Merge pull request 'add missing doc_cfg attr' (#67) from missing-doc-cfg-attr into main

Reviewed-on: #67

CHANGELOG.md

@@ -8,6 +8,139 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+# [v0.11.0-rc.0] 2024-03-04
+
+## Added
+
+- `From<$TY>` for the `EcssEnum$TY` ECSS enum type definitions.
+- `Sub` implementation for `UnixTimestamp` to calculate the duration between two timestamps.
+
+## Changed
+
+- `CcsdsTimeProvider` `subsecond_millis` function now returns `u16` instead of `Option<u16>`.
+- `UnixTimestamp` `subsecond_millis` function now returns `u16` instead of `Option<u16>`.
+
+# [v0.10.0] 2024-02-17
+
+## Added
+
+- Added `value` and `to_vec` methods for the `UnsignedEnum` trait. The value is returned as
+  as `u64`. Renamed former `value` method on `GenericUnsignedByteField` to `value_typed`.
+- Added `value_const` const function for `UnsignedByteField` type.
+- Added `value_typed` const functions for `GenericUnsignedByteField` and `GenericEcssEnumWrapper`.
+
+# [v0.9.0] 2024-02-07
+
+## Added
+
+- `CcsdsPacket`, `PusPacket` and `GenericPusTmSecondaryHeader` implementation for
+  `PusTmZeroCopyWriter`.
+- Additional length checks for `PusTmZeroCopyWriter`.
+
+## Changed
+
+- `PusTmZeroCopyWriter`: Added additional timestamp length argument for `new` constructor.
+
+## Fixed
+
+- Typo: `PUC_TM_MIN_HEADER_LEN` -> `PUS_TM_MIN_HEADER_LEN`
+
+# [v0.8.1] 2024-02-05
+
+## Fixed
+
+- Added `pub` visibility for `PacketSequenceCtrl::const_new`.
+
+# [v0.8.0] 2024-02-05
+
+## Added
+
+- Added `len_written` and `to_vec` methods to the `TimeWriter` trait.
+
+# [v0.7.0] 2024-02-01
+
+# [v0.7.0-beta.4] 2024-01-23
+
+## Fixed
+
+- `MetadataPduCreator`: The serialization function shifted the closure requested information
+  to the wrong position (first reserved bit) inside the raw content field.
+
+# [v0.7.0-beta.3] 2023-12-06
+
+## Added
+
+- Add `WritablePduPacket` trait which is a common trait of all CFDP PDU implementations.
+- Add `CfdpPdu` trait which exposes fields and attributes common to all CFDP PDUs.
+- Add `GenericTlv` and `WritableTlv` trait as abstractions for the various TLV types.
+
+## Fixed
+
+- Set the direction field inside the PDU header field correctly explicitely for all CFDP PDU
+  packets.
+
+## Changed
+
+- Split up `FinishedPdu`into `FinishedPduCreator` and `FinishedPduReader` to expose specialized
+  APIs.
+- Split up `MetadataPdu`into `MetadataPduCreator` and `MetadataPduReader` to expose specialized
+  APIs.
+- Cleaned up CUC time implementation. Added `width` and `counter` getter methods.
+- Renamed `SerializablePusPacket` to `WritablePusPacket`.
+- Renamed `UnsignedPfc` to `PfcUnsigned` and `RealPfc` to `PfcReal`.
+- Renamed `WritablePduPacket.written_len` and `SerializablePusPacket.len_packed` to `len_written`.
+- Introduce custom implementation of `PartialEq` for `CommonPduConfig` which only compares the
+  values for the source entity ID, destination entity ID and transaction sequence number field to
+  allow those fields to have different widths.
+- Removed the `PusError::RawDataTooShort` variant which is already covered by
+  `PusError::ByteConversionError` variant.
+- Ranamed `TlvLvError::ByteConversionError` to `TlvLvError::ByteConversion`.
+- Renamed `PusError::IncorrectCrc` to `PusError::ChecksumFailure`.
+- Some more struct variant changes for error enumerations.
+
+## Removed
+
+- `PusError::NoRawData` variant.
+- `cfdp::LenInBytes` which was not used.
+
+# [v0.7.0-beta.2] 2023-09-26
+
+## Added
+
+- `PacketId` trait impls: `Ord`, `PartialOrd` and `Hash`
+- `SerializablePusPacket` trait: Add `to_vec` method with default implementation.
+
+# [v0.7.0-beta.1] 2023-08-28
+
+- Bump `zerocopy` dependency to v0.7.0
+
+## Changed
+
+- The `Tlv` and `Lv` API return `&[u8]` instead of `Option<&[u8]>`.
+- `ByteConversionError` error variants `ToSliceTooSmall` and `FromSliceTooSmall` are struct
+  variants now. `SizeMissmatch` was removed appropriately.
+- `UnsignedByteFieldError` error variants `ValueTooLargeForWidth` and `InvalidWidth` are struct
+  variants now.
+- `TimestampError` error variant `InvalidTimeCode` is struct variant now.
+
+## Added
+
+- Added `raw_data` API for `Tlv` and `Lv` to retrieve the whole `Lv`/`Tlv` slice if the object
+  was created from a raw bytestream.
+- Added `MsgToUserTlv` helper class which wraps a regular `Tlv` and adds some useful functionality.
+- `UnsignedByteField` and `GenericUnsignedByteField` `new` methods are `const` now.
+- `PduError` variants which contained a tuple variant with multiple fields were converted to a
+  struct variant.
+
+# Added
+
+- Added `pdu_datafield_len` getter function for `PduHeader`
+
+## Removed
+
+- `SizeMissmatch` because it is not required for the `ByteConversionError` error enumeration
+  anymore.
+
 # [v0.7.0-beta.0] 2023-08-16
 
 - Moved MSRV from v1.60 to v1.61.
@@ -60,7 +193,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   `PusTm` object.
 
 ## Changed
- 
+
 - The `EcssEnumeration` now requires the `UnsignedEnum` trait and only adds the `pfc` method to it.
 - Renamed `byte_width` usages to `size` (part of new `UnsignedEnum` trait)
 - Moved `ecss::CRC_CCITT_FALSE` CRC constant to the root module. This CRC type is not just used by

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "spacepackets"
-version = "0.7.0-beta.0"
+version = "0.11.0-rc.0"
 edition = "2021"
 rust-version = "1.61"
 authors = ["Robin Mueller <muellerr@irs.uni-stuttgart.de>"]
@@ -13,16 +13,19 @@ categories = ["aerospace", "aerospace::space-protocols", "no-std", "hardware-sup
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-zerocopy = "0.6"
 crc = "3"
 delegate = ">=0.8, <0.11"
 
+[dependencies.zerocopy]
+version = "0.7"
+features = ["derive"]
+
 [dependencies.thiserror]
 version = "1"
 optional = true
 
 [dependencies.num_enum]
-version = "0.6"
+version = ">0.5, <=0.7"
 default-features = false
 
 [dependencies.serde]
@@ -50,4 +53,4 @@ alloc = ["postcard/alloc", "chrono/alloc"]
 
 [package.metadata.docs.rs]
 all-features = true
-rustdoc-args = ["--cfg", "doc_cfg"]
+rustdoc-args = ["--cfg", "doc_cfg", "--generate-link-to-definition"]

README.md

@@ -1,6 +1,7 @@
 [![Crates.io](https://img.shields.io/crates/v/spacepackets)](https://crates.io/crates/spacepackets)
 [![docs.rs](https://img.shields.io/docsrs/spacepackets)](https://docs.rs/spacepackets)
 [![ci](https://github.com/us-irs/spacepackets-rs/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/us-irs/spacepackets-rs/actions/workflows/ci.yml)
+[![coverage](https://shields.io/endpoint?url=https://absatsw.irs.uni-stuttgart.de/projects/spacepackets/coverage-rs/latest/coverage.json)](https://absatsw.irs.uni-stuttgart.de/projects/spacepackets/coverage-rs/latest/index.html)
 
