
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+            fs_responses,
+            Some(entity_id_tlv),
+        );
+        let finished_pdu_vec = finished_pdu.to_vec().unwrap();
+        let finished_pdu_deserialized = FinishedPduReader::from_bytes(&finished_pdu_vec).unwrap();
+        assert_eq!(finished_pdu_deserialized, finished_pdu);
+    }
+
+    #[test]
+    fn test_deserialization_with_fs_responses_and_fault_location() {
+        let first_name = "first.txt";
+        let first_name_lv = Lv::new_from_str(first_name).unwrap();
+        let fs_response_0 = FilestoreResponseTlv::new_no_filestore_message(
+            crate::cfdp::tlv::FilestoreActionCode::CreateFile,
+            0,
+            first_name_lv,
+            None,
+        )
+        .unwrap();
+        let fs_response_1 = FilestoreResponseTlv::new_no_filestore_message(
+            crate::cfdp::tlv::FilestoreActionCode::DeleteFile,
+            0,
+            first_name_lv,
+            None,
+        )
+        .unwrap();
+        let fs_responses = &[fs_response_0, fs_response_1];
+
+        let pdu_header =
+            PduHeader::new_no_file_data(common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal), 0);
+        let finished_pdu = FinishedPduCreator::new_generic(
+            pdu_header,
+            ConditionCode::NakLimitReached,
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+            fs_responses,
+            None,
+        );
+        let finished_pdu_vec = finished_pdu.to_vec().unwrap();
+        let finished_pdu_deserialized = FinishedPduReader::from_bytes(&finished_pdu_vec).unwrap();
+        assert_eq!(finished_pdu_deserialized, finished_pdu);
     }
 }

src/cfdp/pdu/metadata.rs

@@ -1,18 +1,24 @@
+#[cfg(feature = "alloc")]
+use super::tlv::TlvOwned;
 use crate::cfdp::lv::Lv;
 use crate::cfdp::pdu::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
     FileDirectiveType, PduError, PduHeader,
 };
-use crate::cfdp::tlv::Tlv;
-use crate::cfdp::{ChecksumType, CrcFlag, LargeFileFlag, PduType};
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::cfdp::tlv::{Tlv, WritableTlv};
+use crate::cfdp::{ChecksumType, CrcFlag, Direction, LargeFileFlag, PduType};
+use crate::ByteConversionError;
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::tlv::ReadableTlv;
+use super::{CfdpPdu, WritablePduPacket};
+
 #[derive(Default, Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct MetadataGenericParams {
     pub closure_requested: bool,
     pub checksum_type: ChecksumType,
@@ -48,6 +54,174 @@ pub fn build_metadata_opts_from_vec(
     build_metadata_opts_from_slice(buf, tlvs.as_slice())
 }
 
+#[cfg(feature = "alloc")]
+pub fn build_metadata_opts_from_owned_slice(tlvs: &[TlvOwned]) -> Vec<u8> {
+    let mut sum_vec = Vec::new();
+    for tlv in tlvs {
+        sum_vec.extend(tlv.to_vec());
+    }
+    sum_vec
+}
+
+/// Metadata PDU creator abstraction.
+///
+/// This abstraction exposes a specialized API for creating metadata PDUs as specified in
+/// CFDP chapter 5.2.5.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct MetadataPduCreator<'src_name, 'dest_name, 'opts> {
+    pdu_header: PduHeader,
+    metadata_params: MetadataGenericParams,
+    src_file_name: Lv<'src_name>,
+    dest_file_name: Lv<'dest_name>,
+    options: &'opts [u8],
+}
+
+impl<'src_name, 'dest_name, 'opts> MetadataPduCreator<'src_name, 'dest_name, 'opts> {
+    pub fn new_no_opts(
+        pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+    ) -> Self {
+        Self::new(
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            &[],
+        )
+    }
+
+    pub fn new_with_opts(
+        pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+        options: &'opts [u8],
+    ) -> Self {
+        Self::new(
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            options,
+        )
+    }
+
+    pub fn new(
+        mut pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+        options: &'opts [u8],
+    ) -> Self {
+        pdu_header.pdu_type = PduType::FileDirective;
+        pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
+        let mut pdu = Self {
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            options,
+        };
+        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
+        pdu
+    }
+
+    pub fn metadata_params(&self) -> &MetadataGenericParams {
+        &self.metadata_params
+    }
+
+    pub fn src_file_name(&self) -> Lv<'src_name> {
+        self.src_file_name
+    }
+
+    pub fn dest_file_name(&self) -> Lv<'dest_name> {
+        self.dest_file_name
+    }
+
+    pub fn options(&self) -> &'opts [u8] {
+        self.options
+    }
+
+    /// Yield an iterator which can be used to loop through all options. Returns [None] if the
+    /// options field is empty.
+    pub fn options_iter(&self) -> OptionsIter<'_> {
+        OptionsIter {
+            opt_buf: self.options,
+            current_idx: 0,
+        }
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        // One directve type octet and one byte of the directive parameter field.
+        let mut len = 2;
+        if self.pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
+            len += 8;
+        } else {
+            len += 4;
+        }
+        len += self.src_file_name.len_full();
+        len += self.dest_file_name.len_full();
+        len += self.options().len();
+        if self.crc_flag() == CrcFlag::WithCrc {
+            len += 2;
+        }
+        len
+    }
+}
+
+impl CfdpPdu for MetadataPduCreator<'_, '_, '_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::MetadataPdu)
+    }
+}
+
+impl WritablePduPacket for MetadataPduCreator<'_, '_, '_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::MetadataPdu as u8;
+        current_idx += 1;
+        buf[current_idx] = ((self.metadata_params.closure_requested as u8) << 6)
+            | (self.metadata_params.checksum_type as u8);
+        current_idx += 1;
+        current_idx += write_fss_field(
+            self.pdu_header.common_pdu_conf().file_flag,
+            self.metadata_params.file_size,
+            &mut buf[current_idx..],
+        )?;
+        current_idx += self
+            .src_file_name
+            .write_to_be_bytes(&mut buf[current_idx..])?;
+        current_idx += self
+            .dest_file_name
+            .write_to_be_bytes(&mut buf[current_idx..])?;
+        buf[current_idx..current_idx + self.options.len()].copy_from_slice(self.options);
+        current_idx += self.options.len();
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
 /// Helper structure to loop through all options of a metadata PDU. It should be noted that
 /// iterators in Rust are not fallible, but the TLV creation can fail, for example if the raw TLV
 /// data is invalid for some reason. In that case, the iterator will yield [None] because there
@@ -79,165 +253,29 @@ impl<'opts> Iterator for OptionsIter<'opts> {
     }
 }
 
-/// Metadata PDU abstraction.
+/// Metadata PDU reader abstraction.
 ///
-/// For more information, refer to CFDP chapter 5.2.5.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+/// This abstraction exposes a specialized API for reading a metadata PDU with minimal copying
+/// involved.
+#[derive(Debug)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct MetadataPdu<'src_name, 'dest_name, 'opts> {
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct MetadataPduReader<'buf> {
     pdu_header: PduHeader,
     metadata_params: MetadataGenericParams,
     #[cfg_attr(feature = "serde", serde(borrow))]
-    src_file_name: Lv<'src_name>,
+    src_file_name: Lv<'buf>,
     #[cfg_attr(feature = "serde", serde(borrow))]
-    dest_file_name: Lv<'dest_name>,
-    options: Option<&'opts [u8]>,
+    dest_file_name: Lv<'buf>,
+    options: &'buf [u8],
 }
 
-impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
-    pub fn new_no_opts(
-        pdu_header: PduHeader,
-        metadata_params: MetadataGenericParams,
-        src_file_name: Lv<'src_name>,
-        dest_file_name: Lv<'dest_name>,
-    ) -> Self {
-        Self::new(
-            pdu_header,
-            metadata_params,
-            src_file_name,
-            dest_file_name,
-            None,
-        )
+impl<'raw> MetadataPduReader<'raw> {
+    pub fn new(buf: &'raw [u8]) -> Result<Self, PduError> {
+        Self::from_bytes(buf)
     }
 
-    pub fn new_with_opts(
-        pdu_header: PduHeader,
-        metadata_params: MetadataGenericParams,
-        src_file_name: Lv<'src_name>,
-        dest_file_name: Lv<'dest_name>,
-        options: &'opts [u8],
-    ) -> Self {
-        Self::new(
-            pdu_header,
-            metadata_params,
-            src_file_name,
-            dest_file_name,
-            Some(options),
-        )
-    }
-
-    pub fn new(
-        mut pdu_header: PduHeader,
-        metadata_params: MetadataGenericParams,
-        src_file_name: Lv<'src_name>,
-        dest_file_name: Lv<'dest_name>,
-        options: Option<&'opts [u8]>,
-    ) -> Self {
-        pdu_header.pdu_type = PduType::FileDirective;
-        let mut pdu = Self {
-            pdu_header,
-            metadata_params,
-            src_file_name,
-            dest_file_name,
-            options,
-        };
-        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
-        pdu
-    }
-
-    pub fn metadata_params(&self) -> &MetadataGenericParams {
-        &self.metadata_params
-    }
-
-    pub fn src_file_name(&self) -> Lv<'src_name> {
-        self.src_file_name
-    }
-
-    pub fn dest_file_name(&self) -> Lv<'dest_name> {
-        self.dest_file_name
-    }
-
-    pub fn options(&self) -> Option<&'opts [u8]> {
-        self.options
-    }
-
-    /// Yield an iterator which can be used to loop through all options. Returns [None] if the
-    /// options field is empty.
-    pub fn options_iter(&self) -> Option<OptionsIter<'opts>> {
-        self.options?;
-        Some(OptionsIter {
-            opt_buf: self.options.unwrap(),
-            current_idx: 0,
-        })
-    }
-
-    pub fn written_len(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
-    }
-
-    fn calc_pdu_datafield_len(&self) -> usize {
-        // One directve type octet and one byte of the directive parameter field.
-        let mut len = 2;
-        if self.pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
-            len += 8;
-        } else {
-            len += 4;
-        }
-        len += self.src_file_name.len_full();
-        len += self.dest_file_name.len_full();
-        if let Some(opts) = self.options {
-            len += opts.len();
-        }
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
-            len += 2;
-        }
-        len
-    }
-
-    pub fn pdu_header(&self) -> &PduHeader {
-        &self.pdu_header
-    }
-
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        let expected_len = self.written_len();
-        if buf.len() < expected_len {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: expected_len,
-            })
-            .into());
-        }
-
-        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
-        buf[current_idx] = FileDirectiveType::MetadataPdu as u8;
-        current_idx += 1;
-        buf[current_idx] = ((self.metadata_params.closure_requested as u8) << 7)
-            | (self.metadata_params.checksum_type as u8);
-        current_idx += 1;
-        current_idx += write_fss_field(
-            self.pdu_header.common_pdu_conf().file_flag,
-            self.metadata_params.file_size,
-            &mut buf[current_idx..],
-        )?;
-        current_idx += self
-            .src_file_name
-            .write_to_be_bytes(&mut buf[current_idx..])?;
-        current_idx += self
-            .dest_file_name
-            .write_to_be_bytes(&mut buf[current_idx..])?;
-        if let Some(opts) = self.options {
-            buf[current_idx..current_idx + opts.len()].copy_from_slice(opts);
-            current_idx += opts.len();
-        }
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
-            current_idx = add_pdu_crc(buf, current_idx);
-        }
-        Ok(current_idx)
-    }
-
-    pub fn from_bytes<'longest: 'src_name + 'dest_name + 'opts>(
-        buf: &'longest [u8],
-    ) -> Result<Self, PduError> {
+    pub fn from_bytes(buf: &'raw [u8]) -> Result<Self, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
         let is_large_file = pdu_header.pdu_conf.file_flag == LargeFileFlag::Large;
@@ -248,13 +286,16 @@ impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
         }
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::MetadataPdu))
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::MetadataPdu),
+            }
         })?;
         if directive_type != FileDirectiveType::MetadataPdu {
-            return Err(PduError::WrongDirectiveType((
-                directive_type,
-                FileDirectiveType::MetadataPdu,
-            )));
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::MetadataPdu,
+            });
         }
         current_idx += 1;
         let (fss_len, file_size) =
@@ -271,56 +312,95 @@ impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
         let dest_file_name = Lv::from_bytes(&buf[current_idx..])?;
         current_idx += dest_file_name.len_full();
         // All left-over bytes are options.
-        let mut options = None;
-        if current_idx < full_len_without_crc {
-            options = Some(&buf[current_idx..full_len_without_crc]);
-        }
         Ok(Self {
             pdu_header,
             metadata_params,
             src_file_name,
             dest_file_name,
-            options,
+            options: &buf[current_idx..full_len_without_crc],
         })
     }
+
+    /// Yield an iterator which can be used to loop through all options. Returns [None] if the
+    /// options field is empty.
+    pub fn options_iter(&self) -> Option<OptionsIter<'_>> {
+        Some(OptionsIter {
+            opt_buf: self.options,
+            current_idx: 0,
+        })
+    }
+
+    pub fn options(&self) -> &'raw [u8] {
+        self.options
+    }
+
+    pub fn metadata_params(&self) -> &MetadataGenericParams {
+        &self.metadata_params
+    }
+
+    pub fn src_file_name(&self) -> Lv {
+        self.src_file_name
+    }
+
+    pub fn dest_file_name(&self) -> Lv {
+        self.dest_file_name
+    }
+}
+
+impl CfdpPdu for MetadataPduReader<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::MetadataPdu)
+    }
 }
 
 #[cfg(test)]
 pub mod tests {
+    use alloc::string::ToString;
+
     use crate::cfdp::lv::Lv;
     use crate::cfdp::pdu::metadata::{
         build_metadata_opts_from_slice, build_metadata_opts_from_vec, MetadataGenericParams,
-        MetadataPdu,
+        MetadataPduCreator, MetadataPduReader,
     };
-    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use crate::cfdp::pdu::tests::{
+        common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID,
+    };
+    use crate::cfdp::pdu::{CfdpPdu, PduError, WritablePduPacket};
     use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
-    use crate::cfdp::tlv::{Tlv, TlvType};
+    use crate::cfdp::tlv::{ReadableTlv, Tlv, TlvOwned, TlvType, WritableTlv};
     use crate::cfdp::{
-        ChecksumType, CrcFlag, LargeFileFlag, PduType, SegmentMetadataFlag, SegmentationControl,
+        ChecksumType, CrcFlag, Direction, LargeFileFlag, PduType, SegmentMetadataFlag,
+        SegmentationControl, TransmissionMode,
     };
     use std::vec;
 
-    const SRC_FILENAME: &'static str = "hello-world.txt";
-    const DEST_FILENAME: &'static str = "hello-world2.txt";
+    const SRC_FILENAME: &str = "hello-world.txt";
+    const DEST_FILENAME: &str = "hello-world2.txt";
 
-    fn generic_metadata_pdu<'opts>(
+    fn generic_metadata_pdu(
         crc_flag: CrcFlag,
+        checksum_type: ChecksumType,
+        closure_requested: bool,
         fss: LargeFileFlag,
-        opts: Option<&'opts [u8]>,
+        opts: &[u8],
     ) -> (
         Lv<'static>,
         Lv<'static>,
-        MetadataPdu<'static, 'static, 'opts>,
+        MetadataPduCreator<'static, 'static, '_>,
     ) {
         let pdu_header = PduHeader::new_no_file_data(common_pdu_conf(crc_flag, fss), 0);
-        let metadata_params = MetadataGenericParams::new(false, ChecksumType::Crc32, 0x1010);
+        let metadata_params = MetadataGenericParams::new(closure_requested, checksum_type, 0x1010);
         let src_filename = Lv::new_from_str(SRC_FILENAME).expect("Generating string LV failed");
         let dest_filename =
             Lv::new_from_str(DEST_FILENAME).expect("Generating destination LV failed");
         (
             src_filename,
             dest_filename,
-            MetadataPdu::new(
+            MetadataPduCreator::new(
                 pdu_header,
                 metadata_params,
                 src_filename,
@@ -332,10 +412,15 @@ pub mod tests {
 
     #[test]
     fn test_basic() {
-        let (src_filename, dest_filename, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Normal,
+            &[],
+        );
         assert_eq!(
-            metadata_pdu.written_len(),
+            metadata_pdu.len_written(),
             metadata_pdu.pdu_header().header_len()
                 + 1
                 + 1
@@ -345,60 +430,169 @@ pub mod tests {
         );
         assert_eq!(metadata_pdu.src_file_name(), src_filename);
         assert_eq!(metadata_pdu.dest_file_name(), dest_filename);
-        assert_eq!(metadata_pdu.options(), None);
+        assert!(metadata_pdu.options().is_empty());
+        assert_eq!(metadata_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(metadata_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(metadata_pdu.pdu_type(), PduType::FileDirective);
+        assert!(!metadata_pdu.metadata_params().closure_requested);
+        assert_eq!(
+            metadata_pdu.metadata_params().checksum_type,
+            ChecksumType::Crc32
+        );
+        assert_eq!(
+            metadata_pdu.file_directive_type(),
+            Some(FileDirectiveType::MetadataPdu)
+        );
+        assert_eq!(
+            metadata_pdu.transmission_mode(),
+            TransmissionMode::Acknowledged
+        );
+        assert_eq!(metadata_pdu.direction(), Direction::TowardsReceiver);
+        assert_eq!(metadata_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(metadata_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(metadata_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
     }
 
-    #[test]
-    fn test_serialization() {
-        let (src_filename, dest_filename, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
-        let mut buf: [u8; 64] = [0; 64];
-        let res = metadata_pdu.write_to_bytes(&mut buf);
-        assert!(res.is_ok());
-        let written = res.unwrap();
+    fn check_metadata_raw_fields(
+        metadata_pdu: &MetadataPduCreator,
+        buf: &[u8],
+        written_bytes: usize,
+        checksum_type: ChecksumType,
+        closure_requested: bool,
+        expected_src_filename: &Lv,
+        expected_dest_filename: &Lv,
+    ) {
+        verify_raw_header(metadata_pdu.pdu_header(), buf);
         assert_eq!(
-            written,
+            written_bytes,
             metadata_pdu.pdu_header.header_len()
                 + 1
                 + 1
                 + 4
-                + src_filename.len_full()
-                + dest_filename.len_full()
+                + expected_src_filename.len_full()
+                + expected_dest_filename.len_full()
         );
-        verify_raw_header(metadata_pdu.pdu_header(), &buf);
         assert_eq!(buf[7], FileDirectiveType::MetadataPdu as u8);
-        assert_eq!(buf[8] >> 6, false as u8);
-        assert_eq!(buf[8] & 0b1111, ChecksumType::Crc32 as u8);
+        assert_eq!(buf[8] >> 6, closure_requested as u8);
+        assert_eq!(buf[8] & 0b1111, checksum_type as u8);
         assert_eq!(u32::from_be_bytes(buf[9..13].try_into().unwrap()), 0x1010);
         let mut current_idx = 13;
         let src_name_from_raw =
             Lv::from_bytes(&buf[current_idx..]).expect("Creating source name LV failed");
-        assert_eq!(src_name_from_raw, src_filename);
+        assert_eq!(src_name_from_raw, *expected_src_filename);
         current_idx += src_name_from_raw.len_full();
         let dest_name_from_raw =
             Lv::from_bytes(&buf[current_idx..]).expect("Creating dest name LV failed");
-        assert_eq!(dest_name_from_raw, dest_filename);
+        assert_eq!(dest_name_from_raw, *expected_dest_filename);
         current_idx += dest_name_from_raw.len_full();
         // No options, so no additional data here.
-        assert_eq!(current_idx, written);
+        assert_eq!(current_idx, written_bytes);
+    }
+
+    #[test]
+    fn test_serialization_0() {
+        let checksum_type = ChecksumType::Crc32;
+        let closure_requested = false;
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            checksum_type,
+            closure_requested,
+            LargeFileFlag::Normal,
+            &[],
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let res = metadata_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        check_metadata_raw_fields(
+            &metadata_pdu,
+            &buf,
+            written,
+            checksum_type,
+            closure_requested,
+            &src_filename,
+            &dest_filename,
+        );
+    }
+
+    #[test]
+    fn test_serialization_1() {
+        let checksum_type = ChecksumType::Modular;
+        let closure_requested = true;
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            checksum_type,
+            closure_requested,
+            LargeFileFlag::Normal,
+            &[],
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let res = metadata_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        check_metadata_raw_fields(
+            &metadata_pdu,
+            &buf,
+            written,
+            checksum_type,
+            closure_requested,
+            &src_filename,
+            &dest_filename,
+        );
+    }
+
+    #[test]
+    fn test_write_to_vec() {
+        let (_, _, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Normal,
+            &[],
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let pdu_vec = metadata_pdu.to_vec().unwrap();
+        let written = metadata_pdu.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(buf[0..written], pdu_vec);
+    }
+
+    fn compare_read_pdu_to_written_pdu(written: &MetadataPduCreator, read: &MetadataPduReader) {
+        assert_eq!(written.metadata_params(), read.metadata_params());
+        assert_eq!(written.src_file_name(), read.src_file_name());
+        assert_eq!(written.dest_file_name(), read.dest_file_name());
+        let opts = written.options_iter();
+        for (tlv_written, tlv_read) in opts.zip(read.options_iter().unwrap()) {
+            assert_eq!(&tlv_written, &tlv_read);
+        }
     }
 
     #[test]
     fn test_deserialization() {
-        let (_, _, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
+        let (_, _, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            true,
+            LargeFileFlag::Normal,
+            &[],
+        );
         let mut buf: [u8; 64] = [0; 64];
         metadata_pdu.write_to_bytes(&mut buf).unwrap();
-        let pdu_read_back = MetadataPdu::from_bytes(&buf);
+        let pdu_read_back = MetadataPduReader::from_bytes(&buf);
         assert!(pdu_read_back.is_ok());
         let pdu_read_back = pdu_read_back.unwrap();
-        assert_eq!(pdu_read_back, metadata_pdu);
+        compare_read_pdu_to_written_pdu(&metadata_pdu, &pdu_read_back);
     }
 
     #[test]
     fn test_with_crc_flag() {
-        let (src_filename, dest_filename, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::WithCrc, LargeFileFlag::Normal, None);
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::WithCrc,
+            ChecksumType::Crc32,
+            true,
+            LargeFileFlag::Normal,
+            &[],
+        );
+        assert_eq!(metadata_pdu.crc_flag(), CrcFlag::WithCrc);
         let mut buf: [u8; 64] = [0; 64];
         let write_res = metadata_pdu.write_to_bytes(&mut buf);
         assert!(write_res.is_ok());
@@ -413,14 +607,20 @@ pub mod tests {
                 + dest_filename.len_full()
                 + 2
         );
-        let pdu_read_back = MetadataPdu::from_bytes(&buf).unwrap();
-        assert_eq!(pdu_read_back, metadata_pdu);
+        assert_eq!(written, metadata_pdu.len_written());
+        let pdu_read_back = MetadataPduReader::new(&buf).unwrap();
+        compare_read_pdu_to_written_pdu(&metadata_pdu, &pdu_read_back);
     }
 
     #[test]
     fn test_with_large_file_flag() {
-        let (src_filename, dest_filename, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Large, None);
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Large,
+            &[],
+        );
         let mut buf: [u8; 64] = [0; 64];
         let write_res = metadata_pdu.write_to_bytes(&mut buf);
         assert!(write_res.is_ok());
@@ -434,8 +634,8 @@ pub mod tests {
                 + src_filename.len_full()
                 + dest_filename.len_full()
         );
-        let pdu_read_back = MetadataPdu::from_bytes(&buf).unwrap();
-        assert_eq!(pdu_read_back, metadata_pdu);
+        let pdu_read_back = MetadataPduReader::new(&buf).unwrap();
+        compare_read_pdu_to_written_pdu(&metadata_pdu, &pdu_read_back);
     }
 
     #[test]
@@ -477,13 +677,14 @@ pub mod tests {
         let tlv1 = Tlv::new_empty(TlvType::FlowLabel);
         let msg_to_user: [u8; 4] = [1, 2, 3, 4];
         let tlv2 = Tlv::new(TlvType::MsgToUser, &msg_to_user).unwrap();
-        let tlv_vec = vec![tlv1, tlv2];
-        let mut opts_buf: [u8; 32] = [0; 32];
-        let opts_len = build_metadata_opts_from_vec(&mut opts_buf, &tlv_vec).unwrap();
+        let mut tlv_buf: [u8; 64] = [0; 64];
+        let opts_len = build_metadata_opts_from_slice(&mut tlv_buf, &[tlv1, tlv2]).unwrap();
         let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
             CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
             LargeFileFlag::Normal,
-            Some(&opts_buf[..opts_len]),
+            &tlv_buf[0..opts_len],
         );
         let mut buf: [u8; 128] = [0; 128];
         let write_res = metadata_pdu.write_to_bytes(&mut buf);
@@ -499,19 +700,118 @@ pub mod tests {
                 + dest_filename.len_full()
                 + opts_len
         );
-        let pdu_read_back = MetadataPdu::from_bytes(&buf).unwrap();
-        assert_eq!(pdu_read_back, metadata_pdu);
+        let pdu_read_back = MetadataPduReader::from_bytes(&buf).unwrap();
+        compare_read_pdu_to_written_pdu(&metadata_pdu, &pdu_read_back);
         let opts_iter = pdu_read_back.options_iter();
         assert!(opts_iter.is_some());
         let opts_iter = opts_iter.unwrap();
         let mut accumulated_len = 0;
         for (idx, opt) in opts_iter.enumerate() {
-            assert_eq!(tlv_vec[idx], opt);
+            if idx == 0 {
+                assert_eq!(tlv1, opt);
+            } else if idx == 1 {
+                assert_eq!(tlv2, opt);
+            }
             accumulated_len += opt.len_full();
         }
-        assert_eq!(accumulated_len, pdu_read_back.options().unwrap().len());
+        assert_eq!(accumulated_len, pdu_read_back.options().len());
+    }
+    #[test]
+    fn test_with_owned_opts() {
+        let tlv1 = TlvOwned::new_empty(TlvType::FlowLabel);
+        let msg_to_user: [u8; 4] = [1, 2, 3, 4];
+        let tlv2 = TlvOwned::new(TlvType::MsgToUser, &msg_to_user);
+        let mut all_tlvs = tlv1.to_vec();
+        all_tlvs.extend(tlv2.to_vec());
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Normal,
+            &all_tlvs,
+        );
+        let mut buf: [u8; 128] = [0; 128];
+        let write_res = metadata_pdu.write_to_bytes(&mut buf);
+        assert!(write_res.is_ok());
+        let written = write_res.unwrap();
+        assert_eq!(
+            written,
+            metadata_pdu.pdu_header.header_len()
+                + 1
+                + 1
+                + 4
+                + src_filename.len_full()
+                + dest_filename.len_full()
+                + all_tlvs.len()
+        );
+        let pdu_read_back = MetadataPduReader::from_bytes(&buf).unwrap();
+        compare_read_pdu_to_written_pdu(&metadata_pdu, &pdu_read_back);
+        let opts_iter = pdu_read_back.options_iter();
+        assert!(opts_iter.is_some());
+        let opts_iter = opts_iter.unwrap();
+        let mut accumulated_len = 0;
+        for (idx, opt) in opts_iter.enumerate() {
+            if idx == 0 {
+                assert_eq!(tlv1, opt);
+            } else if idx == 1 {
+                assert_eq!(tlv2, opt);
+            }
+            accumulated_len += opt.len_full();
+        }
+        assert_eq!(accumulated_len, pdu_read_back.options().len());
     }
 
