Merge pull request 'clippy' (#190) from clippy into main

Reviewed-on: #190

.github/workflows/ci.yml

@@ -1,113 +1,77 @@
-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@1.83
+      - run: cargo check --release
 
   cross-check:
-    name: Check Cross
+    name: Check Cross-Compilation
     runs-on: ubuntu-latest
     strategy:
       matrix:
         target:
           - armv7-unknown-linux-gnueabihf
+          - thumbv6m-none-eabi
           - 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, thumbv6m-none-eabi"
+      - 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
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
         with:
-          profile: minimal
-          toolchain: stable
-          override: true
-      - run: rustup component add rustfmt
-      - uses: actions-rs/cargo@v1
-        with:
-          command: fmt
-          args: --all -- --check
+          components: rustfmt
+      - 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
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
         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
+          components: clippy
+      - run: cargo clippy -- -D warnings

CHANGELOG.md

@@ -8,6 +8,372 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+# [v0.17.0] 2025-11-06
+
+## Changed
+
+- `CdsCommon` renamed to `CdsBase`
+- cfdp: Removed `FileDirectiveType` variant `*Pdu` suffix
+- ecss: Renamed `Subservice` to `MessageSubtypeId`
+- Simplified CDS short timestamp, contains one less field which reduced serialization length.
+- Renamed `UnsignedEnum::value` to `UnsignedEnum::value_raw`, `value` is reserved for the `const`
+  value getter.
+- Renamed `CcsdsPrimaryHeader::from_composite_fields` to
+  `CcsdsPrimaryHeader::new_from_composite_fields`
+- Renamed `PusPacket::service` to `PusPacket::service_type_id` and `PusPacket::subservice` to
+  `PusPacket::message_subtype_id`. Also added `PusPacket::message_type_id`. Performed the same
+  change for the ECSS PUS C secondary header traits.
+
+## Added
+
+- Added `CcsdsPacketCreator`, `CcsdsPacketReader`, `CcsdsPacketCreatorWithReservedData` and
+  `CcsdsPacketCreatorOwned` which simplify the process of creating full CCSDS space packets.
+- Added new optional `portable-atomic` because portable atomics might not work on every
+  architecture in addition to requiring atomic CAS support enabled inside for the crate.
+
+## Fixed
+
+- All `core::sync::Atomic?` usages are feature gated properly to allow compilation on systems
+  without atomic CAS.
+
+# [v0.16.1] 2025-09-26
+
+## Fixed
+
+`SpHeader::packet_len` is public now.
+
+# [v0.16.0] 2025-09-24
+
+- Bump Rust MSRV to v1.83
+
+## Changed
+
+- `PusTcCreator` has its own `service`, `subservice` and `apid` methods and does not require trait
+  imports anymore.
+- CFDP NAK PDU `SegmentRequestIter` is not generic over the file size anymore. Instead, the
+  iterator returns pairs of `u64` for both large and normal file size.
+- `PusVersion::VersionNotSupported` contains raw version number instead of `PusVersion` enum now
+  to make it more flexible.
+- `pus_version` API now returns a `Result<PusVersion, u8>` instead of a `PusVersion` to allow
+  modelling invalid version numbers properly.
+- Renamed `CcsdsPacket::total_len` to `CcsdsPacket::packet_len`
+- Renamed `SequenceCountProvider` to `SequenceCounter`
+- Renamed `SeqCountProviderSimple` to `SequenceCounterSimple`
+- Renamed `CcsdsSimpleSeqCountProvider` to `SequenceCounterCcsdsSimple`
+- Renamed `SeqCountProviderSync` to `SequenceCounterSync`
+- Renamed `PusPacket::opt_crc16` to `PusPacket::checksum`
+- Renamed `PacketSequenceCtrl` to `PacketSequenceControl`
+- ECSS checksum generation is now optional as specified in the standard. Added `has_checksum`
+  parameters for ECSS TM/TC creators and readers to reflect this.
+- APID is represented by `arbitrary-int::u11` while the sequence count is represented by
+  `arbitrary-int::u14`. A lot of corresponding checks were removed because the type now ensure
+  value validity.
+- ACK field changed from `u8` to `AckFlags` structure.
+- PUS version raw representation is `u4` now.
+- SC time reference status representation is `u4` now.
+- Renamed `ptype` to `packet_type`
+- Renamed `PduHeader::new_no_file_data` to `PduHeader::new_for_file_directive`
+- Renamd `FinishedPduCreator::new_generic` to `new` and `new_default` to `new_no_error`
+
+## Removed
+
+- `PusVersion::Invalid`, which will be modelled with `Result<PusVersion, u8>` now.
+
+## Added
+
+- `cfdp::pdu::ack::InvalidAckedDirectiveCodeError` which is returned by the `AckPdu` constructor.
+- `cfdp::pdu::nak::NakPduCreatorWithReservedSegReqsBuf` constructor which exposes the segment
+  request buffer mutably to avoid the need for a separate segment request buffer.
+- `SpHeader::packet_len` direct method.
+- `AckFlags` which is implemented with `bitbybit::bitfield`
+- `ApidOutOfRangeError` and `SequenceCountOutOfRangeError`
+- Added PUS A legacy support for telecommands inside the `ecss.tc_pus_a` module
+- Added `SequenceCounter::increment_mut` and `SequenceCounter::get_and_increment_mut`
+- Implemented `SequenceCounter` for `Atomic` unsigned types and references of them
+- `PusPacket::has_checksum` and `WritablePusPacket::has_checksum`
+- PUS TC builder API, either via `PusTcBuilder::new`, or `PusTcCreator::builder`
+
+# [v0.15.0] 2025-07-18
+
+## Added
+
+- `PusTcCreatorWithReservedAppData` and `PusTmCreatorWithReservedSourceData` constructor variants
+  which allow writing source/app data into the serialization buffer directly without
+  requiring an extra buffer.
+
+# [v0.14.0] 2025-05-10
+
+## Changed
+
+- Moved CRC constants/implementations to dedicated `crc` module.
+- `crc::CRC_CCITT_FALSE_NO_TABLE` and `crc::CRC_CCITT_FALSE_BIG_TABLE` variants.
+- Renamed `PusPacket::crc16` to `PusPacket::opt_crc16`.
+
+## Added
+
+- `WritablePusPacket::write_to_bytes_crc_no_table` and `WritablePusPacket::write_to_bytes_no_crc`
+  variants.
+- `PusTmReader::new_crc_no_table` and `PusTcReader::new_crc_no_table` variants.
+- `crc16` methods for PUS TM and PUS TC reader.
+- PUS TM and PUS TC reader now return the reader instance directly instead of a tuple of the reader
+  and the read size. The instance `total_len` method can be used to retrieve the read lenght.
+
+# [v0.13.1] 2025-03-21
+
+- Bugfix due to operator precendence for `PusTcSecondaryHeader::pus_version`,
+  `PusTcSecondaryHeaderWithoutTimestamp::pus_version`, `CdsTime::from_bytes_with_u16_days` and
+  `CdsTime::from_bytes_with_u24_days`
+
+# [v0.13.0] 2024-11-08
+
+- Bumped MSRV to 1.81.0
+- Bump `zerocopy` to v0.8.0
+- Bump `thiserror` to v2.0.0
+
+## Changed
+
+- Migrated all Error implementations to thiserror, improved some naming and error handling in
+  general
+
+# [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
@@ -91,7 +457,7 @@ 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
@@ -311,3 +677,13 @@ The timestamp of `PusTm` is now optional. See Added and Changed section for deta
 
 Initial release with CCSDS Space Packet Primary Header implementation and basic PUS TC and TM
 implementations.
+
+[unreleased]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.17.0...HEAD
+[v0.17.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.16.1...v0.17.0
+[v0.16.1]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.16.0...v0.16.1
+[v0.16.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.15.0...v0.16.0
+[v0.15.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.14.0...v0.15.0
+[v0.14.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.13.1...v0.14.0
+[v0.13.1]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.13.0...v0.13.1
+[v0.13.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.12.0...v0.13.0
+[v0.12.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.11.2...v0.12.0

Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "spacepackets"
-version = "0.7.0-beta.1"
+version = "0.17.0"
 edition = "2021"
-rust-version = "1.61"
+rust-version = "1.83"
 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"
@@ -14,43 +14,34 @@ categories = ["aerospace", "aerospace::space-protocols", "no-std", "hardware-sup
 
 [dependencies]
 crc = "3"
-delegate = ">=0.8, <0.11"
+delegate = "0.13"
+paste = "1"
+zerocopy = { version = "0.8", features = ["derive"] }
+thiserror = { version = "2", default-features = false }
+num_enum = { version = "0.7", default-features = false }
+num-traits = { version = "0.2", default-features = false }
+serde = { version = "1", optional = true, default-features = false, features = ["derive"] }
+arbitrary-int = { version = "2" }
+portable-atomic = { version = "1", optional = true }
+bitbybit = "1.4"
 
-[dependencies.zerocopy]
-version = "0.7"
-features = ["derive"]
-
-[dependencies.thiserror]
-version = "1"
-optional = true
-
-[dependencies.num_enum]
-version = ">0.5, <=0.7"
-default-features = false
-
-[dependencies.serde]
-version = "1"
-optional = true
-default-features = false
-features = ["derive"]
-
-[dependencies.chrono]
-version = "0.4"
-default-features = false
-
-[dependencies.num-traits]
-version = "0.2"
-default-features = false
-
-[dev-dependencies.postcard]
-version = "1"
+time = { version = "0.3", default-features = false, optional = true }
+chrono = { version = "0.4", default-features = false, optional = true }
+defmt = { version = "1", default-features = false, 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"]
+portable-atomic = ["dep:portable-atomic", "portable-atomic/require-cas"]
+defmt = ["dep:defmt", "arbitrary-int/defmt"]
+serde = ["dep:serde", "chrono?/serde", "arbitrary-int/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"]

FUNDING.yml

@@ -0,0 +1 @@
+github: robamu

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)
+[![matrix chat](https://img.shields.io/matrix/sat-rs%3Amatrix.org)](https://matrix.to/#/#sat-rs:matrix.org)
 
 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 +39,36 @@ 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.
+ - [`portable-atomic`](https://github.com/taiki-e/portable-atomic): Basic support for `portable-atomic`
+   crate in addition to the support for core atomic types. This support requires atomic CAS support
+   enabled in the portable atomic crate.
 
 # Examples
 
 You can check the [documentation](https://docs.rs/spacepackets) of individual modules for various
 usage examples.
+
+# Coverage
+
+Coverage can be generated using [`llvm-cov`](https://github.com/taiki-e/cargo-llvm-cov). If you have not done so
+already, install the tool:
+
+```sh
+cargo +stable install cargo-llvm-cov --locked
+```
+
+After this, you can run `cargo llvm-cov nextest` to run all the tests and display coverage.
+
+# 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/'
+          }
+        }
+      }
+    }
+  }
 }

justfile

@@ -0,0 +1,36 @@
+all: check build embedded test clippy check-fmt docs coverage
+
+clippy:
+  cargo clippy -- -D warnings
+
+fmt:
+  cargo fmt --all
+
+check-fmt:
+  cargo fmt --all -- --check
+
+check:
+  cargo check --all-features
+
+embedded:
+  cargo build --target thumbv7em-none-eabihf --no-default-features
+  cargo build --target thumbv6m-none-eabi --no-default-features
+
+test:
+  cargo nextest r --all-features
+  cargo test --doc
+
+build:
+  cargo build --all-features
+
+docs:
+  RUSTDOCFLAGS="--cfg docsrs -Z unstable-options --generate-link-to-definition" cargo +nightly doc --all-features
+
+docs-html:
+  RUSTDOCFLAGS="--cfg docsrs -Z unstable-options --generate-link-to-definition" cargo +nightly doc --all-features --open
+
+coverage:
+  cargo llvm-cov nextest
+
+coverage-html:
+  cargo llvm-cov nextest --html --open

release-checklist.md

@@ -4,11 +4,14 @@ 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.

src/cfdp/lv.rs

@@ -1,5 +1,4 @@
 //! Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
-use crate::cfdp::TlvLvError;
 use crate::ByteConversionError;
 use core::str::Utf8Error;
 #[cfg(feature = "serde")]
@@ -7,6 +6,9 @@ use serde::{Deserialize, Serialize};
 #[cfg(feature = "std")]
 use std::string::String;
 
+use super::TlvLvDataTooLargeError;
+
+/// Minmum length of a CFDP length-value structure in bytes.
 pub const MIN_LV_LEN: usize = 1;
 
 /// Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
@@ -20,6 +22,7 @@ pub const MIN_LV_LEN: usize = 1;
 ///    this will be the lifetime of that data reference.
 #[derive(Debug, Copy, Clone, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct Lv<'data> {
     data: &'data [u8],
     // If the LV was generated from a raw bytestream, this will contain the start of the
@@ -61,9 +64,14 @@ pub(crate) fn generic_len_check_deserialization(
 }
 
 impl<'data> Lv<'data> {
-    pub fn new(data: &[u8]) -> Result<Lv, TlvLvError> {
+    /// Minimum length of a LV structure in bytes.
+    pub const MIN_LEN: usize = MIN_LV_LEN;
+
+    /// Generic constructor.
+    #[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,
@@ -72,6 +80,7 @@ impl<'data> Lv<'data> {
     }
 
     /// Creates a LV with an empty value field.
+    #[inline]
     pub fn new_empty() -> Lv<'data> {
         Lv {
             data: &[],
@@ -81,45 +90,53 @@ impl<'data> Lv<'data> {
 
     /// 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 {
         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.len() == 0
     }
 
+    /// Raw value part of the LV.
+    #[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>> {
         if self.is_empty() {
             return None;
@@ -135,6 +152,7 @@ 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)
@@ -151,6 +169,7 @@ impl<'data> Lv<'data> {
         MIN_LV_LEN + self.data.len()
     }
 
+    #[inline]
     pub(crate) fn from_be_bytes_no_len_check(
         buf: &'data [u8],
     ) -> Result<Lv<'data>, ByteConversionError> {
@@ -164,9 +183,11 @@ impl<'data> Lv<'data> {
 }
 
 #[cfg(test)]
-pub mod tests {
-    use crate::cfdp::lv::Lv;
-    use crate::cfdp::TlvLvError;
+mod tests {
+    use alloc::string::ToString;
+
+    use super::*;
+
     use crate::ByteConversionError;
     use std::string::String;
 
@@ -176,7 +197,7 @@ pub mod tests {
         let lv_res = Lv::new(&lv_data);
         assert!(lv_res.is_ok());
         let lv = lv_res.unwrap();
-        assert!(lv.value().len() > 0);
+        assert!(!lv.value().is_empty());
         let val = lv.value();
         assert_eq!(val[0], 1);
         assert_eq!(val[1], 2);
@@ -257,11 +278,11 @@ 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]

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;
@@ -16,92 +13,147 @@ pub const CFDP_VERSION_2_NAME: &str = "CCSDS 727.0-B-5";
 /// Currently, only this version is supported.
 pub const CFDP_VERSION_2: u8 = 0b001;
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+/// PDU type.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u1, exhaustive = true)]
 #[repr(u8)]
 pub enum PduType {
+    /// File directive PDU.
     FileDirective = 0,
+    /// File data PDU.
     FileData = 1,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+/// PDU direction.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u1, exhaustive = true)]
 #[repr(u8)]
 pub enum Direction {
+    /// Going towards the file receiver.
     TowardsReceiver = 0,
+    /// Going towards the file sender.
     TowardsSender = 1,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+/// PDU transmission mode.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u1, exhaustive = true)]
 #[repr(u8)]
 pub enum TransmissionMode {
+    /// Acknowledged (class 1) transfer.
     Acknowledged = 0,
+    /// Unacknowledged (class 2) transfer.
     Unacknowledged = 1,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+/// CRC flag.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u1, exhaustive = true)]
 #[repr(u8)]
 pub enum CrcFlag {
+    /// No CRC for the packet.
     NoCrc = 0,
+    /// Packet has CRC.
     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)]
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u1, exhaustive = true)]
 #[repr(u8)]
 pub enum SegmentMetadataFlag {
+    /// Segment metadata not present.
     NotPresent = 0,
+    /// Segment metadata present.
     Present = 1,
 }
 