 ECSS and CCSDS Spacepackets
 ======
@@ -47,3 +48,16 @@ deserializing them with an appropriate `serde` provider like
 
 You can check the [documentation](https://docs.rs/spacepackets) of individual modules for various
 usage examples.
+
+# Coverage
+
+Coverage was generated using [`grcov`](https://github.com/mozilla/grcov). If you have not done so
+already, install the `llvm-tools-preview`:
+
+```sh
+rustup component add llvm-tools-preview
+cargo install grcov --locked
+```
+
+After that, you can simply run `coverage.py` to test the project with coverage. You can optionally
+supply the `--open` flag to open the coverage report in your webbrowser.

automation/Dockerfile

@@ -6,10 +6,20 @@ 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
+
+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
+
+# 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 +1,78 @@
 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 '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'
+      }
+    }
+    stage('Run test with Coverage') {
+      when {
+        anyOf {
+          branch 'main';
+          branch pattern: 'cov-deployment*'
+        }
+      }
+      steps {
+        withEnv(['RUSTFLAGS=-Cinstrument-coverage', 'LLVM_PROFILE_FILE=target/coverage/%p-%m.profraw']) {
+          echo "Executing tests with coverage"
+          sh 'cargo clean'
+          sh 'cargo test --all-features'
+          sh 'grcov . -s . --binary-path ./target/debug -t html --branch --ignore-not-existing -o ./target/debug/coverage/'
+          sshagent(credentials: ['documentation-buildfix']) {
+            // Deploy to Apache webserver
+            sh 'rsync --mkpath -r --delete ./target/debug/coverage/ buildfix@documentation.irs.uni-stuttgart.de:/projects/spacepackets/coverage-rs/latest/'
+          }
+        }
+      }
+    }
+  }
 }

coverage.py

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

release-checklist.md

@@ -4,7 +4,7 @@ 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`.
+   `cargo +nightly doc --all-features --config 'rustdocflags=["--cfg", "doc_cfg"]' --open`.
 2. Bump version specifier in `Cargo.toml`.
 3. Update `CHANGELOG.md`: Convert `unreleased` section into version section with date and add new
    `unreleased` section.
@@ -13,6 +13,10 @@ Checklist for new releases
 6. Wait for CI/CD results for EGit and Github. These also check cross-compilation for bare-metal
    targets.
 
+# Release
+
+1. `cargo publish`
+
 # Post-Release
 
 1. Create a new release on `EGit` based on the release branch.

src/cfdp/lv.rs

@@ -1,6 +1,6 @@
 //! Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
 use crate::cfdp::TlvLvError;
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::ByteConversionError;
 use core::str::Utf8Error;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -11,14 +11,26 @@ pub const MIN_LV_LEN: usize = 1;
 
 /// Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
 ///
+/// Please note that this class is zero-copy and does not generate a copy of the value data for
+/// both the regular [Self::new] constructor and the [Self::from_bytes] constructor.
+///
 /// # Lifetimes
 ///  * `data`: If the LV is generated from a raw bytestream, this will be the lifetime of
 ///    the raw bytestream. If the LV is generated from a raw slice or a similar data reference,
 ///    this will be the lifetime of that data reference.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct Lv<'data> {
-    data: Option<&'data [u8]>,
+    data: &'data [u8],
+    // If the LV was generated from a raw bytestream, this will contain the start of the
+    // full LV.
+    pub(crate) raw_data: Option<&'data [u8]>,
+}
+
+impl PartialEq for Lv<'_> {
+    fn eq(&self, other: &Self) -> bool {
+        self.data == other.data
+    }
 }
 
 pub(crate) fn generic_len_check_data_serialization(
@@ -27,10 +39,10 @@ pub(crate) fn generic_len_check_data_serialization(
     min_overhead: usize,
 ) -> Result<(), ByteConversionError> {
     if buf.len() < data_len + min_overhead {
-        return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+        return Err(ByteConversionError::ToSliceTooSmall {
             found: buf.len(),
             expected: data_len + min_overhead,
-        }));
+        });
     }
     Ok(())
 }
@@ -40,10 +52,10 @@ pub(crate) fn generic_len_check_deserialization(
     min_overhead: usize,
 ) -> Result<(), ByteConversionError> {
     if buf.len() < min_overhead {
-        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+        return Err(ByteConversionError::FromSliceTooSmall {
             found: buf.len(),
             expected: min_overhead,
-        }));
+        });
     }
     Ok(())
 }
@@ -53,12 +65,18 @@ impl<'data> Lv<'data> {
         if data.len() > u8::MAX as usize {
             return Err(TlvLvError::DataTooLarge(data.len()));
         }
-        Ok(Lv { data: Some(data) })
+        Ok(Lv {
+            data,
+            raw_data: None,
+        })
     }
 
     /// Creates a LV with an empty value field.
     pub fn new_empty() -> Lv<'data> {
-        Lv { data: None }
+        Lv {
+            data: &[],
+            raw_data: None,
+        }
     }
 
     /// Helper function to build a string LV. This is especially useful for the file or directory
@@ -77,10 +95,7 @@ impl<'data> Lv<'data> {
 
     /// Returns the length of the value part, not including the length byte.
     pub fn len_value(&self) -> usize {
-        if self.data.is_none() {
-            return 0;
-        }
-        self.data.unwrap().len()
+        self.data.len()
     }
 
     /// Returns the full raw length, including the length byte.
@@ -90,18 +105,26 @@ impl<'data> Lv<'data> {
 
     /// Checks whether the value field is empty.
     pub fn is_empty(&self) -> bool {
-        self.data.is_none()
+        self.data.len() == 0
     }
 
-    pub fn value(&self) -> Option<&[u8]> {
+    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.
+    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.
     pub fn value_as_str(&self) -> Option<Result<&'data str, Utf8Error>> {
-        self.data?;
-        Some(core::str::from_utf8(self.data.unwrap()))
+        if self.is_empty() {
+            return None;
+        }
+        Some(core::str::from_utf8(self.data))
     }
 
     /// Writes the LV to a raw buffer. Please note that the first byte will contain the length
@@ -118,15 +141,14 @@ impl<'data> Lv<'data> {
     }
 
     pub(crate) fn write_to_be_bytes_no_len_check(&self, buf: &mut [u8]) -> usize {
-        if self.data.is_none() {
+        if self.is_empty() {
             buf[0] = 0;
             return MIN_LV_LEN;
         }
-        let data = self.data.unwrap();
         // Length check in constructor ensures the length always has a valid value.
-        buf[0] = data.len() as u8;
-        buf[MIN_LV_LEN..data.len() + MIN_LV_LEN].copy_from_slice(data);
-        MIN_LV_LEN + data.len()
+        buf[0] = self.data.len() as u8;
+        buf[MIN_LV_LEN..self.data.len() + MIN_LV_LEN].copy_from_slice(self.data);
+        MIN_LV_LEN + self.data.len()
     }
 
     pub(crate) fn from_be_bytes_no_len_check(
@@ -134,17 +156,18 @@ impl<'data> Lv<'data> {
     ) -> Result<Lv<'data>, ByteConversionError> {
         let value_len = buf[0] as usize;
         generic_len_check_deserialization(buf, value_len + MIN_LV_LEN)?;
-        let mut data = None;
-        if value_len > 0 {
-            data = Some(&buf[MIN_LV_LEN..MIN_LV_LEN + value_len])
-        }
-        Ok(Self { data })
+        Ok(Self {
+            data: &buf[MIN_LV_LEN..MIN_LV_LEN + value_len],
+            raw_data: Some(buf),
+        })
     }
 }
 