+    #[test]
+    fn test_invalid_directive_code() {
+        let (_, _, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            true,
+            LargeFileFlag::Large,
+            &[],
+        );
+        let mut metadata_vec = metadata_pdu.to_vec().unwrap();
+        metadata_vec[7] = 0xff;
+        let metadata_error = MetadataPduReader::from_bytes(&metadata_vec);
+        assert!(metadata_error.is_err());
+        let error = metadata_error.unwrap_err();
+        if let PduError::InvalidDirectiveType { found, expected } = error {
+            assert_eq!(found, 0xff);
+            assert_eq!(expected, Some(FileDirectiveType::MetadataPdu));
+            assert_eq!(
+                error.to_string(),
+                "invalid directive type, found 255, expected Some(MetadataPdu)"
+            );
+        } else {
+            panic!("Expected InvalidDirectiveType error, got {:?}", error);
+        }
+    }
+
+    #[test]
+    fn test_wrong_directive_code() {
+        let (_, _, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Large,
+            &[],
+        );
+        let mut metadata_vec = metadata_pdu.to_vec().unwrap();
+        metadata_vec[7] = FileDirectiveType::EofPdu as u8;
+        let metadata_error = MetadataPduReader::from_bytes(&metadata_vec);
+        assert!(metadata_error.is_err());
+        let error = metadata_error.unwrap_err();
+        if let PduError::WrongDirectiveType { found, expected } = error {
+            assert_eq!(found, FileDirectiveType::EofPdu);
+            assert_eq!(expected, FileDirectiveType::MetadataPdu);
+            assert_eq!(
+                error.to_string(),
+                "wrong directive type, found EofPdu, expected MetadataPdu"
+            );
+        } else {
+            panic!("Expected InvalidDirectiveType error, got {:?}", error);
+        }
+    }
     #[test]
     fn test_corrects_pdu_header() {
         let pdu_header = PduHeader::new_for_file_data(
@@ -524,8 +824,12 @@ pub mod tests {
         let src_filename = Lv::new_from_str(SRC_FILENAME).expect("Generating string LV failed");
         let dest_filename =
             Lv::new_from_str(DEST_FILENAME).expect("Generating destination LV failed");
-        let metadata_pdu =
-            MetadataPdu::new_no_opts(pdu_header, metadata_params, src_filename, dest_filename);
+        let metadata_pdu = MetadataPduCreator::new_no_opts(
+            pdu_header,
+            metadata_params,
+            src_filename,
+            dest_filename,
+        );
         assert_eq!(metadata_pdu.pdu_header().pdu_type(), PduType::FileDirective);
     }
 }

src/cfdp/pdu/mod.rs

@@ -1,19 +1,21 @@
 //! CFDP Packet Data Unit (PDU) support.
 use crate::cfdp::*;
 use crate::util::{UnsignedByteField, UnsignedByteFieldU8, UnsignedEnum};
+use crate::ByteConversionError;
 use crate::CRC_CCITT_FALSE;
-use crate::{ByteConversionError, SizeMissmatch};
-use core::fmt::{Display, Formatter};
-#[cfg(feature = "std")]
-use std::error::Error;
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 
+pub mod ack;
 pub mod eof;
 pub mod file_data;
 pub mod finished;
 pub mod metadata;
+pub mod nak;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum FileDirectiveType {
     EofPdu = 0x04,
@@ -25,128 +27,132 @@ pub enum FileDirectiveType {
     KeepAlivePdu = 0x0c,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, thiserror::Error)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum PduError {
-    ByteConversionError(ByteConversionError),
-    /// Found version ID invalid, not equal to [CFDP_VERSION_2].
+    #[error("byte conversion error: {0}")]
+    ByteConversion(#[from] ByteConversionError),
+    /// Found version ID invalid, not equal to [super::CFDP_VERSION_2].
+    #[error("CFDP version missmatch, found {0}, expected {ver}", ver = super::CFDP_VERSION_2)]
     CfdpVersionMissmatch(u8),
     /// Invalid length for the entity ID detected. Only the values 1, 2, 4 and 8 are supported.
+    #[error("invalid PDU entity ID length {0}, only [1, 2, 4, 8] are allowed")]
     InvalidEntityLen(u8),
     /// Invalid length for the entity ID detected. Only the values 1, 2, 4 and 8 are supported.
+    #[error("invalid transaction ID length {0}")]
     InvalidTransactionSeqNumLen(u8),
-    /// The first entry will be the source entity ID length, the second one the destination entity
-    /// ID length.
-    SourceDestIdLenMissmatch((usize, usize)),
-    /// The first tuple entry will be the found directive type, the second entry the expected entry
-    /// type.
-    WrongDirectiveType((FileDirectiveType, FileDirectiveType)),
-    /// The directive type field contained a value not in the range of permitted values.
-    /// The first tuple entry will be the found raw number, the second entry the expected entry
-    /// type.
-    InvalidDirectiveType((u8, FileDirectiveType)),
+    #[error("missmatch of PDU source ID length {src_id_len} and destination ID length {dest_id_len}")]
+    SourceDestIdLenMissmatch {
+        src_id_len: usize,
+        dest_id_len: usize,
+    },
+    /// Wrong directive type, for example when parsing the directive field for a file directive
+    /// PDU.
+    #[error("wrong directive type, found {found:?}, expected {expected:?}")]
+    WrongDirectiveType {
+        found: FileDirectiveType,
+        expected: FileDirectiveType,
+    },
+    /// The directive type field contained a value not in the range of permitted values. This can
+    /// also happen if an invalid value is passed to the ACK PDU constructor.
+    #[error("invalid directive type, found {found:?}, expected {expected:?}")]
+    InvalidDirectiveType {
+        found: u8,
+        expected: Option<FileDirectiveType>,
+    },
+    #[error("invalid start or end of scope value for NAK PDU")]
+    InvalidStartOrEndOfScopeValue,
     /// Invalid condition code. Contains the raw detected value.
+    #[error("invalid condition code {0}")]
     InvalidConditionCode(u8),
     /// Invalid checksum type which is not part of the checksums listed in the
     /// [SANA Checksum Types registry](https://sanaregistry.org/r/checksum_identifiers/).
+    #[error("invalid checksum type {0}")]
     InvalidChecksumType(u8),
+    #[error("file size {0} too large")]
     FileSizeTooLarge(u64),
     /// If the CRC flag for a PDU is enabled and the checksum check fails. Contains raw 16-bit CRC.
-    ChecksumError(u16),
+    #[error("checksum error for checksum {0}")]
+    Checksum(u16),
     /// Generic error for invalid PDU formats.
-    FormatError,
+    #[error("generic PDU format error")]
+    Format,
     /// Error handling a TLV field.
-    TlvLvError(TlvLvError),
+    #[error("PDU error: {0}")]
+    TlvLv(#[from] TlvLvError),
 }
 
-impl Display for PduError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
-        match self {
-            PduError::InvalidEntityLen(raw_id) => {
-                write!(
-                    f,
-                    "Invalid PDU entity ID length {raw_id}, only [1, 2, 4, 8] are allowed"
-                )
-            }
-            PduError::InvalidTransactionSeqNumLen(raw_id) => {
-                write!(
-                    f,
-                    "invalid PDUtransaction seq num length {raw_id}, only [1, 2, 4, 8] are allowed"
-                )
-            }
-            PduError::CfdpVersionMissmatch(raw) => {
-                write!(
-                    f,
-                    "cfdp version missmatch, found {raw}, expected {CFDP_VERSION_2}"
-                )
-            }
-            PduError::SourceDestIdLenMissmatch((src_len, dest_len)) => {
-                write!(
-                    f,
-                    "missmatch of PDU source length {src_len} and destination length {dest_len}"
-                )
-            }
-            PduError::ByteConversionError(e) => {
-                write!(f, "{}", e)
-            }
-            PduError::FileSizeTooLarge(value) => {
-                write!(f, "file size value {value} exceeds allowed 32 bit width")
-            }
-            PduError::WrongDirectiveType((found, expected)) => {
-                write!(f, "found directive type {found:?}, expected {expected:?}")
-            }
-            PduError::InvalidConditionCode(raw_code) => {
-                write!(f, "found invalid condition code with raw value {raw_code}")
-            }
-            PduError::InvalidDirectiveType((found, expected)) => {
-                write!(
-                    f,
-                    "invalid directive type value {found}, expected {expected:?} ({})",
-                    *expected as u8
-                )
-            }
-            PduError::InvalidChecksumType(checksum_type) => {
-                write!(f, "invalid checksum type {checksum_type}")
-            }
-            PduError::ChecksumError(checksum) => {
-                write!(f, "checksum error for CRC {checksum:#04x}")
-            }
-            PduError::TlvLvError(error) => {
-                write!(f, "pdu tlv error: {error}")
-            }
-            PduError::FormatError => {
-                write!(f, "generic PDU format error")
-            }
-        }
+pub trait WritablePduPacket {
+    fn len_written(&self) -> usize;
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError>;
+    #[cfg(feature = "alloc")]
+    fn to_vec(&self) -> Result<Vec<u8>, PduError> {
+        // This is the correct way to do this. See
+        // [this issue](https://github.com/rust-lang/rust-clippy/issues/4483) for caveats of more
+        // "efficient" implementations.
+        let mut vec = alloc::vec![0; self.len_written()];
+        self.write_to_bytes(&mut vec)?;
+        Ok(vec)
     }
 }
 
-#[cfg(feature = "std")]
-impl Error for PduError {
-    fn source(&self) -> Option<&(dyn Error + 'static)> {
-        match self {
-            PduError::ByteConversionError(e) => Some(e),
-            PduError::TlvLvError(e) => Some(e),
-            _ => None,
-        }
-    }
-}
+/// Abstraction trait for fields and properties common for all PDUs.
+pub trait CfdpPdu {
+    fn pdu_header(&self) -> &PduHeader;
 
-impl From<ByteConversionError> for PduError {
-    fn from(value: ByteConversionError) -> Self {
-        Self::ByteConversionError(value)
+    #[inline]
+    fn source_id(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().source_entity_id
     }
-}
 
-impl From<TlvLvError> for PduError {
-    fn from(e: TlvLvError) -> Self {
-        Self::TlvLvError(e)
+    #[inline]
+    fn dest_id(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().dest_entity_id
     }
+
+    #[inline]
+    fn transaction_seq_num(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().transaction_seq_num
+    }
+
+    #[inline]
+    fn transmission_mode(&self) -> TransmissionMode {
+        self.pdu_header().common_pdu_conf().trans_mode
+    }
+
+    #[inline]
+    fn direction(&self) -> Direction {
+        self.pdu_header().common_pdu_conf().direction
+    }
+
+    #[inline]
+    fn crc_flag(&self) -> CrcFlag {
+        self.pdu_header().common_pdu_conf().crc_flag
+    }
+
+    #[inline]
+    fn file_flag(&self) -> LargeFileFlag {
+        self.pdu_header().common_pdu_conf().file_flag
+    }
+
+    #[inline]
+    fn pdu_type(&self) -> PduType {
+        self.pdu_header().pdu_type()
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType>;
 }
 
 /// Common configuration fields for a PDU.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+///
+/// Please note that this structure has a custom implementation of [PartialEq] which only
+/// compares the values for source entity ID, destination entity ID and transaction sequence
+/// number. This permits that those fields can have different widths, as long as the value is the
+/// same.
+#[derive(Debug, Copy, Clone, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct CommonPduConfig {
     source_entity_id: UnsignedByteField,
     dest_entity_id: UnsignedByteField,
@@ -159,6 +165,7 @@ pub struct CommonPduConfig {
 
 // TODO: Builder pattern might be applicable here..
 impl CommonPduConfig {
+    #[inline]
     pub fn new(
         source_id: impl Into<UnsignedByteField>,
         dest_id: impl Into<UnsignedByteField>,
@@ -190,6 +197,7 @@ impl CommonPduConfig {
         })
     }
 
+    #[inline]
     pub fn new_with_byte_fields(
         source_id: impl Into<UnsignedByteField>,
         dest_id: impl Into<UnsignedByteField>,
@@ -206,10 +214,12 @@ impl CommonPduConfig {
         )
     }
 
+    #[inline]
     pub fn source_id(&self) -> UnsignedByteField {
         self.source_entity_id
     }
 
+    #[inline]
     fn source_dest_id_check(
         source_id: impl Into<UnsignedByteField>,
         dest_id: impl Into<UnsignedByteField>,
@@ -217,10 +227,10 @@ impl CommonPduConfig {
         let source_id = source_id.into();
         let dest_id = dest_id.into();
         if source_id.size() != dest_id.size() {
-            return Err(PduError::SourceDestIdLenMissmatch((
-                source_id.size(),
-                dest_id.size(),
-            )));
+            return Err(PduError::SourceDestIdLenMissmatch {
+                src_id_len: source_id.size(),
+                dest_id_len: dest_id.size(),
+            });
         }
         if source_id.size() != 1
             && source_id.size() != 2
@@ -232,6 +242,7 @@ impl CommonPduConfig {
         Ok((source_id, dest_id))
     }
 
+    #[inline]
     pub fn set_source_and_dest_id(
         &mut self,
         source_id: impl Into<UnsignedByteField>,
@@ -243,6 +254,7 @@ impl CommonPduConfig {
         Ok(())
     }
 
+    #[inline]
     pub fn dest_id(&self) -> UnsignedByteField {
         self.dest_entity_id
     }
@@ -251,6 +263,7 @@ impl CommonPduConfig {
 impl Default for CommonPduConfig {
     /// The defaults for the source ID, destination ID and the transaction sequence number is the
     /// [UnsignedByteFieldU8] with an intitial value of 0
+    #[inline]
     fn default() -> Self {
         // The new function can not fail for these input parameters.
         Self::new(
@@ -266,6 +279,19 @@ impl Default for CommonPduConfig {
     }
 }
 
+impl PartialEq for CommonPduConfig {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.source_entity_id.value() == other.source_entity_id.value()
+            && self.dest_entity_id.value() == other.dest_entity_id.value()
+            && self.transaction_seq_num.value() == other.transaction_seq_num.value()
+            && self.trans_mode == other.trans_mode
+            && self.file_flag == other.file_flag
+            && self.crc_flag == other.crc_flag
+            && self.direction == other.direction
+    }
+}
+
 pub const FIXED_HEADER_LEN: usize = 4;
 
 /// Abstraction for the PDU header common to all CFDP PDUs.
@@ -273,6 +299,7 @@ pub const FIXED_HEADER_LEN: usize = 4;
 /// For detailed information, refer to chapter 5.1 of the CFDP standard.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct PduHeader {
     pdu_type: PduType,
     pdu_conf: CommonPduConfig,
@@ -282,6 +309,7 @@ pub struct PduHeader {
 }
 
 impl PduHeader {
+    #[inline]
     pub fn new_for_file_data(
         pdu_conf: CommonPduConfig,
         pdu_datafield_len: u16,
@@ -297,6 +325,7 @@ impl PduHeader {
         )
     }
 
+    #[inline]
     pub fn new_for_file_data_default(pdu_conf: CommonPduConfig, pdu_datafield_len: u16) -> Self {
         Self::new_generic(
             PduType::FileData,
@@ -306,6 +335,7 @@ impl PduHeader {
             SegmentationControl::NoRecordBoundaryPreservation,
         )
     }
+    #[inline]
     pub fn new_no_file_data(pdu_conf: CommonPduConfig, pdu_datafield_len: u16) -> Self {
         Self::new_generic(
             PduType::FileDirective,
@@ -316,6 +346,7 @@ impl PduHeader {
         )
     }
 
+    #[inline]
     pub fn new_generic(
         pdu_type: PduType,
         pdu_conf: CommonPduConfig,
@@ -333,6 +364,7 @@ impl PduHeader {
     }
 
     /// Returns only the length of the PDU header when written to a raw buffer.
+    #[inline]
     pub fn header_len(&self) -> usize {
         FIXED_HEADER_LEN
             + self.pdu_conf.source_entity_id.size()
@@ -340,8 +372,14 @@ impl PduHeader {
             + self.pdu_conf.dest_entity_id.size()
     }
 
+    #[inline]
+    pub fn pdu_datafield_len(&self) -> usize {
+        self.pdu_datafield_len.into()
+    }
+
     /// Returns the full length of the PDU when written to a raw buffer, which is the header length
     /// plus the PDU datafield length.
+    #[inline]
     pub fn pdu_len(&self) -> usize {
         self.header_len() + self.pdu_datafield_len as usize
     }
@@ -350,20 +388,20 @@ impl PduHeader {
         // Internal note: There is currently no way to pass a PDU configuration like this, but
         // this check is still kept for defensive programming.
         if self.pdu_conf.source_entity_id.size() != self.pdu_conf.dest_entity_id.size() {
-            return Err(PduError::SourceDestIdLenMissmatch((
-                self.pdu_conf.source_entity_id.size(),
-                self.pdu_conf.dest_entity_id.size(),
-            )));
+            return Err(PduError::SourceDestIdLenMissmatch {
+                src_id_len: self.pdu_conf.source_entity_id.size(),
+                dest_id_len: self.pdu_conf.dest_entity_id.size(),
+            });
         }
         if buf.len()
             < FIXED_HEADER_LEN
                 + self.pdu_conf.source_entity_id.size()
                 + self.pdu_conf.transaction_seq_num.size()
         {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: FIXED_HEADER_LEN,
-            })
+            }
             .into());
         }
         let mut current_idx = 0;
@@ -404,17 +442,17 @@ impl PduHeader {
     /// flag is not set, it will simply return the PDU length.
     pub fn verify_length_and_checksum(&self, buf: &[u8]) -> Result<usize, PduError> {
         if buf.len() < self.pdu_len() {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: buf.len(),
                 expected: self.pdu_len(),
-            })
+            }
             .into());
         }
         if self.pdu_conf.crc_flag == CrcFlag::WithCrc {
             let mut digest = CRC_CCITT_FALSE.digest();
             digest.update(&buf[..self.pdu_len()]);
             if digest.finalize() != 0 {
-                return Err(PduError::ChecksumError(u16::from_be_bytes(
+                return Err(PduError::Checksum(u16::from_be_bytes(
                     buf[self.pdu_len() - 2..self.pdu_len()].try_into().unwrap(),
                 )));
             }
@@ -433,11 +471,11 @@ impl PduHeader {
     /// function.
     pub fn from_bytes(buf: &[u8]) -> Result<(Self, usize), PduError> {
         if buf.len() < FIXED_HEADER_LEN {
-            return Err(PduError::ByteConversionError(
-                ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(PduError::ByteConversion(
+                ByteConversionError::FromSliceTooSmall {
                     found: buf.len(),
                     expected: FIXED_HEADER_LEN,
-                }),
+                },
             ));
         }
         let cfdp_version_raw = (buf[0] >> 5) & 0b111;
@@ -472,10 +510,10 @@ impl PduHeader {
             ));
         }
         if buf.len() < (4 + 2 * expected_len_entity_ids + expected_len_seq_num) {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: buf.len(),
                 expected: 4 + 2 * expected_len_entity_ids + expected_len_seq_num,
-            })
+            }
             .into());
         }
         let mut current_idx = 4;
@@ -514,10 +552,13 @@ impl PduHeader {
             current_idx,
         ))
     }
+
+    #[inline]
     pub fn pdu_type(&self) -> PduType {
         self.pdu_type
     }
 
+    #[inline]
     pub fn common_pdu_conf(&self) -> &CommonPduConfig {
         &self.pdu_conf
     }
@@ -525,6 +566,8 @@ impl PduHeader {
     pub fn seg_metadata_flag(&self) -> SegmentMetadataFlag {
         self.seg_metadata_flag
     }
+
+    #[inline]
     pub fn seg_ctrl(&self) -> SegmentationControl {
         self.seg_ctrl
     }
@@ -571,17 +614,17 @@ pub(crate) fn generic_length_checks_pdu_deserialization(
 ) -> Result<(), ByteConversionError> {
     // Buffer too short to hold additional expected minimum datasize.
     if buf.len() < min_expected_len {
-        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+        return Err(ByteConversionError::FromSliceTooSmall {
             found: buf.len(),
             expected: min_expected_len,
-        }));
+        });
     }
     // This can happen if the PDU datafield length value is invalid.
     if full_len_without_crc < min_expected_len {
-        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+        return Err(ByteConversionError::FromSliceTooSmall {
             found: full_len_without_crc,
             expected: min_expected_len,
-        }));
+        });
     }
     Ok(())
 }
@@ -596,23 +639,26 @@ pub(crate) fn add_pdu_crc(buf: &mut [u8], mut current_idx: usize) -> usize {
 
 #[cfg(test)]
 mod tests {
+    use alloc::string::ToString;
+
     use crate::cfdp::pdu::{CommonPduConfig, PduError, PduHeader, FIXED_HEADER_LEN};
     use crate::cfdp::{
         CrcFlag, Direction, LargeFileFlag, PduType, SegmentMetadataFlag, SegmentationControl,
         TransmissionMode, CFDP_VERSION_2,
     };
     use crate::util::{
-        UbfU8, UnsignedByteField, UnsignedByteFieldU16, UnsignedByteFieldU8, UnsignedEnum,
+        UbfU16, UbfU8, UnsignedByteField, UnsignedByteFieldU16, UnsignedByteFieldU8, UnsignedEnum,
     };
     use crate::ByteConversionError;
     use std::format;
 
+    pub(crate) const TEST_SRC_ID: UbfU8 = UbfU8::new(5);
+    pub(crate) const TEST_DEST_ID: UbfU8 = UbfU8::new(10);
+    pub(crate) const TEST_SEQ_NUM: UbfU8 = UbfU8::new(20);
+
     pub(crate) fn common_pdu_conf(crc_flag: CrcFlag, fss: LargeFileFlag) -> CommonPduConfig {
-        let src_id = UbfU8::new(5);
-        let dest_id = UbfU8::new(10);
-        let transaction_seq_num = UbfU8::new(20);
         let mut pdu_conf =
-            CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_num)
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM)
                 .expect("Generating common PDU config");
         pdu_conf.crc_flag = crc_flag;
         pdu_conf.file_flag = fss;
@@ -623,7 +669,6 @@ mod tests {
         assert_eq!((buf[0] >> 5) & 0b111, CFDP_VERSION_2);
         // File directive
         assert_eq!((buf[0] >> 4) & 1, pdu_conf.pdu_type as u8);
-        // Towards receiver
         assert_eq!((buf[0] >> 3) & 1, pdu_conf.pdu_conf.direction as u8);
         // Acknowledged
         assert_eq!((buf[0] >> 2) & 1, pdu_conf.pdu_conf.trans_mode as u8);
@@ -669,7 +714,7 @@ mod tests {
                             .try_into()
                             .unwrap()
                     ),
-                    ubf.value() as u64
+                    ubf.value()
                 ),
                 _ => panic!("invalid entity ID length"),
             }
@@ -704,6 +749,17 @@ mod tests {
         assert_eq!(pdu_header.header_len(), 7);
     }
 
+    #[test]
+    fn test_common_pdu_conf_partial_eq() {
+        let common_pdu_cfg_0 =
+            CommonPduConfig::new_with_byte_fields(UbfU8::new(1), UbfU8::new(2), UbfU8::new(3))
+                .expect("common config creation failed");
+        let common_pdu_cfg_1 =
+            CommonPduConfig::new_with_byte_fields(UbfU16::new(1), UbfU16::new(2), UbfU16::new(3))
+                .expect("common config creation failed");
+        assert_eq!(common_pdu_cfg_0, common_pdu_cfg_1);
+    }
+
     #[test]
     fn test_basic_state_default() {
         let default_conf = CommonPduConfig::default();
@@ -718,6 +774,8 @@ mod tests {
         assert_eq!(default_conf.crc_flag, CrcFlag::NoCrc);
         assert_eq!(default_conf.file_flag, LargeFileFlag::Normal);
     }
+
+    #[test]
     fn test_pdu_header_setter() {
         let src_id = UnsignedByteFieldU8::new(1);
         let dest_id = UnsignedByteFieldU8::new(2);
@@ -747,6 +805,7 @@ mod tests {
         // 4 byte fixed header plus three bytes src, dest ID and transaction ID
         assert_eq!(res.unwrap(), 7);
         verify_raw_header(&pdu_header, &buf);
+        assert_eq!(pdu_header.pdu_datafield_len(), 5);
     }
 