 /// Always 0 and ignored for File Directive PDUs (CCSDS 727.0-B-5 P.75)
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u1, exhaustive = true)]
 #[repr(u8)]
 pub enum SegmentationControl {
+    /// No record boundary preservation.
     NoRecordBoundaryPreservation = 0,
+    /// With record boundary preservation.
     WithRecordBoundaryPreservation = 1,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+/// Fault handler codes according to the CFDP standard.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u3, exhaustive = false)]
 #[repr(u8)]
 pub enum FaultHandlerCode {
+    /// Notice of cancellation fault handler code.
     NoticeOfCancellation = 0b0001,
+    /// Notice of suspension fault handler code.
     NoticeOfSuspension = 0b0010,
+    /// Ignore error fault handler code.
     IgnoreError = 0b0011,
+    /// Abandon transaction fault handler code.
     AbandonTransaction = 0b0100,
 }
 
-#[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)]
+/// CFDP condition codes.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u4, exhaustive = false)]
 #[repr(u8)]
 pub enum ConditionCode {
     /// This is not an error condition for which a faulty handler override can be specified
     NoError = 0b0000,
+    /// Positive acknowledgement limit reached.
     PositiveAckLimitReached = 0b0001,
+    /// Keep-alive limit reached.
     KeepAliveLimitReached = 0b0010,
+    /// Invalid transmission mode.
     InvalidTransmissionMode = 0b0011,
+    /// Filestore rejection.
     FilestoreRejection = 0b0100,
+    /// File checksum error.
     FileChecksumFailure = 0b0101,
+    /// File size error.
     FileSizeError = 0b0110,
+    /// NAK limit reached.
     NakLimitReached = 0b0111,
+    /// Inactivity detected.
     InactivityDetected = 0b1000,
-    CheckLimitReached = 0b1001,
+    /// Check limit reached.
+    CheckLimitReached = 0b1010,
+    /// Unsupported checksum type.
     UnsupportedChecksumType = 0b1011,
     /// Not an actual fault condition for which fault handler overrides can be specified
     SuspendRequestReceived = 0b1110,
@@ -109,8 +161,11 @@ pub enum ConditionCode {
     CancelRequestReceived = 0b1111,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+/// Large file flag.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u1, exhaustive = true)]
 #[repr(u8)]
 pub enum LargeFileFlag {
     /// 32 bit maximum file size and FSS size
@@ -119,91 +174,144 @@ pub enum LargeFileFlag {
     Large = 1,
 }
 
+/// Transaction status for the ACK PDU field according to chapter 5.2.4 of the CFDP standard.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u2, exhaustive = true)]
+#[repr(u8)]
+pub enum TransactionStatus {
+    /// Transaction is not currently active and the CFDP implementation does not retain a
+    /// transaction history.
+    Undefined = 0b00,
+    /// Transaction is currently active.
+    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)]
+#[derive(Default, 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
     Modular = 0,
+    /// CRC32 Proximity-1.
     Crc32Proximity1 = 1,
+    /// CRC32C.
     Crc32C = 2,
-    /// Polynomial: 0x4C11DB7. Preferred checksum for now.
+    /// CRC32. Polynomial: 0x4C11DB7. Preferred checksum for now.
     Crc32 = 3,
+    /// Null checksum (no checksum).
+    #[default]
     NullChecksum = 15,
 }
 
-impl Default for ChecksumType {
-    fn default() -> Self {
-        Self::NullChecksum
-    }
-}
-
+/// Raw null checksum.
 pub const NULL_CHECKSUM_U32: [u8; 4] = [0; 4];
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+/// TLV or LV data larger than allowed [u8::MAX].
+#[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>,
+}
+
+/// Generic TLV/LV error.
+#[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.
+    /// Data too large error.
+    #[error("{0}")]
+    DataTooLarge(#[from] TlvLvDataTooLargeError),
+    /// Byte conversion error.
+    #[error("byte conversion error: {0}")]
+    ByteConversion(#[from] ByteConversionError),
+    /// Invalid TLV type field error.
+    #[error("{0}")]
+    InvalidTlvTypeField(#[from] InvalidTlvTypeFieldError),
+    /// Invalid value length.
+    #[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 +1,404 @@
+//! # Acknowledgement (ACK) PDU packet implementation.
+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};
+
+/// Invalid [FileDirectiveType] of the acknowledged PDU error.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, thiserror::Error)]
+#[error("invalid directive code of acknowledged PDU")]
+pub struct InvalidAckedDirectiveCodeError(pub FileDirectiveType);
+
+/// 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 {
+    /// Constructor.
+    pub fn new(
+        mut pdu_header: PduHeader,
+        directive_code_of_acked_pdu: FileDirectiveType,
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) -> Result<Self, InvalidAckedDirectiveCodeError> {
+        if directive_code_of_acked_pdu == FileDirectiveType::Eof {
+            pdu_header.pdu_conf.direction = Direction::TowardsSender;
+        } else if directive_code_of_acked_pdu == FileDirectiveType::Finished {
+            pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
+        } else {
+            return Err(InvalidAckedDirectiveCodeError(directive_code_of_acked_pdu));
+        }
+        // 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)
+    }
+
+    /// Constructor for an ACK PDU acknowledging an EOF PDU.
+    ///
+    /// Relevant for the file receiver.
+    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::Eof,
+            condition_code,
+            transaction_status,
+        )
+        .unwrap()
+    }
+
+    /// Constructor for an ACK PDU acknowledging a Finished PDU.
+    ///
+    /// Relevant for the file sender.
+    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::Finished,
+            condition_code,
+            transaction_status,
+        )
+        .unwrap()
+    }
+
+    /// PDU header.
+    #[inline]
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    /// Directive code of the acknowledged PDU.
+    #[inline]
+    pub fn directive_code_of_acked_pdu(&self) -> FileDirectiveType {
+        self.directive_code_of_acked_pdu
+    }
+
+    /// Condition code.
+    #[inline]
+    pub fn condition_code(&self) -> ConditionCode {
+        self.condition_code
+    }
+
+    /// Transaction status.
+    #[inline]
+    pub fn transaction_status(&self) -> TransactionStatus {
+        self.transaction_status
+    }
+
+    #[inline]
+    fn calc_pdu_datafield_len(&self) -> usize {
+        if self.crc_flag() == CrcFlag::WithCrc {
+            return 5;
+        }
+        3
+    }
+
+    /// Construct [Self] from the provided byte slice.
+    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::Ack),
+            }
+        })?;
+        if directive_type != FileDirectiveType::Ack {
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::Ack,
+            });
+        }
+        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::Eof
+            && acked_directive_type != FileDirectiveType::Finished
+        {
+            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();
+        // Unwrap okay, validity of acked directive code was checked.
+        Ok(Self::new(
+            pdu_header,
+            acked_directive_type,
+            condition_code,
+            transaction_status,
+        )
+        .unwrap())
+    }
+
+    /// Write [Self] to the provided buffer and returns the written size.
+    pub 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::Ack 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::Finished {
+            // 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)
+    }
+
+    /// Length of the written PDU in bytes.
+    pub fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+impl CfdpPdu for AckPdu {
+    #[inline]
+    fn pdu_header(&self) -> &PduHeader {
+        self.pdu_header()
+    }
+
+    #[inline]
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::Ack)
+    }
+}
+
+impl WritablePduPacket for AckPdu {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        self.write_to_bytes(buf)
+    }
+
+    fn len_written(&self) -> usize {
+        self.len_written()
+    }
+}
+
+#[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::Ack));
+        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_for_file_directive(pdu_conf, 0);
+        let ack_pdu = AckPdu::new(
+            pdu_header,
+            FileDirectiveType::Finished,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        )
+        .expect("creating ACK PDU failed");
+        assert_eq!(
+            ack_pdu.directive_code_of_acked_pdu(),
+            FileDirectiveType::Finished
+        );
+        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_for_file_directive(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::Ack as u8);
+        assert_eq!((buf[8] >> 4) & 0b1111, FileDirectiveType::Finished 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_too_small() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_for_file_directive(pdu_conf, 0);
+        let ack_pdu = AckPdu::new(
+            pdu_header,
+            FileDirectiveType::Finished,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        )
+        .expect("creating ACK PDU failed");
+        if let Err(PduError::ByteConversion(ByteConversionError::ToSliceTooSmall {
+            found,
+            expected,
+        })) = ack_pdu.write_to_bytes(&mut [0; 5])
+        {
+            assert_eq!(found, 5);
+            assert_eq!(expected, ack_pdu.len_written());
+        } else {
+            panic!("serialization should have failed");
+        }
+    }
+
+    #[test]
+    fn test_serialization_fs_error() {
+        generic_serialization_test(ConditionCode::FileSizeError, TransactionStatus::Terminated);
+    }
+    #[test]
+    fn test_invalid_directive_code_of_acked_pdu() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_for_file_directive(pdu_conf, 0);
+        assert_eq!(
+            AckPdu::new(
+                pdu_header,
+                FileDirectiveType::Metadata,
+                ConditionCode::NoError,
+                TransactionStatus::Active,
+            )
+            .unwrap_err(),
+            InvalidAckedDirectiveCodeError(FileDirectiveType::Metadata)
+        );
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_for_file_directive(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_for_file_directive(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_for_file_directive(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::Eof
+        );
+        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_for_file_directive(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

@@ -1,18 +1,22 @@
+//! # End-of-File (EOF) PDU packet implementation.
 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::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,
@@ -22,34 +26,58 @@ pub struct EofPdu {
 }
 
 impl EofPdu {
-    pub fn new_no_error(pdu_header: PduHeader, file_checksum: u32, file_size: u64) -> Self {
+    /// Constructor.
+    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
     }
 
+    /// Constructor for no error EOF PDUs.
+    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,
+        )
+    }
+
+    /// PDU header.
+    #[inline]
     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()
-    }
-
+    /// Condition code.
+    #[inline]
     pub fn condition_code(&self) -> ConditionCode {
         self.condition_code
     }
 
+    /// File checksum.
+    #[inline]
     pub fn file_checksum(&self) -> u32 {
         self.file_checksum
     }
 
+    /// File size.
+    #[inline]
     pub fn file_size(&self) -> u64 {
         self.file_size
     }
@@ -63,39 +91,13 @@ 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 {
-                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)
-    }
-
+    /// Construct [Self] from the provided byte slice.
     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)?;
@@ -108,13 +110,13 @@ impl EofPdu {
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
             PduError::InvalidDirectiveType {
                 found: buf[current_idx],
-                expected: Some(FileDirectiveType::EofPdu),
+                expected: Some(FileDirectiveType::Eof),
             }
         })?;
-        if directive_type != FileDirectiveType::EofPdu {
+        if directive_type != FileDirectiveType::Eof {
             return Err(PduError::WrongDirectiveType {
                 found: directive_type,
-                expected: FileDirectiveType::EofPdu,
+                expected: FileDirectiveType::Eof,
             });
         }
         current_idx += 1;
@@ -139,39 +141,125 @@ impl EofPdu {
             fault_location,
         })
     }
+
+    /// Write [Self] to the provided buffer and returns the written size.
+    pub 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::Eof 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)
+    }
+
+    /// Length of the written PDU in bytes.
+    pub fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+impl CfdpPdu for EofPdu {
+    #[inline]
+    fn pdu_header(&self) -> &PduHeader {
+        self.pdu_header()
+    }
+
+    #[inline]
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::Eof)
+    }
+}
+
+impl WritablePduPacket for EofPdu {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        self.write_to_bytes(buf)
+    }
+
+    fn len_written(&self) -> usize {
+        self.len_written()
+    }
 }
 
 #[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::Eof));
+        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 pdu_header = PduHeader::new_for_file_directive(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]
     fn test_serialization() {
         let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
-        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let pdu_header = PduHeader::new_for_file_directive(pdu_conf, 0);
         let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
         let mut buf: [u8; 64] = [0; 64];
         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;
+        buf[current_idx] = FileDirectiveType::Eof as u8;
         current_idx += 1;
         assert_eq!(
             (buf[current_idx] >> 4) & 0b1111,
@@ -194,16 +282,108 @@ mod tests {
     #[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 pdu_header = PduHeader::new_for_file_directive(pdu_conf, 0);
         let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
         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_for_file_directive(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_for_file_directive(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_for_file_directive(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_for_file_directive(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_for_file_directive(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

@@ -1,3 +1,4 @@
+//! # File Data PDU packet implementation
 use crate::cfdp::pdu::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
     PduError, PduHeader,
@@ -8,16 +9,26 @@ use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+use super::{CfdpPdu, FileDirectiveType, WritablePduPacket};
+
+/// Record continuation state for segment metadata.
+#[derive(Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u2, exhaustive = true)]
 #[repr(u8)]
 pub enum RecordContinuationState {
+    /// No start and no end.
     NoStartNoEnd = 0b00,
+    /// Start without end.
     StartWithoutEnd = 0b01,
+    /// End without start.
     EndWithoutStart = 0b10,
+    /// Start and end.
     StartAndEnd = 0b11,
 }
 
+/// Segment metadata structure.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct SegmentMetadata<'seg_meta> {
@@ -26,6 +37,7 @@ pub struct SegmentMetadata<'seg_meta> {
 }
 
 impl<'seg_meta> SegmentMetadata<'seg_meta> {
+    /// Constructor.
     pub fn new(
         record_continuation_state: RecordContinuationState,
         metadata: Option<&'seg_meta [u8]>,
@@ -41,16 +53,30 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
         })
     }
 
-    pub fn written_len(&self) -> usize {
+    /// Record continuation state.
+    #[inline]
+    pub fn record_continuation_state(&self) -> RecordContinuationState {
+        self.record_continuation_state
+    }
+
+    /// Raw metadata slice.
+    #[inline]
+    pub fn metadata(&self) -> Option<&'seg_meta [u8]> {
+        self.metadata
+    }
+
+    /// Length of the written segment metadata structure.
+    #[inline]
+    pub fn len_written(&self) -> usize {
         // Map empty metadata to 0 and slice to its length.
         1 + self.metadata.map_or(0, |meta| meta.len())
     }
 
     pub(crate) fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        if buf.len() < self.written_len() {
+        if buf.len() < self.len_written() {
             return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
-                expected: self.written_len(),
+                expected: self.len_written(),
             });
         }
         buf[0] = ((self.record_continuation_state as u8) << 6)
@@ -58,7 +84,7 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
         if let Some(metadata) = self.metadata {
             buf[1..1 + metadata.len()].copy_from_slice(metadata)
         }
-        Ok(self.written_len())
+        Ok(self.len_written())
     }
 
     pub(crate) fn from_bytes(buf: &'seg_meta [u8]) -> Result<Self, ByteConversionError> {
@@ -82,95 +108,44 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
     }
 }
 
-/// 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> {
+struct FdPduBase<'seg_meta> {
     pdu_header: PduHeader,
     #[cfg_attr(feature = "serde", serde(borrow))]
     segment_metadata: Option<SegmentMetadata<'seg_meta>>,
     offset: u64,
-    file_data: &'file_data [u8],
 }
 
-impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
-    pub fn new_with_seg_metadata(
-        pdu_header: PduHeader,
-        segment_metadata: SegmentMetadata<'seg_meta>,
-        offset: u64,
-        file_data: &'file_data [u8],
-    ) -> Self {
-        Self::new_generic(pdu_header, Some(segment_metadata), offset, file_data)
+impl CfdpPdu for FdPduBase<'_> {
+    #[inline]
+    fn pdu_header(&self) -> &PduHeader {
+        self.pdu_header()
     }
 
-    pub fn new_no_seg_metadata(
-        pdu_header: PduHeader,
-        offset: u64,
-        file_data: &'file_data [u8],
-    ) -> Self {
-        Self::new_generic(pdu_header, None, offset, file_data)
+    #[inline]
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        None
     }
+}
 
-    pub fn new_generic(
-        mut pdu_header: PduHeader,
-        segment_metadata: Option<SegmentMetadata<'seg_meta>>,
-        offset: u64,
-        file_data: &'file_data [u8],
-    ) -> Self {
-        pdu_header.pdu_type = PduType::FileData;
-        if segment_metadata.is_some() {
-            pdu_header.seg_metadata_flag = SegmentMetadataFlag::Present;
-        }
-        let mut pdu = Self {
-            pdu_header,
-            segment_metadata,
-            offset,
-            file_data,
-        };
-        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
-        pdu
-    }
-
-    fn calc_pdu_datafield_len(&self) -> usize {
+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 += self.segment_metadata.as_ref().unwrap().len_written()
         }
-        len += self.file_data.len();
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+        len += file_data_len as usize;
+        if self.crc_flag() == CrcFlag::WithCrc {
             len += 2;
         }
         len
     }
-    pub fn written_len(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
-    }
 