 #[cfg(test)]
 pub mod tests {
-    use crate::cfdp::lv::Lv;
+    use super::*;
+    use alloc::string::ToString;
+
     use crate::cfdp::TlvLvError;
     use crate::ByteConversionError;
     use std::string::String;
@@ -155,8 +178,8 @@ pub mod tests {
         let lv_res = Lv::new(&lv_data);
         assert!(lv_res.is_ok());
         let lv = lv_res.unwrap();
-        assert!(lv.value().is_some());
-        let val = lv.value().unwrap();
+        assert!(!lv.value().is_empty());
+        let val = lv.value();
         assert_eq!(val[0], 1);
         assert_eq!(val[1], 2);
         assert_eq!(val[2], 3);
@@ -172,7 +195,6 @@ pub mod tests {
         assert_eq!(lv_empty.len_value(), 0);
         assert_eq!(lv_empty.len_full(), 1);
         assert!(lv_empty.is_empty());
-        assert_eq!(lv_empty.value(), None);
         let mut buf: [u8; 4] = [0xff; 4];
         let res = lv_empty.write_to_be_bytes(&mut buf);
         assert!(res.is_ok());
@@ -211,10 +233,11 @@ pub mod tests {
         assert!(lv.is_ok());
         let lv = lv.unwrap();
         assert!(!lv.is_empty());
-        assert!(lv.value().is_some());
         assert_eq!(lv.len_value(), 4);
         assert_eq!(lv.len_full(), 5);
-        let val = lv.value().unwrap();
+        assert!(lv.raw_data().is_some());
+        assert_eq!(lv.raw_data().unwrap(), buf);
+        let val = lv.value();
         assert_eq!(val[0], 1);
         assert_eq!(val[1], 2);
         assert_eq!(val[2], 3);
@@ -228,7 +251,6 @@ pub mod tests {
         assert!(lv_empty.is_ok());
         let lv_empty = lv_empty.unwrap();
         assert!(lv_empty.is_empty());
-        assert!(lv_empty.value().is_none());
     }
 
     #[test]
@@ -239,6 +261,10 @@ pub mod tests {
         let error = lv.unwrap_err();
         if let TlvLvError::DataTooLarge(size) = error {
             assert_eq!(size, u8::MAX as usize + 1);
+            assert_eq!(
+                error.to_string(),
+                "data with size 256 larger than allowed 255 bytes"
+            );
         } else {
             panic!("invalid exception {:?}", error)
         }
@@ -252,9 +278,9 @@ pub mod tests {
         let res = lv.write_to_be_bytes(&mut buf);
         assert!(res.is_err());
         let error = res.unwrap_err();
-        if let ByteConversionError::ToSliceTooSmall(missmatch) = error {
-            assert_eq!(missmatch.expected, 5);
-            assert_eq!(missmatch.found, 3);
+        if let ByteConversionError::ToSliceTooSmall { found, expected } = error {
+            assert_eq!(expected, 5);
+            assert_eq!(found, 3);
         } else {
             panic!("invalid error {}", error);
         }
@@ -267,9 +293,9 @@ pub mod tests {
         let res = Lv::from_bytes(&buf);
         assert!(res.is_err());
         let error = res.unwrap_err();
-        if let ByteConversionError::FromSliceTooSmall(missmatch) = error {
-            assert_eq!(missmatch.found, 3);
-            assert_eq!(missmatch.expected, 5);
+        if let ByteConversionError::FromSliceTooSmall { found, expected } = error {
+            assert_eq!(found, 3);
+            assert_eq!(expected, 5);
         } else {
             panic!("invalid error {}", error);
         }
@@ -282,14 +308,14 @@ pub mod tests {
         let res = res.unwrap();
         assert_eq!(res, 8 + 1);
         assert_eq!(buf[0], 8);
-        assert_eq!(buf[1], 't' as u8);
-        assert_eq!(buf[2], 'e' as u8);
-        assert_eq!(buf[3], 's' as u8);
-        assert_eq!(buf[4], 't' as u8);
-        assert_eq!(buf[5], '.' as u8);
-        assert_eq!(buf[6], 'b' as u8);
-        assert_eq!(buf[7], 'i' as u8);
-        assert_eq!(buf[8], 'n' as u8);
+        assert_eq!(buf[1], b't');
+        assert_eq!(buf[2], b'e');
+        assert_eq!(buf[3], b's');
+        assert_eq!(buf[4], b't');
+        assert_eq!(buf[5], b'.');
+        assert_eq!(buf[6], b'b');
+        assert_eq!(buf[7], b'i');
+        assert_eq!(buf[8], b'n');
     }
     #[test]
     fn test_str_helper() {

src/cfdp/mod.rs

@@ -48,6 +48,24 @@ pub enum CrcFlag {
     WithCrc = 1,
 }
 
+impl From<bool> for CrcFlag {
+    fn from(value: bool) -> Self {
+        if value {
+            return CrcFlag::WithCrc;
+        }
+        CrcFlag::NoCrc
+    }
+}
+
+impl From<CrcFlag> for bool {
+    fn from(value: CrcFlag) -> Self {
+        if value == CrcFlag::WithCrc {
+            return true;
+        }
+        false
+    }
+}
+
 /// Always 0 and ignored for File Directive PDUs (CCSDS 727.0-B-5 P.75)
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
@@ -76,17 +94,6 @@ pub enum FaultHandlerCode {
     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)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[repr(u8)]
@@ -119,6 +126,22 @@ pub enum LargeFileFlag {
     Large = 1,
 }
 
+/// Transaction status for the ACK PDU field according to chapter 5.2.4 of the CFDP standard.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum TransactionStatus {
+    /// Transaction is not currently active and the CFDP implementation does not retain a
+    /// transaction history.
+    Undefined = 0b00,
+    Active = 0b01,
+    /// Transaction was active in the past and was terminated.
+    Terminated = 0b10,
+    /// The CFDP implementation does retain a tranaction history, and the transaction is not and
+    /// never was active at this entity.
+    Unrecognized = 0b11,
+}
+
 /// Checksum types according to the
 /// [SANA Checksum Types registry](https://sanaregistry.org/r/checksum_identifiers/)
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
@@ -146,9 +169,12 @@ pub const NULL_CHECKSUM_U32: [u8; 4] = [0; 4];
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum TlvLvError {
     DataTooLarge(usize),
-    ByteConversionError(ByteConversionError),
+    ByteConversion(ByteConversionError),
     /// First value: Found value. Second value: Expected value if there is one.
-    InvalidTlvTypeField((u8, Option<u8>)),
+    InvalidTlvTypeField {
+        found: u8,
+        expected: 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.
     InvalidValueLength(usize),
@@ -161,7 +187,7 @@ pub enum TlvLvError {
 
 impl From<ByteConversionError> for TlvLvError {
     fn from(value: ByteConversionError) -> Self {
-        Self::ByteConversionError(value)
+        Self::ByteConversion(value)
     }
 }
 