     #[test]
@@ -840,6 +899,10 @@ mod tests {
         let error = res.unwrap_err();
         if let PduError::CfdpVersionMissmatch(raw_version) = error {
             assert_eq!(raw_version, CFDP_VERSION_2 + 1);
+            assert_eq!(
+                error.to_string(),
+                "CFDP version missmatch, found 2, expected 1"
+            );
         } else {
             panic!("invalid exception: {}", error);
         }
@@ -851,11 +914,13 @@ mod tests {
         let res = PduHeader::from_bytes(&buf);
         assert!(res.is_err());
         let error = res.unwrap_err();
-        if let PduError::ByteConversionError(ByteConversionError::FromSliceTooSmall(missmatch)) =
-            error
+        if let PduError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+            found,
+            expected,
+        }) = error
         {
-            assert_eq!(missmatch.found, 3);
-            assert_eq!(missmatch.expected, FIXED_HEADER_LEN);
+            assert_eq!(found, 3);
+            assert_eq!(expected, FIXED_HEADER_LEN);
         } else {
             panic!("invalid exception: {}", error);
         }
@@ -875,11 +940,17 @@ mod tests {
         let header = PduHeader::from_bytes(&buf[0..6]);
         assert!(header.is_err());
         let error = header.unwrap_err();
-        if let PduError::ByteConversionError(ByteConversionError::FromSliceTooSmall(missmatch)) =
-            error
+        if let PduError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+            found,
+            expected,
+        }) = error
         {
-            assert_eq!(missmatch.found, 6);
-            assert_eq!(missmatch.expected, 7);
+            assert_eq!(found, 6);
+            assert_eq!(expected, 7);
+            assert_eq!(
+                error.to_string(),
+                "byte conversion error: source slice with size 6 too small, expected at least 7 bytes"
+            );
         }
     }
 
@@ -907,6 +978,10 @@ mod tests {
         let error = pdu_conf_res.unwrap_err();
         if let PduError::InvalidEntityLen(len) = error {
             assert_eq!(len, 3);
+            assert_eq!(
+                error.to_string(),
+                "invalid PDU entity ID length 3, only [1, 2, 4, 8] are allowed"
+            );
         } else {
             panic!("Invalid exception: {}", error)
         }
@@ -920,9 +995,17 @@ mod tests {
             CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_id);
         assert!(pdu_conf_res.is_err());
         let error = pdu_conf_res.unwrap_err();
-        if let PduError::SourceDestIdLenMissmatch((src_len, dest_len)) = error {
-            assert_eq!(src_len, 1);
-            assert_eq!(dest_len, 2);
+        if let PduError::SourceDestIdLenMissmatch {
+            src_id_len,
+            dest_id_len,
+        } = error
+        {
+            assert_eq!(src_id_len, 1);
+            assert_eq!(dest_id_len, 2);
+            assert_eq!(
+                error.to_string(),
+                "missmatch of PDU source ID length 1 and destination ID length 2"
+            );
         }
     }
 
@@ -973,4 +1056,20 @@ mod tests {
             panic!("invalid exception {:?}", error)
         }
     }
+
+    #[test]
+    fn test_pdu_error_clonable_and_comparable() {
+        let pdu_error = PduError::InvalidEntityLen(0);
+        let pdu_error_2 = pdu_error;
+        assert_eq!(pdu_error, pdu_error_2);
+    }
+
+    #[test]
+    fn test_pdu_config_clonable_and_comparable() {
+        let common_pdu_cfg_0 =
+            CommonPduConfig::new_with_byte_fields(UbfU8::new(1), UbfU8::new(2), UbfU8::new(3))
+                .expect("common config creation failed");
+        let common_pdu_cfg_1 = common_pdu_cfg_0;
+        assert_eq!(common_pdu_cfg_0, common_pdu_cfg_1);
+    }
 }

src/cfdp/pdu/nak.rs

@@ -0,0 +1,806 @@
+use crate::{
+    cfdp::{CrcFlag, Direction, LargeFileFlag},
+    ByteConversionError,
+};
+use core::{marker::PhantomData, mem::size_of};
+
+use super::{
+    add_pdu_crc, generic_length_checks_pdu_deserialization, CfdpPdu, FileDirectiveType, PduError,
+    PduHeader, WritablePduPacket,
+};
+
+/// Helper type to encapsulate both normal file size segment requests and large file size segment
+/// requests.
+#[derive(Debug, PartialEq, Eq, Clone)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum SegmentRequests<'a> {
+    U32Pairs(&'a [(u32, u32)]),
+    U64Pairs(&'a [(u64, u64)]),
+}
+
+impl SegmentRequests<'_> {
+    pub fn is_empty(&self) -> bool {
+        match self {
+            SegmentRequests::U32Pairs(pairs) => pairs.is_empty(),
+            SegmentRequests::U64Pairs(pairs) => pairs.is_empty(),
+        }
+    }
+}
+
+/// NAK PDU abstraction specialized in the creation of NAK PDUs.
+///
+/// It exposes a specialized API which simplifies to generate these NAK PDUs with the
+/// format according to CFDP chapter 5.2.6.
+#[derive(Debug, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct NakPduCreator<'seg_reqs> {
+    pdu_header: PduHeader,
+    start_of_scope: u64,
+    end_of_scope: u64,
+    segment_requests: Option<SegmentRequests<'seg_reqs>>,
+}
+
+impl<'seg_reqs> NakPduCreator<'seg_reqs> {
+    /// Please note that the start of scope and the end of scope need to be smaller or equal
+    /// to [u32::MAX] if the large file flag of the passed PDU configuration is
+    /// [LargeFileFlag::Normal].
+    ///
+    /// ## Errrors
+    ///
+    pub fn new_no_segment_requests(
+        pdu_header: PduHeader,
+        start_of_scope: u64,
+        end_of_scope: u64,
+    ) -> Result<NakPduCreator<'seg_reqs>, PduError> {
+        Self::new_generic(pdu_header, start_of_scope, end_of_scope, None)
+    }
+
+    /// Default constructor for normal file sizes.
+    pub fn new(
+        pdu_header: PduHeader,
+        start_of_scope: u32,
+        end_of_scope: u32,
+        segment_requests: &'seg_reqs [(u32, u32)],
+    ) -> Result<NakPduCreator, PduError> {
+        let mut passed_segment_requests = None;
+        if !segment_requests.is_empty() {
+            passed_segment_requests = Some(SegmentRequests::U32Pairs(segment_requests));
+        }
+        Self::new_generic(
+            pdu_header,
+            start_of_scope.into(),
+            end_of_scope.into(),
+            passed_segment_requests,
+        )
+    }
+
+    pub fn new_large_file_size(
+        pdu_header: PduHeader,
+        start_of_scope: u64,
+        end_of_scope: u64,
+        segment_requests: &'seg_reqs [(u64, u64)],
+    ) -> Result<NakPduCreator, PduError> {
+        let mut passed_segment_requests = None;
+        if !segment_requests.is_empty() {
+            passed_segment_requests = Some(SegmentRequests::U64Pairs(segment_requests));
+        }
+        Self::new_generic(
+            pdu_header,
+            start_of_scope,
+            end_of_scope,
+            passed_segment_requests,
+        )
+    }
+
+    fn new_generic(
+        mut pdu_header: PduHeader,
+        start_of_scope: u64,
+        end_of_scope: u64,
+        segment_requests: Option<SegmentRequests<'seg_reqs>>,
+    ) -> Result<NakPduCreator, PduError> {
+        // Force correct direction flag.
+        pdu_header.pdu_conf.direction = Direction::TowardsSender;
+        if let Some(ref segment_requests) = segment_requests {
+            match segment_requests {
+                SegmentRequests::U32Pairs(_) => {
+                    if start_of_scope > u32::MAX as u64 || end_of_scope > u32::MAX as u64 {
+                        return Err(PduError::InvalidStartOrEndOfScopeValue);
+                    }
+                    pdu_header.pdu_conf.file_flag = LargeFileFlag::Normal;
+                }
+                SegmentRequests::U64Pairs(_) => {
+                    pdu_header.pdu_conf.file_flag = LargeFileFlag::Large;
+                }
+            }
+        };
+        let mut nak_pdu = Self {
+            pdu_header,
+            start_of_scope,
+            end_of_scope,
+            segment_requests,
+        };
+        nak_pdu.pdu_header.pdu_datafield_len = nak_pdu.calc_pdu_datafield_len() as u16;
+        Ok(nak_pdu)
+    }
+
+    pub fn start_of_scope(&self) -> u64 {
+        self.start_of_scope
+    }
+
+    pub fn end_of_scope(&self) -> u64 {
+        self.end_of_scope
+    }
+
+    pub fn segment_requests(&self) -> Option<&SegmentRequests> {
+        self.segment_requests.as_ref()
+    }
+
+    pub fn num_segment_reqs(&self) -> usize {
+        match &self.segment_requests {
+            Some(seg_reqs) => match seg_reqs {
+                SegmentRequests::U32Pairs(pairs) => pairs.len(),
+                SegmentRequests::U64Pairs(pairs) => pairs.len(),
+            },
+            None => 0,
+        }
+    }
+
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        let mut datafield_len = 1;
+        if self.file_flag() == LargeFileFlag::Normal {
+            datafield_len += 8;
+            datafield_len += self.num_segment_reqs() * 8;
+        } else {
+            datafield_len += 16;
+            datafield_len += self.num_segment_reqs() * 16;
+        }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            datafield_len += 2;
+        }
+        datafield_len
+    }
+}
+
+impl CfdpPdu for NakPduCreator<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::NakPdu)
+    }
+}
+
+impl WritablePduPacket for NakPduCreator<'_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::NakPdu as u8;
+        current_idx += 1;
+
+        let mut write_start_end_of_scope_normal = || {
+            let start_of_scope = u32::try_from(self.start_of_scope).unwrap();
+            let end_of_scope = u32::try_from(self.end_of_scope).unwrap();
+            buf[current_idx..current_idx + 4].copy_from_slice(&start_of_scope.to_be_bytes());
+            current_idx += 4;
+            buf[current_idx..current_idx + 4].copy_from_slice(&end_of_scope.to_be_bytes());
+            current_idx += 4;
+        };
+        if let Some(ref seg_reqs) = self.segment_requests {
+            match seg_reqs {
+                SegmentRequests::U32Pairs(pairs) => {
+                    // Unwrap is okay here, the API should prevent invalid values which would trigger a
+                    // panic here.
+                    write_start_end_of_scope_normal();
+                    for (next_start_offset, next_end_offset) in *pairs {
+                        buf[current_idx..current_idx + 4]
+                            .copy_from_slice(&next_start_offset.to_be_bytes());
+                        current_idx += 4;
+                        buf[current_idx..current_idx + 4]
+                            .copy_from_slice(&next_end_offset.to_be_bytes());
+                        current_idx += 4;
+                    }
+                }
+                SegmentRequests::U64Pairs(pairs) => {
+                    buf[current_idx..current_idx + 8]
+                        .copy_from_slice(&self.start_of_scope.to_be_bytes());
+                    current_idx += 8;
+                    buf[current_idx..current_idx + 8]
+                        .copy_from_slice(&self.end_of_scope.to_be_bytes());
+                    current_idx += 8;
+                    for (next_start_offset, next_end_offset) in *pairs {
+                        buf[current_idx..current_idx + 8]
+                            .copy_from_slice(&next_start_offset.to_be_bytes());
+                        current_idx += 8;
+                        buf[current_idx..current_idx + 8]
+                            .copy_from_slice(&next_end_offset.to_be_bytes());
+                        current_idx += 8;
+                    }
+                }
+            }
+        } else {
+            write_start_end_of_scope_normal();
+        }
+
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+/// Special iterator type for the NAK PDU which allows to iterate over both normal and large file
+/// segment requests.
+#[derive(Debug)]
+pub struct SegmentRequestIter<'a, T> {
+    seq_req_raw: &'a [u8],
+    current_idx: usize,
+    phantom: core::marker::PhantomData<T>,
+}
+
+pub trait SegReqFromBytes {
+    fn from_bytes(bytes: &[u8]) -> Self;
+}
+
+impl SegReqFromBytes for u32 {
+    fn from_bytes(bytes: &[u8]) -> u32 {
+        u32::from_be_bytes(bytes.try_into().unwrap())
+    }
+}
+
+impl SegReqFromBytes for u64 {
+    fn from_bytes(bytes: &[u8]) -> u64 {
+        u64::from_be_bytes(bytes.try_into().unwrap())
+    }
+}
+
+impl<'a, T> Iterator for SegmentRequestIter<'a, T>
+where
+    T: SegReqFromBytes,
+{
+    type Item = (T, T);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let value = self.next_at_offset(self.current_idx);
+        self.current_idx += 2 * size_of::<T>();
+        value
+    }
+}
+
+impl<'a, 'b> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'b, u32> {
+    fn eq(&self, other: &SegmentRequests) -> bool {
+        match other {
+            SegmentRequests::U32Pairs(pairs) => self.compare_pairs(pairs),
+            SegmentRequests::U64Pairs(pairs) => {
+                if pairs.is_empty() && self.seq_req_raw.is_empty() {
+                    return true;
+                }
+                false
+            }
+        }
+    }
+}
+
+impl<'a, 'b> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'b, u64> {
+    fn eq(&self, other: &SegmentRequests) -> bool {
+        match other {
+            SegmentRequests::U32Pairs(pairs) => {
+                if pairs.is_empty() && self.seq_req_raw.is_empty() {
+                    return true;
+                }
+                false
+            }
+            SegmentRequests::U64Pairs(pairs) => self.compare_pairs(pairs),
+        }
+    }
+}
+
+impl<'a, T> SegmentRequestIter<'a, T>
+where
+    T: SegReqFromBytes + PartialEq,
+{
+    fn compare_pairs(&self, pairs: &[(T, T)]) -> bool {
+        if pairs.is_empty() && self.seq_req_raw.is_empty() {
+            return true;
+        }
+        let size = size_of::<T>();
+        if pairs.len() * 2 * size != self.seq_req_raw.len() {
+            return false;
+        }
+
+        for (i, pair) in pairs.iter().enumerate() {
+            let next_val = self.next_at_offset(i * 2 * size).unwrap();
+            if next_val != *pair {
+                return false;
+            }
+        }
+
+        true
+    }
+}
+
+impl<T: SegReqFromBytes> SegmentRequestIter<'_, T> {
+    fn next_at_offset(&self, mut offset: usize) -> Option<(T, T)> {
+        if offset + size_of::<T>() * 2 > self.seq_req_raw.len() {
+            return None;
+        }
+
+        let start_offset = T::from_bytes(&self.seq_req_raw[offset..offset + size_of::<T>()]);
+        offset += size_of::<T>();
+
+        let end_offset = T::from_bytes(&self.seq_req_raw[offset..offset + size_of::<T>()]);
+        Some((start_offset, end_offset))
+    }
+}
+
+/// NAK PDU abstraction specialized in the reading NAK PDUs from a raw bytestream.
+///
+/// This is a zero-copy class where the segment requests can be read using a special iterator
+/// API without the need to copy them.
+///
+/// The NAK format is expected to be conforming to CFDP chapter 5.2.6.
+#[derive(Debug, PartialEq, Eq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct NakPduReader<'seg_reqs> {
+    pdu_header: PduHeader,
+    start_of_scope: u64,
+    end_of_scope: u64,
+    seg_reqs_raw: &'seg_reqs [u8],
+}
+
+impl CfdpPdu for NakPduReader<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::NakPdu)
+    }
+}
+
+impl<'seg_reqs> NakPduReader<'seg_reqs> {
+    pub fn new(buf: &'seg_reqs [u8]) -> Result<NakPduReader, PduError> {
+        Self::from_bytes(buf)
+    }
+
+    pub fn from_bytes(buf: &'seg_reqs [u8]) -> Result<NakPduReader, PduError> {
+        let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
+        let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
+        // Minimum length of 9: 1 byte directive field and start and end of scope for normal file
+        // size.
+        generic_length_checks_pdu_deserialization(buf, 9, full_len_without_crc)?;
+        let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::NakPdu),
+            }
+        })?;
+        if directive_type != FileDirectiveType::NakPdu {
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::AckPdu,
+            });
+        }
+        current_idx += 1;
+        let start_of_scope;
+        let end_of_scope;
+        if pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
+            if current_idx + 16 > buf.len() {
+                return Err(PduError::ByteConversion(
+                    ByteConversionError::FromSliceTooSmall {
+                        found: buf.len(),
+                        expected: current_idx + 16,
+                    },
+                ));
+            }
+            start_of_scope =
+                u64::from_be_bytes(buf[current_idx..current_idx + 8].try_into().unwrap());
+            current_idx += 8;
+            end_of_scope =
+                u64::from_be_bytes(buf[current_idx..current_idx + 8].try_into().unwrap());
+            current_idx += 8;
+        } else {
+            start_of_scope =
+                u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap()) as u64;
+            current_idx += 4;
+            end_of_scope =
+                u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap()) as u64;
+            current_idx += 4;
+        }
+        Ok(Self {
+            pdu_header,
+            start_of_scope,
+            end_of_scope,
+            seg_reqs_raw: &buf[current_idx..full_len_without_crc],
+        })
+    }
+
+    pub fn start_of_scope(&self) -> u64 {
+        self.start_of_scope
+    }
+
+    pub fn end_of_scope(&self) -> u64 {
+        self.end_of_scope
+    }
+
+    pub fn num_segment_reqs(&self) -> usize {
+        if self.seg_reqs_raw.is_empty() {
+            return 0;
+        }
+        if self.file_flag() == LargeFileFlag::Normal {
+            self.seg_reqs_raw.len() / 8
+        } else {
+            self.seg_reqs_raw.len() / 16
+        }
+    }
+
+    /// This function returns [None] if this NAK PDUs contains segment requests for a large file.
+    pub fn get_normal_segment_requests_iterator(&self) -> Option<SegmentRequestIter<'_, u32>> {
+        if self.file_flag() == LargeFileFlag::Large {
+            return None;
+        }
+        Some(SegmentRequestIter {
+            seq_req_raw: self.seg_reqs_raw,
+            current_idx: 0,
+            phantom: PhantomData,
+        })
+    }
+
+    /// This function returns [None] if this NAK PDUs contains segment requests for a normal file.
+    pub fn get_large_segment_requests_iterator(&self) -> Option<SegmentRequestIter<'_, u64>> {
+        if self.file_flag() == LargeFileFlag::Normal {
+            return None;
+        }
+        Some(SegmentRequestIter {
+            seq_req_raw: self.seg_reqs_raw,
+            current_idx: 0,
+            phantom: PhantomData,
+        })
+    }
+}
+
+impl<'a, 'b> PartialEq<NakPduCreator<'a>> for NakPduReader<'b> {
+    fn eq(&self, other: &NakPduCreator<'a>) -> bool {
+        if self.pdu_header() != other.pdu_header()
+            || self.end_of_scope() != other.end_of_scope()
+            || self.start_of_scope() != other.start_of_scope()
+        {
+            return false;
+        }
+
+        // Check if both segment requests are empty or None
+        match (self.seg_reqs_raw.is_empty(), other.segment_requests()) {
+            (true, None) => true,
+            (true, Some(seg_reqs)) => seg_reqs.is_empty(),
+            (false, None) => false,
+            _ => {
+                // Compare based on file_flag
+                if self.file_flag() == LargeFileFlag::Normal {
+                    let normal_iter = self.get_normal_segment_requests_iterator().unwrap();
+                    normal_iter == *other.segment_requests().unwrap()
+                } else {
+                    let large_iter = self.get_large_segment_requests_iterator().unwrap();
+                    large_iter == *other.segment_requests().unwrap()
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use alloc::string::ToString;
+
+    use crate::cfdp::{
+        pdu::tests::{common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID},
+        PduType, TransmissionMode,
+    };
+
+    use super::*;
+
+    fn check_generic_fields(nak_pdu: &impl CfdpPdu) {
+        assert_eq!(nak_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(nak_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(nak_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            nak_pdu.file_directive_type(),
+            Some(FileDirectiveType::NakPdu),
+        );
+        assert_eq!(nak_pdu.transmission_mode(), TransmissionMode::Acknowledged);
+        assert_eq!(nak_pdu.direction(), Direction::TowardsSender);
+        assert_eq!(nak_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(nak_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(nak_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
+    }
+
+    #[test]
+    fn test_seg_request_api() {
+        let seg_req = SegmentRequests::U32Pairs(&[]);
+        assert!(seg_req.is_empty());
+        let seg_req = SegmentRequests::U64Pairs(&[]);
+        assert!(seg_req.is_empty());
+    }
+
+    #[test]
+    fn test_basic_creator() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 0, 0)
+            .expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu.start_of_scope(), 0);
+        assert_eq!(nak_pdu.end_of_scope(), 0);
+        assert_eq!(nak_pdu.segment_requests(), None);
+        assert_eq!(nak_pdu.num_segment_reqs(), 0);
+        check_generic_fields(&nak_pdu);
+    }
+
+    #[test]
+    fn test_serialization_empty() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 100, 300)
+            .expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu.start_of_scope(), 100);
+        assert_eq!(nak_pdu.end_of_scope(), 300);
+        let mut buf: [u8; 64] = [0; 64];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        verify_raw_header(nak_pdu.pdu_header(), &buf);
+        let mut current_idx = nak_pdu.pdu_header().header_len();
+        assert_eq!(current_idx + 9, nak_pdu.len_written());
+        assert_eq!(buf[current_idx], FileDirectiveType::NakPdu as u8);
+        current_idx += 1;
+        let start_of_scope =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(start_of_scope, 100);
+        current_idx += 4;
+        let end_of_scope =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(end_of_scope, 300);
+        current_idx += 4;
+        assert_eq!(current_idx, nak_pdu.len_written());
+    }
+
+    #[test]
+    fn test_serialization_two_segments() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new(pdu_header, 100, 300, &[(0, 0), (32, 64)])
+            .expect("creating NAK PDU creator failed");
+        let mut buf: [u8; 64] = [0; 64];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        verify_raw_header(nak_pdu.pdu_header(), &buf);
+        let mut current_idx = nak_pdu.pdu_header().header_len();
+        assert_eq!(current_idx + 9 + 16, nak_pdu.len_written());
+        assert_eq!(buf[current_idx], FileDirectiveType::NakPdu as u8);
+        current_idx += 1;
+        let start_of_scope =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(start_of_scope, 100);
+        current_idx += 4;
+        let end_of_scope =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(end_of_scope, 300);
+        current_idx += 4;
+        let first_seg_start =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(first_seg_start, 0);
+        current_idx += 4;
+        let first_seg_end =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(first_seg_end, 0);
+        current_idx += 4;
+        let second_seg_start =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(second_seg_start, 32);
+        current_idx += 4;
+        let second_seg_end =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(second_seg_end, 64);
+        current_idx += 4;
+        assert_eq!(current_idx, nak_pdu.len_written());
+    }
+
+    #[test]
+    fn test_deserialization_empty() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 100, 300)
+            .expect("creating NAK PDU creator failed");
+        let mut buf: [u8; 64] = [0; 64];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        let nak_pdu_deser = NakPduReader::from_bytes(&buf).expect("deserializing NAK PDU failed");
+        assert_eq!(nak_pdu_deser, nak_pdu);
+        check_generic_fields(&nak_pdu_deser);
+    }
+
+    #[test]
+    fn test_deserialization_large_segments() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Large);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu =
+            NakPduCreator::new_large_file_size(pdu_header, 100, 300, &[(50, 100), (200, 300)])
+                .expect("creating NAK PDU creator failed");
+        let mut buf: [u8; 128] = [0; 128];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        let nak_pdu_deser = NakPduReader::from_bytes(&buf).expect("deserializing NAK PDU failed");
+        assert_eq!(nak_pdu_deser, nak_pdu);
+        assert_eq!(nak_pdu_deser.start_of_scope(), 100);
+        assert_eq!(nak_pdu_deser.end_of_scope(), 300);
+        assert_eq!(nak_pdu_deser.num_segment_reqs(), 2);
+        assert!(nak_pdu_deser
+            .get_large_segment_requests_iterator()
+            .is_some());
+        assert!(nak_pdu_deser
+            .get_normal_segment_requests_iterator()
+            .is_none());
+        assert_eq!(
+            nak_pdu_deser
+                .get_large_segment_requests_iterator()
+                .unwrap()
+                .count(),
+            2
+        );
+        for (idx, large_segments) in nak_pdu_deser
+            .get_large_segment_requests_iterator()
+            .unwrap()
+            .enumerate()
+        {
+            if idx == 0 {
+                assert_eq!(large_segments.0, 50);
+                assert_eq!(large_segments.1, 100);
+            } else {
+                assert_eq!(large_segments.0, 200);
+                assert_eq!(large_segments.1, 300);
+            }
+        }
+    }
+
+    #[test]
+    fn test_deserialization_normal_segments() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new(pdu_header, 100, 300, &[(50, 100), (200, 300)])
+            .expect("creating NAK PDU creator failed");
+        let mut buf: [u8; 128] = [0; 128];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        let nak_pdu_deser = NakPduReader::from_bytes(&buf).expect("deserializing NAK PDU failed");
+        assert_eq!(nak_pdu_deser, nak_pdu);
+        assert_eq!(nak_pdu_deser.start_of_scope(), 100);
+        assert_eq!(nak_pdu_deser.end_of_scope(), 300);
+        assert_eq!(nak_pdu_deser.num_segment_reqs(), 2);
+        assert!(nak_pdu_deser
+            .get_normal_segment_requests_iterator()
+            .is_some());
+        assert!(nak_pdu_deser
+            .get_large_segment_requests_iterator()
+            .is_none());
+        assert_eq!(
+            nak_pdu_deser
+                .get_normal_segment_requests_iterator()
+                .unwrap()
+                .count(),
+            2
+        );
+        for (idx, large_segments) in nak_pdu_deser
+            .get_normal_segment_requests_iterator()
+            .unwrap()
+            .enumerate()
+        {
+            if idx == 0 {
+                assert_eq!(large_segments.0, 50);
+                assert_eq!(large_segments.1, 100);
+            } else {
+                assert_eq!(large_segments.0, 200);
+                assert_eq!(large_segments.1, 300);
+            }
+        }
+    }
+
+    #[test]
+    fn test_empty_is_empty() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu_0 =
+            NakPduCreator::new(pdu_header, 100, 300, &[]).expect("creating NAK PDU creator failed");
+        let nak_pdu_1 = NakPduCreator::new_no_segment_requests(pdu_header, 100, 300)
+            .expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu_0, nak_pdu_1);
+        // Assert the segment request is mapped to None.
+        assert!(nak_pdu_0.segment_requests().is_none());
+    }
+
+    #[test]
+    fn test_new_generic_invalid_input() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let u32_list = SegmentRequests::U32Pairs(&[(0, 50), (50, 100)]);
+        //let error = NakPduCreator::new_generic(pdu_header, 100, 300, Some(u32_list));
+        let error = NakPduCreator::new_generic(
+            pdu_header,
+            u32::MAX as u64 + 1,
+            u32::MAX as u64 + 2,
+            Some(u32_list),
+        );
+        assert!(error.is_err());
+        let error = error.unwrap_err();
+        if let PduError::InvalidStartOrEndOfScopeValue = error {
+            assert_eq!(
+                error.to_string(),
+                "invalid start or end of scope value for NAK PDU"
+            );
+        } else {
+            panic!("unexpected error {error}");
+        }
+    }
+
+    #[test]
+    fn test_target_buf_too_small() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 100, 300)
+            .expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu.start_of_scope(), 100);
+        assert_eq!(nak_pdu.end_of_scope(), 300);
+        let mut buf: [u8; 5] = [0; 5];
+        let error = nak_pdu.write_to_bytes(&mut buf);
+        assert!(error.is_err());
+        let e = error.unwrap_err();
+        match e {
+            PduError::ByteConversion(conv_error) => match conv_error {
+                ByteConversionError::ToSliceTooSmall { found, expected } => {
+                    assert_eq!(expected, nak_pdu.len_written());
+                    assert_eq!(found, 5);
+                }
+                _ => panic!("unexpected error {conv_error}"),
+            },
+            _ => panic!("unexpected error {e}"),
+        }
+    }
+
+    #[test]
+    fn test_with_crc() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 0, 0)
+            .expect("creating NAK PDU creator failed");
+        let mut nak_vec = nak_pdu.to_vec().expect("writing NAK to vector failed");
+        assert_eq!(nak_vec.len(), pdu_header.header_len() + 9 + 2);
+        assert_eq!(nak_vec.len(), nak_pdu.len_written());
+        let nak_pdu_deser = NakPduReader::new(&nak_vec).expect("reading NAK PDU failed");
+        assert_eq!(nak_pdu_deser, nak_pdu);
+        nak_vec[nak_pdu.len_written() - 1] -= 1;
+        let nak_pdu_deser = NakPduReader::new(&nak_vec);
+        assert!(nak_pdu_deser.is_err());
+        if let Err(PduError::Checksum(raw)) = nak_pdu_deser {
+            assert_eq!(
+                raw,
+                u16::from_be_bytes(nak_vec[nak_pdu.len_written() - 2..].try_into().unwrap())
+            );
+        }
+    }
+}