-    pub fn offset(&self) -> u64 {
-        self.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 {
-                found: buf.len(),
-                expected: self.written_len(),
-            }
-            .into());
-        }
+    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
@@ -184,17 +159,100 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
             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> {
+    #[inline]
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+}
+
+/// 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> {
+    #[cfg_attr(feature = "serde", serde(borrow))]
+    common: FdPduBase<'seg_meta>,
+    file_data: &'file_data [u8],
+}
+
+impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
+    /// Constructor for a file data PDU including segment metadata.
+    pub fn new_with_seg_metadata(
+        pdu_header: PduHeader,
+        segment_metadata: SegmentMetadata<'seg_meta>,
+        offset: u64,
+        file_data: &'file_data [u8],
+    ) -> Self {
+        Self::new(pdu_header, Some(segment_metadata), offset, file_data)
+    }
+
+    /// Constructor for a file data PDU without segment metadata.
+    pub fn new_no_seg_metadata(
+        pdu_header: PduHeader,
+        offset: u64,
+        file_data: &'file_data [u8],
+    ) -> Self {
+        Self::new(pdu_header, None, offset, file_data)
+    }
+
+    /// Generic constructor for a file data PDU.
+    pub fn new(
+        mut pdu_header: PduHeader,
+        segment_metadata: Option<SegmentMetadata<'seg_meta>>,
+        offset: u64,
+        file_data: &'file_data [u8],
+    ) -> 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,
+        };
+        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() as u64)
+    }
+
+    /// Optional segment metadata.
+    #[inline]
+    pub fn segment_metadata(&self) -> Option<&SegmentMetadata<'_>> {
+        self.common.segment_metadata.as_ref()
+    }
+
+    /// PDU header.
+    #[inline]
+    pub fn pdu_header(&self) -> &PduHeader {
+        self.common.pdu_header()
+    }
+
+    /// File data offset.
+    #[inline]
+    pub fn offset(&self) -> u64 {
+        self.common.offset
+    }
+
+    /// File data.
+    #[inline]
+    pub fn file_data(&self) -> &'file_data [u8] {
+        self.file_data
+    }
+
+    /// Read [Self] from the provided buffer.
+    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>();
@@ -202,7 +260,7 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
         let mut segment_metadata = None;
         if pdu_header.seg_metadata_flag == SegmentMetadataFlag::Present {
             segment_metadata = Some(SegmentMetadata::from_bytes(&buf[current_idx..])?);
-            current_idx += segment_metadata.as_ref().unwrap().written_len();
+            current_idx += segment_metadata.as_ref().unwrap().len_written();
         }
         let (fss, offset) = read_fss_field(pdu_header.pdu_conf.file_flag, &buf[current_idx..]);
         current_idx += fss;
@@ -214,28 +272,236 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
             .into());
         }
         Ok(Self {
-            pdu_header,
-            segment_metadata,
-            offset,
+            common: FdPduBase {
+                pdu_header,
+                segment_metadata,
+                offset,
+            },
             file_data: &buf[current_idx..full_len_without_crc],
         })
     }
+
+    /// Write [Self] to the provided buffer and returns the written size.
+    pub 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)
+    }
+
+    /// Length of the written PDU.
+    pub fn len_written(&self) -> usize {
+        self.common.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+impl CfdpPdu for FileDataPdu<'_, '_> {
+    #[inline]
+    fn pdu_header(&self) -> &PduHeader {
+        &self.common.pdu_header
+    }
+
+    #[inline]
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        None
+    }
+}
+
+impl WritablePduPacket for FileDataPdu<'_, '_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        self.write_to_bytes(buf)
+    }
+
+    fn len_written(&self) -> usize {
+        self.len_written()
+    }
+}
+
+/// 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> {
+    /// Constructor for a file data PDU including segment metadata.
+    pub fn new_with_seg_metadata(
+        pdu_header: PduHeader,
+        segment_metadata: SegmentMetadata<'seg_meta>,
+        offset: u64,
+        file_data_len: u64,
+    ) -> Self {
+        Self::new(pdu_header, Some(segment_metadata), offset, file_data_len)
+    }
+
+    /// Constructor for a file data PDU without segment metadata.
+    pub fn new_no_seg_metadata(pdu_header: PduHeader, offset: u64, file_data_len: u64) -> Self {
+        Self::new(pdu_header, None, offset, file_data_len)
+    }
+
+    /// Generic constructor.
+    pub fn new(
+        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)
+    }
+
+    /// Length of the written PDU.
+    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<'_> {
+    /// Mutable access to the file data field.
+    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 let Some(segment_metadata) = segment_metadata {
+        subtract += 1 + segment_metadata.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 +509,25 @@ 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 +537,11 @@ 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 +557,22 @@ 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 +584,33 @@ 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 +626,8 @@ 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 +637,7 @@ 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 +666,13 @@ 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 +694,177 @@ 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

@@ -1,28 +1,44 @@
+//! # Finished PDU packet implementation.
 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::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};
+
+/// Delivery code enumeration.
 #[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 {
+    /// Completed delivery.
     Complete = 0,
+    /// Incomplete delivery.
     Incomplete = 1,
 }
 
+/// File status enumeration.
 #[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 {
+    /// File was discarded deliberately.
     DiscardDeliberately = 0b00,
+    /// File was rejected by the filestore.
     DiscardedFsRejection = 0b01,
+    /// File was retained (but not necesarilly complete).
     Retained = 0b10,
+    /// Unreported file status.
     Unreported = 0b11,
 }
 
@@ -30,33 +46,35 @@ 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(
+    pub fn new_no_error(
         pdu_header: PduHeader,
         delivery_code: DeliveryCode,
         file_status: FileStatus,
     ) -> Self {
-        Self::new_generic(
+        Self::new(
             pdu_header,
             ConditionCode::NoError,
             delivery_code,
             file_status,
-            None,
+            &[],
             None,
         )
     }
 
+    /// Constructor where the fault location is provided.
     pub fn new_with_error(
         pdu_header: PduHeader,
         condition_code: ConditionCode,
@@ -64,25 +82,32 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         file_status: FileStatus,
         fault_location: EntityIdTlv,
     ) -> Self {
-        Self::new_generic(
+        Self::new(
             pdu_header,
             condition_code,
             delivery_code,
             file_status,
-            None,
+            &[],
             Some(fault_location),
         )
     }
 
-    pub fn new_generic(
+    /// Generic constructor.
+    pub fn new(
         mut 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>,
     ) -> 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,
@@ -94,47 +119,60 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         finished_pdu.pdu_header.pdu_datafield_len = finished_pdu.calc_pdu_datafield_len() as u16;
         finished_pdu
     }
+
+    /// PDU header.
+    #[inline]
     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()
-    }
-
+    /// Condition code.
+    #[inline]
     pub fn condition_code(&self) -> ConditionCode {
         self.condition_code
     }
 
+    /// Delivery code.
+    #[inline]
     pub fn delivery_code(&self) -> DeliveryCode {
         self.delivery_code
     }
 
+    /// File status.
+    #[inline]
     pub fn file_status(&self) -> FileStatus {
         self.file_status
     }
 
-    pub fn filestore_responses(&self) -> Option<&'fs_responses [u8]> {
+    /// Filestore responses as a slice.
+    #[inline]
+    pub fn filestore_responses(&self) -> &[FilestoreResponseTlv<'_, '_, '_>] {
         self.fs_responses
     }
 
+    /// Optional fault location [EntityIdTlv].
+    #[inline]
     pub fn fault_location(&self) -> Option<EntityIdTlv> {
         self.fault_location
     }
 
     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
     }
 
+    /// Write [Self] to the provided buffer and returns the written size.
     pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        let expected_len = self.written_len();
+        let expected_len = self.len_written();
         if buf.len() < expected_len {
             return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
@@ -144,27 +182,104 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         }
 
         let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
-        buf[current_idx] = FileDirectiveType::FinishedPdu as u8;
+        buf[current_idx] = FileDirectiveType::Finished as u8;
         current_idx += 1;
         buf[current_idx] = ((self.condition_code as u8) << 4)
             | ((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)
     }
 
+    /// Length of the written PDU in bytes.
+    pub fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+impl CfdpPdu for FinishedPduCreator<'_> {
+    #[inline]
+    fn pdu_header(&self) -> &PduHeader {
+        self.pdu_header()
+    }
+
+    #[inline]
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::Finished)
+    }
+}
+
+impl WritablePduPacket for FinishedPduCreator<'_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        self.write_to_bytes(buf)
+    }
+
+    fn len_written(&self) -> usize {
+        self.len_written()
+    }
+}
+
+/// 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)
+    }
+}
+
+/// Fnished PDU reader structure.
+#[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;
@@ -172,13 +287,13 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
             PduError::InvalidDirectiveType {
                 found: buf[current_idx],
-                expected: Some(FileDirectiveType::FinishedPdu),
+                expected: Some(FileDirectiveType::Finished),
             }
         })?;
-        if directive_type != FileDirectiveType::FinishedPdu {
+        if directive_type != FileDirectiveType::Finished {
             return Err(PduError::WrongDirectiveType {
                 found: directive_type,
-                expected: FileDirectiveType::FinishedPdu,
+                expected: FileDirectiveType::Finished,
             });
         }
         current_idx += 1;
@@ -188,24 +303,69 @@ 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,
         })
     }
 
+    /// Raw filestore responses.
+    #[inline]
+    pub fn fs_responses_raw(&self) -> &[u8] {
+        self.fs_responses_raw
+    }
+
+    /// Iterator over the filestore responses.
+    #[inline]
+    pub fn fs_responses_iter(&self) -> FilestoreResponseIterator<'_> {
+        FilestoreResponseIterator {
+            responses_buf: self.fs_responses_raw,
+            current_idx: 0,
+        }
+    }
+
+    /// Condition code.
+    #[inline]
+    pub fn condition_code(&self) -> ConditionCode {
+        self.condition_code
+    }
+
+    /// Delivery code.
+    #[inline]
+    pub fn delivery_code(&self) -> DeliveryCode {
+        self.delivery_code
+    }
+
+    /// File status.
+    #[inline]
+    pub fn file_status(&self) -> FileStatus {
+        self.file_status
+    }
+
+    /// Optional fault location [EntityIdTlv].
+    #[inline]
+    pub fn fault_location(&self) -> Option<EntityIdTlv> {
+        self.fault_location
+    }
+
+    /// PDU header.
+    #[inline]
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
     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.
@@ -216,12 +376,12 @@ 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();
@@ -229,14 +389,26 @@ 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(),
+                    ));
                 }
             }
         }
@@ -244,21 +416,57 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
     }
 }
 
+impl CfdpPdu for FinishedPduReader<'_> {
+    #[inline]
+    fn pdu_header(&self) -> &PduHeader {
+        self.pdu_header()
+    }
+
+    #[inline]
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::Finished)
+    }
+}
+
+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> {
-        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<'static> {
+        let pdu_header = PduHeader::new_for_file_directive(common_pdu_conf(crc_flag, fss), 0);
+        FinishedPduCreator::new_no_error(pdu_header, delivery_code, file_status)
     }
 
     #[test]
@@ -270,11 +478,31 @@ 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::Finished)
+        );
+        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) {
@@ -288,11 +516,16 @@ 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);
+        assert_eq!(buf[current_idx], FileDirectiveType::Finished as u8);
         current_idx += 1;
         assert_eq!(
             (buf[current_idx] >> 4) & 0b1111,
@@ -321,6 +554,20 @@ 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(
@@ -331,9 +578,177 @@ 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_for_file_directive(
+            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());
+        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_for_file_directive(
+            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_for_file_directive(
+            common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal),
+            0,
+        );
+        let finished_pdu = FinishedPduCreator::new(
+            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_for_file_directive(
+            common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal),
+            0,
+        );
+        let finished_pdu = FinishedPduCreator::new(
+            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

@@ -1,25 +1,37 @@
+//! # Metadata PDU packet implementation.
+#[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::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};
+
+/// Generic metadata parameters.
 #[derive(Default, Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct MetadataGenericParams {
+    /// Closure requested flag.
     pub closure_requested: bool,
+    /// Checksum type.
     pub checksum_type: ChecksumType,
+    /// File size.
     pub file_size: u64,
 }
 
 impl MetadataGenericParams {
+    /// Constructor.
     pub fn new(closure_requested: bool, checksum_type: ChecksumType, file_size: u64) -> Self {
         Self {
             closure_requested,
@@ -29,6 +41,7 @@ impl MetadataGenericParams {
     }
 }
 
+/// Build the metadata options from a slice of [Tlv]s
 pub fn build_metadata_opts_from_slice(
     buf: &mut [u8],
     tlvs: &[Tlv],
@@ -40,6 +53,7 @@ pub fn build_metadata_opts_from_slice(
     Ok(written)
 }
 
+/// Build the metadata options from a vector of [Tlv]s
 #[cfg(feature = "alloc")]
 pub fn build_metadata_opts_from_vec(
     buf: &mut [u8],
@@ -48,6 +62,204 @@ pub fn build_metadata_opts_from_vec(
     build_metadata_opts_from_slice(buf, tlvs.as_slice())
 }
 
+/// Build the metadata options from a slice of [TlvOwned]s
+#[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> {
+    /// Constructor for a metadata PDU without options.
+    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,
+            &[],
+        )
+    }
+
+    /// Constructor for a metadata PDU with options.
+    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,
+        )
+    }
+
+    /// Generic constructor for a metadata PDU.
+    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
+    }
+
+    /// Metadata generic parameters.
+    #[inline]
+    pub fn metadata_params(&self) -> &MetadataGenericParams {
+        &self.metadata_params
+    }
+
+    /// Source file name as a [Lv].
+    #[inline]
+    pub fn src_file_name(&self) -> Lv<'src_name> {
+        self.src_file_name
+    }
+
+    /// Destination file name as a [Lv].
+    #[inline]
+    pub fn dest_file_name(&self) -> Lv<'dest_name> {
+        self.dest_file_name
+    }
+
+    /// PDU header.
+    #[inline]
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    /// Raw options.
+    #[inline]
+    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
+    }
+
+    /// Write [Self] to the provided buffer and returns the written size.
+    pub 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::Metadata 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)
+    }
+
+    /// Length of the written PDU in bytes.
+    pub fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+impl CfdpPdu for MetadataPduCreator<'_, '_, '_> {
+    #[inline]
+    fn pdu_header(&self) -> &PduHeader {
+        self.pdu_header()
+    }
+
+    #[inline]
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::Metadata)
+    }
+}
+
+impl WritablePduPacket for MetadataPduCreator<'_, '_, '_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        self.write_to_bytes(buf)
+    }
+
+    fn len_written(&self) -> usize {
+        self.len_written()
+    }
+}
+
 /// 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 +291,31 @@ 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> {
+    /// Constructor from raw bytes.
+    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 {
-                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> {
+    /// Constructor from raw bytes.
+    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;
@@ -250,13 +328,13 @@ impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
             PduError::InvalidDirectiveType {
                 found: buf[current_idx],
-                expected: Some(FileDirectiveType::MetadataPdu),
+                expected: Some(FileDirectiveType::Metadata),
             }
         })?;
-        if directive_type != FileDirectiveType::MetadataPdu {
+        if directive_type != FileDirectiveType::Metadata {
             return Err(PduError::WrongDirectiveType {
                 found: directive_type,
-                expected: FileDirectiveType::MetadataPdu,
+                expected: FileDirectiveType::Metadata,
             });
         }
         current_idx += 1;
@@ -274,56 +352,110 @@ 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,
+        })
+    }
+
+    /// PDU header.
+    #[inline]
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    /// Raw options.
+    #[inline]
+    pub fn options(&self) -> &'raw [u8] {
+        self.options
+    }
+
+    /// Generic metadata parameters.
+    #[inline]
+    pub fn metadata_params(&self) -> &MetadataGenericParams {
+        &self.metadata_params
+    }
+
+    /// Source file name as a [Lv].
+    #[inline]
+    pub fn src_file_name(&self) -> Lv<'_> {
+        self.src_file_name
+    }
+
+    /// Destination file name as a [Lv].
+    #[inline]
+    pub fn dest_file_name(&self) -> Lv<'_> {
+        self.dest_file_name
+    }
+}
+
+impl CfdpPdu for MetadataPduReader<'_> {
+    #[inline]
+    fn pdu_header(&self) -> &PduHeader {
+        self.pdu_header()
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::Metadata)
+    }
 }
 