@@ -176,17 +202,17 @@ impl Display for TlvLvError {
                     u8::MAX
                 )
             }
-            TlvLvError::ByteConversionError(e) => {
-                write!(f, "{}", e)
+            TlvLvError::ByteConversion(e) => {
+                write!(f, "tlv or lv byte conversion: {}", e)
             }
-            TlvLvError::InvalidTlvTypeField((found, expected)) => {
+            TlvLvError::InvalidTlvTypeField { found, expected } => {
                 write!(
                     f,
-                    "invalid TLV type field, found {found}, possibly expected {expected:?}"
+                    "invalid TLV type field, found {found}, expected {expected:?}"
                 )
             }
             TlvLvError::InvalidValueLength(len) => {
-                write!(f, "invalid value length {len} detected")
+                write!(f, "invalid value length {len}")
             }
             TlvLvError::SecondNameMissing => {
                 write!(f, "second name missing for filestore request or response")
@@ -202,8 +228,65 @@ impl Display for TlvLvError {
 impl Error for TlvLvError {
     fn source(&self) -> Option<&(dyn Error + 'static)> {
         match self {
-            TlvLvError::ByteConversionError(e) => Some(e),
+            TlvLvError::ByteConversion(e) => Some(e),
             _ => None,
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
+
+    #[test]
+    fn test_crc_from_bool() {
+        assert_eq!(CrcFlag::from(false), CrcFlag::NoCrc);
+    }
+
+    #[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 +1,334 @@
+use crate::{
+    cfdp::{ConditionCode, CrcFlag, Direction, TransactionStatus},
+    ByteConversionError,
+};
+
+use super::{
+    add_pdu_crc, generic_length_checks_pdu_deserialization, CfdpPdu, FileDirectiveType, PduError,
+    PduHeader, WritablePduPacket,
+};
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+/// ACK PDU abstraction.
+///
+/// For more information, refer to CFDP chapter 5.2.4.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct AckPdu {
+    pdu_header: PduHeader,
+    directive_code_of_acked_pdu: FileDirectiveType,
+    condition_code: ConditionCode,
+    transaction_status: TransactionStatus,
+}
+
+impl AckPdu {
+    pub fn new(
+        mut pdu_header: PduHeader,
+        directive_code_of_acked_pdu: FileDirectiveType,
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) -> Result<Self, PduError> {
+        if directive_code_of_acked_pdu == FileDirectiveType::EofPdu {
+            pdu_header.pdu_conf.direction = Direction::TowardsSender;
+        } else if directive_code_of_acked_pdu == FileDirectiveType::FinishedPdu {
+            pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
+        } else {
+            return Err(PduError::InvalidDirectiveType {
+                found: directive_code_of_acked_pdu as u8,
+                expected: None,
+            });
+        }
+        // Force correct direction flag.
+        let mut ack_pdu = Self {
+            pdu_header,
+            directive_code_of_acked_pdu,
+            condition_code,
+            transaction_status,
+        };
+        ack_pdu.pdu_header.pdu_datafield_len = ack_pdu.calc_pdu_datafield_len() as u16;
+        Ok(ack_pdu)
+    }
+
+    pub fn new_for_eof_pdu(
+        pdu_header: PduHeader,
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) -> Self {
+        // Unwrap okay here, [new] can only fail on invalid directive codes.
+        Self::new(
+            pdu_header,
+            FileDirectiveType::EofPdu,
+            condition_code,
+            transaction_status,
+        )
+        .unwrap()
+    }
+
+    pub fn new_for_finished_pdu(
+        pdu_header: PduHeader,
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) -> Self {
+        // Unwrap okay here, [new] can only fail on invalid directive codes.
+        Self::new(
+            pdu_header,
+            FileDirectiveType::FinishedPdu,
+            condition_code,
+            transaction_status,
+        )
+        .unwrap()
+    }
+
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    pub fn directive_code_of_acked_pdu(&self) -> FileDirectiveType {
+        self.directive_code_of_acked_pdu
+    }
+
+    pub fn condition_code(&self) -> ConditionCode {
+        self.condition_code
+    }
+
+    pub fn transaction_status(&self) -> TransactionStatus {
+        self.transaction_status
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        if self.crc_flag() == CrcFlag::WithCrc {
+            return 5;
+        }
+        3
+    }
+
+    pub fn from_bytes(buf: &[u8]) -> Result<AckPdu, PduError> {
+        let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
+        let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
+        generic_length_checks_pdu_deserialization(buf, current_idx + 3, full_len_without_crc)?;
+        let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::AckPdu),
+            }
+        })?;
+        if directive_type != FileDirectiveType::AckPdu {
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::AckPdu,
+            });
+        }
+        current_idx += 1;
+        let acked_directive_type =
+            FileDirectiveType::try_from(buf[current_idx] >> 4).map_err(|_| {
+                PduError::InvalidDirectiveType {
+                    found: buf[current_idx],
+                    expected: None,
+                }
+            })?;
+        if acked_directive_type != FileDirectiveType::EofPdu
+            && acked_directive_type != FileDirectiveType::FinishedPdu
+        {
+            return Err(PduError::InvalidDirectiveType {
+                found: acked_directive_type as u8,
+                expected: None,
+            });
+        }
+        current_idx += 1;
+        let condition_code = ConditionCode::try_from((buf[current_idx] >> 4) & 0b1111)
+            .map_err(|_| PduError::InvalidConditionCode((buf[current_idx] >> 4) & 0b1111))?;
+        let transaction_status = TransactionStatus::try_from(buf[current_idx] & 0b11).unwrap();
+        Self::new(
+            pdu_header,
+            acked_directive_type,
+            condition_code,
+            transaction_status,
+        )
+    }
+}
+
+impl CfdpPdu for AckPdu {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::AckPdu)
+    }
+}
+
+impl WritablePduPacket for AckPdu {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::AckPdu as u8;
+        current_idx += 1;
+
+        buf[current_idx] = (self.directive_code_of_acked_pdu as u8) << 4;
+        if self.directive_code_of_acked_pdu == FileDirectiveType::FinishedPdu {
+            // This is the directive subtype code. It needs to be set to 0b0001 if the ACK PDU
+            // acknowledges a Finished PDU, and to 0b0000 otherwise.
+            buf[current_idx] |= 0b0001;
+        }
+        current_idx += 1;
+        buf[current_idx] = ((self.condition_code as u8) << 4) | (self.transaction_status as u8);
+        current_idx += 1;
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::cfdp::{
+        pdu::tests::{common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID},
+        LargeFileFlag, PduType, TransmissionMode,
+    };
+
+    use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
+
+    fn verify_state(ack_pdu: &AckPdu, expected_crc_flag: CrcFlag, expected_dir: Direction) {
+        assert_eq!(ack_pdu.condition_code(), ConditionCode::NoError);
+        assert_eq!(ack_pdu.transaction_status(), TransactionStatus::Active);
+
+        assert_eq!(ack_pdu.crc_flag(), expected_crc_flag);
+        assert_eq!(ack_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(ack_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            ack_pdu.file_directive_type(),
+            Some(FileDirectiveType::AckPdu)
+        );
+        assert_eq!(ack_pdu.transmission_mode(), TransmissionMode::Acknowledged);
+        assert_eq!(ack_pdu.direction(), expected_dir);
+        assert_eq!(ack_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(ack_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(ack_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
+    }
+
+    #[test]
+    fn test_basic() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new(
+            pdu_header,
+            FileDirectiveType::FinishedPdu,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        )
+        .expect("creating ACK PDU failed");
+        assert_eq!(
+            ack_pdu.directive_code_of_acked_pdu(),
+            FileDirectiveType::FinishedPdu
+        );
+        verify_state(&ack_pdu, CrcFlag::NoCrc, Direction::TowardsReceiver);
+    }
+
+    fn generic_serialization_test(
+        condition_code: ConditionCode,
+        transaction_status: TransactionStatus,
+    ) {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_finished_pdu(pdu_header, condition_code, transaction_status);
+        let mut buf: [u8; 64] = [0; 64];
+        let res = ack_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(written, ack_pdu.len_written());
+        verify_raw_header(ack_pdu.pdu_header(), &buf);
+
+        assert_eq!(buf[7], FileDirectiveType::AckPdu as u8);
+        assert_eq!((buf[8] >> 4) & 0b1111, FileDirectiveType::FinishedPdu as u8);
+        assert_eq!(buf[8] & 0b1111, 0b0001);
+        assert_eq!(buf[9] >> 4 & 0b1111, condition_code as u8);
+        assert_eq!(buf[9] & 0b11, transaction_status as u8);
+        assert_eq!(written, 10);
+    }
+
+    #[test]
+    fn test_serialization_no_error() {
+        generic_serialization_test(ConditionCode::NoError, TransactionStatus::Active);
+    }
+
+    #[test]
+    fn test_serialization_fs_error() {
+        generic_serialization_test(ConditionCode::FileSizeError, TransactionStatus::Terminated);
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_finished_pdu(
+            pdu_header,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        );
+        let ack_vec = ack_pdu.to_vec().unwrap();
+        let ack_deserialized =
+            AckPdu::from_bytes(&ack_vec).expect("ACK PDU deserialization failed");
+        assert_eq!(ack_deserialized, ack_pdu);
+    }
+
+    #[test]
+    fn test_with_crc() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_finished_pdu(
+            pdu_header,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        );
+        let ack_vec = ack_pdu.to_vec().unwrap();
+        assert_eq!(ack_vec.len(), ack_pdu.len_written());
+        assert_eq!(ack_vec.len(), 12);
+        let ack_deserialized =
+            AckPdu::from_bytes(&ack_vec).expect("ACK PDU deserialization failed");
+        assert_eq!(ack_deserialized, ack_pdu);
+    }
+
+    #[test]
+    fn test_for_eof_pdu() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_eof_pdu(
+            pdu_header,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        );
+        assert_eq!(
+            ack_pdu.directive_code_of_acked_pdu(),
+            FileDirectiveType::EofPdu
+        );
+        verify_state(&ack_pdu, CrcFlag::WithCrc, Direction::TowardsSender);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_ack_pdu_serialization() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let ack_pdu = AckPdu::new_for_eof_pdu(
+            pdu_header,
+            ConditionCode::NoError,
+            TransactionStatus::Active,
+        );
+        generic_serde_test(ack_pdu);
+    }
+}