src/cfdp/tlv.rs

@@ -1,765 +0,0 @@
-//! Generic CFDP type-length-value (TLV) abstraction as specified in CFDP 5.1.9.
-use crate::cfdp::lv::{
-    generic_len_check_data_serialization, generic_len_check_deserialization, Lv, MIN_LV_LEN,
-};
-use crate::cfdp::TlvLvError;
-use crate::util::{UnsignedByteField, UnsignedByteFieldError, UnsignedEnum};
-use crate::{ByteConversionError, SizeMissmatch};
-use num_enum::{IntoPrimitive, TryFromPrimitive};
-#[cfg(feature = "serde")]
-use serde::{Deserialize, Serialize};
-
-pub const MIN_TLV_LEN: usize = 2;
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-#[repr(u8)]
-pub enum TlvType {
-    FilestoreRequest = 0x00,
-    FilestoreResponse = 0x01,
-    MsgToUser = 0x02,
-    FaultHandler = 0x04,
-    FlowLabel = 0x05,
-    EntityId = 0x06,
-}
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub enum TlvTypeField {
-    Standard(TlvType),
-    Custom(u8),
-}
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-#[repr(u8)]
-pub enum FilestoreActionCode {
-    CreateFile = 0b0000,
-    DeleteFile = 0b0001,
-    RenameFile = 0b0010,
-    /// This operation appends one file to another. The first specified name will form the first
-    /// part of the new file and the name of the new file. This function can be used to get
-    /// similar functionality to the UNIX cat utility (albeit for only two files).
-    AppendFile = 0b0011,
-    /// This operation replaces the content of the first specified file with the content of
-    /// the secondly specified file.
-    ReplaceFile = 0b0100,
-    CreateDirectory = 0b0101,
-    RemoveDirectory = 0b0110,
-    DenyFile = 0b0111,
-    DenyDirectory = 0b1000,
-}
-
-impl From<u8> for TlvTypeField {
-    fn from(value: u8) -> Self {
-        match TlvType::try_from(value) {
-            Ok(tlv_type) => TlvTypeField::Standard(tlv_type),
-            Err(_) => TlvTypeField::Custom(value),
-        }
-    }
-}
-
-impl From<TlvTypeField> for u8 {
-    fn from(value: TlvTypeField) -> Self {
-        match value {
-            TlvTypeField::Standard(std) => std as u8,
-            TlvTypeField::Custom(custom) => custom,
-        }
-    }
-}
-
-/// Generic CFDP type-length-value (TLV) abstraction as specified in CFDP 5.1.9.
-///
-/// # Lifetimes
-///  * `data`: If the TLV is generated from a raw bytestream, this will be the lifetime of
-///    the raw bytestream. If the TLV is generated from a raw slice or a similar data reference,
-///    this will be the lifetime of that data reference.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct Tlv<'data> {
-    tlv_type_field: TlvTypeField,
-    #[cfg_attr(feature = "serde", serde(borrow))]
-    lv: Lv<'data>,
-}
-
-impl<'data> Tlv<'data> {
-    pub fn new(tlv_type: TlvType, data: &[u8]) -> Result<Tlv, TlvLvError> {
-        Ok(Tlv {
-            tlv_type_field: TlvTypeField::Standard(tlv_type),
-            lv: Lv::new(data)?,
-        })
-    }
-
-    /// Creates a TLV with an empty value field.
-    pub fn new_empty(tlv_type: TlvType) -> Tlv<'data> {
-        Tlv {
-            tlv_type_field: TlvTypeField::Standard(tlv_type),
-            lv: Lv::new_empty(),
-        }
-    }
-
-    pub fn tlv_type_field(&self) -> TlvTypeField {
-        self.tlv_type_field
-    }
-
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        generic_len_check_data_serialization(buf, self.len_value(), MIN_TLV_LEN)?;
-        buf[0] = self.tlv_type_field.into();
-        self.lv.write_to_be_bytes_no_len_check(&mut buf[1..]);
-        Ok(self.len_full())
-    }
-
-    pub fn value(&self) -> Option<&[u8]> {
-        self.lv.value()
-    }
-
-    /// Returns the length of the value part, not including the length byte.
-    pub fn len_value(&self) -> usize {
-        self.lv.len_value()
-    }
-
-    /// Returns the full raw length, including the length byte.
-    pub fn len_full(&self) -> usize {
-        self.lv.len_full() + 1
-    }
-
-    /// Checks whether the value field is empty.
-    pub fn is_empty(&self) -> bool {
-        self.lv.is_empty()
-    }
-
-    /// Creates a TLV give a raw bytestream. Please note that is is not necessary to pass the
-    /// bytestream with the exact size of the expected TLV. This function will take care
-    /// of parsing the length byte, and the length of the parsed TLV can be retrieved using
-    /// [Self::len_full].
-    pub fn from_bytes(buf: &'data [u8]) -> Result<Tlv<'data>, TlvLvError> {
-        generic_len_check_deserialization(buf, MIN_TLV_LEN)?;
-        Ok(Self {
-            tlv_type_field: TlvTypeField::from(buf[0]),
-            lv: Lv::from_bytes(&buf[MIN_LV_LEN..])?,
-        })
-    }
-}
-
-pub(crate) fn verify_tlv_type(raw_type: u8, expected_tlv_type: TlvType) -> Result<(), TlvLvError> {
-    let tlv_type = TlvType::try_from(raw_type)
-        .map_err(|_| TlvLvError::InvalidTlvTypeField((raw_type, Some(expected_tlv_type as u8))))?;
-    if tlv_type != expected_tlv_type {
-        return Err(TlvLvError::InvalidTlvTypeField((
-            tlv_type as u8,
-            Some(expected_tlv_type as u8),
-        )));
-    }
-    Ok(())
-}
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct EntityIdTlv {
-    entity_id: UnsignedByteField,
-}
-
-impl EntityIdTlv {
-    pub fn new(entity_id: UnsignedByteField) -> Self {
-        Self { entity_id }
-    }
-
-    fn len_check(buf: &[u8]) -> Result<(), ByteConversionError> {
-        if buf.len() < 2 {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: 2,
-            }));
-        }
-        Ok(())
-    }
-
-    pub fn len_value(&self) -> usize {
-        self.entity_id.size()
-    }
-
-    pub fn len_full(&self) -> usize {
-        2 + self.entity_id.size()
-    }
-
-    pub fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        Self::len_check(buf)?;
-        buf[0] = TlvType::EntityId as u8;
-        buf[1] = self.entity_id.size() as u8;
-        self.entity_id.write_to_be_bytes(&mut buf[2..])
-    }
-
-    pub fn from_bytes(buf: &[u8]) -> Result<Self, TlvLvError> {
-        Self::len_check(buf)?;
-        verify_tlv_type(buf[0], TlvType::EntityId)?;
-        let len = buf[1];
-        if len != 1 && len != 2 && len != 4 && len != 8 {
-            return Err(TlvLvError::InvalidValueLength(len as usize));
-        }
-        // Okay to unwrap here. The checks before make sure that the deserialization never fails
-        let entity_id = UnsignedByteField::new_from_be_bytes(len as usize, &buf[2..]).unwrap();
-        Ok(Self { entity_id })
-    }
-
-    /// Convert to a generic [Tlv], which also erases the programmatic type information.
-    pub fn to_tlv(self, buf: &mut [u8]) -> Result<Tlv, ByteConversionError> {
-        Self::len_check(buf)?;
-        self.entity_id
-            .write_to_be_bytes(&mut buf[2..2 + self.entity_id.size()])?;
-        Tlv::new(TlvType::EntityId, &buf[2..2 + self.entity_id.size()]).map_err(|e| match e {
-            TlvLvError::ByteConversionError(e) => e,
-            // All other errors are impossible.
-            _ => panic!("unexpected TLV error"),
-        })
-    }
-}
-
-impl<'data> TryFrom<Tlv<'data>> for EntityIdTlv {
-    type Error = TlvLvError;
-
-    fn try_from(value: Tlv) -> Result<Self, Self::Error> {
-        match value.tlv_type_field {
-            TlvTypeField::Standard(tlv_type) => {
-                if tlv_type != TlvType::EntityId {
-                    return Err(TlvLvError::InvalidTlvTypeField((
-                        tlv_type as u8,
-                        Some(TlvType::EntityId as u8),
-                    )));
-                }
-            }
-            TlvTypeField::Custom(val) => {
-                return Err(TlvLvError::InvalidTlvTypeField((
-                    val,
-                    Some(TlvType::EntityId as u8),
-                )));
-            }
-        }
-        if value.len_value() != 1
-            && value.len_value() != 2
-            && value.len_value() != 4
-            && value.len_value() != 8
-        {
-            return Err(TlvLvError::InvalidValueLength(value.len_value()));
-        }
-        Ok(Self::new(
-            UnsignedByteField::new_from_be_bytes(value.len_value(), value.value().unwrap())
-                .map_err(|e| match e {
-                    UnsignedByteFieldError::ByteConversionError(e) => e,
-                    // This can not happen, we checked for the length validity, and the data is always smaller than
-                    // 255 bytes.
-                    _ => panic!("unexpected error"),
-                })?,
-        ))
-    }
-}
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct FilestoreRequestTlv<'first_name, 'second_name> {
-    action_code: FilestoreActionCode,
-    #[cfg_attr(feature = "serde", serde(borrow))]
-    first_name: Lv<'first_name>,
-    #[cfg_attr(feature = "serde", serde(borrow))]
-    second_name: Option<Lv<'second_name>>,
-}
-
-impl<'first_name, 'second_name> FilestoreRequestTlv<'first_name, 'second_name> {
-    pub fn new_create_file(first_name: Lv<'first_name>) -> Result<Self, TlvLvError> {
-        Self::new(FilestoreActionCode::CreateFile, first_name, None)
-    }
-
-    pub fn new_delete_file(first_name: Lv<'first_name>) -> Result<Self, TlvLvError> {
-        Self::new(FilestoreActionCode::DeleteFile, first_name, None)
-    }
-
-    pub fn new_rename_file(
-        source_name: Lv<'first_name>,
-        target_name: Lv<'second_name>,
-    ) -> Result<Self, TlvLvError> {
-        Self::new(
-            FilestoreActionCode::RenameFile,
-            source_name,
-            Some(target_name),
-        )
-    }
-
-    /// This operation appends one file to another. The first specified name will form the first
-    /// part of the new file and the name of the new file. This function can be used to get
-    /// similar functionality to the UNIX cat utility (albeit for only two files).
-    pub fn new_append_file(
-        first_file: Lv<'first_name>,
-        second_file: Lv<'second_name>,
-    ) -> Result<Self, TlvLvError> {
-        Self::new(
-            FilestoreActionCode::AppendFile,
-            first_file,
-            Some(second_file),
-        )
-    }
-
-    /// This operation replaces the content of the first specified file with the content of
-    /// the secondly specified file. This function can be used to get similar functionality to
-    /// the UNIX copy (cp) utility if the target file already exists.
-    pub fn new_replace_file(
-        replaced_file: Lv<'first_name>,
-        new_file: Lv<'second_name>,
-    ) -> Result<Self, TlvLvError> {
-        Self::new(
-            FilestoreActionCode::ReplaceFile,
-            replaced_file,
-            Some(new_file),
-        )
-    }
-
-    pub fn new_create_directory(dir_name: Lv<'first_name>) -> Result<Self, TlvLvError> {
-        Self::new(FilestoreActionCode::CreateDirectory, dir_name, None)
-    }
-
-    pub fn new_remove_directory(dir_name: Lv<'first_name>) -> Result<Self, TlvLvError> {
-        Self::new(FilestoreActionCode::RemoveDirectory, dir_name, None)
-    }
-
-    pub fn new_deny_file(file_name: Lv<'first_name>) -> Result<Self, TlvLvError> {
-        Self::new(FilestoreActionCode::DenyFile, file_name, None)
-    }
-
-    pub fn new_deny_directory(dir_name: Lv<'first_name>) -> Result<Self, TlvLvError> {
-        Self::new(FilestoreActionCode::DenyDirectory, dir_name, None)
-    }
-
-    /// This function will return [None] if the respective action code requires two names but
-    /// only one is passed. It will also returns [None] if the cumulative length of the first
-    /// name and the second name exceeds 255 bytes.
-    ///
-    /// This is the case for the rename, append and replace filestore request.
-    pub fn new(
-        action_code: FilestoreActionCode,
-        first_name: Lv<'first_name>,
-        second_name: Option<Lv<'second_name>>,
-    ) -> Result<Self, TlvLvError> {
-        let mut base_value_len = first_name.len_full();
-        if Self::has_second_filename(action_code) {
-            if second_name.is_none() {
-                return Err(TlvLvError::SecondNameMissing);
-            }
-            base_value_len += second_name.as_ref().unwrap().len_full();
-        }
-        if base_value_len > u8::MAX as usize {
-            return Err(TlvLvError::InvalidValueLength(base_value_len));
-        }
-        Ok(Self {
-            action_code,
-            first_name,
-            second_name,
-        })
-    }
-
-    pub fn has_second_filename(action_code: FilestoreActionCode) -> bool {
-        if action_code == FilestoreActionCode::RenameFile
-            || action_code == FilestoreActionCode::AppendFile
-            || action_code == FilestoreActionCode::ReplaceFile
-        {
-            return true;
-        }
-        false
-    }
-
-    pub fn action_code(&self) -> FilestoreActionCode {
-        self.action_code
-    }
-
-    pub fn first_name(&self) -> Lv<'first_name> {
-        self.first_name
-    }
-
-    pub fn second_name(&self) -> Option<Lv<'second_name>> {
-        self.second_name
-    }
-
-    pub fn len_value(&self) -> usize {
-        let mut len = 1 + self.first_name.len_full();
-        if let Some(second_name) = self.second_name {
-            len += second_name.len_full();
-        }
-        len
-    }
-
-    pub fn len_full(&self) -> usize {
-        2 + self.len_value()
-    }
-
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        if buf.len() < self.len_full() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: self.len_full(),
-            }));
-        }
-        buf[0] = TlvType::FilestoreRequest as u8;
-        buf[1] = self.len_value() as u8;
-        buf[2] = (self.action_code as u8) << 4;
-        let mut current_idx = 3;
-        // Length checks were already performed.
-        self.first_name.write_to_be_bytes_no_len_check(
-            &mut buf[current_idx..current_idx + self.first_name.len_full()],
-        );
-        current_idx += self.first_name.len_full();
-        if let Some(second_name) = self.second_name {
-            second_name.write_to_be_bytes_no_len_check(
-                &mut buf[current_idx..current_idx + second_name.len_full()],
-            );
-            current_idx += second_name.len_full();
-        }
-        Ok(current_idx)
-    }
-
-    pub fn from_bytes<'longest: 'first_name + 'second_name>(
-        buf: &'longest [u8],
-    ) -> Result<Self, TlvLvError> {
-        if buf.len() < 2 {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: 2,
-            })
-            .into());
-        }
-        verify_tlv_type(buf[0], TlvType::FilestoreRequest)?;
-        let len = buf[1] as usize;
-        let mut current_idx = 2;
-        let action_code = FilestoreActionCode::try_from((buf[2] >> 4) & 0b1111)
-            .map_err(|_| TlvLvError::InvalidFilestoreActionCode((buf[2] >> 4) & 0b1111))?;
-        current_idx += 1;
-        let first_name = Lv::from_bytes(&buf[current_idx..])?;
-        let mut second_name = None;
-
-        current_idx += first_name.len_full();
-        if Self::has_second_filename(action_code) {
-            if current_idx >= 2 + len {
-                return Err(TlvLvError::SecondNameMissing);
-            }
-            second_name = Some(Lv::from_bytes(&buf[current_idx..])?);
-        }
-        Ok(Self {
-            action_code,
-            first_name,
-            second_name,
-        })
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::cfdp::lv::Lv;
-    use crate::cfdp::tlv::{FilestoreActionCode, FilestoreRequestTlv, Tlv, TlvType, TlvTypeField};
-    use crate::cfdp::TlvLvError;
-    use crate::util::{UbfU8, UnsignedEnum};
-
-    const TLV_TEST_STR_0: &'static str = "hello.txt";
-    const TLV_TEST_STR_1: &'static str = "hello2.txt";
-
-    #[test]
-    fn test_basic() {
-        let entity_id = UbfU8::new(5);
-        let mut buf: [u8; 4] = [0; 4];
-        assert!(entity_id.write_to_be_bytes(&mut buf).is_ok());
-        let tlv_res = Tlv::new(TlvType::EntityId, &buf[0..1]);
-        assert!(tlv_res.is_ok());
-        let tlv_res = tlv_res.unwrap();
-        assert_eq!(
-            tlv_res.tlv_type_field(),
-            TlvTypeField::Standard(TlvType::EntityId)
-        );
-        assert_eq!(tlv_res.len_full(), 3);
-        assert_eq!(tlv_res.len_value(), 1);
-        assert!(!tlv_res.is_empty());
-        assert!(tlv_res.value().is_some());
-        assert_eq!(tlv_res.value().unwrap()[0], 5);
-    }
-
-    #[test]
-    fn test_serialization() {
-        let entity_id = UbfU8::new(5);
-        let mut buf: [u8; 4] = [0; 4];
-        assert!(entity_id.write_to_be_bytes(&mut buf).is_ok());
-        let tlv_res = Tlv::new(TlvType::EntityId, &buf[0..1]);
-        assert!(tlv_res.is_ok());
-        let tlv_res = tlv_res.unwrap();
-        let mut ser_buf: [u8; 4] = [0; 4];
-        assert!(tlv_res.write_to_bytes(&mut ser_buf).is_ok());
-        assert_eq!(ser_buf[0], TlvType::EntityId as u8);
-        assert_eq!(ser_buf[1], 1);
-        assert_eq!(ser_buf[2], 5);
-    }
-
-    #[test]
-    fn test_deserialization() {
-        let entity_id = UbfU8::new(5);
-        let mut buf: [u8; 4] = [0; 4];
-        assert!(entity_id.write_to_be_bytes(&mut buf[2..]).is_ok());
-        buf[0] = TlvType::EntityId as u8;
-        buf[1] = 1;
-        let tlv_from_raw = Tlv::from_bytes(&mut buf);
-        assert!(tlv_from_raw.is_ok());
-        let tlv_from_raw = tlv_from_raw.unwrap();
-        assert_eq!(
-            tlv_from_raw.tlv_type_field(),
-            TlvTypeField::Standard(TlvType::EntityId)
-        );
-        assert_eq!(tlv_from_raw.len_value(), 1);
-        assert_eq!(tlv_from_raw.len_full(), 3);
-        assert!(tlv_from_raw.value().is_some());
-        assert_eq!(tlv_from_raw.value().unwrap()[0], 5);
-    }
-
-    #[test]
-    fn test_empty() {
-        let tlv_empty = Tlv::new_empty(TlvType::MsgToUser);
-        assert!(tlv_empty.value().is_none());
-        assert!(tlv_empty.is_empty());
-        assert_eq!(tlv_empty.len_full(), 2);
-        assert_eq!(tlv_empty.len_value(), 0);
-        assert_eq!(
-            tlv_empty.tlv_type_field(),
-            TlvTypeField::Standard(TlvType::MsgToUser)
-        );
-    }
-
-    #[test]
-    fn test_empty_serialization() {
-        let tlv_empty = Tlv::new_empty(TlvType::MsgToUser);
-        let mut buf: [u8; 4] = [0; 4];
-        assert!(tlv_empty.write_to_bytes(&mut buf).is_ok());
-        assert_eq!(buf[0], TlvType::MsgToUser as u8);
-        assert_eq!(buf[1], 0);
-    }
-
-    #[test]
-    fn test_empty_deserialization() {
-        let mut buf: [u8; 4] = [0; 4];
-        buf[0] = TlvType::MsgToUser as u8;
-        buf[1] = 0;
-        let tlv_empty = Tlv::from_bytes(&mut buf);
-        assert!(tlv_empty.is_ok());
-        let tlv_empty = tlv_empty.unwrap();
-        assert!(tlv_empty.is_empty());
-        assert!(tlv_empty.value().is_none());
-        assert_eq!(
-            tlv_empty.tlv_type_field(),
-            TlvTypeField::Standard(TlvType::MsgToUser)
-        );
-        assert_eq!(tlv_empty.len_full(), 2);
-        assert_eq!(tlv_empty.len_value(), 0);
-    }
-
-    #[test]
-    fn test_buf_too_large() {
-        let buf_too_large: [u8; u8::MAX as usize + 1] = [0; u8::MAX as usize + 1];
-        let tlv_res = Tlv::new(TlvType::MsgToUser, &buf_too_large);
-        assert!(tlv_res.is_err());
-        let error = tlv_res.unwrap_err();
-        if let TlvLvError::DataTooLarge(size) = error {
-            assert_eq!(size, u8::MAX as usize + 1);
-        } else {
-            panic!("unexpected error {:?}", error);
-        }
-    }
-
-    #[test]
-    fn test_deserialization_custom_tlv_type() {
-        let mut buf: [u8; 4] = [0; 4];
-        buf[0] = 3;
-        buf[1] = 1;
-        buf[2] = 5;
-        let tlv = Tlv::from_bytes(&mut buf);
-        assert!(tlv.is_ok());
-        let tlv = tlv.unwrap();
-        assert_eq!(tlv.tlv_type_field(), TlvTypeField::Custom(3));
-        assert_eq!(tlv.len_value(), 1);
-        assert_eq!(tlv.len_full(), 3);
-    }
-
-    fn generic_fs_request_test_one_file(
-        action_code: FilestoreActionCode,
-    ) -> FilestoreRequestTlv<'static, 'static> {
-        assert!(!FilestoreRequestTlv::has_second_filename(action_code));
-        let first_name = Lv::new_from_str(TLV_TEST_STR_0).unwrap();
-        let fs_request = match action_code {
-            FilestoreActionCode::CreateFile => FilestoreRequestTlv::new_create_file(first_name),
-            FilestoreActionCode::DeleteFile => FilestoreRequestTlv::new_delete_file(first_name),
-            FilestoreActionCode::CreateDirectory => {
-                FilestoreRequestTlv::new_create_directory(first_name)
-            }
-            FilestoreActionCode::RemoveDirectory => {
-                FilestoreRequestTlv::new_remove_directory(first_name)
-            }
-            FilestoreActionCode::DenyFile => FilestoreRequestTlv::new_deny_file(first_name),
-            FilestoreActionCode::DenyDirectory => {
-                FilestoreRequestTlv::new_deny_directory(first_name)
-            }
-            _ => panic!("invalid action code"),
-        };
-        assert!(fs_request.is_ok());
-        let fs_request = fs_request.unwrap();
-        assert_eq!(fs_request.len_value(), 1 + first_name.len_full());
-        assert_eq!(fs_request.len_full(), fs_request.len_value() + 2);
-        assert_eq!(fs_request.action_code(), action_code);
-        assert_eq!(fs_request.first_name(), first_name);
-        assert_eq!(fs_request.second_name(), None);
-        fs_request
-    }
-
-    fn generic_fs_request_test_two_files(
-        action_code: FilestoreActionCode,
-    ) -> FilestoreRequestTlv<'static, 'static> {
-        assert!(FilestoreRequestTlv::has_second_filename(action_code));
-        let first_name = Lv::new_from_str(TLV_TEST_STR_0).unwrap();
-        let second_name = Lv::new_from_str(TLV_TEST_STR_1).unwrap();
-        let fs_request = match action_code {
-            FilestoreActionCode::ReplaceFile => {
-                FilestoreRequestTlv::new_replace_file(first_name, second_name)
-            }
-            FilestoreActionCode::AppendFile => {
-                FilestoreRequestTlv::new_append_file(first_name, second_name)
-            }
-            FilestoreActionCode::RenameFile => {
-                FilestoreRequestTlv::new_rename_file(first_name, second_name)
-            }
-            _ => panic!("invalid action code"),
-        };
-        assert!(fs_request.is_ok());
-        let fs_request = fs_request.unwrap();
-        assert_eq!(
-            fs_request.len_value(),
-            1 + first_name.len_full() + second_name.len_full()
-        );
-        assert_eq!(fs_request.len_full(), fs_request.len_value() + 2);
-        assert_eq!(fs_request.action_code(), action_code);
-        assert_eq!(fs_request.first_name(), first_name);
-        assert!(fs_request.second_name().is_some());
-        assert_eq!(fs_request.second_name().unwrap(), second_name);
-        fs_request
-    }
-
-    #[test]
-    fn test_fs_request_basic_create_file() {
-        generic_fs_request_test_one_file(FilestoreActionCode::CreateFile);
-    }
-
-    #[test]
-    fn test_fs_request_basic_delete() {
-        generic_fs_request_test_one_file(FilestoreActionCode::DeleteFile);
-    }
-
-    #[test]
-    fn test_fs_request_basic_create_dir() {
-        generic_fs_request_test_one_file(FilestoreActionCode::CreateDirectory);
-    }
-
-    #[test]
-    fn test_fs_request_basic_remove_dir() {
-        generic_fs_request_test_one_file(FilestoreActionCode::RemoveDirectory);
-    }
-
-    #[test]
-    fn test_fs_request_basic_deny_file() {
-        generic_fs_request_test_one_file(FilestoreActionCode::DenyFile);
-    }
-
-    #[test]
-    fn test_fs_request_basic_deny_dir() {
-        generic_fs_request_test_one_file(FilestoreActionCode::DenyDirectory);
-    }
-
-    #[test]
-    fn test_fs_request_basic_append_file() {
-        generic_fs_request_test_two_files(FilestoreActionCode::AppendFile);
-    }
-
-    #[test]
-    fn test_fs_request_basic_rename_file() {
-        generic_fs_request_test_two_files(FilestoreActionCode::RenameFile);
-    }
-
-    #[test]
-    fn test_fs_request_basic_replace_file() {
-        generic_fs_request_test_two_files(FilestoreActionCode::ReplaceFile);
-    }
-
-    fn check_fs_request_first_part(
-        buf: &[u8],
-        action_code: FilestoreActionCode,
-        expected_val_len: u8,
-    ) -> usize {
-        assert_eq!(buf[0], TlvType::FilestoreRequest as u8);
-        assert_eq!(buf[1], expected_val_len);
-        assert_eq!((buf[2] >> 4) & 0b1111, action_code as u8);
-        let lv = Lv::from_bytes(&buf[3..]);
-        assert!(lv.is_ok());
-        let lv = lv.unwrap();
-        assert_eq!(lv.value_as_str().unwrap().unwrap(), TLV_TEST_STR_0);
-        3 + lv.len_full()
-    }
-
-    #[test]
-    fn test_fs_request_serialization_one_file() {
-        let req = generic_fs_request_test_one_file(FilestoreActionCode::CreateFile);
-        let mut buf: [u8; 64] = [0; 64];
-        let res = req.write_to_bytes(&mut buf);
-        assert!(res.is_ok());
-        let written = res.unwrap();
-        assert_eq!(written, 3 + 1 + TLV_TEST_STR_0.len());
-        assert_eq!(written, req.len_full());
-        check_fs_request_first_part(
-            &buf,
-            FilestoreActionCode::CreateFile,
-            1 + 1 + TLV_TEST_STR_0.len() as u8,
-        );
-    }
-
-    #[test]
-    fn test_fs_request_deserialization_one_file() {
-        let req = generic_fs_request_test_one_file(FilestoreActionCode::CreateFile);
-        let mut buf: [u8; 64] = [0; 64];
-        let res = req.write_to_bytes(&mut buf);
-        assert!(res.is_ok());
-        let req_conv_back = FilestoreRequestTlv::from_bytes(&buf);
-        assert!(req_conv_back.is_ok());
-        let req_conv_back = req_conv_back.unwrap();
-        assert_eq!(req_conv_back, req);
-    }
-
-    #[test]
-    fn test_fs_request_serialization_two_files() {
-        let req = generic_fs_request_test_two_files(FilestoreActionCode::RenameFile);
-        let mut buf: [u8; 64] = [0; 64];
-        let res = req.write_to_bytes(&mut buf);
-        assert!(res.is_ok());
-        let written = res.unwrap();
-        assert_eq!(written, req.len_full());
-        assert_eq!(
-            written,
-            3 + 1 + TLV_TEST_STR_0.len() + 1 + TLV_TEST_STR_1.len()
-        );
-        let current_idx = check_fs_request_first_part(
-            &buf,
-            FilestoreActionCode::RenameFile,
-            1 + 1 + TLV_TEST_STR_0.len() as u8 + 1 + TLV_TEST_STR_1.len() as u8,
-        );
-        let second_lv = Lv::from_bytes(&buf[current_idx..]);
-        assert!(second_lv.is_ok());
-        let second_lv = second_lv.unwrap();
-        assert_eq!(second_lv.value_as_str().unwrap().unwrap(), TLV_TEST_STR_1);
-        assert_eq!(current_idx + second_lv.len_full(), req.len_full());
-    }
-
-    #[test]
-    fn test_fs_request_deserialization_two_files() {
-        let req = generic_fs_request_test_two_files(FilestoreActionCode::RenameFile);
-        let mut buf: [u8; 64] = [0; 64];
-        req.write_to_bytes(&mut buf).unwrap();
-        let req_conv_back = FilestoreRequestTlv::from_bytes(&buf);
-        assert!(req_conv_back.is_ok());
-        let req_conv_back = req_conv_back.unwrap();
-        assert_eq!(req_conv_back, req);
-    }
-}