 #[cfg(test)]
-pub mod tests {
+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 pdu_header = PduHeader::new_for_file_directive(common_pdu_conf(crc_flag, fss), 0);
+        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,
@@ -335,10 +467,15 @@ 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
@@ -348,60 +485,169 @@ 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::Metadata)
+        );
+        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[7], FileDirectiveType::Metadata 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());
@@ -416,14 +662,20 @@ 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());
@@ -437,8 +689,8 @@ 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]
@@ -480,13 +732,14 @@ 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);
@@ -502,19 +755,118 @@ 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::Metadata));
+            assert_eq!(
+                error.to_string(),
+                "invalid directive type, found 255, expected Some(Metadata)"
+            );
+        } 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::Eof 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::Eof);
+            assert_eq!(expected, FileDirectiveType::Metadata);
+            assert_eq!(
+                error.to_string(),
+                "wrong directive type, found Eof, expected Metadata"
+            );
+        } else {
+            panic!("Expected InvalidDirectiveType error, got {:?}", error);
+        }
+    }
     #[test]
     fn test_corrects_pdu_header() {
         let pdu_header = PduHeader::new_for_file_data(
@@ -527,8 +879,12 @@ 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

@@ -1,169 +1,225 @@
 //! CFDP Packet Data Unit (PDU) support.
+use crate::cfdp::pdu::ack::InvalidAckedDirectiveCodeError;
+use crate::cfdp::pdu::nak::InvalidStartOrEndOfScopeError;
 use crate::cfdp::*;
+use crate::crc::CRC_CCITT_FALSE;
 use crate::util::{UnsignedByteField, UnsignedByteFieldU8, UnsignedEnum};
 use crate::ByteConversionError;
-use crate::CRC_CCITT_FALSE;
-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;
 
+/// File directive type.
 #[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,
-    FinishedPdu = 0x05,
-    AckPdu = 0x06,
-    MetadataPdu = 0x07,
-    NakPdu = 0x08,
-    PromptPdu = 0x09,
-    KeepAlivePdu = 0x0c,
+    /// EOF.
+    Eof = 0x04,
+    /// Finished.
+    Finished = 0x05,
+    /// ACK.
+    Ack = 0x06,
+    /// Metadata.
+    Metadata = 0x07,
+    /// NAK.
+    Nak = 0x08,
+    /// Prompt.
+    Prompt = 0x09,
+    /// Keep Alive.
+    KeepAlive = 0x0c,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+/// PDU error.
+#[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].
+    /// Byte conversion error.
+    #[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),
+    /// Source and destination entity ID lengths do not match.
+    #[error(
+        "missmatch of PDU source ID length {src_id_len} and destination ID length {dest_id_len}"
+    )]
     SourceDestIdLenMissmatch {
+        /// Source ID length.
         src_id_len: usize,
+        /// Destination ID length.
         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 directive type.
         found: FileDirectiveType,
+        /// Expected directive type.
         expected: FileDirectiveType,
     },
-    /// The directive type field contained a value not in the range of permitted values.
+    /// 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 reader.
+    #[error("invalid directive type, found {found:?}, expected {expected:?}")]
     InvalidDirectiveType {
+        /// Found raw directive type.
         found: u8,
+        /// Expected raw directive type if applicable.
         expected: Option<FileDirectiveType>,
     },
+    /// Invalid start or end of scope for a NAK PDU.
+    #[error("nak pdu: {0}")]
+    InvalidStartOrEndOfScope(#[from] InvalidStartOrEndOfScopeError),
     /// 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),
+    /// File size is too large.
+    #[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_id_len,
-                dest_id_len,
-            } => {
-                write!(
-                    f,
-                    "missmatch of PDU source length {src_id_len} and destination length {dest_id_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:?}"
-                )
-            }
-            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")
-            }
+impl From<InvalidAckedDirectiveCodeError> for PduError {
+    fn from(value: InvalidAckedDirectiveCodeError) -> Self {
+        Self::InvalidDirectiveType {
+            found: value.0 as u8,
+            expected: None,
         }
     }
 }
 
-#[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,
-        }
+/// Generic trait for a PDU which can be written to bytes.
+pub trait WritablePduPacket {
+    /// Length when written to bytes.
+    fn len_written(&self) -> usize;
+
+    /// Write the PDU to a raw buffer, returning the written length.
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError>;
+
+    /// Convert the PDU to an owned vector of bytes.
+    #[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)
     }
 }
 
-impl From<ByteConversionError> for PduError {
-    fn from(value: ByteConversionError) -> Self {
-        Self::ByteConversionError(value)
-    }
-}
+/// Abstraction trait for fields and properties common for all PDUs.
+pub trait CfdpPdu {
+    /// PDU header.
+    fn pdu_header(&self) -> &PduHeader;
 
-impl From<TlvLvError> for PduError {
-    fn from(e: TlvLvError) -> Self {
-        Self::TlvLvError(e)
+    /// Source ID (file sender).
+    #[inline]
+    fn source_id(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().source_entity_id
     }
+
+    /// Destination ID (file sender).
+    #[inline]
+    fn dest_id(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().dest_entity_id
+    }
+
+    /// Transaction sequence number.
+    #[inline]
+    fn transaction_seq_num(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().transaction_seq_num
+    }
+
+    /// Transmission mode.
+    #[inline]
+    fn transmission_mode(&self) -> TransmissionMode {
+        self.pdu_header().common_pdu_conf().trans_mode
+    }
+
+    /// Direction.
+    #[inline]
+    fn direction(&self) -> Direction {
+        self.pdu_header().common_pdu_conf().direction
+    }
+
+    /// CRC flag.
+    #[inline]
+    fn crc_flag(&self) -> CrcFlag {
+        self.pdu_header().common_pdu_conf().crc_flag
+    }
+
+    /// File flag.
+    #[inline]
+    fn file_flag(&self) -> LargeFileFlag {
+        self.pdu_header().common_pdu_conf().file_flag
+    }
+
+    /// PDU type.
+    #[inline]
+    fn pdu_type(&self) -> PduType {
+        self.pdu_header().pdu_type()
+    }
+
+    /// File directive type when applicable.
+    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,
+    /// Transaction sequence number.
     pub transaction_seq_num: UnsignedByteField,
+    /// Transmission mode.
     pub trans_mode: TransmissionMode,
+    /// File flag.
     pub file_flag: LargeFileFlag,
+    /// CRC flag.
     pub crc_flag: CrcFlag,
+    /// Direction.
     pub direction: Direction,
 }
 
 // TODO: Builder pattern might be applicable here..
 impl CommonPduConfig {
+    /// Generic constructor.
+    #[inline]
     pub fn new(
         source_id: impl Into<UnsignedByteField>,
         dest_id: impl Into<UnsignedByteField>,
@@ -195,6 +251,8 @@ impl CommonPduConfig {
         })
     }
 
+    /// Constructor for custom byte field with default field values for the other fields.
+    #[inline]
     pub fn new_with_byte_fields(
         source_id: impl Into<UnsignedByteField>,
         dest_id: impl Into<UnsignedByteField>,
@@ -211,10 +269,13 @@ impl CommonPduConfig {
         )
     }
 
+    /// Source ID (file sender).
+    #[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>,
@@ -237,6 +298,8 @@ impl CommonPduConfig {
         Ok((source_id, dest_id))
     }
 
+    /// Set the source and destination ID field.
+    #[inline]
     pub fn set_source_and_dest_id(
         &mut self,
         source_id: impl Into<UnsignedByteField>,
@@ -248,6 +311,8 @@ impl CommonPduConfig {
         Ok(())
     }
 
+    /// Destination ID (file receiver).
+    #[inline]
     pub fn dest_id(&self) -> UnsignedByteField {
         self.dest_entity_id
     }
@@ -256,6 +321,7 @@ 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(
@@ -271,6 +337,20 @@ 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
+    }
+}
+
+/// Fixed header length of the PDU header.
 pub const FIXED_HEADER_LEN: usize = 4;
 
 /// Abstraction for the PDU header common to all CFDP PDUs.
@@ -278,6 +358,7 @@ 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,
@@ -287,6 +368,11 @@ pub struct PduHeader {
 }
 
 impl PduHeader {
+    /// Fixed length of the PDU header when written to a raw buffer.
+    pub const FIXED_LEN: usize = FIXED_HEADER_LEN;
+
+    /// Constructor for a File Data PDU header.
+    #[inline]
     pub fn new_for_file_data(
         pdu_conf: CommonPduConfig,
         pdu_datafield_len: u16,
@@ -302,6 +388,8 @@ impl PduHeader {
         )
     }
 
+    /// Constructor for a file data PDU.
+    #[inline]
     pub fn new_for_file_data_default(pdu_conf: CommonPduConfig, pdu_datafield_len: u16) -> Self {
         Self::new_generic(
             PduType::FileData,
@@ -311,7 +399,10 @@ impl PduHeader {
             SegmentationControl::NoRecordBoundaryPreservation,
         )
     }
-    pub fn new_no_file_data(pdu_conf: CommonPduConfig, pdu_datafield_len: u16) -> Self {
+
+    /// Constructor for a file directive PDU.
+    #[inline]
+    pub fn new_for_file_directive(pdu_conf: CommonPduConfig, pdu_datafield_len: u16) -> Self {
         Self::new_generic(
             PduType::FileDirective,
             pdu_conf,
@@ -321,6 +412,20 @@ impl PduHeader {
         )
     }
 
+    /// Constructor from a given [CommonPduConfig] and for a file directive PDU.
+    #[inline]
+    pub fn from_pdu_conf_for_file_directive(pdu_conf: CommonPduConfig) -> Self {
+        Self::new_generic(
+            PduType::FileDirective,
+            pdu_conf,
+            0,
+            SegmentMetadataFlag::NotPresent,
+            SegmentationControl::NoRecordBoundaryPreservation,
+        )
+    }
+
+    /// Generic constructor.
+    #[inline]
     pub fn new_generic(
         pdu_type: PduType,
         pdu_conf: CommonPduConfig,
@@ -338,6 +443,7 @@ 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()
@@ -345,25 +451,28 @@ impl PduHeader {
             + self.pdu_conf.dest_entity_id.size()
     }
 
+    /// PDU data field length.
+    #[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
     }
 
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        // 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 {
-                src_id_len: self.pdu_conf.source_entity_id.size(),
-                dest_id_len: self.pdu_conf.dest_entity_id.size(),
-            });
-        }
+    /// Write the header to a raw buffer, returning the written length on success.
+    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        // The API does not allow passing entity IDs with different sizes, so this should
+        // never happen.
+        assert_eq!(
+            self.pdu_conf.source_entity_id.size(),
+            self.pdu_conf.dest_entity_id.size(),
+            "unexpected missmatch of source and destination entity ID length"
+        );
         if buf.len()
             < FIXED_HEADER_LEN
                 + self.pdu_conf.source_entity_id.size()
@@ -372,8 +481,7 @@ impl PduHeader {
             return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: FIXED_HEADER_LEN,
-            }
-            .into());
+            });
         }
         let mut current_idx = 0;
         buf[current_idx] = (CFDP_VERSION_2 << 5)
@@ -423,7 +531,7 @@ impl PduHeader {
             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(),
                 )));
             }
@@ -442,7 +550,7 @@ impl PduHeader {
     /// function.
     pub fn from_bytes(buf: &[u8]) -> Result<(Self, usize), PduError> {
         if buf.len() < FIXED_HEADER_LEN {
-            return Err(PduError::ByteConversionError(
+            return Err(PduError::ByteConversion(
                 ByteConversionError::FromSliceTooSmall {
                     found: buf.len(),
                     expected: FIXED_HEADER_LEN,
@@ -523,17 +631,27 @@ impl PduHeader {
             current_idx,
         ))
     }
+
+    /// PDU type.
+    #[inline]
     pub fn pdu_type(&self) -> PduType {
         self.pdu_type
     }
 
+    /// Common PDU configuration fields.
+    #[inline]
     pub fn common_pdu_conf(&self) -> &CommonPduConfig {
         &self.pdu_conf
     }
 
+    /// Segment metadata flag.
+    #[inline]
     pub fn seg_metadata_flag(&self) -> SegmentMetadataFlag {
         self.seg_metadata_flag
     }
+
+    /// Segmentation Control.
+    #[inline]
     pub fn seg_ctrl(&self) -> SegmentationControl {
         self.seg_ctrl
     }
@@ -605,23 +723,26 @@ 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;
@@ -632,7 +753,6 @@ 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);
@@ -678,7 +798,7 @@ mod tests {
                             .try_into()
                             .unwrap()
                     ),
-                    ubf.value() as u64
+                    ubf.value()
                 ),
                 _ => panic!("invalid entity ID length"),
             }
@@ -696,7 +816,7 @@ mod tests {
         let transaction_id = UnsignedByteFieldU8::new(3);
         let common_pdu_cfg = CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_id)
             .expect("common config creation failed");
-        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let pdu_header = PduHeader::new_for_file_directive(common_pdu_cfg, 5);
         assert_eq!(pdu_header.pdu_type(), PduType::FileDirective);
         let common_conf_ref = pdu_header.common_pdu_conf();
         assert_eq!(*common_conf_ref, common_pdu_cfg);
@@ -713,6 +833,17 @@ 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();
@@ -751,13 +882,14 @@ mod tests {
         let transaction_id = UnsignedByteFieldU8::new(3);
         let common_pdu_cfg = CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_id)
             .expect("common config creation failed");
-        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let pdu_header = PduHeader::new_for_file_directive(common_pdu_cfg, 5);
         let mut buf: [u8; 7] = [0; 7];
         let res = pdu_header.write_to_bytes(&mut buf);
         assert!(res.is_ok());
         // 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]
@@ -767,7 +899,7 @@ mod tests {
         let transaction_id = UnsignedByteFieldU8::new(3);
         let common_pdu_cfg = CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_id)
             .expect("common config creation failed");
-        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let pdu_header = PduHeader::new_for_file_directive(common_pdu_cfg, 5);
         let mut buf: [u8; 7] = [0; 7];
         let res = pdu_header.write_to_bytes(&mut buf);
         assert!(res.is_ok());
@@ -840,7 +972,7 @@ mod tests {
         let transaction_id = UnsignedByteFieldU8::new(3);
         let common_pdu_cfg = CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_id)
             .expect("common config creation failed");
-        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let pdu_header = PduHeader::new_for_file_directive(common_pdu_cfg, 5);
         let mut buf: [u8; 7] = [0; 7];
         let res = pdu_header.write_to_bytes(&mut buf);
         assert!(res.is_ok());
@@ -851,6 +983,10 @@ 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);
         }
@@ -862,7 +998,7 @@ mod tests {
         let res = PduHeader::from_bytes(&buf);
         assert!(res.is_err());
         let error = res.unwrap_err();
-        if let PduError::ByteConversionError(ByteConversionError::FromSliceTooSmall {
+        if let PduError::ByteConversion(ByteConversionError::FromSliceTooSmall {
             found,
             expected,
         }) = error
@@ -881,20 +1017,24 @@ mod tests {
         let transaction_id = UnsignedByteFieldU8::new(3);
         let common_pdu_cfg = CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_id)
             .expect("common config creation failed");
-        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let pdu_header = PduHeader::new_for_file_directive(common_pdu_cfg, 5);
         let mut buf: [u8; 7] = [0; 7];
         let res = pdu_header.write_to_bytes(&mut buf);
         assert!(res.is_ok());
         let header = PduHeader::from_bytes(&buf[0..6]);
         assert!(header.is_err());
         let error = header.unwrap_err();
-        if let PduError::ByteConversionError(ByteConversionError::FromSliceTooSmall {
+        if let PduError::ByteConversion(ByteConversionError::FromSliceTooSmall {
             found,
             expected,
         }) = error
         {
             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"
+            );
         }
     }
 
@@ -922,6 +1062,10 @@ 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)
         }
@@ -942,6 +1086,10 @@ mod tests {
         {
             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"
+            );
         }
     }
 