src/cfdp/pdu/eof.rs

@@ -2,12 +2,14 @@ use crate::cfdp::pdu::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
     FileDirectiveType, PduError, PduHeader,
 };
-use crate::cfdp::tlv::EntityIdTlv;
-use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::cfdp::tlv::{EntityIdTlv, WritableTlv};
+use crate::cfdp::{ConditionCode, CrcFlag, Direction, LargeFileFlag};
+use crate::ByteConversionError;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::{CfdpPdu, WritablePduPacket};
+
 /// Finished PDU abstraction.
 ///
 /// For more information, refer to CFDP chapter 5.2.2.
@@ -22,7 +24,9 @@ pub struct EofPdu {
 }
 
 impl EofPdu {
-    pub fn new_no_error(pdu_header: PduHeader, file_checksum: u32, file_size: u64) -> Self {
+    pub fn new_no_error(mut pdu_header: PduHeader, file_checksum: u32, file_size: u64) -> Self {
+        // Force correct direction flag.
+        pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
         let mut eof_pdu = Self {
             pdu_header,
             condition_code: ConditionCode::NoError,
@@ -38,10 +42,6 @@ impl EofPdu {
         &self.pdu_header
     }
 
-    pub fn written_len(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
-    }
-
     pub fn condition_code(&self) -> ConditionCode {
         self.condition_code
     }
@@ -63,39 +63,12 @@ impl EofPdu {
         if let Some(fault_location) = self.fault_location {
             len += fault_location.len_full();
         }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            len += 2;
+        }
         len
     }
 
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        let expected_len = self.written_len();
-        if buf.len() < expected_len {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: expected_len,
-            })
-            .into());
-        }
-        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
-        buf[current_idx] = FileDirectiveType::EofPdu as u8;
-        current_idx += 1;
-        buf[current_idx] = (self.condition_code as u8) << 4;
-        current_idx += 1;
-        buf[current_idx..current_idx + 4].copy_from_slice(&self.file_checksum.to_be_bytes());
-        current_idx += 4;
-        current_idx += write_fss_field(
-            self.pdu_header.pdu_conf.file_flag,
-            self.file_size,
-            &mut buf[current_idx..],
-        )?;
-        if let Some(fault_location) = self.fault_location {
-            current_idx += fault_location.write_to_be_bytes(buf)?;
-        }
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
-            current_idx = add_pdu_crc(buf, current_idx);
-        }
-        Ok(current_idx)
-    }
-
     pub fn from_bytes(buf: &[u8]) -> Result<EofPdu, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
@@ -106,13 +79,16 @@ impl EofPdu {
         }
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::EofPdu))
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::EofPdu),
+            }
         })?;
         if directive_type != FileDirectiveType::EofPdu {
-            return Err(PduError::WrongDirectiveType((
-                directive_type,
-                FileDirectiveType::EofPdu,
-            )));
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::EofPdu,
+            });
         }
         current_idx += 1;
         let condition_code = ConditionCode::try_from((buf[current_idx] >> 4) & 0b1111)
@@ -138,22 +114,89 @@ impl EofPdu {
     }
 }
 
+impl CfdpPdu for EofPdu {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::EofPdu)
+    }
+}
+
+impl WritablePduPacket for EofPdu {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::EofPdu as u8;
+        current_idx += 1;
+        buf[current_idx] = (self.condition_code as u8) << 4;
+        current_idx += 1;
+        buf[current_idx..current_idx + 4].copy_from_slice(&self.file_checksum.to_be_bytes());
+        current_idx += 4;
+        current_idx += write_fss_field(
+            self.pdu_header.pdu_conf.file_flag,
+            self.file_size,
+            &mut buf[current_idx..],
+        )?;
+        if let Some(fault_location) = self.fault_location {
+            current_idx += fault_location.write_to_bytes(buf)?;
+        }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
 #[cfg(test)]
 mod tests {
-    use crate::cfdp::pdu::eof::EofPdu;
-    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use super::*;
+    use crate::cfdp::pdu::tests::{
+        common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID,
+    };
     use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
-    use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
+    use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag, PduType, TransmissionMode};
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
+
+    fn verify_state(&eof_pdu: &EofPdu, file_flag: LargeFileFlag) {
+        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.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(eof_pdu.file_flag(), file_flag);
+        assert_eq!(eof_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            eof_pdu.file_directive_type(),
+            Some(FileDirectiveType::EofPdu)
+        );
+        assert_eq!(eof_pdu.transmission_mode(), TransmissionMode::Acknowledged);
+        assert_eq!(eof_pdu.direction(), Direction::TowardsReceiver);
+        assert_eq!(eof_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(eof_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(eof_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
+    }
 
     #[test]
     fn test_basic() {
         let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
         let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
         let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
-        assert_eq!(eof_pdu.written_len(), pdu_header.header_len() + 2 + 4 + 4);
-        assert_eq!(eof_pdu.file_checksum(), 0x01020304);
-        assert_eq!(eof_pdu.file_size(), 12);
-        assert_eq!(eof_pdu.condition_code(), ConditionCode::NoError);
+        assert_eq!(eof_pdu.len_written(), pdu_header.header_len() + 2 + 4 + 4);
+        verify_state(&eof_pdu, LargeFileFlag::Normal);
     }
 
     #[test]
@@ -165,7 +208,7 @@ mod tests {
         let res = eof_pdu.write_to_bytes(&mut buf);
         assert!(res.is_ok());
         let written = res.unwrap();
-        assert_eq!(written, eof_pdu.written_len());
+        assert_eq!(written, eof_pdu.len_written());
         verify_raw_header(eof_pdu.pdu_header(), &buf);
         let mut current_idx = eof_pdu.pdu_header().header_len();
         buf[current_idx] = FileDirectiveType::EofPdu as u8;
@@ -196,11 +239,59 @@ mod tests {
         let mut buf: [u8; 64] = [0; 64];
         eof_pdu.write_to_bytes(&mut buf).unwrap();
         let eof_read_back = EofPdu::from_bytes(&buf);
-        if !eof_read_back.is_ok() {
-            let e = eof_read_back.unwrap_err();
+        if let Err(e) = eof_read_back {
             panic!("deserialization failed with: {e}")
         }
         let eof_read_back = eof_read_back.unwrap();
         assert_eq!(eof_read_back, eof_pdu);
     }
+
+    #[test]
+    fn test_write_to_vec() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        let mut buf: [u8; 64] = [0; 64];
+        let written = eof_pdu.write_to_bytes(&mut buf).unwrap();
+        let pdu_vec = eof_pdu.to_vec().unwrap();
+        assert_eq!(buf[0..written], pdu_vec);
+    }
+
+    #[test]
+    fn test_with_crc() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        let mut buf: [u8; 64] = [0; 64];
+        let written = eof_pdu.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(written, eof_pdu.len_written());
+        let eof_from_raw = EofPdu::from_bytes(&buf).expect("creating EOF PDU failed");
+        assert_eq!(eof_from_raw, eof_pdu);
+        buf[written - 1] -= 1;
+        let crc: u16 = ((buf[written - 2] as u16) << 8) as u16 | buf[written - 1] as u16;
+        let error = EofPdu::from_bytes(&buf).unwrap_err();
+        if let PduError::ChecksumError(e) = error {
+            assert_eq!(e, crc);
+        } else {
+            panic!("expected crc error");
+        }
+    }
+
+    #[test]
+    fn test_with_large_file_flag() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Large);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        verify_state(&eof_pdu, LargeFileFlag::Large);
+        assert_eq!(eof_pdu.len_written(), pdu_header.header_len() + 2 + 8 + 4);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_eof_serde() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        generic_serde_test(eof_pdu);
+    }
 }