src/cfdp/tlv/msg_to_user.rs

@@ -0,0 +1,224 @@
+//! Abstractions for the Message to User CFDP TLV subtype.
+#[cfg(feature = "alloc")]
+use super::TlvOwned;
+use super::{GenericTlv, ReadableTlv, Tlv, TlvLvError, TlvType, TlvTypeField, WritableTlv};
+use crate::{cfdp::{InvalidTlvTypeFieldError, TlvLvDataTooLargeError}, ByteConversionError};
+use delegate::delegate;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct MsgToUserTlv<'data> {
+    pub tlv: Tlv<'data>,
+}
+
+impl<'data> MsgToUserTlv<'data> {
+    /// Create a new message to user TLV where the type field is set correctly.
+    pub fn new(value: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvDataTooLargeError> {
+        Ok(Self {
+            tlv: Tlv::new(TlvType::MsgToUser, value)?,
+        })
+    }
+
+    delegate! {
+        to self.tlv {
+            pub fn value(&self) -> &[u8];
+            /// Helper method to retrieve the length of the value. Simply calls the [slice::len] method of
+            /// [Self::value]
+            pub fn len_value(&self) -> usize;
+            /// Returns the full raw length, including the length byte.
+            pub fn len_full(&self) -> usize;
+            /// Checks whether the value field is empty.
+            pub fn is_empty(&self) -> bool;
+            /// If the TLV was generated from a raw bytestream using [Self::from_bytes], the raw start
+            /// of the TLV can be retrieved with this method.
+            pub fn raw_data(&self) -> Option<&[u8]>;
+        }
+    }
+
+    pub fn is_standard_tlv(&self) -> bool {
+        true
+    }
+
+    pub fn tlv_type(&self) -> Option<TlvType> {
+        Some(TlvType::MsgToUser)
+    }
+
+    /// Check whether this message is a reserved CFDP message like a Proxy Operation Message.
+    pub fn is_reserved_cfdp_msg(&self) -> bool {
+        if self.value().len() < 4 {
+            return false;
+        }
+        let value = self.value();
+        if value[0] == b'c' && value[1] == b'f' && value[2] == b'd' && value[3] == b'p' {
+            return true;
+        }
+        false
+    }
+
+    /// This is a thin wrapper around [Tlv::from_bytes] with the additional type check.
+    pub fn from_bytes(buf: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvError> {
+        let msg_to_user = Self {
+            tlv: Tlv::from_bytes(buf)?,
+        };
+        match msg_to_user.tlv.tlv_type_field() {
+            TlvTypeField::Standard(tlv_type) => {
+                if tlv_type != TlvType::MsgToUser {
+                    return Err(InvalidTlvTypeFieldError {
+                        found: tlv_type as u8,
+                        expected: Some(TlvType::MsgToUser as u8),
+                    }.into());
+                }
+            }
+            TlvTypeField::Custom(raw) => {
+                return Err(InvalidTlvTypeFieldError {
+                    found: raw,
+                    expected: Some(TlvType::MsgToUser as u8),
+                }.into());
+            }
+        }
+        Ok(msg_to_user)
+    }
+
+    pub fn to_tlv(&self) -> Tlv<'data> {
+        self.tlv
+    }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        self.tlv.to_owned()
+    }
+}
+
+impl<'a> From<MsgToUserTlv<'a>> for Tlv<'a> {
+    fn from(value: MsgToUserTlv<'a>) -> Tlv<'a> {
+        value.to_tlv()
+    }
+}
+
+impl WritableTlv for MsgToUserTlv<'_> {
+    fn len_written(&self) -> usize {
+        self.len_full()
+    }
+
+    delegate!(
+        to self.tlv {
+            fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
+        }
+    );
+}
+
+impl GenericTlv for MsgToUserTlv<'_> {
+    fn tlv_type_field(&self) -> TlvTypeField {
+        self.tlv.tlv_type_field()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_basic() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value);
+        assert!(msg_to_user.is_ok());
+        let msg_to_user = msg_to_user.unwrap();
+        assert!(msg_to_user.is_standard_tlv());
+        assert_eq!(msg_to_user.tlv_type().unwrap(), TlvType::MsgToUser);
+        assert_eq!(
+            msg_to_user.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::MsgToUser)
+        );
+        assert_eq!(msg_to_user.value(), custom_value);
+        assert_eq!(msg_to_user.value().len(), 4);
+        assert_eq!(msg_to_user.len_value(), 4);
+        assert_eq!(msg_to_user.len_full(), 6);
+        assert!(!msg_to_user.is_empty());
+        assert!(msg_to_user.raw_data().is_none());
+        assert!(!msg_to_user.is_reserved_cfdp_msg());
+    }
+
+    #[test]
+    fn test_reserved_msg_serialization() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let mut buf: [u8; 6] = [0; 6];
+        msg_to_user.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(
+            buf,
+            [
+                TlvType::MsgToUser as u8,
+                custom_value.len() as u8,
+                1,
+                2,
+                3,
+                4
+            ]
+        );
+    }
+
+    #[test]
+    fn test_msg_to_user_type_reduction() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let tlv = msg_to_user.to_tlv();
+        assert_eq!(
+            tlv.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::MsgToUser)
+        );
+
+        assert_eq!(tlv.value(), custom_value);
+    }
+
+    #[test]
+    fn test_msg_to_user_to_tlv() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let tlv: Tlv = msg_to_user.into();
+        assert_eq!(msg_to_user.to_tlv(), tlv);
+    }
+
+    #[test]
+    fn test_msg_to_user_owner_converter() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let tlv = msg_to_user.to_owned();
+        assert_eq!(
+            tlv.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::MsgToUser)
+        );
+
+        assert_eq!(tlv.value(), custom_value);
+    }
+
+    #[test]
+    fn test_reserved_msg_deserialization() {
+        let custom_value: [u8; 3] = [1, 2, 3];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let msg_to_user_vec = msg_to_user.to_vec();
+        let msg_to_user_from_bytes = MsgToUserTlv::from_bytes(&msg_to_user_vec).unwrap();
+        assert!(!msg_to_user.is_reserved_cfdp_msg());
+        assert_eq!(msg_to_user_from_bytes, msg_to_user);
+        assert_eq!(msg_to_user_from_bytes.value(), msg_to_user.value());
+        assert_eq!(msg_to_user_from_bytes.tlv_type(), msg_to_user.tlv_type());
+    }
+    #[test]
+    fn test_reserved_msg_deserialization_invalid_type() {
+        let trash: [u8; 5] = [TlvType::FlowLabel as u8, 3, 1, 2, 3];
+        let error = MsgToUserTlv::from_bytes(&trash).unwrap_err();
+        if let TlvLvError::InvalidTlvTypeField(inner) = error {
+            assert_eq!(inner.found, TlvType::FlowLabel as u8);
+            assert_eq!(inner.expected, Some(TlvType::MsgToUser as u8));
+        } else {
+            panic!("Wrong error type returned: {:?}", error);
+        }
+    }
+
+    #[test]
+    fn test_reserved_msg() {
+        let reserved_str = "cfdp";
+        let msg_to_user = MsgToUserTlv::new(reserved_str.as_bytes());
+        assert!(msg_to_user.is_ok());
+        let msg_to_user = msg_to_user.unwrap();
+        assert!(msg_to_user.is_reserved_cfdp_msg());
+    }
+}

src/ecss/hk.rs

@@ -5,6 +5,7 @@ use serde::{Deserialize, Serialize};
 
 #[derive(Debug, Eq, PartialEq, Copy, Clone, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 pub enum Subservice {
     // Regular HK
@@ -29,3 +30,33 @@ pub enum Subservice {
     TcGenerateOneShotDiag = 28,
     TcModifyDiagCollectionInterval = 32,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_try_from_u8() {
+        let hk_report_subservice_raw = 25;
+        let hk_report: Subservice = Subservice::try_from(hk_report_subservice_raw).unwrap();
+        assert_eq!(hk_report, Subservice::TmHkPacket);
+    }
+
+    #[test]
+    fn test_into_u8() {
+        let hk_report_raw: u8 = Subservice::TmHkPacket.into();
+        assert_eq!(hk_report_raw, 25);
+    }
+
+    #[test]
+    fn test_partial_eq() {
+        let hk_report_raw = Subservice::TmHkPacket;
+        assert_ne!(hk_report_raw, Subservice::TcGenerateOneShotHk);
+        assert_eq!(hk_report_raw, Subservice::TmHkPacket);
+    }
+    #[test]
+    fn test_copy_clone() {
+        let hk_report = Subservice::TmHkPacket;
+        let hk_report_copy = hk_report;
+        assert_eq!(hk_report, hk_report_copy);
+    }
+}

src/ecss/mod.rs

@@ -1,16 +1,16 @@
 //! Common definitions and helpers required to create PUS TMTC packets according to
 //! [ECSS-E-ST-70-41C](https://ecss.nl/standard/ecss-e-st-70-41c-space-engineering-telemetry-and-telecommand-packet-utilization-15-april-2016/)
 //!
-//! You can find the PUS telecommand definitions in the [tc] module and ithe PUS telemetry definitions
-//! inside the [tm] module.
+//! You can find the PUS telecommand types in the [tc] module and the the PUS telemetry
+//! types inside the [tm] module.
 use crate::{ByteConversionError, CcsdsPacket, CRC_CCITT_FALSE};
-use core::fmt::{Debug, Display, Formatter};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
+use core::fmt::Debug;
 use core::mem::size_of;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
-#[cfg(feature = "std")]
-use std::error::Error;
 
 pub mod event;
 pub mod hk;
@@ -20,7 +20,6 @@ pub mod tm;
 pub mod verification;
 
 pub type CrcType = u16;
-pub const CCSDS_HEADER_LEN: usize = size_of::<crate::zc::SpHeader>();
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
@@ -72,6 +71,8 @@ pub enum PusServiceId {
 /// All PUS versions. Only PUS C is supported by this library.
 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[non_exhaustive]
 pub enum PusVersion {
     EsaPus = 0,
     PusA = 1,
@@ -93,8 +94,9 @@ impl TryFrom<u8> for PusVersion {
 }
 
 /// ECSS Packet Type Codes (PTC)s.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
 pub enum PacketTypeCodes {
     Boolean = 1,
     Enumerated = 2,
@@ -113,9 +115,10 @@ pub enum PacketTypeCodes {
 pub type Ptc = PacketTypeCodes;
 
 /// ECSS Packet Field Codes (PFC)s for the unsigned [Ptc].
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub enum UnsignedPfc {
+#[repr(u8)]
+pub enum PfcUnsigned {
     OneByte = 4,
     TwelveBits = 8,
     TwoBytes = 12,
@@ -129,9 +132,10 @@ pub enum UnsignedPfc {
 }
 
 /// ECSS Packet Field Codes (PFC)s for the real (floating point) [Ptc].
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub enum RealPfc {
+#[repr(u8)]
+pub enum PfcReal {
     /// 4 octets simple precision format (IEEE)
     Float = 1,
     /// 8 octets simple precision format (IEEE)
@@ -142,60 +146,19 @@ pub enum RealPfc {
     DoubleMilStd = 4,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, thiserror::Error)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum PusError {
+    #[error("PUS version {0:?} not supported")]
     VersionNotSupported(PusVersion),
-    IncorrectCrc(u16),
-    RawDataTooShort(usize),
-    NoRawData,
+    #[error("checksum verification for crc16 {0:#06x} failed")]
+    ChecksumFailure(u16),
     /// CRC16 needs to be calculated first
-    CrcCalculationMissing,
-    ByteConversion(ByteConversionError),
-}
-
-impl Display for PusError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
-        match self {
-            PusError::VersionNotSupported(v) => {
-                write!(f, "PUS version {v:?} not supported")
-            }
-            PusError::IncorrectCrc(crc) => {
-                write!(f, "crc16 {crc:#04x} is incorrect")
-            }
-            PusError::RawDataTooShort(size) => {
-                write!(
-                    f,
-                    "deserialization error, provided raw data with size {size} too short"
-                )
-            }
-            PusError::NoRawData => {
-                write!(f, "no raw data provided")
-            }
-            PusError::CrcCalculationMissing => {
-                write!(f, "crc16 was not calculated")
-            }
-            PusError::ByteConversion(e) => {
-                write!(f, "low level byte conversion error: {e}")
-            }
-        }
-    }
-}
-
-#[cfg(feature = "std")]
-impl Error for PusError {
-    fn source(&self) -> Option<&(dyn Error + 'static)> {
-        if let PusError::ByteConversion(e) = self {
-            return Some(e);
-        }
-        None
-    }
-}
-
-impl From<ByteConversionError> for PusError {
-    fn from(e: ByteConversionError) -> Self {
-        PusError::ByteConversion(e)
-    }
+    //#[error("crc16 was not calculated")]
+    //CrcCalculationMissing,
+    #[error("pus error: {0}")]
+    ByteConversion(#[from] ByteConversionError),
 }
 
 /// Generic trait to describe common attributes for both PUS Telecommands (TC) and PUS Telemetry
@@ -210,9 +173,12 @@ pub trait PusPacket: CcsdsPacket {
     fn crc16(&self) -> Option<u16>;
 }
 
-pub(crate) fn crc_from_raw_data(raw_data: &[u8]) -> Result<u16, PusError> {
+pub(crate) fn crc_from_raw_data(raw_data: &[u8]) -> Result<u16, ByteConversionError> {
     if raw_data.len() < 2 {
-        return Err(PusError::RawDataTooShort(raw_data.len()));
+        return Err(ByteConversionError::FromSliceTooSmall {
+            found: raw_data.len(),
+            expected: 2,
+        });
     }
     Ok(u16::from_be_bytes(
         raw_data[raw_data.len() - 2..raw_data.len()]
@@ -227,32 +193,16 @@ pub(crate) fn calc_pus_crc16(bytes: &[u8]) -> u16 {
     digest.finalize()
 }
 
-pub(crate) fn crc_procedure(
-    calc_on_serialization: bool,
-    cached_crc16: &Option<u16>,
-    start_idx: usize,
-    curr_idx: usize,
-    slice: &[u8],
-) -> Result<u16, PusError> {
-    let crc16;
-    if calc_on_serialization {
-        crc16 = calc_pus_crc16(&slice[start_idx..curr_idx])
-    } else if cached_crc16.is_none() {
-        return Err(PusError::CrcCalculationMissing);
-    } else {
-        crc16 = cached_crc16.unwrap();
-    }
-    Ok(crc16)
-}
-
 pub(crate) fn user_data_from_raw(
     current_idx: usize,
     total_len: usize,
-    raw_data_len: usize,
     slice: &[u8],
-) -> Result<&[u8], PusError> {
+) -> Result<&[u8], ByteConversionError> {
     match current_idx {
-        _ if current_idx > total_len - 2 => Err(PusError::RawDataTooShort(raw_data_len)),
+        _ if current_idx > total_len - 2 => Err(ByteConversionError::FromSliceTooSmall {
+            found: total_len - 2,
+            expected: current_idx,
+        }),
         _ => Ok(&slice[current_idx..total_len - 2]),
     }
 }
@@ -262,8 +212,8 @@ pub(crate) fn verify_crc16_ccitt_false_from_raw_to_pus_error(
     crc16: u16,
 ) -> Result<(), PusError> {
     verify_crc16_ccitt_false_from_raw(raw_data)
-        .then(|| ())
-        .ok_or(PusError::IncorrectCrc(crc16))
+        .then_some(())
+        .ok_or(PusError::ChecksumFailure(crc16))
 }
 
 pub(crate) fn verify_crc16_ccitt_false_from_raw(raw_data: &[u8]) -> bool {
@@ -278,9 +228,13 @@ pub(crate) fn verify_crc16_ccitt_false_from_raw(raw_data: &[u8]) -> bool {
 macro_rules! ccsds_impl {
     () => {
         delegate!(to self.sp_header {
+            #[inline]
             fn ccsds_version(&self) -> u8;
+            #[inline]
             fn packet_id(&self) -> crate::PacketId;
+            #[inline]
             fn psc(&self) -> crate::PacketSequenceCtrl;
+            #[inline]
             fn data_len(&self) -> u16;
         });
     }
@@ -289,8 +243,11 @@ macro_rules! ccsds_impl {
 macro_rules! sp_header_impls {
     () => {
         delegate!(to self.sp_header {
+            #[inline]
             pub fn set_apid(&mut self, apid: u16) -> bool;
+            #[inline]
             pub fn set_seq_count(&mut self, seq_count: u16) -> bool;
+            #[inline]
             pub fn set_seq_flags(&mut self, seq_flag: SequenceFlags);
         });
     }
@@ -313,15 +270,19 @@ pub trait EcssEnumerationExt: EcssEnumeration + Debug + Copy + Clone + PartialEq
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct GenericEcssEnumWrapper<TYPE> {
+pub struct GenericEcssEnumWrapper<TYPE: Copy + Into<u64>> {
     field: GenericUnsignedByteField<TYPE>,
 }
 
-impl<TYPE> GenericEcssEnumWrapper<TYPE> {
+impl<TYPE: Copy + Into<u64>> GenericEcssEnumWrapper<TYPE> {
     pub const fn ptc() -> PacketTypeCodes {
         PacketTypeCodes::Enumerated
     }
 
+    pub const fn value_typed(&self) -> TYPE {
+        self.field.value_typed()
+    }
+
     pub fn new(val: TYPE) -> Self {
         Self {
             field: GenericUnsignedByteField::new(val),
@@ -329,7 +290,7 @@ impl<TYPE> GenericEcssEnumWrapper<TYPE> {
     }
 }
 
-impl<TYPE: ToBeBytes> UnsignedEnum for GenericEcssEnumWrapper<TYPE> {
+impl<TYPE: Copy + ToBeBytes + Into<u64>> UnsignedEnum for GenericEcssEnumWrapper<TYPE> {
     fn size(&self) -> usize {
         (self.pfc() / 8) as usize
     }
@@ -337,45 +298,97 @@ impl<TYPE: ToBeBytes> UnsignedEnum for GenericEcssEnumWrapper<TYPE> {
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         self.field.write_to_be_bytes(buf)
     }
+
+    fn value(&self) -> u64 {
+        self.field.value()
+    }
 }
 
-impl<TYPE: ToBeBytes> EcssEnumeration for GenericEcssEnumWrapper<TYPE> {
+impl<TYPE: Copy + ToBeBytes + Into<u64>> EcssEnumeration for GenericEcssEnumWrapper<TYPE> {
     fn pfc(&self) -> u8 {
         size_of::<TYPE>() as u8 * 8_u8
     }
 }
 
-impl<TYPE: Debug + Copy + Clone + PartialEq + Eq + ToBeBytes> EcssEnumerationExt
+impl<TYPE: Debug + Copy + Clone + PartialEq + Eq + ToBeBytes + Into<u64>> EcssEnumerationExt
     for GenericEcssEnumWrapper<TYPE>
 {
 }
 
-pub type EcssEnumU8 = GenericEcssEnumWrapper<u8>;
-pub type EcssEnumU16 = GenericEcssEnumWrapper<u16>;
-pub type EcssEnumU32 = GenericEcssEnumWrapper<u32>;
-pub type EcssEnumU64 = GenericEcssEnumWrapper<u64>;
+impl<T: Copy + Into<u64>> From<T> for GenericEcssEnumWrapper<T> {
+    fn from(value: T) -> Self {
+        Self::new(value)
+    }
+}
+
+macro_rules! generic_ecss_enum_typedefs_and_from_impls {
+    ($($ty:ty => $Enum:ident),*) => {
+        $(
+            pub type $Enum = GenericEcssEnumWrapper<$ty>;
+
+            impl From<$Enum> for $ty {
+                fn from(value: $Enum) -> Self {
+                    value.value_typed()
+                }
+            }
+        )*
+    };
+}
+
+// Generates EcssEnum<$TY> type definitions as well as a From<$TY> for EcssEnum<$TY>
+// implementation.
+generic_ecss_enum_typedefs_and_from_impls! {
+    u8 => EcssEnumU8,
+    u16 => EcssEnumU16,
+    u32 => EcssEnumU32,
+    u64 => EcssEnumU64
+}
 