@@ -952,7 +1100,7 @@ mod tests {
         let transaction_id = UnsignedByteFieldU8::new(3);
         let common_pdu_cfg = CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_id)
             .expect("common config creation failed");
-        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let pdu_header = PduHeader::new_for_file_directive(common_pdu_cfg, 5);
         let mut buf: [u8; 7] = [0; 7];
         let res = pdu_header.write_to_bytes(&mut buf);
         assert!(res.is_ok());
@@ -976,7 +1124,7 @@ mod tests {
         let transaction_id = UnsignedByteFieldU8::new(3);
         let common_pdu_cfg = CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_id)
             .expect("common config creation failed");
-        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let pdu_header = PduHeader::new_for_file_directive(common_pdu_cfg, 5);
         let mut buf: [u8; 7] = [0; 7];
         let res = pdu_header.write_to_bytes(&mut buf);
         assert!(res.is_ok());
@@ -992,4 +1140,28 @@ 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);
+    }
+
+    #[test]
+    fn test_ctor_from_pdu_conf() {
+        assert_eq!(
+            PduHeader::from_pdu_conf_for_file_directive(CommonPduConfig::default()),
+            PduHeader::new_for_file_directive(CommonPduConfig::default(), 0)
+        );
+    }
 }

src/cfdp/tlv/msg_to_user.rs

@@ -1,16 +1,23 @@
 //! Abstractions for the Message to User CFDP TLV subtype.
-use super::{Tlv, TlvLvError, TlvType, TlvTypeField};
-use crate::ByteConversionError;
+#[cfg(feature = "alloc")]
+use super::TlvOwned;
+use super::{GenericTlv, ReadableTlv, Tlv, TlvLvError, TlvType, TlvTypeField, WritableTlv};
+use crate::{
+    cfdp::{InvalidTlvTypeFieldError, TlvLvDataTooLargeError},
+    ByteConversionError,
+};
 use delegate::delegate;
 
+/// Message To User TLV structure.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub struct MsgToUserTlv<'data> {
+    /// Wrapped generic TLV structure.
     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>, TlvLvError> {
+    pub fn new(value: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvDataTooLargeError> {
         Ok(Self {
             tlv: Tlv::new(TlvType::MsgToUser, value)?,
         })
@@ -18,9 +25,9 @@ impl<'data> MsgToUserTlv<'data> {
 
     delegate! {
         to self.tlv {
-            pub fn tlv_type_field(&self) -> TlvTypeField;
-            pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
+            /// Value field of the 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;
@@ -34,12 +41,16 @@ impl<'data> MsgToUserTlv<'data> {
         }
     }
 
+    /// Is this a standard TLV?
+    #[inline]
     pub fn is_standard_tlv(&self) -> bool {
         true
     }
 
-    pub fn tlv_type(&self) -> Option<TlvType> {
-        Some(TlvType::MsgToUser)
+    /// TLV type field.
+    #[inline]
+    pub fn tlv_type(&self) -> TlvType {
+        TlvType::MsgToUser
     }
 
     /// Check whether this message is a reserved CFDP message like a Proxy Operation Message.
@@ -59,29 +70,80 @@ impl<'data> MsgToUserTlv<'data> {
         let msg_to_user = Self {
             tlv: Tlv::from_bytes(buf)?,
         };
-        match msg_to_user.tlv_type_field() {
+        match msg_to_user.tlv.tlv_type_field() {
             TlvTypeField::Standard(tlv_type) => {
                 if tlv_type != TlvType::MsgToUser {
-                    return Err(TlvLvError::InvalidTlvTypeField((
-                        tlv_type as u8,
-                        Some(TlvType::MsgToUser as u8),
-                    )));
+                    return Err(InvalidTlvTypeFieldError {
+                        found: tlv_type as u8,
+                        expected: Some(TlvType::MsgToUser as u8),
+                    }
+                    .into());
                 }
             }
             TlvTypeField::Custom(raw) => {
-                return Err(TlvLvError::InvalidTlvTypeField((
-                    raw,
-                    Some(TlvType::MsgToUser as u8),
-                )));
+                return Err(InvalidTlvTypeFieldError {
+                    found: raw,
+                    expected: Some(TlvType::MsgToUser as u8),
+                }
+                .into());
             }
         }
         Ok(msg_to_user)
     }
+
+    /// Convert to a generic [Tlv].
+    #[inline]
+    pub fn to_tlv(&self) -> Tlv<'data> {
+        self.tlv
+    }
+
+    /// Convert to an [TlvOwned].
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        self.tlv.to_owned()
+    }
+
+    #[inline]
+    fn len_written(&self) -> usize {
+        self.len_full()
+    }
+
+    delegate!(
+        to self.tlv {
+            /// Write the TLV to a byte buffer.
+            pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
+        }
+    );
+}
+
+impl<'a> From<MsgToUserTlv<'a>> for Tlv<'a> {
+    fn from(value: MsgToUserTlv<'a>) -> Tlv<'a> {
+        value.to_tlv()
+    }
+}
+
+impl WritableTlv for MsgToUserTlv<'_> {
+    #[inline]
+    fn len_written(&self) -> usize {
+        self.len_written()
+    }
+
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        self.tlv.write_to_bytes(buf)
+    }
+}
+
+impl GenericTlv for MsgToUserTlv<'_> {
+    #[inline]
+    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];
@@ -89,7 +151,11 @@ mod tests {
         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(), 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);
@@ -99,6 +165,82 @@ mod tests {
         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";

src/crc.rs

@@ -0,0 +1,15 @@
+//! # CRC checksum support.
+//!
+//! Thin wrapper around the [crc] crate.
+
+/// CRC algorithm used by the PUS standard, the CCSDS TC standard and the CFDP standard, using
+/// a [crc::NoTable] as the CRC implementation.
+pub const CRC_CCITT_FALSE_NO_TABLE: crc::Crc<u16, crc::NoTable> =
+    crc::Crc::<u16, crc::NoTable>::new(&crc::CRC_16_IBM_3740);
+/// CRC algorithm used by the PUS standard, the CCSDS TC standard and the CFDP standard, using
+/// [crc::Table<1>] as the CRC implementation.
+pub const CRC_CCITT_FALSE: crc::Crc<u16> = crc::Crc::<u16>::new(&crc::CRC_16_IBM_3740);
+/// CRC algorithm used by the PUS standard, the CCSDS TC standard and the CFDP standard, using
+/// a [crc::Table<16>] large table as the CRC implementation.
+pub const CRC_CCITT_FALSE_BIG_TABLE: crc::Crc<u16, crc::Table<16>> =
+    crc::Crc::<u16, crc::Table<16>>::new(&crc::CRC_16_IBM_3740);

src/ecss/event.rs

@@ -3,17 +3,26 @@ use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+/// Event service subtype ID.
 #[derive(Debug, Eq, PartialEq, Copy, Clone, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[repr(u8)]
-pub enum Subservice {
+pub enum MessageSubtypeId {
+    /// Telemetry - Info report.
     TmInfoReport = 1,
+    /// Telemetry - Low severity report.
     TmLowSeverityReport = 2,
+    /// Telemetry - Medium severity report.
     TmMediumSeverityReport = 3,
+    /// Telemetry - High severity report.
     TmHighSeverityReport = 4,
+    /// Telecommand - Enable event generation.
     TcEnableEventGeneration = 5,
+    /// Telecommand - Disable event generation.
     TcDisableEventGeneration = 6,
+    /// Telecommand - Report disabled list.
     TcReportDisabledList = 7,
+    /// Telemetry - Disabled events report.
     TmDisabledEventsReport = 8,
 }
 
@@ -23,19 +32,19 @@ mod tests {
 
     #[test]
     fn test_conv_into_u8() {
-        let subservice: u8 = Subservice::TmLowSeverityReport.into();
+        let subservice: u8 = MessageSubtypeId::TmLowSeverityReport.into();
         assert_eq!(subservice, 2);
     }
 
     #[test]
     fn test_conv_from_u8() {
-        let subservice: Subservice = 2.try_into().unwrap();
-        assert_eq!(subservice, Subservice::TmLowSeverityReport);
+        let subservice: MessageSubtypeId = 2.try_into().unwrap();
+        assert_eq!(subservice, MessageSubtypeId::TmLowSeverityReport);
     }
 
     #[test]
     fn test_conv_fails() {
-        let conversion = Subservice::try_from(9);
+        let conversion = MessageSubtypeId::try_from(9);
         assert!(conversion.is_err());
         let err = conversion.unwrap_err();
         assert_eq!(err.number, 9);

src/ecss/hk.rs

@@ -3,29 +3,79 @@ use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+/// Housekeeping service subtype ID.
 #[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 {
+pub enum MessageSubtypeId {
     // Regular HK
+    /// Telecommand - Create Housekeeping Report Structure.
     TcCreateHkReportStructure = 1,
+    /// Telecommand - Delete HK report structures.
     TcDeleteHkReportStructures = 3,
+    /// Telecommand - Enable HK generation.
     TcEnableHkGeneration = 5,
+    /// Telecommand - Disable HK generation.
     TcDisableHkGeneration = 6,
+    /// Telecommand - Report HK report structures.
     TcReportHkReportStructures = 9,
+    /// Telemetry - HK report.
     TmHkPacket = 25,
+    /// Telecommand - Generate one-shot report.
     TcGenerateOneShotHk = 27,
+    /// Telecommand - Modify collection interval.
     TcModifyHkCollectionInterval = 31,
 
-    // Diagnostics HK
+    /// Telecommand - Create diagnostics report structures.
     TcCreateDiagReportStructure = 2,
+    /// Telecommand - Delete diagnostics report structures.
     TcDeleteDiagReportStructures = 4,
+    /// Telecommand - Enable diagnostics generation.
     TcEnableDiagGeneration = 7,
+    /// Telecommand - Disable diagnostics generation.
     TcDisableDiagGeneration = 8,
+    /// Telemetry - HK structures report.
     TmHkStructuresReport = 10,
+    /// Telecommand - Report diagnostics report structures.
     TcReportDiagReportStructures = 11,
+    /// Telemetry - Diagnostics report structures.
     TmDiagStructuresReport = 12,
+    /// Telemetry - Diagnostics packet.
     TmDiagPacket = 26,
+    /// Telecommand - Generate one-shot diagnostics report.
     TcGenerateOneShotDiag = 28,
+    /// Telecommand - Modify diagnostics interval report.
     TcModifyDiagCollectionInterval = 32,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_try_from_u8() {
+        let hk_report_subservice_raw = 25;
+        let hk_report: MessageSubtypeId =
+            MessageSubtypeId::try_from(hk_report_subservice_raw).unwrap();
+        assert_eq!(hk_report, MessageSubtypeId::TmHkPacket);
+    }
+
+    #[test]
+    fn test_into_u8() {
+        let hk_report_raw: u8 = MessageSubtypeId::TmHkPacket.into();
+        assert_eq!(hk_report_raw, 25);
+    }
+
+    #[test]
+    fn test_partial_eq() {
+        let hk_report_raw = MessageSubtypeId::TmHkPacket;
+        assert_ne!(hk_report_raw, MessageSubtypeId::TcGenerateOneShotHk);
+        assert_eq!(hk_report_raw, MessageSubtypeId::TmHkPacket);
+    }
+    #[test]
+    fn test_copy_clone() {
+        let hk_report = MessageSubtypeId::TmHkPacket;
+        let hk_report_copy = hk_report;
+        assert_eq!(hk_report, hk_report_copy);
+    }
+}

src/ecss/mod.rs

@@ -1,137 +1,180 @@
 //! 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.
-use crate::{ByteConversionError, CcsdsPacket, CRC_CCITT_FALSE};
-use core::fmt::{Debug, Display, Formatter};
+//! You can find the PUS telecommand types in the [tc] module and the the PUS telemetry
+//! types inside the [tm] module.
+use crate::{
+    crc::{CRC_CCITT_FALSE, CRC_CCITT_FALSE_NO_TABLE},
+    ByteConversionError, CcsdsPacket,
+};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
+use arbitrary_int::u4;
+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;
 pub mod scheduling;
 pub mod tc;
+pub mod tc_pus_a;
 pub mod tm;
+pub mod tm_pus_a;
 pub mod verification;
 
+/// Type alias for the CRC16 type.
 pub type CrcType = u16;
-pub const CCSDS_HEADER_LEN: usize = size_of::<crate::zc::SpHeader>();
 
+/// Standard PUS service IDs.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
 #[non_exhaustive]
 pub enum PusServiceId {
-    /// Service 1
+    /// Service 1 Verification
     Verification = 1,
-    /// Service 2
+    /// Service 2 Device Access
     DeviceAccess = 2,
-    /// Service 3
+    /// Service 3 Housekeeping
     Housekeeping = 3,
-    /// Service 4
+    /// Service 4 Parameter Statistics
     ParameterStatistics = 4,
-    /// Service 5
+    /// Service 5 Event
     Event = 5,
-    /// Service 6
+    /// Service 6 Memory Management
     MemoryManagement = 6,
-    /// Service 8
+    /// Service 8 Action
     Action = 8,
-    /// Service 9
+    /// Service 9 Time Management
     TimeManagement = 9,
-    /// Service 11
+    /// Service 11 Scheduling
     Scheduling = 11,
-    /// Service 12
+    /// Service 12 On-Board Monitoring
     OnBoardMonitoring = 12,
-    /// Service 13
+    /// Service 13 Large Packet Transfer
     LargePacketTransfer = 13,
-    /// Service 14
+    /// Service 14 Real-Time Forwarding Control
     RealTimeForwardingControl = 14,
-    /// Service 15
+    /// Service 15 Storage And Retrival
     StorageAndRetrival = 15,
-    /// Service 17
+    /// Service 17 Test
     Test = 17,
-    /// Service 18
+    /// Service 18 Operations And Procedures
     OpsAndProcedures = 18,
-    /// Service 19
+    /// Service 19 Event Action
     EventAction = 19,
-    /// Service 20
+    /// Service 20 Parameter
     Parameter = 20,
-    /// Service 21
+    /// Service 21 Request Sequencing
     RequestSequencing = 21,
-    /// Service 22
+    /// Service 22 Position Based Scheduling
     PositionBasedScheduling = 22,
-    /// Service 23
+    /// Service 23 File Management
     FileManagement = 23,
 }
 
 /// All PUS versions. Only PUS C is supported by this library.
-#[derive(PartialEq, Eq, Copy, Clone, Debug)]
+#[derive(PartialEq, Eq, Debug, num_enum::TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[bitbybit::bitenum(u4, exhaustive = false)]
+#[repr(u8)]
+#[non_exhaustive]
 pub enum PusVersion {
+    /// ESA PUS
     EsaPus = 0,
+    /// PUS A
     PusA = 1,
+    /// PUS C
     PusC = 2,
-    Invalid = 0b1111,
 }
 
-impl TryFrom<u8> for PusVersion {
-    type Error = ();
+impl TryFrom<u4> for PusVersion {
+    type Error = u4;
 
-    fn try_from(value: u8) -> Result<Self, Self::Error> {
+    fn try_from(value: u4) -> Result<Self, Self::Error> {
         match value {
-            x if x == PusVersion::EsaPus as u8 => Ok(PusVersion::EsaPus),
-            x if x == PusVersion::PusA as u8 => Ok(PusVersion::PusA),
-            x if x == PusVersion::PusC as u8 => Ok(PusVersion::PusC),
-            _ => Err(()),
+            x if x == PusVersion::EsaPus.raw_value() => Ok(PusVersion::EsaPus),
+            x if x == PusVersion::PusA.raw_value() => Ok(PusVersion::PusA),
+            x if x == PusVersion::PusC.raw_value() => Ok(PusVersion::PusC),
+            _ => Err(value),
         }
     }
 }
 
 /// 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))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
 pub enum PacketTypeCodes {
+    /// Boolean.
     Boolean = 1,
+    /// Enumerated.
     Enumerated = 2,
+    /// Unsigned Integer.
     UnsignedInt = 3,
+    /// Signed Integer.
     SignedInt = 4,
+    /// Real (floating point).
     Real = 5,
+    /// Bit string.
     BitString = 6,
+    /// Octet (byte) string.
     OctetString = 7,
+    /// Character string.
     CharString = 8,
+    /// Absolute time.
     AbsoluteTime = 9,
+    /// Relative time.
     RelativeTime = 10,
+    /// Deduced.
     Deduced = 11,
+    /// Packet.
     Packet = 12,
 }
 
+/// Type alias for the ECSS Packet Type Codes (PTC)s.
 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 {
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
+pub enum PfcUnsigned {
+    /// 1 byte.
     OneByte = 4,
+    /// 12 bits.
     TwelveBits = 8,
+    /// 2 bytes.
     TwoBytes = 12,
+    /// 3 bytes.
     ThreeBytes = 13,
+    /// 4 bytes.
     FourBytes = 14,
+    /// 6 bytes.
     SixBytes = 15,
+    /// 8 bytes.
     EightBytes = 16,
+    /// 1 bit.
     OneBit = 17,
+    /// 2 bits.
     TwoBits = 18,
+    /// 3 bits.
     ThreeBits = 19,
 }
 