src/cfdp/pdu/file_data.rs

@@ -3,11 +3,13 @@ use crate::cfdp::pdu::{
     PduError, PduHeader,
 };
 use crate::cfdp::{CrcFlag, LargeFileFlag, PduType, SegmentMetadataFlag};
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::ByteConversionError;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::{CfdpPdu, FileDirectiveType, WritablePduPacket};
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[repr(u8)]
@@ -41,6 +43,14 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
         })
     }
 
+    pub fn record_continuation_state(&self) -> RecordContinuationState {
+        self.record_continuation_state
+    }
+
+    pub fn metadata(&self) -> Option<&'seg_meta [u8]> {
+        self.metadata
+    }
+
     pub fn written_len(&self) -> usize {
         // Map empty metadata to 0 and slice to its length.
         1 + self.metadata.map_or(0, |meta| meta.len())
@@ -48,10 +58,10 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
 
     pub(crate) fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         if buf.len() < self.written_len() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: self.written_len(),
-            }));
+            });
         }
         buf[0] = ((self.record_continuation_state as u8) << 6)
             | self.metadata.map_or(0, |meta| meta.len() as u8);
@@ -63,10 +73,10 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
 
     pub(crate) fn from_bytes(buf: &'seg_meta [u8]) -> Result<Self, ByteConversionError> {
         if buf.is_empty() {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: buf.len(),
                 expected: 2,
-            }));
+            });
         }
         let mut metadata = None;
         let seg_metadata_len = (buf[0] & 0b111111) as usize;
@@ -142,14 +152,11 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
             len += self.segment_metadata.as_ref().unwrap().written_len()
         }
         len += self.file_data.len();
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+        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
@@ -163,12 +170,50 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
         self.segment_metadata.as_ref()
     }
 
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        if buf.len() < self.written_len() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+    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>();
+        generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
+        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();
+        }
+        let (fss, offset) = read_fss_field(pdu_header.pdu_conf.file_flag, &buf[current_idx..]);
+        current_idx += fss;
+        if current_idx > full_len_without_crc {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: current_idx,
+                expected: full_len_without_crc,
+            }
+            .into());
+        }
+        Ok(Self {
+            pdu_header,
+            segment_metadata,
+            offset,
+            file_data: &buf[current_idx..full_len_without_crc],
+        })
+    }
+}
+impl CfdpPdu for FileDataPdu<'_, '_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        None
+    }
+}
+
+impl WritablePduPacket for FileDataPdu<'_, '_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        if buf.len() < self.len_written() {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
-                expected: self.written_len(),
-            })
+                expected: self.len_written(),
+            }
             .into());
         }
         let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
@@ -186,56 +231,30 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
         )?;
         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 {
+        if self.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> {
-        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>();
-        generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
-        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();
-        }
-        let (fss, offset) = read_fss_field(pdu_header.pdu_conf.file_flag, &buf[current_idx..]);
-        current_idx += fss;
-        if current_idx > full_len_without_crc {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
-                found: current_idx,
-                expected: full_len_without_crc,
-            })
-            .into());
-        }
-        Ok(Self {
-            pdu_header,
-            segment_metadata,
-            offset,
-            file_data: &buf[current_idx..full_len_without_crc],
-        })
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
     }
 }
 
 #[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 +262,25 @@ mod tests {
         assert_eq!(fd_pdu.offset(), 10);
         assert!(fd_pdu.segment_metadata().is_none());
         assert_eq!(
-            fd_pdu.written_len(),
+            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);
@@ -284,12 +310,22 @@ 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 +337,33 @@ 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::ChecksumError(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,
@@ -323,7 +379,7 @@ 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.len_written(),
             fd_pdu.pdu_header.header_len()
                 + 1
                 + seg_metadata.len()
@@ -363,16 +419,13 @@ 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 +447,39 @@ 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);
+    }
 }

src/cfdp/pdu/finished.rs

@@ -1,13 +1,17 @@
 use crate::cfdp::pdu::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, FileDirectiveType, PduError, PduHeader,
 };
-use crate::cfdp::tlv::{EntityIdTlv, Tlv, TlvType, TlvTypeField};
-use crate::cfdp::{ConditionCode, CrcFlag, PduType, TlvLvError};
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::cfdp::tlv::{
+    EntityIdTlv, FilestoreResponseTlv, GenericTlv, Tlv, TlvType, TlvTypeField, WritableTlv,
+};
+use crate::cfdp::{ConditionCode, CrcFlag, Direction, PduType, TlvLvError};
+use crate::ByteConversionError;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::{CfdpPdu, WritablePduPacket};
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[repr(u8)]
@@ -30,17 +34,17 @@ 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> {
+pub struct FinishedPduCreator<'fs_responses> {
     pdu_header: PduHeader,
     condition_code: ConditionCode,
     delivery_code: DeliveryCode,
     file_status: FileStatus,
-    fs_responses: Option<&'fs_responses [u8]>,
+    fs_responses:
+        &'fs_responses [FilestoreResponseTlv<'fs_responses, 'fs_responses, 'fs_responses>],
     fault_location: Option<EntityIdTlv>,
 }
 
-impl<'fs_responses> FinishedPdu<'fs_responses> {
+impl<'fs_responses> FinishedPduCreator<'fs_responses> {
     /// Default finished PDU: No error (no fault location field) and no filestore responses.
     pub fn new_default(
         pdu_header: PduHeader,
@@ -52,7 +56,7 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
             ConditionCode::NoError,
             delivery_code,
             file_status,
-            None,
+            &[],
             None,
         )
     }
@@ -69,7 +73,7 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
             condition_code,
             delivery_code,
             file_status,
-            None,
+            &[],
             Some(fault_location),
         )
     }
@@ -79,10 +83,16 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         condition_code: ConditionCode,
         delivery_code: DeliveryCode,
         file_status: FileStatus,
-        fs_responses: Option<&'fs_responses [u8]>,
+        fs_responses: &'fs_responses [FilestoreResponseTlv<
+            'fs_responses,
+            'fs_responses,
+            'fs_responses,
+        >],
         fault_location: Option<EntityIdTlv>,
     ) -> Self {
         pdu_header.pdu_type = PduType::FileDirective;
+        // Enforce correct direction bit.
+        pdu_header.pdu_conf.direction = Direction::TowardsSender;
         let mut finished_pdu = Self {
             pdu_header,
             condition_code,
@@ -94,13 +104,6 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         finished_pdu.pdu_header.pdu_datafield_len = finished_pdu.calc_pdu_datafield_len() as u16;
         finished_pdu
     }
-    pub fn pdu_header(&self) -> &PduHeader {
-        &self.pdu_header
-    }
-
-    pub fn written_len(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
-    }
 
     pub fn condition_code(&self) -> ConditionCode {
         self.condition_code
@@ -114,7 +117,8 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         self.file_status
     }
 