 /// Generic trait for PUS packet abstractions which can written to a raw slice as their raw
 /// byte representation. This is especially useful for generic abstractions which depend only
 /// on the serialization of those packets.
-pub trait SerializablePusPacket {
-    fn len_packed(&self) -> usize;
+pub trait WritablePusPacket {
+    fn len_written(&self) -> usize;
     fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError>;
+    #[cfg(feature = "alloc")]
+    fn to_vec(&self) -> Result<Vec<u8>, PusError> {
+        // This is the correct way to do this. See
+        // [this issue](https://github.com/rust-lang/rust-clippy/issues/4483) for caveats of more
+        // "efficient" implementations.
+        let mut vec = alloc::vec![0; self.len_written()];
+        self.write_to_bytes(&mut vec)?;
+        Ok(vec)
+    }
 }
 
 #[cfg(test)]
 mod tests {
+    use alloc::string::ToString;
+
     use crate::ecss::{EcssEnumU16, EcssEnumU32, EcssEnumU8, UnsignedEnum};
     use crate::ByteConversionError;
 
+    use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
+
     #[test]
     fn test_enum_u8() {
         let mut buf = [0, 0, 0];
         let my_enum = EcssEnumU8::new(1);
+        assert_eq!(EcssEnumU8::ptc(), Ptc::Enumerated);
+        assert_eq!(my_enum.size(), 1);
+        assert_eq!(my_enum.pfc(), 8);
         my_enum
             .write_to_be_bytes(&mut buf[1..2])
             .expect("To byte conversion of u8 failed");
         assert_eq!(buf[1], 1);
+        assert_eq!(my_enum.value(), 1);
+        assert_eq!(my_enum.value_typed(), 1);
+        let enum_as_u8: u8 = my_enum.into();
+        assert_eq!(enum_as_u8, 1);
+        let vec = my_enum.to_vec();
+        assert_eq!(vec, buf[1..2]);
     }
 
     #[test]
@@ -385,8 +398,16 @@ mod tests {
         my_enum
             .write_to_be_bytes(&mut buf[1..3])
             .expect("To byte conversion of u8 failed");
+        assert_eq!(my_enum.size(), 2);
+        assert_eq!(my_enum.pfc(), 16);
         assert_eq!(buf[1], 0x1f);
         assert_eq!(buf[2], 0x2f);
+        assert_eq!(my_enum.value(), 0x1f2f);
+        assert_eq!(my_enum.value_typed(), 0x1f2f);
+        let enum_as_raw: u16 = my_enum.into();
+        assert_eq!(enum_as_raw, 0x1f2f);
+        let vec = my_enum.to_vec();
+        assert_eq!(vec, buf[1..3]);
     }
 
     #[test]
@@ -397,9 +418,9 @@ mod tests {
         assert!(res.is_err());
         let error = res.unwrap_err();
         match error {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.expected, 2);
-                assert_eq!(missmatch.found, 1);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(expected, 2);
+                assert_eq!(found, 1);
             }
             _ => {
                 panic!("Unexpected error {:?}", error);
@@ -418,6 +439,12 @@ mod tests {
         assert_eq!(buf[2], 0x2f);
         assert_eq!(buf[3], 0x3f);
         assert_eq!(buf[4], 0x4f);
+        assert_eq!(my_enum.value(), 0x1f2f3f4f);
+        assert_eq!(my_enum.value_typed(), 0x1f2f3f4f);
+        let enum_as_raw: u32 = my_enum.into();
+        assert_eq!(enum_as_raw, 0x1f2f3f4f);
+        let vec = my_enum.to_vec();
+        assert_eq!(vec, buf[1..5]);
     }
 
     #[test]
@@ -428,13 +455,108 @@ mod tests {
         assert!(res.is_err());
         let error = res.unwrap_err();
         match error {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.expected, 4);
-                assert_eq!(missmatch.found, 3);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(expected, 4);
+                assert_eq!(found, 3);
             }
             _ => {
                 panic!("Unexpected error {:?}", error);
             }
         }
     }
+
+    #[test]
+    fn test_enum_u64() {
+        let mut buf = [0; 8];
+        let my_enum = EcssEnumU64::new(0x1f2f3f4f5f);
+        my_enum
+            .write_to_be_bytes(&mut buf)
+            .expect("To byte conversion of u64 failed");
+        assert_eq!(buf[3], 0x1f);
+        assert_eq!(buf[4], 0x2f);
+        assert_eq!(buf[5], 0x3f);
+        assert_eq!(buf[6], 0x4f);
+        assert_eq!(buf[7], 0x5f);
+        assert_eq!(my_enum.value(), 0x1f2f3f4f5f);
+        assert_eq!(my_enum.value_typed(), 0x1f2f3f4f5f);
+        let enum_as_raw: u64 = my_enum.into();
+        assert_eq!(enum_as_raw, 0x1f2f3f4f5f);
+        assert_eq!(u64::from_be_bytes(buf), 0x1f2f3f4f5f);
+        let vec = my_enum.to_vec();
+        assert_eq!(vec, buf);
+    }
+
+    #[test]
+    fn test_pus_error_display() {
+        let unsupport_version = PusError::VersionNotSupported(super::PusVersion::EsaPus);
+        let write_str = unsupport_version.to_string();
+        assert_eq!(write_str, "PUS version EsaPus not supported")
+    }
+
+    #[test]
+    fn test_service_id_from_u8() {
+        let verification_id_raw = 1;
+        let verification_id = PusServiceId::try_from(verification_id_raw).unwrap();
+        assert_eq!(verification_id, PusServiceId::Verification);
+    }
+
+    #[test]
+    fn test_ptc_from_u8() {
+        let ptc_raw = Ptc::AbsoluteTime as u8;
+        let ptc = Ptc::try_from(ptc_raw).unwrap();
+        assert_eq!(ptc, Ptc::AbsoluteTime);
+    }
+
+    #[test]
+    fn test_unsigned_pfc_from_u8() {
+        let pfc_raw = PfcUnsigned::OneByte as u8;
+        let pfc = PfcUnsigned::try_from(pfc_raw).unwrap();
+        assert_eq!(pfc, PfcUnsigned::OneByte);
+    }
+
+    #[test]
+    fn test_real_pfc_from_u8() {
+        let pfc_raw = PfcReal::Double as u8;
+        let pfc = PfcReal::try_from(pfc_raw).unwrap();
+        assert_eq!(pfc, PfcReal::Double);
+    }
+
+    #[test]
+    fn test_pus_error_eq_impl() {
+        assert_eq!(
+            PusError::VersionNotSupported(PusVersion::EsaPus),
+            PusError::VersionNotSupported(PusVersion::EsaPus)
+        );
+    }
+
+    #[test]
+    fn test_pus_error_clonable() {
+        let pus_error = PusError::ChecksumFailure(0x0101);
+        let cloned = pus_error;
+        assert_eq!(pus_error, cloned);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_pus_service_id() {
+        generic_serde_test(PusServiceId::Verification);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_ptc() {
+        generic_serde_test(Ptc::AbsoluteTime);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_pfc_unsigned() {
+        generic_serde_test(PfcUnsigned::EightBytes);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_pfc_real() {
+        generic_serde_test(PfcReal::Double);
+    }
 }

src/ecss/scheduling.rs

@@ -54,6 +54,7 @@ pub enum SchedStatus {
 }
 
 impl From<bool> for SchedStatus {
+    #[inline]
     fn from(value: bool) -> Self {
         if value {
             SchedStatus::Enabled
@@ -76,6 +77,8 @@ pub enum TimeWindowType {
 #[cfg(test)]
 mod tests {
     use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
 
     #[test]
     fn test_bool_conv_0() {
@@ -102,4 +105,22 @@ mod tests {
         let subservice: Subservice = 22u8.try_into().unwrap();
         assert_eq!(subservice, Subservice::TcCreateScheduleGroup);
     }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_subservice_id() {
+        generic_serde_test(Subservice::TcEnableScheduling);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_sched_status() {
+        generic_serde_test(SchedStatus::Enabled);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_time_window_type() {
+        generic_serde_test(TimeWindowType::SelectAll);
+    }
 }

src/seq_count.rs

@@ -0,0 +1,250 @@
+use crate::MAX_SEQ_COUNT;
+use core::cell::Cell;
+use paste::paste;
+#[cfg(feature = "std")]
+pub use stdmod::*;
+
+/// Core trait for objects which can provide a sequence count.
+///
+/// The core functions are not mutable on purpose to allow easier usage with
+/// static structs when using the interior mutability pattern. This can be achieved by using
+/// [Cell], [core::cell::RefCell] or atomic types.
+pub trait SequenceCountProvider {
+    type Raw: Into<u64>;
+    const MAX_BIT_WIDTH: usize;
+
+    fn get(&self) -> Self::Raw;
+
+    fn increment(&self);
+
+    fn get_and_increment(&self) -> Self::Raw {
+        let val = self.get();
+        self.increment();
+        val
+    }
+}
+
+#[derive(Clone)]
+pub struct SeqCountProviderSimple<T: Copy> {
+    seq_count: Cell<T>,
+    max_val: T,
+}
+
+macro_rules! impl_for_primitives {
+    ($($ty: ident,)+) => {
+        $(
+            paste! {
+                impl SeqCountProviderSimple<$ty> {
+                    pub fn [<new_custom_max_val_ $ty>](max_val: $ty) -> Self {
+                        Self {
+                            seq_count: Cell::new(0),
+                            max_val,
+                        }
+                    }
+                    pub fn [<new_ $ty>]() -> Self {
+                        Self {
+                            seq_count: Cell::new(0),
+                            max_val: $ty::MAX
+                        }
+                    }
+                }
+
+                impl Default for SeqCountProviderSimple<$ty> {
+                    fn default() -> Self {
+                        Self::[<new_ $ty>]()
+                    }
+                }
+
+                impl SequenceCountProvider for SeqCountProviderSimple<$ty> {
+                    type Raw = $ty;
+                    const MAX_BIT_WIDTH: usize = core::mem::size_of::<Self::Raw>() * 8;
+
+                    fn get(&self) -> Self::Raw {
+                        self.seq_count.get()
+                    }
+
+                    fn increment(&self) {
+                        self.get_and_increment();
+                    }
+
+                    fn get_and_increment(&self) -> Self::Raw {
+                        let curr_count = self.seq_count.get();
+
+                        if curr_count == self.max_val {
+                            self.seq_count.set(0);
+                        } else {
+                            self.seq_count.set(curr_count + 1);
+                        }
+                        curr_count
+                    }
+                }
+            }
+        )+
+    }
+}
+
+impl_for_primitives!(u8, u16, u32, u64,);
+
+/// This is a sequence count provider which wraps around at [MAX_SEQ_COUNT].
+#[derive(Clone)]
+pub struct CcsdsSimpleSeqCountProvider {
+    provider: SeqCountProviderSimple<u16>,
+}
+
+impl Default for CcsdsSimpleSeqCountProvider {
+    fn default() -> Self {
+        Self {
+            provider: SeqCountProviderSimple::new_custom_max_val_u16(MAX_SEQ_COUNT),
+        }
+    }
+}
+
+impl SequenceCountProvider for CcsdsSimpleSeqCountProvider {
+    type Raw = u16;
+    const MAX_BIT_WIDTH: usize = core::mem::size_of::<Self::Raw>() * 8;
+    delegate::delegate! {
+        to self.provider {
+            fn get(&self) -> u16;
+            fn increment(&self);
+            fn get_and_increment(&self) -> u16;
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+pub mod stdmod {
+    use super::*;
+    use std::sync::{Arc, Mutex};
+
+    macro_rules! sync_clonable_seq_counter_impl {
+         ($($ty: ident,)+) => {
+             $(paste! {
+                 /// These sequence counters can be shared between threads and can also be
+                 /// configured to wrap around at specified maximum values. Please note that
+                 /// that the API provided by this class will not panic und [Mutex] lock errors,
+                 /// but it will yield 0 for the getter functions.
+                 #[derive(Clone, Default)]
+                 pub struct [<SeqCountProviderSync $ty:upper>] {
+                     seq_count: Arc<Mutex<$ty>>,
+                     max_val: $ty
+                 }
+
+                 impl [<SeqCountProviderSync $ty:upper>] {
+                     pub fn new() -> Self {
+                        Self::new_with_max_val($ty::MAX)
+                     }
+
+                     pub fn new_with_max_val(max_val: $ty) -> Self {
+                         Self {
+                             seq_count: Arc::default(),
+                             max_val
+                         }
+                     }
+                 }
+                 impl SequenceCountProvider for [<SeqCountProviderSync $ty:upper>] {
+                    type Raw = $ty;
+                    const MAX_BIT_WIDTH: usize = core::mem::size_of::<Self::Raw>() * 8;
+
+                    fn get(&self) -> $ty {
+                        match self.seq_count.lock() {
+                            Ok(counter) => *counter,
+                            Err(_) => 0
+                        }
+                    }
+
+                    fn increment(&self) {
+                        self.get_and_increment();
+                    }
+
+                    fn get_and_increment(&self) -> $ty {
+                        match self.seq_count.lock() {
+                            Ok(mut counter) => {
+                                let val = *counter;
+                                if val == self.max_val {
+                                    *counter = 0;
+                                } else {
+                                    *counter += 1;
+                                }
+                                val
+                            }
+                            Err(_) => 0,
+                        }
+                    }
+                 }
+             })+
+         }
+    }
+    sync_clonable_seq_counter_impl!(u8, u16, u32, u64,);
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::seq_count::{
+        CcsdsSimpleSeqCountProvider, SeqCountProviderSimple, SeqCountProviderSyncU8,
+        SequenceCountProvider,
+    };
+    use crate::MAX_SEQ_COUNT;
+
+    #[test]
+    fn test_u8_counter() {
+        let u8_counter = SeqCountProviderSimple::<u8>::default();
+        assert_eq!(u8_counter.get(), 0);
+        assert_eq!(u8_counter.get_and_increment(), 0);
+        assert_eq!(u8_counter.get_and_increment(), 1);
+        assert_eq!(u8_counter.get(), 2);
+    }
+
+    #[test]
+    fn test_u8_counter_overflow() {
+        let u8_counter = SeqCountProviderSimple::new_u8();
+        for _ in 0..256 {
+            u8_counter.increment();
+        }
+        assert_eq!(u8_counter.get(), 0);
+    }
+
+    #[test]
+    fn test_ccsds_counter() {
+        let ccsds_counter = CcsdsSimpleSeqCountProvider::default();
+        assert_eq!(ccsds_counter.get(), 0);
+        assert_eq!(ccsds_counter.get_and_increment(), 0);
+        assert_eq!(ccsds_counter.get_and_increment(), 1);
+        assert_eq!(ccsds_counter.get(), 2);
+    }
+
+    #[test]
+    fn test_ccsds_counter_overflow() {
+        let ccsds_counter = CcsdsSimpleSeqCountProvider::default();
+        for _ in 0..MAX_SEQ_COUNT + 1 {
+            ccsds_counter.increment();
+        }
+        assert_eq!(ccsds_counter.get(), 0);
+    }
+
+    #[test]
+    fn test_atomic_ref_counters() {
+        let sync_u8_counter = SeqCountProviderSyncU8::new();
+        assert_eq!(sync_u8_counter.get(), 0);
+        assert_eq!(sync_u8_counter.get_and_increment(), 0);
+        assert_eq!(sync_u8_counter.get_and_increment(), 1);
+        assert_eq!(sync_u8_counter.get(), 2);
+    }
+
+    #[test]
+    fn test_atomic_ref_counters_overflow() {
+        let sync_u8_counter = SeqCountProviderSyncU8::new();
+        for _ in 0..u8::MAX as u16 + 1 {
+            sync_u8_counter.increment();
+        }
+        assert_eq!(sync_u8_counter.get(), 0);
+    }
+
+    #[test]
+    fn test_atomic_ref_counters_overflow_custom_max_val() {
+        let sync_u8_counter = SeqCountProviderSyncU8::new_with_max_val(128);
+        for _ in 0..129 {
+            sync_u8_counter.increment();
+        }
+        assert_eq!(sync_u8_counter.get(), 0);
+    }
+}

src/time/ascii.rs

@@ -2,11 +2,8 @@
 //! [CCSDS 301.0-B-4](https://public.ccsds.org/Pubs/301x0b4e1.pdf) section 3.5 .
 //! See [chrono::DateTime::format] for a usage example of the generated
 //! [chrono::format::DelayedFormat] structs.
-#[cfg(feature = "alloc")]
-use chrono::{
-    format::{DelayedFormat, StrftimeItems},
-    DateTime, Utc,
-};
+#[cfg(all(feature = "alloc", feature = "chrono"))]
+pub use alloc_mod_chrono::*;
 
 /// Tuple of format string and formatted size for time code A.
 ///
@@ -34,36 +31,37 @@ pub const FMT_STR_CODE_B_WITH_SIZE: (&str, usize) = ("%Y-%jT%T%.3f", 21);
 /// Three digits are used for the decimal fraction and a terminator is added at the end.
 pub const FMT_STR_CODE_B_TERMINATED_WITH_SIZE: (&str, usize) = ("%Y-%jT%T%.3fZ", 22);
 
-/// Generates a time code formatter using the [FMT_STR_CODE_A_WITH_SIZE] format.
-#[cfg(feature = "alloc")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-pub fn generate_time_code_a(date: &DateTime<Utc>) -> DelayedFormat<StrftimeItems<'static>> {
-    date.format(FMT_STR_CODE_A_WITH_SIZE.0)
-}
+#[cfg(all(feature = "alloc", feature = "chrono"))]
+pub mod alloc_mod_chrono {
+    use super::*;
+    use chrono::{
+        format::{DelayedFormat, StrftimeItems},
+        DateTime, Utc,
+    };
 
-/// Generates a time code formatter using the [FMT_STR_CODE_A_TERMINATED_WITH_SIZE] format.
-#[cfg(feature = "alloc")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-pub fn generate_time_code_a_terminated(
-    date: &DateTime<Utc>,
-) -> DelayedFormat<StrftimeItems<'static>> {
-    date.format(FMT_STR_CODE_A_TERMINATED_WITH_SIZE.0)
-}
+    /// Generates a time code formatter using the [FMT_STR_CODE_A_WITH_SIZE] format.
+    pub fn generate_time_code_a(date: &DateTime<Utc>) -> DelayedFormat<StrftimeItems<'static>> {
+        date.format(FMT_STR_CODE_A_WITH_SIZE.0)
+    }
 
-/// Generates a time code formatter using the [FMT_STR_CODE_B_WITH_SIZE] format.
-#[cfg(feature = "alloc")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-pub fn generate_time_code_b(date: &DateTime<Utc>) -> DelayedFormat<StrftimeItems<'static>> {
-    date.format(FMT_STR_CODE_B_WITH_SIZE.0)
-}
+    /// Generates a time code formatter using the [FMT_STR_CODE_A_TERMINATED_WITH_SIZE] format.
+    pub fn generate_time_code_a_terminated(
+        date: &DateTime<Utc>,
+    ) -> DelayedFormat<StrftimeItems<'static>> {
+        date.format(FMT_STR_CODE_A_TERMINATED_WITH_SIZE.0)
+    }
 
-/// Generates a time code formatter using the [FMT_STR_CODE_B_TERMINATED_WITH_SIZE] format.
-#[cfg(feature = "alloc")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-pub fn generate_time_code_b_terminated(
-    date: &DateTime<Utc>,
-) -> DelayedFormat<StrftimeItems<'static>> {
-    date.format(FMT_STR_CODE_B_TERMINATED_WITH_SIZE.0)
+    /// Generates a time code formatter using the [FMT_STR_CODE_B_WITH_SIZE] format.
+    pub fn generate_time_code_b(date: &DateTime<Utc>) -> DelayedFormat<StrftimeItems<'static>> {
+        date.format(FMT_STR_CODE_B_WITH_SIZE.0)
+    }
+
+    /// Generates a time code formatter using the [FMT_STR_CODE_B_TERMINATED_WITH_SIZE] format.
+    pub fn generate_time_code_b_terminated(
+        date: &DateTime<Utc>,
+    ) -> DelayedFormat<StrftimeItems<'static>> {
+        date.format(FMT_STR_CODE_B_TERMINATED_WITH_SIZE.0)
+    }
 }
 
 #[cfg(test)]
@@ -73,25 +71,54 @@ mod tests {
     use std::format;
 
     #[test]
-    fn test_ascii_timestamp_a_unterminated() {
-        let date = Utc::now();
+    fn test_ascii_timestamp_a_unterminated_epoch() {
+        let date = chrono::DateTime::UNIX_EPOCH;
         let stamp_formatter = generate_time_code_a(&date);
         let stamp = format!("{}", stamp_formatter);
-        let t_sep = stamp.find("T");
+        let t_sep = stamp.find('T');
         assert!(t_sep.is_some());
         assert_eq!(t_sep.unwrap(), 10);
         assert_eq!(stamp.len(), FMT_STR_CODE_A_WITH_SIZE.1);
     }
 
     #[test]
-    fn test_ascii_timestamp_a_terminated() {
+    #[cfg_attr(miri, ignore)]
+    fn test_ascii_timestamp_a_unterminated_now() {
+        let date = Utc::now();
+        let stamp_formatter = generate_time_code_a(&date);
+        let stamp = format!("{}", stamp_formatter);
+        let t_sep = stamp.find('T');
+        assert!(t_sep.is_some());
+        assert_eq!(t_sep.unwrap(), 10);
+        assert_eq!(stamp.len(), FMT_STR_CODE_A_WITH_SIZE.1);
+    }
+
+    #[test]
+    fn test_ascii_timestamp_a_terminated_epoch() {
+        let date = chrono::DateTime::UNIX_EPOCH;
+        let stamp_formatter = generate_time_code_a_terminated(&date);
+        let stamp = format!("{}", stamp_formatter);
+        let t_sep = stamp.find('T');
+        assert!(t_sep.is_some());
+        assert_eq!(t_sep.unwrap(), 10);
+        let z_terminator = stamp.find('Z');
+        assert!(z_terminator.is_some());
+        assert_eq!(
+            z_terminator.unwrap(),
+            FMT_STR_CODE_A_TERMINATED_WITH_SIZE.1 - 1
+        );
+        assert_eq!(stamp.len(), FMT_STR_CODE_A_TERMINATED_WITH_SIZE.1);
+    }
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_ascii_timestamp_a_terminated_now() {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_a_terminated(&date);
         let stamp = format!("{}", stamp_formatter);
-        let t_sep = stamp.find("T");
+        let t_sep = stamp.find('T');
         assert!(t_sep.is_some());
         assert_eq!(t_sep.unwrap(), 10);
-        let z_terminator = stamp.find("Z");
+        let z_terminator = stamp.find('Z');
         assert!(z_terminator.is_some());
         assert_eq!(
             z_terminator.unwrap(),
@@ -101,25 +128,55 @@ mod tests {
     }
 
     #[test]
-    fn test_ascii_timestamp_b_unterminated() {
-        let date = Utc::now();
+    fn test_ascii_timestamp_b_unterminated_epoch() {
+        let date = chrono::DateTime::UNIX_EPOCH;
         let stamp_formatter = generate_time_code_b(&date);
         let stamp = format!("{}", stamp_formatter);
-        let t_sep = stamp.find("T");
+        let t_sep = stamp.find('T');
         assert!(t_sep.is_some());
         assert_eq!(t_sep.unwrap(), 8);
         assert_eq!(stamp.len(), FMT_STR_CODE_B_WITH_SIZE.1);
     }
 
     #[test]
-    fn test_ascii_timestamp_b_terminated() {
+    #[cfg_attr(miri, ignore)]
+    fn test_ascii_timestamp_b_unterminated_now() {
+        let date = Utc::now();
+        let stamp_formatter = generate_time_code_b(&date);
+        let stamp = format!("{}", stamp_formatter);
+        let t_sep = stamp.find('T');
+        assert!(t_sep.is_some());
+        assert_eq!(t_sep.unwrap(), 8);
+        assert_eq!(stamp.len(), FMT_STR_CODE_B_WITH_SIZE.1);
+    }
+
+    #[test]
+    fn test_ascii_timestamp_b_terminated_epoch() {
+        let date = chrono::DateTime::UNIX_EPOCH;
+        let stamp_formatter = generate_time_code_b_terminated(&date);
+        let stamp = format!("{}", stamp_formatter);
+        let t_sep = stamp.find('T');
+        assert!(t_sep.is_some());
+        assert_eq!(t_sep.unwrap(), 8);
+        let z_terminator = stamp.find('Z');
+        assert!(z_terminator.is_some());
+        assert_eq!(
+            z_terminator.unwrap(),
+            FMT_STR_CODE_B_TERMINATED_WITH_SIZE.1 - 1
+        );
+        assert_eq!(stamp.len(), FMT_STR_CODE_B_TERMINATED_WITH_SIZE.1);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_ascii_timestamp_b_terminated_now() {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_b_terminated(&date);
         let stamp = format!("{}", stamp_formatter);
-        let t_sep = stamp.find("T");
+        let t_sep = stamp.find('T');
         assert!(t_sep.is_some());
         assert_eq!(t_sep.unwrap(), 8);
-        let z_terminator = stamp.find("Z");
+        let z_terminator = stamp.find('Z');
         assert!(z_terminator.is_some());
         assert_eq!(
             z_terminator.unwrap(),

src/time/mod.rs

@@ -1,9 +1,10 @@
 //! CCSDS Time Code Formats according to [CCSDS 301.0-B-4](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
-use crate::{ByteConversionError, SizeMissmatch};
-use chrono::{DateTime, LocalResult, TimeZone, Utc};
+use crate::ByteConversionError;
+#[cfg(feature = "chrono")]
+use chrono::{TimeZone, Utc};
 use core::cmp::Ordering;
 use core::fmt::{Display, Formatter};
-use core::ops::{Add, AddAssign};
+use core::ops::{Add, AddAssign, Sub};
 use core::time::Duration;
 