 /// 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 {
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
+pub enum PfcReal {
     /// 4 octets simple precision format (IEEE)
     Float = 1,
     /// 8 octets simple precision format (IEEE)
@@ -142,77 +185,84 @@ pub enum RealPfc {
     DoubleMilStd = 4,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+/// Generic PUS error.
+#[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 {
-    VersionNotSupported(PusVersion),
-    IncorrectCrc(u16),
-    RawDataTooShort(usize),
-    NoRawData,
+    /// PUS version is not supported.
+    #[error("PUS version {0:?} not supported")]
+    VersionNotSupported(u4),
+    /// Checksum failure.
+    #[error("checksum verification for crc16 {0:#06x} failed")]
+    ChecksumFailure(u16),
     /// CRC16 needs to be calculated first
-    CrcCalculationMissing,
-    ByteConversion(ByteConversionError),
+    //#[error("crc16 was not calculated")]
+    //CrcCalculationMissing,
+    #[error("pus error: {0}")]
+    ByteConversion(#[from] 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}")
-            }
+/// Message type ID field.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct MessageTypeId {
+    /// Service type ID.
+    pub type_id: u8,
+    /// Subtype ID.
+    pub subtype_id: u8,
+}
+
+impl MessageTypeId {
+    /// Generic constructor.
+    pub const fn new(type_id: u8, subtype_id: u8) -> Self {
+        Self {
+            type_id,
+            subtype_id,
         }
     }
 }
 
-#[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)
-    }
-}
-
 /// Generic trait to describe common attributes for both PUS Telecommands (TC) and PUS Telemetry
 /// (TM) packets. All PUS packets are also a special type of [CcsdsPacket]s.
 pub trait PusPacket: CcsdsPacket {
-    const PUS_VERSION: PusVersion = PusVersion::PusC;
+    /// PUS version.
+    fn pus_version(&self) -> Result<PusVersion, u4>;
 
-    fn pus_version(&self) -> PusVersion;
-    fn service(&self) -> u8;
-    fn subservice(&self) -> u8;
+    /// Message type ID.
+    fn message_type_id(&self) -> MessageTypeId;
+
+    /// Service type ID.
+    #[inline]
+    fn service_type_id(&self) -> u8 {
+        self.message_type_id().type_id
+    }
+
+    /// Message subtype ID.
+    #[inline]
+    fn message_subtype_id(&self) -> u8 {
+        self.message_type_id().subtype_id
+    }
+
+    /// User data field.
     fn user_data(&self) -> &[u8];
-    fn crc16(&self) -> Option<u16>;
+
+    /// CRC-16-CCITT checksum.
+    fn checksum(&self) -> Option<u16>;
+
+    /// The presence of the CRC-16-CCITT checksum is optional.
+    fn has_checksum(&self) -> bool {
+        self.checksum().is_some()
+    }
 }
 
-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()]
@@ -227,46 +277,48 @@ 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> {
-    match current_idx {
-        _ if current_idx > total_len - 2 => Err(PusError::RawDataTooShort(raw_data_len)),
-        _ => Ok(&slice[current_idx..total_len - 2]),
+    has_checksum: bool,
+) -> Result<&[u8], ByteConversionError> {
+    if has_checksum {
+        if current_idx > total_len - 2 {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: total_len - 2,
+                expected: current_idx,
+            });
+        }
+        Ok(&slice[current_idx..total_len - 2])
+    } else {
+        Ok(&slice[current_idx..total_len])
     }
 }
 
-pub(crate) fn verify_crc16_ccitt_false_from_raw_to_pus_error(
+/// Verify the CRC16 of a raw packet and return a [PusError] on failure.
+pub fn verify_crc16_ccitt_false_from_raw_to_pus_error(
     raw_data: &[u8],
     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 {
+/// Verify the CRC16 of a raw packet using a table-less implementation and return a [PusError] on
+/// failure.
+pub fn verify_crc16_ccitt_false_from_raw_to_pus_error_no_table(
+    raw_data: &[u8],
+    crc16: u16,
+) -> Result<(), PusError> {
+    verify_crc16_ccitt_false_from_raw_no_table(raw_data)
+        .then_some(())
+        .ok_or(PusError::ChecksumFailure(crc16))
+}
+
+/// Verify the CRC16 of a raw packet.
+pub fn verify_crc16_ccitt_false_from_raw(raw_data: &[u8]) -> bool {
     let mut digest = CRC_CCITT_FALSE.digest();
     digest.update(raw_data);
     if digest.finalize() == 0 {
@@ -275,29 +327,35 @@ pub(crate) fn verify_crc16_ccitt_false_from_raw(raw_data: &[u8]) -> bool {
     false
 }
 
-macro_rules! ccsds_impl {
-    () => {
-        delegate!(to self.sp_header {
-            fn ccsds_version(&self) -> u8;
-            fn packet_id(&self) -> crate::PacketId;
-            fn psc(&self) -> crate::PacketSequenceCtrl;
-            fn data_len(&self) -> u16;
-        });
+/// Verify the CRC16 of a raw packet, using the table-less implementation.
+pub fn verify_crc16_ccitt_false_from_raw_no_table(raw_data: &[u8]) -> bool {
+    let mut digest = CRC_CCITT_FALSE_NO_TABLE.digest();
+    digest.update(raw_data);
+    if digest.finalize() == 0 {
+        return true;
     }
+    false
 }
 
 macro_rules! sp_header_impls {
     () => {
         delegate!(to self.sp_header {
-            pub fn set_apid(&mut self, apid: u16) -> bool;
-            pub fn set_seq_count(&mut self, seq_count: u16) -> bool;
+            /// Set the CCSDS APID.
+            #[inline]
+            pub fn set_apid(&mut self, apid: u11);
+
+            /// Set the CCSDS sequence count.
+            #[inline]
+            pub fn set_seq_count(&mut self, seq_count: u14);
+
+            /// Set the CCSDS sequence flags.
+            #[inline]
             pub fn set_seq_flags(&mut self, seq_flag: SequenceFlags);
         });
     }
 }
 
 use crate::util::{GenericUnsignedByteField, ToBeBytes, UnsignedEnum};
-pub(crate) use ccsds_impl;
 pub(crate) use sp_header_impls;
 
 /// Generic trait for ECSS enumeration which consist of a PFC field denoting their bit length
@@ -309,73 +367,191 @@ pub trait EcssEnumeration: UnsignedEnum {
     fn pfc(&self) -> u8;
 }
 
+/// Extension trait for [EcssEnumeration] which adds common trait bounds.
 pub trait EcssEnumerationExt: EcssEnumeration + Debug + Copy + Clone + PartialEq + Eq {}
 
+/// ECSS enumerated type wrapper.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct GenericEcssEnumWrapper<TYPE> {
-    field: GenericUnsignedByteField<TYPE>,
-}
+pub struct GenericEcssEnumWrapper<TYPE: Copy + Into<u64>>(GenericUnsignedByteField<TYPE>);
 
-impl<TYPE> GenericEcssEnumWrapper<TYPE> {
+impl<TYPE: Copy + Into<u64>> GenericEcssEnumWrapper<TYPE> {
+    /// Returns [PacketTypeCodes::Enumerated].
     pub const fn ptc() -> PacketTypeCodes {
         PacketTypeCodes::Enumerated
     }
 
-    pub fn new(val: TYPE) -> Self {
-        Self {
-            field: GenericUnsignedByteField::new(val),
-        }
+    /// Value.
+    pub const fn value(&self) -> TYPE {
+        self.0.value()
+    }
+
+    /// Generic constructor.
+    pub const fn new(val: TYPE) -> Self {
+        Self(GenericUnsignedByteField::new(val))
     }
 }
 
-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
     }
 
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        self.field.write_to_be_bytes(buf)
+        self.0.write_to_be_bytes(buf)
+    }
+
+    fn value_raw(&self) -> u64 {
+        self.0.value().into()
     }
 }
 
-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),*) => {
+        $(
+            /// Type alias for ECSS enumeration wrapper around `$ty`
+            pub type $Enum = GenericEcssEnumWrapper<$ty>;
+
+            impl From<$Enum> for $ty {
+                fn from(value: $Enum) -> Self {
+                    value.value()
+                }
+            }
+        )*
+    };
+}
+
+// Generates EcssEnum<$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;
-    fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError>;
+pub trait WritablePusPacket {
+    /// The length here also includes the CRC length.
+    fn len_written(&self) -> usize;
+
+    /// Checksum generation is enabled for the packet.
+    fn has_checksum(&self) -> bool;
+
+    /// Writes the packet to the given slice without writing the CRC checksum.
+    ///
+    /// The returned size is the written size WITHOUT the CRC checksum.
+    /// If the checksum generation is disabled, this function is identical to the APIs which
+    /// generate a checksum.
+    fn write_to_bytes_no_checksum(&self, slice: &mut [u8]) -> Result<usize, PusError>;
+
+    /// First uses [Self::write_to_bytes_no_checksum] to write the packet to the given slice and
+    /// then uses the [CRC_CCITT_FALSE] to calculate the CRC and write it to the slice if the
+    /// packet is configured to include a checksum.
+    fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        let mut curr_idx = self.write_to_bytes_no_checksum(slice)?;
+        if self.has_checksum() {
+            let mut digest = CRC_CCITT_FALSE.digest();
+            digest.update(&slice[0..curr_idx]);
+            slice[curr_idx..curr_idx + 2].copy_from_slice(&digest.finalize().to_be_bytes());
+            curr_idx += 2;
+        }
+        Ok(curr_idx)
+    }
+
+    /// First uses [Self::write_to_bytes_no_checksum] to write the packet to the given slice and then
+    /// uses the [CRC_CCITT_FALSE_NO_TABLE] to calculate the CRC and write it to the slice if
+    /// the paket is configured to include a checksum.
+    fn write_to_bytes_checksum_no_table(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        let mut curr_idx = self.write_to_bytes_no_checksum(slice)?;
+        if self.has_checksum() {
+            let mut digest = CRC_CCITT_FALSE_NO_TABLE.digest();
+            digest.update(&slice[0..curr_idx]);
+            slice[curr_idx..curr_idx + 2].copy_from_slice(&digest.finalize().to_be_bytes());
+            curr_idx += 2;
+        }
+        Ok(curr_idx)
+    }
+
+    /// Converts the packet into an owned [alloc::vec::Vec].
+    #[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)
+    }
+}
+
+/// PUS packet creator configuration.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct CreatorConfig {
+    /// Set the CCSDS data length field on construction.
+    pub set_ccsds_len: bool,
+    /// CRC-16-CCITT Checksum is present.
+    pub has_checksum: bool,
+}
+
+impl Default for CreatorConfig {
+    fn default() -> Self {
+        Self {
+            set_ccsds_len: true,
+            has_checksum: true,
+        }
+    }
 }
 
 #[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(), 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 +561,16 @@ 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(), 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]
@@ -418,6 +602,12 @@ 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(), 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]
@@ -437,4 +627,100 @@ mod tests {
             }
         }
     }
+
+    #[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(), 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.raw_value());
+        let write_str = unsupport_version.to_string();
+        assert_eq!(write_str, "PUS version 0 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.raw_value()),
+            PusError::VersionNotSupported(PusVersion::EsaPus.raw_value())
+        );
+    }
+
+    #[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

@@ -3,57 +3,90 @@ use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+/// Scheduling service subtype ID.
 #[derive(Debug, PartialEq, Eq, Copy, Clone, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(u8)]
-pub enum Subservice {
+pub enum MessageSubtypeId {
     // Core subservices
+    /// Telecommand - Enable scheduling.
     TcEnableScheduling = 1,
+    /// Telecommand - Disable scheduling.
     TcDisableScheduling = 2,
+    /// Telecommand - Reset scheduling.
     TcResetScheduling = 3,
+    /// Telecommand - Insert activity.
     TcInsertActivity = 4,
+    /// Telecommand - Delete activity by request ID.
     TcDeleteActivityByRequestId = 5,
+    /// Telecommand - Delete activity by filter.
     TcDeleteActivitiesByFilter = 6,
 
     // Time shift subservices
+    /// Telecommand - Time shift activity by request ID.
     TcTimeShiftActivityWithRequestId = 7,
+    /// Telecommand - Time shift activity by filter.
     TcTimeShiftActivitiesByFilter = 8,
+    /// Telecommand - Time shift all.
     TcTimeShiftAll = 15,
 
     // Reporting subservices
+    /// Telecommand - Detail report by request ID.
     TcDetailReportByRequestId = 9,
+    /// Telemetry - Detail report.
     TmDetailReport = 10,
+    /// Telecommand - Detail report by filter.
     TcDetailReportByFilter = 11,
+    /// Telecommand - Summary report by request ID.
     TcSummaryReportByRequestId = 12,
+    /// Telemetry - Summary report.
     TmSummaryReport = 13,
+    /// Telecommand - Summary report by filter.
     TcSummaryReportByFilter = 14,
+    /// Telecommand - Detail report all.
     TcDetailReportAll = 16,
+    /// Telecommand - Summary report all.
     TcSummaryReportAll = 17,
 
     // Subschedule subservices
+    /// Telecommand - Report subschedule status.
     TcReportSubscheduleStatus = 18,
+    /// Telemetry - Subschedule status report.
     TmReportSubscheduleStatus = 19,
+    /// Telecommand - Enable subschedule.
     TcEnableSubschedule = 20,
+    /// Telecommand - Disable subschedule.
     TcDisableSubschedule = 21,
 
     // Group subservices
+    /// Telecommand - Create schedule group.
     TcCreateScheduleGroup = 22,
+    /// Telecommand - Delete schedule group.
     TcDeleteScheduleGroup = 23,
+    /// Telecommand - Enable schedule group.
     TcEnableScheduleGroup = 24,
+    /// Telecommand - Disable schedule group.
     TcDisableScheduleGroup = 25,
+    /// Telecommand - Report all group status.
     TcReportAllGroupsStatus = 26,
+    /// Telemetry - All group status report.
     TmReportAllGroupsStatus = 27,
 }
 
 /// This status applies to sub-schedules and groups as well as specified in ECSS-E-ST-70-41C 8.11.3
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum SchedStatus {
+    /// Scheduling disabled.
     Disabled = 0,
+    /// Scheduling enabled.
     Enabled = 1,
 }
 
 impl From<bool> for SchedStatus {
+    #[inline]
     fn from(value: bool) -> Self {
         if value {
             SchedStatus::Enabled
@@ -65,17 +98,24 @@ impl From<bool> for SchedStatus {
 
 /// Time window types as specified in  ECSS-E-ST-70-41C 8.11.3
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum TimeWindowType {
+    /// Select all.
     SelectAll = 0,
+    /// From time tag to time tag.
     TimeTagToTimeTag = 1,
+    /// Starting from a time tag.
     FromTimeTag = 2,
+    /// Until a time tag.
     ToTimeTag = 3,
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
 
     #[test]
     fn test_bool_conv_0() {
@@ -93,13 +133,31 @@ mod tests {
 
     #[test]
     fn test_conv_into_u8() {
-        let subservice: u8 = Subservice::TcCreateScheduleGroup.into();
+        let subservice: u8 = MessageSubtypeId::TcCreateScheduleGroup.into();
         assert_eq!(subservice, 22);
     }
 
     #[test]
     fn test_conv_from_u8() {
-        let subservice: Subservice = 22u8.try_into().unwrap();
-        assert_eq!(subservice, Subservice::TcCreateScheduleGroup);
+        let subservice: MessageSubtypeId = 22u8.try_into().unwrap();
+        assert_eq!(subservice, MessageSubtypeId::TcCreateScheduleGroup);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_subservice_id() {
+        generic_serde_test(MessageSubtypeId::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/ecss/verification.rs

@@ -3,17 +3,27 @@ use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+/// Message subtype ID.
 #[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 {
+pub enum MessageSubtypeId {
+    /// Telemetry - Acceptance success.
     TmAcceptanceSuccess = 1,
+    /// Telemetry - Acceptance failure.
     TmAcceptanceFailure = 2,
+    /// Telemetry - Start success.
     TmStartSuccess = 3,
+    /// Telemetry - Start failure.
     TmStartFailure = 4,
+    /// Telemetry - Step success.
     TmStepSuccess = 5,
+    /// Telemetry - Step failure.
     TmStepFailure = 6,
+    /// Telemetry - Completion success.
     TmCompletionSuccess = 7,
+    /// Telemetry - Completion failure.
     TmCompletionFailure = 8,
 }
 