-    pub fn filestore_responses(&self) -> Option<&'fs_responses [u8]> {
+    // If there are no filestore responses, an empty slice will be returned.
+    pub fn filestore_responses(&self) -> &[FilestoreResponseTlv<'_, '_, '_>] {
         self.fs_responses
     }
 
@@ -123,23 +127,38 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
     }
 
     fn calc_pdu_datafield_len(&self) -> usize {
-        let mut base_len = 2;
-        if let Some(fs_responses) = self.fs_responses {
-            base_len += fs_responses.len();
+        let mut datafield_len = 2;
+        for fs_response in self.fs_responses {
+            datafield_len += fs_response.len_full();
         }
         if let Some(fault_location) = self.fault_location {
-            base_len += fault_location.len_full();
+            datafield_len += fault_location.len_full();
         }
-        base_len
+        if self.crc_flag() == CrcFlag::WithCrc {
+            datafield_len += 2;
+        }
+        datafield_len
+    }
+}
+
+impl CfdpPdu for FinishedPduCreator<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
     }
 
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        let expected_len = self.written_len();
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::FinishedPdu)
+    }
+}
+
+impl WritablePduPacket for FinishedPduCreator<'_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
         if buf.len() < expected_len {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: expected_len,
-            })
+            }
             .into());
         }
 
@@ -150,33 +169,88 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
             | ((self.delivery_code as u8) << 2)
             | self.file_status as u8;
         current_idx += 1;
-        if let Some(fs_responses) = self.fs_responses {
-            buf[current_idx..current_idx + fs_responses.len()].copy_from_slice(fs_responses);
-            current_idx += fs_responses.len();
+        for fs_responses in self.fs_responses {
+            current_idx += fs_responses.write_to_bytes(&mut buf[current_idx..])?;
         }
         if let Some(fault_location) = self.fault_location {
-            current_idx += fault_location.write_to_be_bytes(&mut buf[current_idx..])?;
+            current_idx += fault_location.write_to_bytes(&mut buf[current_idx..])?;
         }
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+        if self.crc_flag() == CrcFlag::WithCrc {
             current_idx = add_pdu_crc(buf, current_idx);
         }
         Ok(current_idx)
     }
 
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+/// Helper structure to loop through all filestore responses of a read Finished PDU. It should be
+/// noted that iterators in Rust are not fallible, but the TLV creation can fail, for example if
+/// the raw TLV data is invalid for some reason. In that case, the iterator will yield [None]
+/// because there is no way to recover from this.
+///
+/// The user can accumulate the length of all TLVs yielded by the iterator and compare it against
+/// the full length of the options to check whether the iterator was able to parse all TLVs
+/// successfully.
+pub struct FilestoreResponseIterator<'buf> {
+    responses_buf: &'buf [u8],
+    current_idx: usize,
+}
+
+impl<'buf> Iterator for FilestoreResponseIterator<'buf> {
+    type Item = FilestoreResponseTlv<'buf, 'buf, 'buf>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current_idx == self.responses_buf.len() {
+            return None;
+        }
+        let tlv = FilestoreResponseTlv::from_bytes(&self.responses_buf[self.current_idx..]);
+        // There are not really fallible iterators so we can't continue here..
+        if tlv.is_err() {
+            return None;
+        }
+        let tlv = tlv.unwrap();
+        self.current_idx += tlv.len_full();
+        Some(tlv)
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct FinishedPduReader<'buf> {
+    pdu_header: PduHeader,
+    condition_code: ConditionCode,
+    delivery_code: DeliveryCode,
+    file_status: FileStatus,
+    fs_responses_raw: &'buf [u8],
+    fault_location: Option<EntityIdTlv>,
+}
+
+impl<'buf> FinishedPduReader<'buf> {
     /// Generates [Self] from a raw bytestream.
-    pub fn from_bytes(buf: &'fs_responses [u8]) -> Result<Self, PduError> {
+    pub fn new(buf: &'buf [u8]) -> Result<Self, PduError> {
+        Self::from_bytes(buf)
+    }
+
+    /// Generates [Self] from a raw bytestream.
+    pub fn from_bytes(buf: &'buf [u8]) -> Result<Self, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
         let min_expected_len = current_idx + 2;
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::FinishedPdu))
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::FinishedPdu),
+            }
         })?;
         if directive_type != FileDirectiveType::FinishedPdu {
-            return Err(PduError::WrongDirectiveType((
-                directive_type,
-                FileDirectiveType::FinishedPdu,
-            )));
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::FinishedPdu,
+            });
         }
         current_idx += 1;
         let condition_code = ConditionCode::try_from((buf[current_idx] >> 4) & 0b1111)
@@ -185,24 +259,51 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         let delivery_code = DeliveryCode::try_from((buf[current_idx] >> 2) & 0b1).unwrap();
         let file_status = FileStatus::try_from(buf[current_idx] & 0b11).unwrap();
         current_idx += 1;
-        let (fs_responses, fault_location) =
+        let (fs_responses_raw, fault_location) =
             Self::parse_tlv_fields(current_idx, full_len_without_crc, buf)?;
         Ok(Self {
             pdu_header,
             condition_code,
             delivery_code,
             file_status,
-            fs_responses,
+            fs_responses_raw,
             fault_location,
         })
     }
 
+    pub fn fs_responses_raw(&self) -> &[u8] {
+        self.fs_responses_raw
+    }
+
+    pub fn fs_responses_iter(&self) -> FilestoreResponseIterator<'_> {
+        FilestoreResponseIterator {
+            responses_buf: self.fs_responses_raw,
+            current_idx: 0,
+        }
+    }
+
+    pub fn condition_code(&self) -> ConditionCode {
+        self.condition_code
+    }
+
+    pub fn delivery_code(&self) -> DeliveryCode {
+        self.delivery_code
+    }
+
+    pub fn file_status(&self) -> FileStatus {
+        self.file_status
+    }
+
+    pub fn fault_location(&self) -> Option<EntityIdTlv> {
+        self.fault_location
+    }
+
     fn parse_tlv_fields(
         mut current_idx: usize,
         full_len_without_crc: usize,
-        buf: &'fs_responses [u8],
-    ) -> Result<(Option<&'fs_responses [u8]>, Option<EntityIdTlv>), PduError> {
-        let mut fs_responses = None;
+        buf: &[u8],
+    ) -> Result<(&[u8], Option<EntityIdTlv>), PduError> {
+        let mut fs_responses: &[u8] = &[];
         let mut fault_location = None;
         let start_of_fs_responses = current_idx;
         // There are leftover filestore response(s) and/or a fault location field.
@@ -213,12 +314,12 @@ 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();
@@ -229,11 +330,19 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
                             return Err(PduError::FormatError);
                         }
                     } else {
-                        return Err(TlvLvError::InvalidTlvTypeField((tlv_type as u8, None)).into());
+                        return Err(TlvLvError::InvalidTlvTypeField {
+                            found: tlv_type.into(),
+                            expected: Some(TlvType::FilestoreResponse.into()),
+                        }
+                        .into());
                     }
                 }
                 TlvTypeField::Custom(raw) => {
-                    return Err(TlvLvError::InvalidTlvTypeField((raw, None)).into());
+                    return Err(TlvLvError::InvalidTlvTypeField {
+                        found: raw,
+                        expected: None,
+                    }
+                    .into());
                 }
             }
         }
@@ -241,21 +350,55 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
     }
 }
 