 #[allow(unused_imports)]
@@ -12,6 +13,7 @@ use num_traits::float::FloatCore;
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
+
 #[cfg(feature = "std")]
 use std::error::Error;
 #[cfg(feature = "std")]
@@ -26,10 +28,12 @@ pub mod cuc;
 pub const DAYS_CCSDS_TO_UNIX: i32 = -4383;
 pub const SECONDS_PER_DAY: u32 = 86400;
 pub const MS_PER_DAY: u32 = SECONDS_PER_DAY * 1000;
+pub const NANOS_PER_SECOND: u32 = 1_000_000_000;
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub enum CcsdsTimeCodes {
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum CcsdsTimeCode {
     CucCcsdsEpoch = 0b001,
     CucAgencyEpoch = 0b010,
     Cds = 0b100,
@@ -37,16 +41,16 @@ pub enum CcsdsTimeCodes {
     AgencyDefined = 0b110,
 }
 
-impl TryFrom<u8> for CcsdsTimeCodes {
+impl TryFrom<u8> for CcsdsTimeCode {
     type Error = ();
 
     fn try_from(value: u8) -> Result<Self, Self::Error> {
         match value {
-            x if x == CcsdsTimeCodes::CucCcsdsEpoch as u8 => Ok(CcsdsTimeCodes::CucCcsdsEpoch),
-            x if x == CcsdsTimeCodes::CucAgencyEpoch as u8 => Ok(CcsdsTimeCodes::CucAgencyEpoch),
-            x if x == CcsdsTimeCodes::Cds as u8 => Ok(CcsdsTimeCodes::Cds),
-            x if x == CcsdsTimeCodes::Ccs as u8 => Ok(CcsdsTimeCodes::Ccs),
-            x if x == CcsdsTimeCodes::AgencyDefined as u8 => Ok(CcsdsTimeCodes::AgencyDefined),
+            x if x == CcsdsTimeCode::CucCcsdsEpoch as u8 => Ok(CcsdsTimeCode::CucCcsdsEpoch),
+            x if x == CcsdsTimeCode::CucAgencyEpoch as u8 => Ok(CcsdsTimeCode::CucAgencyEpoch),
+            x if x == CcsdsTimeCode::Cds as u8 => Ok(CcsdsTimeCode::Cds),
+            x if x == CcsdsTimeCode::Ccs as u8 => Ok(CcsdsTimeCode::Ccs),
+            x if x == CcsdsTimeCode::AgencyDefined as u8 => Ok(CcsdsTimeCode::AgencyDefined),
             _ => Err(()),
         }
     }
@@ -54,45 +58,46 @@ impl TryFrom<u8> for CcsdsTimeCodes {
 
 /// Retrieve the CCSDS time code from the p-field. If no valid time code identifier is found, the
 /// value of the raw time code identification field is returned.
-pub fn ccsds_time_code_from_p_field(pfield: u8) -> Result<CcsdsTimeCodes, u8> {
+pub fn ccsds_time_code_from_p_field(pfield: u8) -> Result<CcsdsTimeCode, u8> {
     let raw_bits = (pfield >> 4) & 0b111;
-    CcsdsTimeCodes::try_from(raw_bits).map_err(|_| raw_bits)
+    CcsdsTimeCode::try_from(raw_bits).map_err(|_| raw_bits)
 }
 
+#[derive(Debug, PartialEq, Eq, Copy, Clone, thiserror::Error)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[error("date before ccsds epoch: {0:?}")]
+pub struct DateBeforeCcsdsEpochError(UnixTime);
+
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[non_exhaustive]
 pub enum TimestampError {
-    /// Contains tuple where first value is the expected time code and the second
-    /// value is the found raw value
-    InvalidTimeCode(CcsdsTimeCodes, u8),
+    InvalidTimeCode { expected: CcsdsTimeCode, found: u8 },
     ByteConversion(ByteConversionError),
     Cds(cds::CdsError),
     Cuc(cuc::CucError),
-    DateBeforeCcsdsEpoch(DateTime<Utc>),
     CustomEpochNotSupported,
 }
 
 impl Display for TimestampError {
     fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
         match self {
-            TimestampError::InvalidTimeCode(time_code, raw_val) => {
+            TimestampError::InvalidTimeCode { expected, found } => {
                 write!(
                     f,
-                    "invalid raw time code value {raw_val} for time code {time_code:?}"
+                    "invalid raw time code value {found} for time code {expected:?}"
                 )
             }
             TimestampError::Cds(e) => {
-                write!(f, "cds error {e}")
+                write!(f, "cds error: {e}")
             }
             TimestampError::Cuc(e) => {
-                write!(f, "cuc error {e}")
+                write!(f, "cuc error: {e}")
             }
             TimestampError::ByteConversion(e) => {
-                write!(f, "byte conversion error {e}")
-            }
-            TimestampError::DateBeforeCcsdsEpoch(e) => {
-                write!(f, "datetime with date before ccsds epoch: {e}")
+                write!(f, "time stamp: {e}")
             }
             TimestampError::CustomEpochNotSupported => {
                 write!(f, "custom epochs are not supported")
@@ -112,6 +117,7 @@ impl Error for TimestampError {
         }
     }
 }
+
 impl From<cds::CdsError> for TimestampError {
     fn from(e: cds::CdsError) -> Self {
         TimestampError::Cds(e)
@@ -125,7 +131,6 @@ impl From<cuc::CucError> for TimestampError {
 }
 
 #[cfg(feature = "std")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
 pub mod std_mod {
     use crate::time::TimestampError;
     use std::time::SystemTimeError;
@@ -133,7 +138,7 @@ pub mod std_mod {
 
     #[derive(Debug, Clone, Error)]
     pub enum StdTimestampError {
-        #[error("system time error: {0}")]
+        #[error("system time error: {0:?}")]
         SystemTime(#[from] SystemTimeError),
         #[error("timestamp error: {0}")]
         Timestamp(#[from] TimestampError),
@@ -141,7 +146,6 @@ pub mod std_mod {
 }
 
 #[cfg(feature = "std")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
 pub fn seconds_since_epoch() -> f64 {
     SystemTime::now()
         .duration_since(SystemTime::UNIX_EPOCH)
@@ -153,6 +157,7 @@ pub fn seconds_since_epoch() -> f64 {
 ///
 ///  - CCSDS epoch: 1958-01-01T00:00:00+00:00
 ///  - UNIX Epoch: 1970-01-01T00:00:00+00:00
+#[inline]
 pub const fn unix_to_ccsds_days(unix_days: i64) -> i64 {
     unix_days - DAYS_CCSDS_TO_UNIX as i64
 }
@@ -161,22 +166,24 @@ pub const fn unix_to_ccsds_days(unix_days: i64) -> i64 {
 ///
 ///  - CCSDS epoch: 1958-01-01T00:00:00+00:00
 ///  - UNIX Epoch: 1970-01-01T00:00:00+00:00
+#[inline]
 pub const fn ccsds_to_unix_days(ccsds_days: i64) -> i64 {
     ccsds_days + DAYS_CCSDS_TO_UNIX as i64
 }
 
 /// Similar to [unix_to_ccsds_days] but converts the epoch instead, which is the number of elpased
 /// seconds since the CCSDS and UNIX epoch times.
+#[inline]
 pub const fn unix_epoch_to_ccsds_epoch(unix_epoch: i64) -> i64 {
     unix_epoch - (DAYS_CCSDS_TO_UNIX as i64 * SECONDS_PER_DAY as i64)
 }
 
+#[inline]
 pub const fn ccsds_epoch_to_unix_epoch(ccsds_epoch: i64) -> i64 {
     ccsds_epoch + (DAYS_CCSDS_TO_UNIX as i64 * SECONDS_PER_DAY as i64)
 }
 
 #[cfg(feature = "std")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
 pub fn ms_of_day_using_sysclock() -> u32 {
     ms_of_day(seconds_since_epoch())
 }
@@ -190,21 +197,29 @@ pub fn ms_of_day(seconds_since_epoch: f64) -> u32 {
 }
 
 pub trait TimeWriter {
+    fn len_written(&self) -> usize;
+
     /// Generic function to convert write a timestamp into a raw buffer.
     /// Returns the number of written bytes on success.
     fn write_to_bytes(&self, bytes: &mut [u8]) -> Result<usize, TimestampError>;
+
+    #[cfg(feature = "alloc")]
+    fn to_vec(&self) -> Result<alloc::vec::Vec<u8>, TimestampError> {
+        let mut vec = alloc::vec![0; self.len_written()];
+        self.write_to_bytes(&mut vec)?;
+        Ok(vec)
+    }
 }
 
-pub trait TimeReader {
-    fn from_bytes(buf: &[u8]) -> Result<Self, TimestampError>
-    where
-        Self: Sized;
+pub trait TimeReader: Sized {
+    fn from_bytes(buf: &[u8]) -> Result<Self, TimestampError>;
 }
 
 /// Trait for generic CCSDS time providers.
 ///
-/// The UNIX helper methods and the [Self::date_time] method are not strictly necessary but extremely
+/// The UNIX helper methods and the helper method are not strictly necessary but extremely
 /// practical because they are a very common and simple exchange format for time information.
+/// Therefore, it was decided to keep them in this trait as well.
 pub trait CcsdsTimeProvider {
     fn len_as_bytes(&self) -> usize;
 
@@ -213,148 +228,244 @@ pub trait CcsdsTimeProvider {
     /// entry denotes the length of the pfield and the second entry is the value of the pfield
     /// in big endian format.
     fn p_field(&self) -> (usize, [u8; 2]);
-    fn ccdsd_time_code(&self) -> CcsdsTimeCodes;
+    fn ccdsd_time_code(&self) -> CcsdsTimeCode;
 
-    fn unix_seconds(&self) -> i64;
-    fn subsecond_millis(&self) -> Option<u16>;
-    fn unix_stamp(&self) -> UnixTimestamp {
-        if self.subsecond_millis().is_none() {
-            return UnixTimestamp::new_only_seconds(self.unix_seconds());
-        }
-        UnixTimestamp::const_new(self.unix_seconds(), self.subsecond_millis().unwrap())
+    fn unix_secs(&self) -> i64;
+    fn subsec_nanos(&self) -> u32;
+
+    fn subsec_millis(&self) -> u16 {
+        (self.subsec_nanos() / 1_000_000) as u16
     }
 
-    fn date_time(&self) -> Option<DateTime<Utc>>;
+    fn unix_time(&self) -> UnixTime {
+        UnixTime::new(self.unix_secs(), self.subsec_nanos())
+    }
+
+    #[cfg(feature = "chrono")]
+    fn chrono_date_time(&self) -> chrono::LocalResult<chrono::DateTime<chrono::Utc>> {
+        chrono::Utc.timestamp_opt(self.unix_secs(), self.subsec_nanos())
+    }
+
+    #[cfg(feature = "timelib")]
+    fn timelib_date_time(&self) -> Result<time::OffsetDateTime, time::error::ComponentRange> {
+        Ok(time::OffsetDateTime::from_unix_timestamp(self.unix_secs())?
+            + time::Duration::nanoseconds(self.subsec_nanos().into()))
+    }
 }
 
-/// UNIX timestamp: Elapsed seconds since 1970-01-01T00:00:00+00:00.
+/// UNIX time: Elapsed non-leap seconds since 1970-01-01T00:00:00+00:00 UTC.
 ///
-/// Also can optionally include subsecond millisecond for greater accuracy. Please note that a
-/// subsecond millisecond value of 0 gets converted to [None].
+/// This is a commonly used time format and can therefore also be used as a generic format to
+/// convert other CCSDS time formats to and from. The subsecond precision is in nanoseconds
+/// similarly to other common time formats and libraries.
 #[derive(Default, Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct UnixTimestamp {
-    pub unix_seconds: i64,
-    subsecond_millis: Option<u16>,
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct UnixTime {
+    secs: i64,
+    subsec_nanos: u32,
 }
 
-impl UnixTimestamp {
-    /// Returns none if the subsecond millisecond value is larger than 999. 0 is converted to
-    /// a [None] value.
-    pub fn new(unix_seconds: i64, subsec_millis: u16) -> Option<Self> {
-        if subsec_millis > 999 {
+impl UnixTime {
+    /// The UNIX epoch time: 1970-01-01T00:00:00+00:00 UTC.
+    pub const EPOCH: Self = Self {
+        secs: 0,
+        subsec_nanos: 0,
+    };
+
+    /// The minimum possible `UnixTime`.
+    pub const MIN: Self = Self {
+        secs: i64::MIN,
+        subsec_nanos: 0,
+    };
+
+    /// The maximum possible `UnixTime`.
+    pub const MAX: Self = Self {
+        secs: i64::MAX,
+        subsec_nanos: NANOS_PER_SECOND - 1,
+    };
+
+    /// Returns [None] if the subsecond nanosecond value is invalid (larger than fraction of a
+    /// second)
+    pub fn new_checked(unix_seconds: i64, subsec_nanos: u32) -> Option<Self> {
+        if subsec_nanos >= NANOS_PER_SECOND {
             return None;
         }
-        Some(Self::const_new(unix_seconds, subsec_millis))
+        Some(Self::new(unix_seconds, subsec_nanos))
     }
 
-    /// Like [Self::new] but const. Panics if the subsecond value is larger than 999.
-    pub const fn const_new(unix_seconds: i64, subsec_millis: u16) -> Self {
-        if subsec_millis > 999 {
-            panic!("subsec milliseconds exceeds 999");
+    /// Returns [None] if the subsecond millisecond value is invalid (larger than fraction of a
+    /// second)
+    pub fn new_subsec_millis_checked(unix_seconds: i64, subsec_millis: u16) -> Option<Self> {
+        if subsec_millis >= 1000 {
+            return None;
+        }
+        Self::new_checked(unix_seconds, subsec_millis as u32 * 1_000_000)
+    }
+
+    /// This function will panic if the subsecond value is larger than the fraction of a second.
+    /// Use [Self::new_checked] if you want to handle this case without a panic.
+    pub const fn new(unix_seconds: i64, subsecond_nanos: u32) -> Self {
+        if subsecond_nanos >= NANOS_PER_SECOND {
+            panic!("invalid subsecond nanos value");
         }
-        let subsecond_millis = if subsec_millis == 0 {
-            None
-        } else {
-            Some(subsec_millis)
-        };
         Self {
-            unix_seconds,
-            subsecond_millis,
+            secs: unix_seconds,
+            subsec_nanos: subsecond_nanos,
         }
     }
 
-    pub fn new_only_seconds(unix_seconds: i64) -> Self {
+    /// This function will panic if the subsecond value is larger than the fraction of a second.
+    /// Use [Self::new_subsec_millis_checked] if you want to handle this case without a panic.
+    pub const fn new_subsec_millis(unix_seconds: i64, subsecond_millis: u16) -> Self {
+        if subsecond_millis >= 1000 {
+            panic!("invalid subsecond millisecond value");
+        }
         Self {
-            unix_seconds,
-            subsecond_millis: None,
+            secs: unix_seconds,
+            subsec_nanos: subsecond_millis as u32 * 1_000_000,
         }
     }
 
-    pub fn subsecond_millis(&self) -> Option<u16> {
-        self.subsecond_millis
-    }
-
-    #[cfg(feature = "std")]
-    #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
-    pub fn from_now() -> Result<Self, SystemTimeError> {
-        let now = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)?;
-        let epoch = now.as_secs();
-        Ok(Self::const_new(epoch as i64, now.subsec_millis() as u16))
+    pub fn new_only_secs(unix_seconds: i64) -> Self {
+        Self {
+            secs: unix_seconds,
+            subsec_nanos: 0,
+        }
     }
 
     #[inline]
-    pub fn unix_seconds_f64(&self) -> f64 {
-        let mut secs = self.unix_seconds as f64;
-        if let Some(subsec_millis) = self.subsecond_millis {
-            secs += subsec_millis as f64 / 1000.0;
-        }
-        secs
+    pub fn subsec_millis(&self) -> u16 {
+        (self.subsec_nanos / 1_000_000) as u16
     }
 
-    pub fn as_date_time(&self) -> LocalResult<DateTime<Utc>> {
-        Utc.timestamp_opt(
-            self.unix_seconds,
-            self.subsecond_millis.unwrap_or(0) as u32 * 10_u32.pow(6),
-        )
+    pub fn subsec_nanos(&self) -> u32 {
+        self.subsec_nanos
+    }
+
+    #[cfg(feature = "std")]
+    pub fn now() -> Result<Self, SystemTimeError> {
+        let now = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)?;
+        let epoch = now.as_secs();
+        Ok(Self::new(epoch as i64, now.subsec_nanos()))
+    }
+
+    #[inline]
+    pub fn unix_secs_f64(&self) -> f64 {
+        self.secs as f64 + (self.subsec_nanos as f64 / 1_000_000_000.0)
+    }
+
+    pub fn as_secs(&self) -> i64 {
+        self.secs
+    }
+
+    #[cfg(feature = "chrono")]
+    pub fn chrono_date_time(&self) -> chrono::LocalResult<chrono::DateTime<chrono::Utc>> {
+        Utc.timestamp_opt(self.secs, self.subsec_nanos)
+    }
+
+    #[cfg(feature = "timelib")]
+    pub fn timelib_date_time(&self) -> Result<time::OffsetDateTime, time::error::ComponentRange> {
+        Ok(time::OffsetDateTime::from_unix_timestamp(self.as_secs())?
+            + time::Duration::nanoseconds(self.subsec_nanos().into()))
+    }
+
+    // Calculate the difference in milliseconds between two UnixTimestamps
+    pub fn diff_in_millis(&self, other: &UnixTime) -> Option<i64> {
+        let seconds_difference = self.secs.checked_sub(other.secs)?;
+        // Convert seconds difference to milliseconds
+        let milliseconds_difference = seconds_difference.checked_mul(1000)?;
+
+        // Calculate the difference in subsecond milliseconds directly
+        let subsecond_difference_nanos = self.subsec_nanos as i64 - other.subsec_nanos as i64;
+
+        // Combine the differences
+        Some(milliseconds_difference + (subsecond_difference_nanos / 1_000_000))
     }
 }
 
-impl From<DateTime<Utc>> for UnixTimestamp {
-    fn from(value: DateTime<Utc>) -> Self {
-        Self::const_new(value.timestamp(), value.timestamp_subsec_millis() as u16)
+#[cfg(feature = "chrono")]
+impl From<chrono::DateTime<chrono::Utc>> for UnixTime {
+    fn from(value: chrono::DateTime<chrono::Utc>) -> Self {
+        Self::new(value.timestamp(), value.timestamp_subsec_nanos())
     }
 }
 
-impl PartialOrd for UnixTimestamp {
+#[cfg(feature = "timelib")]
+impl From<time::OffsetDateTime> for UnixTime {
+    fn from(value: time::OffsetDateTime) -> Self {
+        Self::new(value.unix_timestamp(), value.nanosecond())
+    }
+}
+
+impl PartialOrd for UnixTime {
     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for UnixTime {
+    fn cmp(&self, other: &Self) -> Ordering {
         if self == other {
-            return Some(Ordering::Equal);
+            return Ordering::Equal;
         }
-        match self.unix_seconds.cmp(&other.unix_seconds) {
-            Ordering::Less => return Some(Ordering::Less),
-            Ordering::Greater => return Some(Ordering::Greater),
+        match self.secs.cmp(&other.secs) {
+            Ordering::Less => return Ordering::Less,
+            Ordering::Greater => return Ordering::Greater,
             _ => (),
         }
 
-        match self
-            .subsecond_millis()
-            .unwrap_or(0)
-            .cmp(&other.subsecond_millis().unwrap_or(0))
-        {
+        match self.subsec_millis().cmp(&other.subsec_millis()) {
             Ordering::Less => {
-                return if self.unix_seconds < 0 {
-                    Some(Ordering::Greater)
+                return if self.secs < 0 {
+                    Ordering::Greater
                 } else {
-                    Some(Ordering::Less)
+                    Ordering::Less
                 }
             }
             Ordering::Greater => {
-                return if self.unix_seconds < 0 {
-                    Some(Ordering::Less)
+                return if self.secs < 0 {
+                    Ordering::Less
                 } else {
-                    Some(Ordering::Greater)
+                    Ordering::Greater
                 }
             }
             Ordering::Equal => (),
         }
-        Some(Ordering::Equal)
+        Ordering::Equal
     }
 }
 
-impl Ord for UnixTimestamp {
-    fn cmp(&self, other: &Self) -> Ordering {
-        PartialOrd::partial_cmp(self, other).unwrap()
+/// Difference between two UNIX timestamps. The [Duration] type can not contain negative durations,
+/// so the sign information is supplied separately.
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct StampDiff {
+    pub positive_duration: bool,
+    pub duration_absolute: Duration,
+}
+
+impl Sub for UnixTime {
+    type Output = Option<StampDiff>;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        let difference = self.diff_in_millis(&rhs)?;
+        Some(if difference < 0 {
+            StampDiff {
+                positive_duration: false,
+                duration_absolute: Duration::from_millis(-difference as u64),
+            }
+        } else {
+            StampDiff {
+                positive_duration: true,
+                duration_absolute: Duration::from_millis(difference as u64),
+            }
+        })
     }
 }
 
-fn get_new_stamp_after_addition(
-    current_stamp: &UnixTimestamp,
-    duration: Duration,
-) -> UnixTimestamp {
-    let mut new_subsec_millis =
-        current_stamp.subsecond_millis().unwrap_or(0) + duration.subsec_millis() as u16;
-    let mut new_unix_seconds = current_stamp.unix_seconds;
+fn get_new_stamp_after_addition(current_stamp: &UnixTime, duration: Duration) -> UnixTime {
+    let mut new_subsec_nanos = current_stamp.subsec_nanos() + duration.subsec_nanos();
+    let mut new_unix_seconds = current_stamp.secs;
     let mut increment_seconds = |value: u32| {
         if new_unix_seconds < 0 {
             new_unix_seconds = new_unix_seconds
@@ -366,8 +477,8 @@ fn get_new_stamp_after_addition(
                 .expect("new unix seconds would exceed i64::MAX");
         }
     };
-    if new_subsec_millis >= 1000 {
-        new_subsec_millis -= 1000;
+    if new_subsec_nanos >= 1_000_000_000 {
+        new_subsec_nanos -= 1_000_000_000;
         increment_seconds(1);
     }
     increment_seconds(
@@ -376,7 +487,7 @@ fn get_new_stamp_after_addition(
             .try_into()
             .expect("duration seconds exceeds u32::MAX"),
     );
-    UnixTimestamp::const_new(new_unix_seconds, new_subsec_millis)
+    UnixTime::new(new_unix_seconds, new_subsec_nanos)
 }
 
 /// Please note that this operation will panic on the following conditions:
@@ -384,7 +495,7 @@ fn get_new_stamp_after_addition(
 /// - Unix seconds after subtraction for stamps before the unix epoch exceeds [i64::MIN].
 /// - Unix seconds after addition  exceeds [i64::MAX].
 /// - Seconds from duration to add exceeds [u32::MAX].
-impl AddAssign<Duration> for UnixTimestamp {
+impl AddAssign<Duration> for UnixTime {
     fn add_assign(&mut self, duration: Duration) {
         *self = get_new_stamp_after_addition(self, duration);
     }
@@ -395,7 +506,7 @@ impl AddAssign<Duration> for UnixTimestamp {
 /// - Unix seconds after subtraction for stamps before the unix epoch exceeds [i64::MIN].
 /// - Unix seconds after addition  exceeds [i64::MAX].
 /// - Unix seconds exceeds [u32::MAX].
-impl Add<Duration> for UnixTimestamp {
+impl Add<Duration> for UnixTime {
     type Output = Self;
 
     fn add(self, duration: Duration) -> Self::Output {
@@ -403,8 +514,8 @@ impl Add<Duration> for UnixTimestamp {
     }
 }
 
-impl Add<Duration> for &UnixTimestamp {
-    type Output = UnixTimestamp;
+impl Add<Duration> for &UnixTime {
+    type Output = UnixTime;
 
     fn add(self, duration: Duration) -> Self::Output {
         get_new_stamp_after_addition(self, duration)
@@ -413,7 +524,16 @@ impl Add<Duration> for &UnixTimestamp {
 
 #[cfg(all(test, feature = "std"))]
 mod tests {
-    use super::*;
+    use alloc::string::ToString;
+    use chrono::{Datelike, Timelike};
+    use std::{format, println};
+
+    use super::{cuc::CucError, *};
+
+    #[allow(dead_code)]
+    const UNIX_STAMP_CONST: UnixTime = UnixTime::new(5, 999_999_999);
+    #[allow(dead_code)]
+    const UNIX_STAMP_CONST_2: UnixTime = UnixTime::new_subsec_millis(5, 999);
 
     #[test]
     fn test_days_conversion() {
@@ -422,12 +542,22 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_get_current_time() {
         let sec_floats = seconds_since_epoch();
         assert!(sec_floats > 0.0);
     }
 
     #[test]
+    fn test_ms_of_day() {
+        let ms = ms_of_day(0.0);
+        assert_eq!(ms, 0);
+        let ms = ms_of_day(5.0);
+        assert_eq!(ms, 5000);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_ccsds_epoch() {
         let now = SystemTime::now()
             .duration_since(SystemTime::UNIX_EPOCH)
@@ -442,29 +572,29 @@ mod tests {
 