@@ -23,13 +33,13 @@ mod tests {
 
     #[test]
     fn test_conv_into_u8() {
-        let subservice: u8 = Subservice::TmCompletionSuccess.into();
+        let subservice: u8 = MessageSubtypeId::TmCompletionSuccess.into();
         assert_eq!(subservice, 7);
     }
 
     #[test]
     fn test_conv_from_u8() {
-        let subservice: Subservice = 7.try_into().unwrap();
-        assert_eq!(subservice, Subservice::TmCompletionSuccess);
+        let subservice: MessageSubtypeId = 7.try_into().unwrap();
+        assert_eq!(subservice, MessageSubtypeId::TmCompletionSuccess);
     }
 }

src/seq_count.rs

@@ -0,0 +1,473 @@
+//! # Sequence counter module.
+//!
+//! CCSDS and ECSS packet standard oftentimes use sequence counters, for example to allow detecting
+//! packet gaps. This module provides basic abstractions and helper components to implement
+//! sequence counters.
+use crate::MAX_SEQ_COUNT;
+use arbitrary_int::traits::Integer;
+use core::cell::Cell;
+use paste::paste;
+
+/// 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 SequenceCounter {
+    /// Raw type of the counter.
+    type Raw: Into<u64>;
+
+    /// Bit width of the counter.
+    const MAX_BIT_WIDTH: usize;
+
+    /// Get the current sequence count value.
+    fn get(&self) -> Self::Raw;
+
+    /// Increment the sequence count by one.
+    fn increment(&self);
+
+    /// Increment the sequence count by one, mutable API.
+    fn increment_mut(&mut self) {
+        self.increment();
+    }
+
+    /// Get the current sequence count value and increment the counter by one.
+    fn get_and_increment(&self) -> Self::Raw {
+        let val = self.get();
+        self.increment();
+        val
+    }
+
+    /// Get the current sequence count value and increment the counter by one, mutable API.
+    fn get_and_increment_mut(&mut self) -> Self::Raw {
+        self.get_and_increment()
+    }
+}
+
+/// Simple sequence counter which wraps at ´T::MAX´.
+#[derive(Clone)]
+pub struct SequenceCounterSimple<T: Copy> {
+    seq_count: Cell<T>,
+    // The maximum value
+    max_val: T,
+}
+
+macro_rules! impl_for_primitives {
+    ($($ty: ident,)+) => {
+        $(
+            paste! {
+                impl SequenceCounterSimple<$ty> {
+                    /// Constructor with a custom maximum value.
+                    pub fn [<new_custom_max_val_ $ty>](max_val: $ty) -> Self {
+                        Self {
+                            seq_count: Cell::new(0),
+                            max_val,
+                        }
+                    }
+
+                    /// Generic constructor.
+                    pub fn [<new_ $ty>]() -> Self {
+                        Self {
+                            seq_count: Cell::new(0),
+                            max_val: $ty::MAX
+                        }
+                    }
+                }
+
+                impl Default for SequenceCounterSimple<$ty> {
+                    fn default() -> Self {
+                        Self::[<new_ $ty>]()
+                    }
+                }
+
+                impl SequenceCounter for SequenceCounterSimple<$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 SequenceCounterCcsdsSimple {
+    provider: SequenceCounterSimple<u16>,
+}
+
+impl Default for SequenceCounterCcsdsSimple {
+    fn default() -> Self {
+        Self {
+            provider: SequenceCounterSimple::new_custom_max_val_u16(MAX_SEQ_COUNT.as_u16()),
+        }
+    }
+}
+
+impl SequenceCounter for SequenceCounterCcsdsSimple {
+    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(target_has_atomic = "8")]
+impl SequenceCounter for core::sync::atomic::AtomicU8 {
+    type Raw = u8;
+
+    const MAX_BIT_WIDTH: usize = 8;
+
+    fn get(&self) -> Self::Raw {
+        self.load(core::sync::atomic::Ordering::Relaxed)
+    }
+
+    fn increment(&self) {
+        self.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+    }
+}
+
+#[cfg(target_has_atomic = "16")]
+impl SequenceCounter for core::sync::atomic::AtomicU16 {
+    type Raw = u16;
+
+    const MAX_BIT_WIDTH: usize = 16;
+
+    fn get(&self) -> Self::Raw {
+        self.load(core::sync::atomic::Ordering::Relaxed)
+    }
+
+    fn increment(&self) {
+        self.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+    }
+}
+
+#[cfg(target_has_atomic = "32")]
+impl SequenceCounter for core::sync::atomic::AtomicU32 {
+    type Raw = u32;
+
+    const MAX_BIT_WIDTH: usize = 32;
+
+    fn get(&self) -> Self::Raw {
+        self.load(core::sync::atomic::Ordering::Relaxed)
+    }
+
+    fn increment(&self) {
+        self.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+    }
+}
+
+#[cfg(target_has_atomic = "64")]
+impl SequenceCounter for core::sync::atomic::AtomicU64 {
+    type Raw = u64;
+
+    const MAX_BIT_WIDTH: usize = 64;
+
+    fn get(&self) -> Self::Raw {
+        self.load(core::sync::atomic::Ordering::Relaxed)
+    }
+
+    fn increment(&self) {
+        self.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+    }
+}
+
+#[cfg(feature = "portable-atomic")]
+impl SequenceCounter for portable_atomic::AtomicU8 {
+    type Raw = u8;
+
+    const MAX_BIT_WIDTH: usize = 8;
+
+    fn get(&self) -> Self::Raw {
+        self.load(portable_atomic::Ordering::Relaxed)
+    }
+
+    fn increment(&self) {
+        self.fetch_add(1, portable_atomic::Ordering::Relaxed);
+    }
+}
+
+#[cfg(feature = "portable-atomic")]
+impl SequenceCounter for portable_atomic::AtomicU16 {
+    type Raw = u16;
+
+    const MAX_BIT_WIDTH: usize = 16;
+
+    fn get(&self) -> Self::Raw {
+        self.load(portable_atomic::Ordering::Relaxed)
+    }
+
+    fn increment(&self) {
+        self.fetch_add(1, portable_atomic::Ordering::Relaxed);
+    }
+}
+
+#[cfg(feature = "portable-atomic")]
+impl SequenceCounter for portable_atomic::AtomicU32 {
+    type Raw = u32;
+
+    const MAX_BIT_WIDTH: usize = 32;
+
+    fn get(&self) -> Self::Raw {
+        self.load(portable_atomic::Ordering::Relaxed)
+    }
+
+    fn increment(&self) {
+        self.fetch_add(1, portable_atomic::Ordering::Relaxed);
+    }
+}
+
+#[cfg(feature = "portable-atomic")]
+impl SequenceCounter for portable_atomic::AtomicU64 {
+    type Raw = u64;
+
+    const MAX_BIT_WIDTH: usize = 64;
+
+    fn get(&self) -> Self::Raw {
+        self.load(portable_atomic::Ordering::Relaxed)
+    }
+
+    fn increment(&self) {
+        self.fetch_add(1, portable_atomic::Ordering::Relaxed);
+    }
+}
+
+impl<T: SequenceCounter + ?Sized> SequenceCounter for &T {
+    type Raw = T::Raw;
+    const MAX_BIT_WIDTH: usize = T::MAX_BIT_WIDTH;
+
+    fn get(&self) -> Self::Raw {
+        (**self).get()
+    }
+
+    fn increment(&self) {
+        (**self).increment()
+    }
+}
+
+#[cfg(any(
+    target_has_atomic = "8",
+    target_has_atomic = "16",
+    target_has_atomic = "32",
+    target_has_atomic = "64"
+))]
+macro_rules! sync_clonable_seq_counter_impl {
+    ($ty: ident) => {
+        paste::paste! {
+            /// This can be used if a custom wrap value is required when using a thread-safe
+            /// atomic based sequence counter.
+            #[derive(Debug)]
+            pub struct [<SequenceCounterSyncCustomWrap $ty:upper>] {
+                seq_count: core::sync::atomic::[<Atomic $ty:upper>],
+                max_val: $ty,
+            }
+
+            impl [<SequenceCounterSyncCustomWrap $ty:upper>] {
+                /// Generic constructor.
+                pub fn new(max_val: $ty) -> Self {
+                    Self {
+                        seq_count: core::sync::atomic::[<Atomic $ty:upper>]::new(0),
+                        max_val,
+                    }
+                }
+            }
+
+            impl SequenceCounter for [<SequenceCounterSyncCustomWrap $ty:upper>] {
+                type Raw = $ty;
+                const MAX_BIT_WIDTH: usize = core::mem::size_of::<Self::Raw>() * 8;
+
+                fn get(&self) -> $ty {
+                    self.seq_count.load(core::sync::atomic::Ordering::Relaxed)
+                }
+
+                fn increment(&self) {
+                    self.get_and_increment();
+                }
+
+                fn get_and_increment(&self) -> $ty {
+                    self.seq_count.fetch_update(
+                        core::sync::atomic::Ordering::Relaxed,
+                        core::sync::atomic::Ordering::Relaxed,
+                        |cur| {
+                            // compute the next value, wrapping at MAX_VAL
+                            let next = if cur == self.max_val { 0 } else { cur + 1 };
+                            Some(next)
+                        },
+                    ).unwrap()
+                }
+            }
+        }
+    };
+}
+
+#[cfg(target_has_atomic = "8")]
+sync_clonable_seq_counter_impl!(u8);
+#[cfg(target_has_atomic = "16")]
+sync_clonable_seq_counter_impl!(u16);
+#[cfg(target_has_atomic = "32")]
+sync_clonable_seq_counter_impl!(u32);
+#[cfg(target_has_atomic = "64")]
+sync_clonable_seq_counter_impl!(u64);
+
+#[cfg(test)]
+mod tests {
+    use core::sync::atomic::{AtomicU16, AtomicU32, AtomicU64, AtomicU8};
+
+    use crate::seq_count::{
+        SequenceCounter, SequenceCounterCcsdsSimple, SequenceCounterSimple,
+        SequenceCounterSyncCustomWrapU8,
+    };
+    use crate::MAX_SEQ_COUNT;
+
+    #[test]
+    fn test_u8_counter() {
+        let u8_counter = SequenceCounterSimple::<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 = SequenceCounterSimple::new_u8();
+        for _ in 0..256 {
+            u8_counter.increment();
+        }
+        assert_eq!(u8_counter.get(), 0);
+    }
+
+    #[test]
+    fn test_ccsds_counter() {
+        let ccsds_counter = SequenceCounterCcsdsSimple::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 = SequenceCounterCcsdsSimple::default();
+        for _ in 0..MAX_SEQ_COUNT.value() + 1 {
+            ccsds_counter.increment();
+        }
+        assert_eq!(ccsds_counter.get(), 0);
+    }
+
+    fn common_counter_test(seq_counter: &mut impl SequenceCounter) {
+        assert_eq!(seq_counter.get().into(), 0);
+        assert_eq!(seq_counter.get_and_increment().into(), 0);
+        assert_eq!(seq_counter.get_and_increment().into(), 1);
+        assert_eq!(seq_counter.get().into(), 2);
+        seq_counter.increment_mut();
+        assert_eq!(seq_counter.get().into(), 3);
+        assert_eq!(seq_counter.get_and_increment_mut().into(), 3);
+        assert_eq!(seq_counter.get().into(), 4);
+    }
+
+    #[test]
+    fn test_atomic_counter_u8() {
+        let mut sync_u8_counter = AtomicU8::new(0);
+        common_counter_test(&mut sync_u8_counter);
+    }
+
+    #[test]
+    fn test_atomic_counter_u16() {
+        let mut sync_u16_counter = AtomicU16::new(0);
+        common_counter_test(&mut sync_u16_counter);
+    }
+
+    #[test]
+    fn test_atomic_counter_u32() {
+        let mut sync_u32_counter = AtomicU32::new(0);
+        common_counter_test(&mut sync_u32_counter);
+    }
+
+    #[test]
+    fn test_atomic_counter_u64() {
+        let mut sync_u64_counter = AtomicU64::new(0);
+        common_counter_test(&mut sync_u64_counter);
+    }
+
+    #[test]
+    #[cfg(feature = "portable-atomic")]
+    fn test_portable_atomic_counter_u8() {
+        let mut sync_u8_counter = portable_atomic::AtomicU8::new(0);
+        common_counter_test(&mut sync_u8_counter);
+    }
+
+    #[test]
+    #[cfg(feature = "portable-atomic")]
+    fn test_portable_atomic_counter_u16() {
+        let mut sync_u16_counter = portable_atomic::AtomicU16::new(0);
+        common_counter_test(&mut sync_u16_counter);
+    }
+
+    #[test]
+    #[cfg(feature = "portable-atomic")]
+    fn test_portable_atomic_counter_u32() {
+        let mut sync_u32_counter = portable_atomic::AtomicU32::new(0);
+        common_counter_test(&mut sync_u32_counter);
+    }
+
+    #[test]
+    #[cfg(feature = "portable-atomic")]
+    fn test_portable_atomic_counter_u64() {
+        let mut sync_u64_counter = portable_atomic::AtomicU64::new(0);
+        common_counter_test(&mut sync_u64_counter);
+    }
+
+    fn common_overflow_test_u8(seq_counter: &impl SequenceCounter) {
+        for _ in 0..u8::MAX as u16 + 1 {
+            seq_counter.increment();
+        }
+        assert_eq!(seq_counter.get().into(), 0);
+    }
+
+    #[test]
+    fn test_atomic_u8_counter_overflow() {
+        let sync_u8_counter = AtomicU8::new(0);
+        common_overflow_test_u8(&sync_u8_counter);
+    }
+
+    #[test]
+    #[cfg(feature = "portable-atomic")]
+    fn test_portable_atomic_u8_counter_overflow() {
+        let sync_u8_counter = portable_atomic::AtomicU8::new(0);
+        common_overflow_test_u8(&sync_u8_counter);
+    }
+
+    #[test]
+    fn test_atomic_ref_counters_overflow_custom_max_val() {
+        let sync_u8_counter = SequenceCounterSyncCustomWrapU8::new(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 +31,38 @@ 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)
-}
+/// Functions requiring both [chrono] and [alloc] support.
+#[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 +72,54 @@ 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 +129,55 @@ 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

@@ -1,11 +1,10 @@
 //! CCSDS Time Code Formats according to [CCSDS 301.0-B-4](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
 use crate::ByteConversionError;
-use chrono::{DateTime, LocalResult, TimeZone, Utc};
+#[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;
-use core::u8;
 
 #[allow(unused_imports)]
 #[cfg(not(feature = "std"))]
@@ -13,8 +12,7 @@ use num_traits::float::FloatCore;
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
-#[cfg(feature = "std")]
-use std::error::Error;
+
 #[cfg(feature = "std")]
 use std::time::{SystemTime, SystemTimeError};
 #[cfg(feature = "std")]
@@ -24,30 +22,42 @@ pub mod ascii;
 pub mod cds;
 pub mod cuc;
 
+/// Conversion constant for converting CCSDS days to UNIX days.
 pub const DAYS_CCSDS_TO_UNIX: i32 = -4383;
+/// Seconds per day.
 pub const SECONDS_PER_DAY: u32 = 86400;
+/// Milliseconds per day.
 pub const MS_PER_DAY: u32 = SECONDS_PER_DAY * 1000;
+/// Nanoseconds per second.
+pub const NANOS_PER_SECOND: u32 = 1_000_000_000;
 