     #[test]
     fn basic_unix_stamp_test() {
-        let stamp = UnixTimestamp::new_only_seconds(-200);
-        assert_eq!(stamp.unix_seconds, -200);
-        assert!(stamp.subsecond_millis().is_none());
-        let stamp = UnixTimestamp::new_only_seconds(250);
-        assert_eq!(stamp.unix_seconds, 250);
-        assert!(stamp.subsecond_millis().is_none());
+        let stamp = UnixTime::new_only_secs(-200);
+        assert_eq!(stamp.secs, -200);
+        assert_eq!(stamp.subsec_millis(), 0);
+        let stamp = UnixTime::new_only_secs(250);
+        assert_eq!(stamp.secs, 250);
+        assert_eq!(stamp.subsec_millis(), 0);
     }
 
     #[test]
     fn basic_float_unix_stamp_test() {
-        let stamp = UnixTimestamp::new(500, 600).unwrap();
-        assert!(stamp.subsecond_millis.is_some());
-        assert_eq!(stamp.unix_seconds, 500);
-        let subsec_millis = stamp.subsecond_millis().unwrap();
+        let stamp = UnixTime::new_subsec_millis_checked(500, 600).unwrap();
+        assert_eq!(stamp.secs, 500);
+        let subsec_millis = stamp.subsec_millis();
         assert_eq!(subsec_millis, 600);
-        assert!((500.6 - stamp.unix_seconds_f64()).abs() < 0.0001);
+        println!("{:?}", (500.6 - stamp.unix_secs_f64()).to_string());
+        assert!((500.6 - stamp.unix_secs_f64()).abs() < 0.0001);
     }
 
     #[test]
     fn test_ord_larger() {
-        let stamp0 = UnixTimestamp::new_only_seconds(5);
-        let stamp1 = UnixTimestamp::new(5, 500).unwrap();
-        let stamp2 = UnixTimestamp::new_only_seconds(6);
+        let stamp0 = UnixTime::new_only_secs(5);
+        let stamp1 = UnixTime::new_subsec_millis_checked(5, 500).unwrap();
+        let stamp2 = UnixTime::new_only_secs(6);
         assert!(stamp1 > stamp0);
         assert!(stamp2 > stamp0);
         assert!(stamp2 > stamp1);
@@ -472,9 +602,9 @@ mod tests {
 
     #[test]
     fn test_ord_smaller() {
-        let stamp0 = UnixTimestamp::new_only_seconds(5);
-        let stamp1 = UnixTimestamp::new(5, 500).unwrap();
-        let stamp2 = UnixTimestamp::new_only_seconds(6);
+        let stamp0 = UnixTime::new_only_secs(5);
+        let stamp1 = UnixTime::new_subsec_millis_checked(5, 500).unwrap();
+        let stamp2 = UnixTime::new_only_secs(6);
         assert!(stamp0 < stamp1);
         assert!(stamp0 < stamp2);
         assert!(stamp1 < stamp2);
@@ -482,9 +612,9 @@ mod tests {
 
     #[test]
     fn test_ord_larger_neg_numbers() {
-        let stamp0 = UnixTimestamp::new_only_seconds(-5);
-        let stamp1 = UnixTimestamp::new(-5, 500).unwrap();
-        let stamp2 = UnixTimestamp::new_only_seconds(-6);
+        let stamp0 = UnixTime::new_only_secs(-5);
+        let stamp1 = UnixTime::new_subsec_millis_checked(-5, 500).unwrap();
+        let stamp2 = UnixTime::new_only_secs(-6);
         assert!(stamp0 > stamp1);
         assert!(stamp0 > stamp2);
         assert!(stamp1 > stamp2);
@@ -494,9 +624,9 @@ mod tests {
 
     #[test]
     fn test_ord_smaller_neg_numbers() {
-        let stamp0 = UnixTimestamp::new_only_seconds(-5);
-        let stamp1 = UnixTimestamp::new(-5, 500).unwrap();
-        let stamp2 = UnixTimestamp::new_only_seconds(-6);
+        let stamp0 = UnixTime::new_only_secs(-5);
+        let stamp1 = UnixTime::new_subsec_millis_checked(-5, 500).unwrap();
+        let stamp2 = UnixTime::new_only_secs(-6);
         assert!(stamp2 < stamp1);
         assert!(stamp2 < stamp0);
         assert!(stamp1 < stamp0);
@@ -504,10 +634,11 @@ mod tests {
         assert!(stamp2 <= stamp1);
     }
 
+    #[allow(clippy::nonminimal_bool)]
     #[test]
     fn test_eq() {
-        let stamp0 = UnixTimestamp::new(5, 0).unwrap();
-        let stamp1 = UnixTimestamp::new_only_seconds(5);
+        let stamp0 = UnixTime::new(5, 0);
+        let stamp1 = UnixTime::new_only_secs(5);
         assert_eq!(stamp0, stamp1);
         assert!(stamp0 <= stamp1);
         assert!(stamp0 >= stamp1);
@@ -517,32 +648,115 @@ mod tests {
 
     #[test]
     fn test_addition() {
-        let mut stamp0 = UnixTimestamp::new_only_seconds(1);
+        let mut stamp0 = UnixTime::new_only_secs(1);
         stamp0 += Duration::from_secs(5);
-        assert_eq!(stamp0.unix_seconds, 6);
-        assert!(stamp0.subsecond_millis().is_none());
+        assert_eq!(stamp0.as_secs(), 6);
+        assert_eq!(stamp0.subsec_millis(), 0);
         let stamp1 = stamp0 + Duration::from_millis(500);
-        assert_eq!(stamp1.unix_seconds, 6);
-        assert!(stamp1.subsecond_millis().is_some());
-        assert_eq!(stamp1.subsecond_millis().unwrap(), 500);
+        assert_eq!(stamp1.secs, 6);
+        assert_eq!(stamp1.subsec_millis(), 500);
     }
 
     #[test]
     fn test_addition_on_ref() {
-        let stamp0 = &UnixTimestamp::new(20, 500).unwrap();
+        let stamp0 = &UnixTime::new_subsec_millis_checked(20, 500).unwrap();
         let stamp1 = stamp0 + Duration::from_millis(2500);
-        assert_eq!(stamp1.unix_seconds, 23);
-        assert!(stamp1.subsecond_millis().is_none());
+        assert_eq!(stamp1.secs, 23);
+        assert_eq!(stamp1.subsec_millis(), 0);
+    }
+
+    #[test]
+    fn test_as_dt() {
+        let stamp = UnixTime::new_only_secs(0);
+        let dt = stamp.chrono_date_time().unwrap();
+        assert_eq!(dt.year(), 1970);
+        assert_eq!(dt.month(), 1);
+        assert_eq!(dt.day(), 1);
+        assert_eq!(dt.hour(), 0);
+        assert_eq!(dt.minute(), 0);
+        assert_eq!(dt.second(), 0);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_from_now() {
+        let stamp_now = UnixTime::now().unwrap();
+        let dt_now = stamp_now.chrono_date_time().unwrap();
+        assert!(dt_now.year() >= 2020);
+    }
+
+    #[test]
+    fn test_stamp_diff_positive_0() {
+        let stamp_later = UnixTime::new(2, 0);
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = (stamp_later - UnixTime::new(1, 0)).expect("stamp diff error");
+        assert!(positive_duration);
+        assert_eq!(duration_absolute, Duration::from_secs(1));
+    }
+
+    #[test]
+    fn test_stamp_diff_positive_1() {
+        let stamp_later = UnixTime::new(3, 800 * 1_000_000);
+        let stamp_earlier = UnixTime::new_subsec_millis_checked(1, 900).unwrap();
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = (stamp_later - stamp_earlier).expect("stamp diff error");
+        assert!(positive_duration);
+        assert_eq!(duration_absolute, Duration::from_millis(1900));
+    }
+
+    #[test]
+    fn test_stamp_diff_negative() {
+        let stamp_later = UnixTime::new_subsec_millis_checked(3, 800).unwrap();
+        let stamp_earlier = UnixTime::new_subsec_millis_checked(1, 900).unwrap();
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = (stamp_earlier - stamp_later).expect("stamp diff error");
+        assert!(!positive_duration);
+        assert_eq!(duration_absolute, Duration::from_millis(1900));
     }
 
     #[test]
     fn test_addition_spillover() {
-        let mut stamp0 = UnixTimestamp::new(1, 900).unwrap();
+        let mut stamp0 = UnixTime::new_subsec_millis_checked(1, 900).unwrap();
         stamp0 += Duration::from_millis(100);
-        assert_eq!(stamp0.unix_seconds, 2);
-        assert!(stamp0.subsecond_millis().is_none());
+        assert_eq!(stamp0.secs, 2);
+        assert_eq!(stamp0.subsec_millis(), 0);
         stamp0 += Duration::from_millis(1100);
-        assert_eq!(stamp0.unix_seconds, 3);
-        assert_eq!(stamp0.subsecond_millis().unwrap(), 100);
+        assert_eq!(stamp0.secs, 3);
+        assert_eq!(stamp0.subsec_millis(), 100);
+    }
+
+    #[test]
+    fn test_cuc_error_printout() {
+        let cuc_error = CucError::InvalidCounterWidth(12);
+        let stamp_error = TimestampError::from(cuc_error);
+        assert_eq!(stamp_error.to_string(), format!("cuc error: {cuc_error}"));
+    }
+
+    #[test]
+    #[cfg(feature = "timelib")]
+    fn test_unix_stamp_as_timelib_datetime() {
+        let stamp_epoch = UnixTime::EPOCH;
+        let timelib_dt = stamp_epoch.timelib_date_time().unwrap();
+        assert_eq!(timelib_dt.year(), 1970);
+        assert_eq!(timelib_dt.month(), time::Month::January);
+        assert_eq!(timelib_dt.day(), 1);
+        assert_eq!(timelib_dt.hour(), 0);
+        assert_eq!(timelib_dt.minute(), 0);
+        assert_eq!(timelib_dt.second(), 0);
+    }
+
+    #[test]
+    #[cfg(feature = "timelib")]
+    fn test_unix_stamp_from_timelib_datetime() {
+        let timelib_dt = time::OffsetDateTime::UNIX_EPOCH;
+        let unix_time = UnixTime::from(timelib_dt);
+        let timelib_converted_back = unix_time.timelib_date_time().unwrap();
+        assert_eq!(timelib_dt, timelib_converted_back);
     }
 }

src/util.rs

@@ -1,4 +1,4 @@
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::ByteConversionError;
 use core::fmt::{Debug, Display, Formatter};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -15,10 +15,12 @@ pub trait ToBeBytes {
 impl ToBeBytes for () {
     type ByteArray = [u8; 0];
 
+    #[inline]
     fn written_len(&self) -> usize {
         0
     }
 
+    #[inline]
     fn to_be_bytes(&self) -> Self::ByteArray {
         []
     }
@@ -27,9 +29,12 @@ impl ToBeBytes for () {
 impl ToBeBytes for u8 {
     type ByteArray = [u8; 1];
 
+    #[inline]
     fn written_len(&self) -> usize {
         1
     }
+
+    #[inline]
     fn to_be_bytes(&self) -> Self::ByteArray {
         u8::to_be_bytes(*self)
     }
@@ -38,9 +43,12 @@ impl ToBeBytes for u8 {
 impl ToBeBytes for u16 {
     type ByteArray = [u8; 2];
 
+    #[inline]
     fn written_len(&self) -> usize {
         2
     }
+
+    #[inline]
     fn to_be_bytes(&self) -> Self::ByteArray {
         u16::to_be_bytes(*self)
     }
@@ -49,9 +57,12 @@ impl ToBeBytes for u16 {
 impl ToBeBytes for u32 {
     type ByteArray = [u8; 4];
 
+    #[inline]
     fn written_len(&self) -> usize {
         4
     }
+
+    #[inline]
     fn to_be_bytes(&self) -> Self::ByteArray {
         u32::to_be_bytes(*self)
     }
@@ -60,9 +71,12 @@ impl ToBeBytes for u32 {
 impl ToBeBytes for u64 {
     type ByteArray = [u8; 8];
 
+    #[inline]
     fn written_len(&self) -> usize {
         8
     }
+
+    #[inline]
     fn to_be_bytes(&self) -> Self::ByteArray {
         u64::to_be_bytes(*self)
     }
@@ -73,6 +87,15 @@ pub trait UnsignedEnum {
     fn size(&self) -> usize;
     /// Write the unsigned enumeration to a raw buffer. Returns the written size on success.
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
+
+    fn value(&self) -> u64;
+
+    #[cfg(feature = "alloc")]
+    fn to_vec(&self) -> alloc::vec::Vec<u8> {
+        let mut buf = alloc::vec![0; self.size()];
+        self.write_to_be_bytes(&mut buf).unwrap();
+        buf
+    }
 }
 
 pub trait UnsignedEnumExt: UnsignedEnum + Debug + Copy + Clone + PartialEq + Eq {}
@@ -80,16 +103,22 @@ pub trait UnsignedEnumExt: UnsignedEnum + Debug + Copy + Clone + PartialEq + Eq
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum UnsignedByteFieldError {
-    /// Value is too large for specified width of byte field. The first value contains the width,
-    /// the second value contains the detected value.
-    ValueTooLargeForWidth((usize, u64)),
+    /// Value is too large for specified width of byte field.
+    ValueTooLargeForWidth {
+        width: usize,
+        value: u64,
+    },
     /// Only 1, 2, 4 and 8 are allow width values. Optionally contains the expected width if
     /// applicable, for example for conversions.
-    InvalidWidth(usize, Option<usize>),
+    InvalidWidth {
+        found: usize,
+        expected: Option<usize>,
+    },
     ByteConversionError(ByteConversionError),
 }
 
 impl From<ByteConversionError> for UnsignedByteFieldError {
+    #[inline]
     fn from(value: ByteConversionError) -> Self {
         Self::ByteConversionError(value)
     }
@@ -101,10 +130,10 @@ impl Display for UnsignedByteFieldError {
             Self::ByteConversionError(e) => {
                 write!(f, "low level byte conversion error: {e}")
             }
-            Self::InvalidWidth(val, _) => {
-                write!(f, "invalid width {val}, only 1, 2, 4 and 8 are allowed.")
+            Self::InvalidWidth { found, .. } => {
+                write!(f, "invalid width {found}, only 1, 2, 4 and 8 are allowed.")
             }
-            Self::ValueTooLargeForWidth((width, value)) => {
+            Self::ValueTooLargeForWidth { width, value } => {
                 write!(f, "value {value} too large for width {width}")
             }
         }
@@ -117,26 +146,30 @@ impl Error for UnsignedByteFieldError {}
 /// Type erased variant.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct UnsignedByteField {
     width: usize,
     value: u64,
 }
 
 impl UnsignedByteField {
-    pub fn new(width: usize, value: u64) -> Self {
+    #[inline]
+    pub const fn new(width: usize, value: u64) -> Self {
         Self { width, value }
     }
 
-    pub fn value(&self) -> u64 {
+    #[inline]
+    pub const fn value_const(&self) -> u64 {
         self.value
     }
 
+    #[inline]
     pub fn new_from_be_bytes(width: usize, buf: &[u8]) -> Result<Self, UnsignedByteFieldError> {
         if width > buf.len() {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 expected: width,
                 found: buf.len(),
-            })
+            }
             .into());
         }
         match width {
@@ -154,22 +187,31 @@ impl UnsignedByteField {
                 width,
                 u64::from_be_bytes(buf[0..8].try_into().unwrap()),
             )),
-            _ => Err(UnsignedByteFieldError::InvalidWidth(width, None)),
+            _ => Err(UnsignedByteFieldError::InvalidWidth {
+                found: width,
+                expected: None,
+            }),
         }
     }
 }
 
 impl UnsignedEnum for UnsignedByteField {
+    #[inline]
     fn size(&self) -> usize {
         self.width
     }
 
+    #[inline]
+    fn value(&self) -> u64 {
+        self.value_const()
+    }
+
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         if buf.len() < self.size() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 expected: self.size(),
                 found: buf.len(),
-            }));
+            });
         }
         match self.size() {
             0 => Ok(0),
@@ -199,31 +241,42 @@ impl UnsignedEnum for UnsignedByteField {
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct GenericUnsignedByteField<TYPE> {
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct GenericUnsignedByteField<TYPE: Copy + Into<u64>> {
     value: TYPE,
 }
 
-impl<TYPE> GenericUnsignedByteField<TYPE> {
-    pub fn new(val: TYPE) -> Self {
+impl<TYPE: Copy + Into<u64>> GenericUnsignedByteField<TYPE> {
+    pub const fn new(val: TYPE) -> Self {
         Self { value: val }
     }
+
+    pub const fn value_typed(&self) -> TYPE {
+        self.value
+    }
 }
 
-impl<TYPE: ToBeBytes> UnsignedEnum for GenericUnsignedByteField<TYPE> {
+impl<TYPE: Copy + ToBeBytes + Into<u64>> UnsignedEnum for GenericUnsignedByteField<TYPE> {
+    #[inline]
     fn size(&self) -> usize {
         self.value.written_len()
     }
 
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         if buf.len() < self.size() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: self.size(),
-            }));
+            });
         }
-        buf[0..self.size()].copy_from_slice(self.value.to_be_bytes().as_ref());
+        buf[..self.size()].copy_from_slice(self.value.to_be_bytes().as_ref());
         Ok(self.value.written_len())
     }
+
+    #[inline]
+    fn value(&self) -> u64 {
+        self.value_typed().into()
+    }
 }
 
 pub type UnsignedByteFieldEmpty = GenericUnsignedByteField<()>;
@@ -246,15 +299,20 @@ impl From<UnsignedByteFieldU8> for UnsignedByteField {
 impl TryFrom<UnsignedByteField> for UnsignedByteFieldU8 {
     type Error = UnsignedByteFieldError;
 
+    #[inline]
     fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
         if value.width != 1 {
-            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(1)));
+            return Err(UnsignedByteFieldError::InvalidWidth {
+                found: value.width,
+                expected: Some(1),
+            });
         }
         Ok(Self::new(value.value as u8))
     }
 }
 
 impl From<UnsignedByteFieldU16> for UnsignedByteField {
+    #[inline]
     fn from(value: UnsignedByteFieldU16) -> Self {
         Self::new(2, value.value as u64)
     }
@@ -263,15 +321,20 @@ impl From<UnsignedByteFieldU16> for UnsignedByteField {
 impl TryFrom<UnsignedByteField> for UnsignedByteFieldU16 {
     type Error = UnsignedByteFieldError;
 
+    #[inline]
     fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
         if value.width != 2 {
-            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(2)));
+            return Err(UnsignedByteFieldError::InvalidWidth {
+                found: value.width,
+                expected: Some(2),
+            });
         }
         Ok(Self::new(value.value as u16))
     }
 }
 
 impl From<UnsignedByteFieldU32> for UnsignedByteField {
+    #[inline]
     fn from(value: UnsignedByteFieldU32) -> Self {
         Self::new(4, value.value as u64)
     }
@@ -280,15 +343,20 @@ impl From<UnsignedByteFieldU32> for UnsignedByteField {
 impl TryFrom<UnsignedByteField> for UnsignedByteFieldU32 {
     type Error = UnsignedByteFieldError;
 
+    #[inline]
     fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
         if value.width != 4 {
-            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(4)));
+            return Err(UnsignedByteFieldError::InvalidWidth {
+                found: value.width,
+                expected: Some(4),
+            });
         }
         Ok(Self::new(value.value as u32))
     }
 }
 
 impl From<UnsignedByteFieldU64> for UnsignedByteField {
+    #[inline]
     fn from(value: UnsignedByteFieldU64) -> Self {
         Self::new(8, value.value)
     }
@@ -297,9 +365,13 @@ impl From<UnsignedByteFieldU64> for UnsignedByteField {
 impl TryFrom<UnsignedByteField> for UnsignedByteFieldU64 {
     type Error = UnsignedByteFieldError;
 
+    #[inline]
     fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
         if value.width != 8 {
-            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(8)));
+            return Err(UnsignedByteFieldError::InvalidWidth {
+                found: value.width,
+                expected: Some(8),
+            });
         }
         Ok(Self::new(value.value))
     }
@@ -324,9 +396,11 @@ pub mod tests {
             .expect("writing to raw buffer failed");
         assert_eq!(len, 1);
         assert_eq!(buf[0], 5);
-        for i in 1..8 {
-            assert_eq!(buf[i], 0);
+        for val in buf.iter().skip(1) {
+            assert_eq!(*val, 0);
         }
+        assert_eq!(u8.value_typed(), 5);
+        assert_eq!(u8.value(), 5);
     }
 
     #[test]
@@ -340,9 +414,11 @@ pub mod tests {
         assert_eq!(len, 2);
         let raw_val = u16::from_be_bytes(buf[0..2].try_into().unwrap());
         assert_eq!(raw_val, 3823);
-        for i in 2..8 {
-            assert_eq!(buf[i], 0);
+        for val in buf.iter().skip(2) {
+            assert_eq!(*val, 0);
         }
+        assert_eq!(u16.value_typed(), 3823);
+        assert_eq!(u16.value(), 3823);
     }
 
     #[test]
@@ -356,9 +432,11 @@ pub mod tests {
         assert_eq!(len, 4);
         let raw_val = u32::from_be_bytes(buf[0..4].try_into().unwrap());
         assert_eq!(raw_val, 80932);
-        for i in 4..8 {
+        (4..8).for_each(|i| {
             assert_eq!(buf[i], 0);
-        }
+        });
+        assert_eq!(u32.value_typed(), 80932);
+        assert_eq!(u32.value(), 80932);
     }
 
     #[test]
@@ -372,6 +450,8 @@ pub mod tests {
         assert_eq!(len, 8);
         let raw_val = u64::from_be_bytes(buf[0..8].try_into().unwrap());
         assert_eq!(raw_val, 5999999);
+        assert_eq!(u64.value_typed(), 5999999);
+        assert_eq!(u64.value(), 5999999);
     }
 
     #[test]
@@ -393,8 +473,11 @@ pub mod tests {
         assert!(conv_fails.is_err());
         let err = conv_fails.unwrap_err();
         match err {
-            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
-                assert_eq!(width, 2);
+            UnsignedByteFieldError::InvalidWidth {
+                found,
+                expected: Some(expected),
+            } => {
+                assert_eq!(found, 2);
                 assert_eq!(expected, 1);
             }
             _ => {
@@ -422,8 +505,11 @@ pub mod tests {
         assert!(conv_fails.is_err());
         let err = conv_fails.unwrap_err();
         match err {
-            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
-                assert_eq!(width, 4);
+            UnsignedByteFieldError::InvalidWidth {
+                found,
+                expected: Some(expected),
+            } => {
+                assert_eq!(found, 4);
                 assert_eq!(expected, 2);
             }
             _ => {
@@ -451,8 +537,11 @@ pub mod tests {
         assert!(conv_fails.is_err());
         let err = conv_fails.unwrap_err();
         match err {
-            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
-                assert_eq!(width, 8);
+            UnsignedByteFieldError::InvalidWidth {
+                found,
+                expected: Some(expected),
+            } => {
+                assert_eq!(found, 8);
                 assert_eq!(expected, 4);
             }
             _ => {
@@ -480,8 +569,11 @@ pub mod tests {
         assert!(conv_fails.is_err());
         let err = conv_fails.unwrap_err();
         match err {
-            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
-                assert_eq!(width, 4);
+            UnsignedByteFieldError::InvalidWidth {
+                found,
+                expected: Some(expected),
+            } => {
+                assert_eq!(found, 4);
                 assert_eq!(expected, 8);
             }
             _ => {
@@ -498,9 +590,9 @@ pub mod tests {
         u8.write_to_be_bytes(&mut buf)
             .expect("writing to raw buffer failed");
         assert_eq!(buf[0], 5);
-        for i in 1..8 {
+        (1..8).for_each(|i| {
             assert_eq!(buf[i], 0);
-        }
+        });
     }
 
     #[test]
@@ -512,8 +604,8 @@ pub mod tests {
             .expect("writing to raw buffer failed");
         let raw_val = u16::from_be_bytes(buf[0..2].try_into().unwrap());
         assert_eq!(raw_val, 3823);
-        for i in 2..8 {
-            assert_eq!(buf[i], 0);
+        for val in buf.iter().skip(2) {
+            assert_eq!(*val, 0);
         }
     }
 
@@ -526,9 +618,9 @@ pub mod tests {
             .expect("writing to raw buffer failed");
         let raw_val = u32::from_be_bytes(buf[0..4].try_into().unwrap());
         assert_eq!(raw_val, 80932);
-        for i in 4..8 {
+        (4..8).for_each(|i| {
             assert_eq!(buf[i], 0);
-        }
+        });
     }
 
     #[test]
@@ -582,9 +674,9 @@ pub mod tests {
         assert!(res.is_err());
         let err = res.unwrap_err();
         match err {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.found, 1);
-                assert_eq!(missmatch.expected, 2);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(found, 1);
+                assert_eq!(expected, 2);
             }
             _ => {
                 panic!("invalid exception")
@@ -600,9 +692,9 @@ pub mod tests {
         assert!(res.is_err());
         let err = res.unwrap_err();
         match err {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.found, 1);
-                assert_eq!(missmatch.expected, 2);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(found, 1);
+                assert_eq!(expected, 2);
             }
             _ => {
                 panic!("invalid exception {}", err)
@@ -612,11 +704,11 @@ pub mod tests {
         assert!(u16.is_err());
         let err = u16.unwrap_err();
         if let UnsignedByteFieldError::ByteConversionError(
-            ByteConversionError::FromSliceTooSmall(missmatch),
+            ByteConversionError::FromSliceTooSmall { found, expected },
         ) = err
         {
-            assert_eq!(missmatch.expected, 2);
-            assert_eq!(missmatch.found, 1);
+            assert_eq!(expected, 2);
+            assert_eq!(found, 1);
         } else {
             panic!("unexpected exception {}", err);
         }
@@ -630,9 +722,9 @@ pub mod tests {
         assert!(res.is_err());
         let err = res.unwrap_err();
         match err {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.found, 3);
-                assert_eq!(missmatch.expected, 4);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(found, 3);
+                assert_eq!(expected, 4);
             }
             _ => {
                 panic!("invalid exception")