+/// CCSDS time code identifiers.
 #[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 {
+    /// CUC with a CCSDS epoch (1958-01-01T00:00:00+00:00).
     CucCcsdsEpoch = 0b001,
+    /// CUC with a custom agency epoch.
     CucAgencyEpoch = 0b010,
+    /// CDS time code.
     Cds = 0b100,
+    /// CCS time code.
     Ccs = 0b101,
+    /// Agency defined time code.
     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(()),
         }
     }
@@ -55,92 +65,67 @@ 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)]
+/// Date is before the CCSDS epoch.
+#[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);
+
+/// Generic timestamp error.
+#[derive(Debug, PartialEq, Eq, Copy, Clone, thiserror::Error)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[non_exhaustive]
 pub enum TimestampError {
-    InvalidTimeCode { expected: CcsdsTimeCodes, found: u8 },
-    ByteConversion(ByteConversionError),
-    Cds(cds::CdsError),
-    Cuc(cuc::CucError),
-    DateBeforeCcsdsEpoch(DateTime<Utc>),
+    /// Invalid time code.
+    #[error("invalid time code, expected {expected:?}, found {found}")]
+    InvalidTimeCode {
+        /// Expected time code.
+        expected: CcsdsTimeCode,
+        /// Found raw time code.
+        found: u8,
+    },
+    /// Byte conversion error.
+    #[error("time stamp: byte conversion error: {0}")]
+    ByteConversion(#[from] ByteConversionError),
+    /// CDS timestamp error.
+    #[error("CDS error: {0}")]
+    Cds(#[from] cds::CdsError),
+    /// CUC timestamp error.
+    #[error("CUC error: {0}")]
+    Cuc(#[from] cuc::CucError),
+    /// Custom epoch is not supported.
+    #[error("custom epoch not supported")]
     CustomEpochNotSupported,
 }
 
-impl Display for TimestampError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
-        match self {
-            TimestampError::InvalidTimeCode { expected, found } => {
-                write!(
-                    f,
-                    "invalid raw time code value {found} for time code {expected:?}"
-                )
-            }
-            TimestampError::Cds(e) => {
-                write!(f, "cds error {e}")
-            }
-            TimestampError::Cuc(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}")
-            }
-            TimestampError::CustomEpochNotSupported => {
-                write!(f, "custom epochs are not supported")
-            }
-        }
-    }
-}
-
+/// [std] module.
 #[cfg(feature = "std")]
-impl Error for TimestampError {
-    fn source(&self) -> Option<&(dyn Error + 'static)> {
-        match self {
-            TimestampError::ByteConversion(e) => Some(e),
-            TimestampError::Cds(e) => Some(e),
-            TimestampError::Cuc(e) => Some(e),
-            _ => None,
-        }
-    }
-}
-impl From<cds::CdsError> for TimestampError {
-    fn from(e: cds::CdsError) -> Self {
-        TimestampError::Cds(e)
-    }
-}
-
-impl From<cuc::CucError> for TimestampError {
-    fn from(e: cuc::CucError) -> Self {
-        TimestampError::Cuc(e)
-    }
-}
-
-#[cfg(feature = "std")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
 pub mod std_mod {
     use crate::time::TimestampError;
     use std::time::SystemTimeError;
     use thiserror::Error;
 
+    /// [std] timestamp error.
     #[derive(Debug, Clone, Error)]
     pub enum StdTimestampError {
-        #[error("system time error: {0}")]
+        /// System time error.
+        #[error("system time error: {0:?}")]
         SystemTime(#[from] SystemTimeError),
+        /// Generic timestamp error.
         #[error("timestamp error: {0}")]
         Timestamp(#[from] TimestampError),
     }
 }
 
+/// Seconds since epoch for the current system time.
 #[cfg(feature = "std")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
 pub fn seconds_since_epoch() -> f64 {
     SystemTime::now()
         .duration_since(SystemTime::UNIX_EPOCH)
@@ -152,6 +137,7 @@ 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
 }
@@ -160,26 +146,31 @@ 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)
 }
 
+/// Convert CCSDS epoch to UNIX epoch.
+#[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)
 }
 
+/// Milliseconds of day for the current system time.
 #[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())
 }
 
+/// Milliseconds for the given seconds since epoch.
 pub fn ms_of_day(seconds_since_epoch: f64) -> u32 {
     let fraction_ms = seconds_since_epoch - seconds_since_epoch.floor();
     let ms_of_day: u32 = (((seconds_since_epoch.floor() as u32 % SECONDS_PER_DAY) * 1000) as f64
@@ -188,23 +179,37 @@ pub fn ms_of_day(seconds_since_epoch: f64) -> u32 {
     ms_of_day
 }
 
+/// Generic writable timestamp trait.
 pub trait TimeWriter {
+    /// Written length.
+    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>;
+
+    /// Convert to a owned [alloc::vec::Vec].
+    #[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;
+/// Genmeric readable timestamp trait.
+pub trait TimeReader: Sized {
+    /// Create a timestamp from a raw byte buffer.
+    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 {
+    /// Length when written to bytes.
     fn len_as_bytes(&self) -> usize;
 
     /// Returns the pfield of the time provider. The pfield can have one or two bytes depending
@@ -212,148 +217,267 @@ 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 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())
+    /// CCSDS time code field.
+    fn ccdsd_time_code(&self) -> CcsdsTimeCode;
+
+    /// UNIX time as seconds.
+    fn unix_secs(&self) -> i64 {
+        self.unix_time().secs
     }
 
-    fn date_time(&self) -> Option<DateTime<Utc>>;
+    /// Subsecond nanoseconds.
+    fn subsec_nanos(&self) -> u32 {
+        self.unix_time().subsec_nanos
+    }
+
+    /// Subsecond milliseconds.
+    fn subsec_millis(&self) -> u16 {
+        (self.subsec_nanos() / 1_000_000) as u16
+    }
+
+    /// UNIX time.
+    fn unix_time(&self) -> UnixTime {
+        UnixTime::new(self.unix_secs(), self.subsec_nanos())
+    }
+
+    /// [chrono] date time.
+    #[cfg(feature = "chrono")]
+    fn chrono_date_time(&self) -> chrono::LocalResult<chrono::DateTime<chrono::Utc>> {
+        chrono::Utc.timestamp_opt(self.unix_secs(), self.subsec_nanos())
+    }
+
+    /// [time] library date] library date time.
+    #[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
+    /// New UNIX time with only seconds, subseconds set to zero.
+    pub fn new_only_secs(unix_seconds: i64) -> Self {
+        Self {
+            secs: unix_seconds,
+            subsec_nanos: 0,
+        }
     }
 
+    /// Sub-second milliseconds.
+    #[inline]
+    pub fn subsec_millis(&self) -> u16 {
+        (self.subsec_nanos / 1_000_000) as u16
+    }
+
+    /// Sub-second nanoseconds.
+    pub fn subsec_nanos(&self) -> u32 {
+        self.subsec_nanos
+    }
+
+    /// Create a UNIX timestamp from the current system time.
     #[cfg(feature = "std")]
-    #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
-    pub fn from_now() -> Result<Self, SystemTimeError> {
+    pub fn 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))
+        Ok(Self::new(epoch as i64, now.subsec_nanos()))
     }
 
+    /// UNIX timestamp as a floating point number in seconds.
     #[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 unix_secs_f64(&self) -> f64 {
+        self.secs as f64 + (self.subsec_nanos as f64 / 1_000_000_000.0)
     }
 
-    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),
-        )
+    /// UNIX timestamp as seconds, discards the sub-second part.
+    pub fn as_secs(&self) -> i64 {
+        self.secs
+    }
+
+    /// UNIX timestamp as [chrono] date time.
+    #[cfg(feature = "chrono")]
+    pub fn chrono_date_time(&self) -> chrono::LocalResult<chrono::DateTime<chrono::Utc>> {
+        Utc.timestamp_opt(self.secs, self.subsec_nanos)
+    }
+
+    /// UNIX timestamp as [time] library date time.
+    #[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 {
+    /// Positive duration flag.
+    pub positive_duration: bool,
+    /// Absolute duration.
+    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
@@ -365,8 +489,8 @@ 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(
@@ -375,7 +499,7 @@ 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:
@@ -383,7 +507,7 @@ 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);
     }
@@ -394,7 +518,7 @@ 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 {
@@ -402,8 +526,8 @@ 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)
@@ -412,7 +536,16 @@ 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() {
@@ -421,12 +554,22 @@ 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)
@@ -441,29 +584,29 @@ 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);
@@ -471,9 +614,9 @@ 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);
@@ -481,9 +624,9 @@ 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);
@@ -493,9 +636,9 @@ 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);
@@ -503,10 +646,11 @@ 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);
@@ -516,32 +660,115 @@ 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

@@ -1,24 +1,28 @@
+//! # Utility module.
 use crate::ByteConversionError;
-use core::fmt::{Debug, Display, Formatter};
+use core::fmt::Debug;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
-#[cfg(feature = "std")]
-use std::error::Error;
 
+/// Helper traits for types which can be converted to a byte array.
 pub trait ToBeBytes {
+    /// Concrete byte array type.
     type ByteArray: AsRef<[u8]>;
     /// Length when written to big endian bytes.
     fn written_len(&self) -> usize;
+    /// Convert to big endian byte array.
     fn to_be_bytes(&self) -> Self::ByteArray;
 }
 
 impl ToBeBytes for () {
     type ByteArray = [u8; 0];
 
+    #[inline]
     fn written_len(&self) -> usize {
         0
     }
 
+    #[inline]
     fn to_be_bytes(&self) -> Self::ByteArray {
         []
     }
@@ -27,9 +31,12 @@ 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 +45,12 @@ 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 +59,12 @@ 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)
     }
@@ -60,82 +73,90 @@ 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)
     }
 }
 
+/// Helper trait for unsigned enumerations.
 pub trait UnsignedEnum {
     /// Size of the unsigned enumeration in bytes.
     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>;
+
+    /// Type-erased raw value.
+    fn value_raw(&self) -> u64;
+
+    /// Convert to a [alloc::vec::Vec].
+    #[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
+    }
 }
 
+/// Extension trait for unsigned enumerations.
 pub trait UnsignedEnumExt: UnsignedEnum + Debug + Copy + Clone + PartialEq + Eq {}
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+/// Unsigned byte field errors.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, thiserror::Error)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum UnsignedByteFieldError {
     /// Value is too large for specified width of byte field.
+    #[error("value {value} too large for width {width}")]
     ValueTooLargeForWidth {
+        /// Width in bytes.
         width: usize,
+        /// Value.
         value: u64,
     },
     /// Only 1, 2, 4 and 8 are allow width values. Optionally contains the expected width if
     /// applicable, for example for conversions.
+    #[error("invalid width {found}, expected {expected:?}")]
     InvalidWidth {
+        /// Found width.
         found: usize,
+        /// Expected width.
         expected: Option<usize>,
     },
-    ByteConversionError(ByteConversionError),
+    /// Error during byte conversion.
+    #[error("byte conversion error: {0}")]
+    ByteConversionError(#[from] ByteConversionError),
 }
 
-impl From<ByteConversionError> for UnsignedByteFieldError {
-    fn from(value: ByteConversionError) -> Self {
-        Self::ByteConversionError(value)
-    }
-}
-
-impl Display for UnsignedByteFieldError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
-        match self {
-            Self::ByteConversionError(e) => {
-                write!(f, "low level byte conversion error: {e}")
-            }
-            Self::InvalidWidth { found, .. } => {
-                write!(f, "invalid width {found}, only 1, 2, 4 and 8 are allowed.")
-            }
-            Self::ValueTooLargeForWidth { width, value } => {
-                write!(f, "value {value} too large for width {width}")
-            }
-        }
-    }
-}
-
-#[cfg(feature = "std")]
-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 {
+    /// Generic constructor.
+    #[inline]
     pub const fn new(width: usize, value: u64) -> Self {
         Self { width, value }
     }
 
-    pub fn value(&self) -> u64 {
+    /// Type-erased raw value.
+    #[inline]
+    pub const fn value(&self) -> u64 {
         self.value
     }
 
+    /// Construct from raw bytes, assuming big-endian byte order.
+    #[inline]
     pub fn new_from_be_bytes(width: usize, buf: &[u8]) -> Result<Self, UnsignedByteFieldError> {
         if width > buf.len() {
             return Err(ByteConversionError::FromSliceTooSmall {
@@ -168,10 +189,16 @@ impl UnsignedByteField {
 }
 
 impl UnsignedEnum for UnsignedByteField {
+    #[inline]
     fn size(&self) -> usize {
         self.width
     }
 
+    #[inline]
+    fn value_raw(&self) -> u64 {
+        self.value()
+    }
+
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         if buf.len() < self.size() {
             return Err(ByteConversionError::ToSliceTooSmall {
@@ -205,19 +232,28 @@ impl UnsignedEnum for UnsignedByteField {
     }
 }
 
+/// Generic type erased unsigned byte field.
 #[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> {
+impl<TYPE: Copy + Into<u64>> GenericUnsignedByteField<TYPE> {
+    /// Generic constructor.
     pub const fn new(val: TYPE) -> Self {
         Self { value: val }
     }
+
+    /// Raw value.
+    pub const fn value(&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()
     }
@@ -229,20 +265,34 @@ impl<TYPE: ToBeBytes> UnsignedEnum for GenericUnsignedByteField<TYPE> {
                 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_raw(&self) -> u64 {
+        self.value().into()
+    }
 }
 
+/// Alias for [GenericUnsignedByteField] with [()] generic.
 pub type UnsignedByteFieldEmpty = GenericUnsignedByteField<()>;
+/// Alias for [GenericUnsignedByteField] with [u8] generic.
 pub type UnsignedByteFieldU8 = GenericUnsignedByteField<u8>;
+/// Alias for [GenericUnsignedByteField] with [u16] generic.
 pub type UnsignedByteFieldU16 = GenericUnsignedByteField<u16>;
+/// Alias for [GenericUnsignedByteField] with [u32] generic.
 pub type UnsignedByteFieldU32 = GenericUnsignedByteField<u32>;
+/// Alias for [GenericUnsignedByteField] with [u64] generic.
 pub type UnsignedByteFieldU64 = GenericUnsignedByteField<u64>;
 
+/// Alias for [UnsignedByteFieldU8]
 pub type UbfU8 = UnsignedByteFieldU8;
+/// Alias for [UnsignedByteFieldU16]
 pub type UbfU16 = UnsignedByteFieldU16;
+/// Alias for [UnsignedByteFieldU32]
 pub type UbfU32 = UnsignedByteFieldU32;
+/// Alias for [UnsignedByteFieldU64]
 pub type UbfU64 = UnsignedByteFieldU64;
 
 impl From<UnsignedByteFieldU8> for UnsignedByteField {
@@ -254,6 +304,7 @@ 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 {
@@ -266,6 +317,7 @@ impl TryFrom<UnsignedByteField> for UnsignedByteFieldU8 {
 }
 
 impl From<UnsignedByteFieldU16> for UnsignedByteField {
+    #[inline]
     fn from(value: UnsignedByteFieldU16) -> Self {
         Self::new(2, value.value as u64)
     }
@@ -274,6 +326,7 @@ 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 {
@@ -286,6 +339,7 @@ impl TryFrom<UnsignedByteField> for UnsignedByteFieldU16 {
 }
 
 impl From<UnsignedByteFieldU32> for UnsignedByteField {
+    #[inline]
     fn from(value: UnsignedByteFieldU32) -> Self {
         Self::new(4, value.value as u64)
     }
@@ -294,6 +348,7 @@ 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 {
@@ -306,6 +361,7 @@ impl TryFrom<UnsignedByteField> for UnsignedByteFieldU32 {
 }
 
 impl From<UnsignedByteFieldU64> for UnsignedByteField {
+    #[inline]
     fn from(value: UnsignedByteFieldU64) -> Self {
         Self::new(8, value.value)
     }
@@ -314,6 +370,7 @@ 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 {
@@ -326,7 +383,7 @@ impl TryFrom<UnsignedByteField> for UnsignedByteFieldU64 {
 }
 
 #[cfg(test)]
-pub mod tests {
+mod tests {
     use crate::util::{
         UnsignedByteField, UnsignedByteFieldError, UnsignedByteFieldU16, UnsignedByteFieldU32,
         UnsignedByteFieldU64, UnsignedByteFieldU8, UnsignedEnum,
@@ -344,9 +401,11 @@ 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_raw(), 5);
+        assert_eq!(u8.value(), 5);
     }
 
     #[test]
@@ -360,9 +419,11 @@ 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_raw(), 3823);
+        assert_eq!(u16.value(), 3823);
     }
 
     #[test]
@@ -376,9 +437,11 @@ 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_raw(), 80932);
+        assert_eq!(u32.value(), 80932);
     }
 
     #[test]
@@ -392,6 +455,8 @@ 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_raw(), 5999999);
+        assert_eq!(u64.value(), 5999999);
     }
 
     #[test]
@@ -530,9 +595,9 @@ 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]
@@ -544,8 +609,8 @@ 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);
         }
     }
 
@@ -558,9 +623,9 @@ 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]