+impl CfdpPdu for FinishedPduReader<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::FinishedPdu)
+    }
+}
+
+impl PartialEq<FinishedPduCreator<'_>> for FinishedPduReader<'_> {
+    fn eq(&self, other: &FinishedPduCreator<'_>) -> bool {
+        self.pdu_header == other.pdu_header
+            && self.condition_code == other.condition_code
+            && self.delivery_code == other.delivery_code
+            && self.file_status == other.file_status
+            && self.fault_location == other.fault_location
+            && self
+                .fs_responses_iter()
+                .zip(other.filestore_responses().iter())
+                .all(|(a, b)| a == *b)
+    }
+}
+
+impl PartialEq<FinishedPduReader<'_>> for FinishedPduCreator<'_> {
+    fn eq(&self, other: &FinishedPduReader<'_>) -> bool {
+        other.eq(self)
+    }
+}
+
 #[cfg(test)]
 mod tests {
-    use crate::cfdp::pdu::finished::{DeliveryCode, FileStatus, FinishedPdu};
-    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use super::*;
+    use crate::cfdp::lv::Lv;
+    use crate::cfdp::pdu::tests::{
+        common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID,
+    };
     use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
-    use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
+    use crate::cfdp::tlv::FilestoreResponseTlv;
+    use crate::cfdp::{ConditionCode, CrcFlag, Direction, LargeFileFlag, TransmissionMode};
 
     fn generic_finished_pdu(
         crc_flag: CrcFlag,
         fss: LargeFileFlag,
         delivery_code: DeliveryCode,
         file_status: FileStatus,
-    ) -> FinishedPdu<'static> {
+    ) -> FinishedPduCreator<'static> {
         let pdu_header = PduHeader::new_no_file_data(common_pdu_conf(crc_flag, fss), 0);
-        FinishedPdu::new_default(pdu_header, delivery_code, file_status)
+        FinishedPduCreator::new_default(pdu_header, delivery_code, file_status)
     }
 
     #[test]
@@ -267,11 +410,31 @@ mod tests {
             FileStatus::Retained,
         );
         assert_eq!(finished_pdu.condition_code(), ConditionCode::NoError);
+        assert_eq!(
+            finished_pdu.pdu_header().pdu_conf.direction,
+            Direction::TowardsSender
+        );
         assert_eq!(finished_pdu.delivery_code(), DeliveryCode::Complete);
         assert_eq!(finished_pdu.file_status(), FileStatus::Retained);
-        assert_eq!(finished_pdu.filestore_responses(), None);
+        assert_eq!(finished_pdu.filestore_responses(), &[]);
         assert_eq!(finished_pdu.fault_location(), None);
         assert_eq!(finished_pdu.pdu_header().pdu_datafield_len, 2);
+
+        assert_eq!(finished_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(finished_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(finished_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            finished_pdu.file_directive_type(),
+            Some(FileDirectiveType::FinishedPdu)
+        );
+        assert_eq!(
+            finished_pdu.transmission_mode(),
+            TransmissionMode::Acknowledged
+        );
+        assert_eq!(finished_pdu.direction(), Direction::TowardsSender);
+        assert_eq!(finished_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(finished_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(finished_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
     }
 
     fn generic_serialization_test_no_error(delivery_code: DeliveryCode, file_status: FileStatus) {
@@ -285,8 +448,13 @@ mod tests {
         let written = finished_pdu.write_to_bytes(&mut buf);
         assert!(written.is_ok());
         let written = written.unwrap();
-        assert_eq!(written, finished_pdu.written_len());
+        assert_eq!(written, 9);
+        assert_eq!(written, finished_pdu.len_written());
         assert_eq!(written, finished_pdu.pdu_header().header_len() + 2);
+        assert_eq!(
+            finished_pdu.pdu_header().pdu_conf.direction,
+            Direction::TowardsSender
+        );
         verify_raw_header(finished_pdu.pdu_header(), &buf);
         let mut current_idx = finished_pdu.pdu_header().header_len();
         assert_eq!(buf[current_idx], FileDirectiveType::FinishedPdu as u8);
@@ -318,6 +486,20 @@ mod tests {
         generic_serialization_test_no_error(DeliveryCode::Incomplete, FileStatus::Unreported);
     }
 
+    #[test]
+    fn test_write_to_vec() {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::NoCrc,
+            LargeFileFlag::Normal,
+            DeliveryCode::Complete,
+            FileStatus::Retained,
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let written = finished_pdu.write_to_bytes(&mut buf).unwrap();
+        let pdu_vec = finished_pdu.to_vec().unwrap();
+        assert_eq!(buf[0..written], pdu_vec);
+    }
+
     #[test]
     fn test_deserialization_simple() {
         let finished_pdu = generic_finished_pdu(
@@ -328,9 +510,169 @@ mod tests {
         );
         let mut buf: [u8; 64] = [0; 64];
         finished_pdu.write_to_bytes(&mut buf).unwrap();
-        let read_back = FinishedPdu::from_bytes(&buf);
+        let read_back = FinishedPduReader::from_bytes(&buf);
         assert!(read_back.is_ok());
         let read_back = read_back.unwrap();
         assert_eq!(finished_pdu, read_back);
+        // Use all getter functions here explicitely once.
+        assert_eq!(finished_pdu.pdu_header(), read_back.pdu_header());
+        assert_eq!(finished_pdu.condition_code(), read_back.condition_code());
+        assert_eq!(finished_pdu.fault_location(), read_back.fault_location());
+        assert_eq!(finished_pdu.file_status(), read_back.file_status());
+        assert_eq!(finished_pdu.delivery_code(), read_back.delivery_code());
+    }
+
+    #[test]
+    fn test_serialization_buf_too_small() {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::NoCrc,
+            LargeFileFlag::Normal,
+            DeliveryCode::Complete,
+            FileStatus::Retained,
+        );
+        let mut buf: [u8; 8] = [0; 8];
+        let error = finished_pdu.write_to_bytes(&mut buf);
+        assert!(error.is_err());
+        if let PduError::ByteConversion(ByteConversionError::ToSliceTooSmall { found, expected }) =
+            error.unwrap_err()
+        {
+            assert_eq!(found, 8);
+            assert_eq!(expected, 9);
+        } else {
+            panic!("expected to_slice_too_small error");
+        }
+    }
+
+    #[test]
+    fn test_with_crc() {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::WithCrc,
+            LargeFileFlag::Normal,
+            DeliveryCode::Complete,
+            FileStatus::Retained,
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let written = finished_pdu.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(written, finished_pdu.len_written());
+        let finished_pdu_from_raw = FinishedPduReader::new(&buf).unwrap();
+        assert_eq!(finished_pdu, finished_pdu_from_raw);
+        buf[written - 1] -= 1;
+        let crc: u16 = ((buf[written - 2] as u16) << 8) as u16 | buf[written - 1] as u16;
+        let error = FinishedPduReader::new(&buf).unwrap_err();
+        if let PduError::ChecksumError(e) = error {
+            assert_eq!(e, crc);
+        } else {
+            panic!("expected crc error");
+        }
+    }
+
+    #[test]
+    fn test_with_fault_location() {
+        let pdu_header =
+            PduHeader::new_no_file_data(common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal), 0);
+        let finished_pdu = FinishedPduCreator::new_with_error(
+            pdu_header,
+            ConditionCode::NakLimitReached,
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+            EntityIdTlv::new(TEST_DEST_ID.into()),
+        );
+        let finished_pdu_vec = finished_pdu.to_vec().unwrap();
+        assert_eq!(finished_pdu_vec.len(), 12);
+        assert_eq!(finished_pdu_vec[9], TlvType::EntityId.into());
+        assert_eq!(finished_pdu_vec[10], 1);
+        assert_eq!(finished_pdu_vec[11], TEST_DEST_ID.value_typed());
+        assert_eq!(
+            finished_pdu.fault_location().unwrap().entity_id(),
+            &TEST_DEST_ID.into()
+        );
+    }
+
+    #[test]
+    fn test_deserialization_with_fault_location() {
+        let pdu_header =
+            PduHeader::new_no_file_data(common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal), 0);
+        let entity_id_tlv = EntityIdTlv::new(TEST_DEST_ID.into());
+        let finished_pdu = FinishedPduCreator::new_with_error(
+            pdu_header,
+            ConditionCode::NakLimitReached,
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+            entity_id_tlv,
+        );
+        let finished_pdu_vec = finished_pdu.to_vec().unwrap();
+        let finished_pdu_deserialized = FinishedPduReader::from_bytes(&finished_pdu_vec).unwrap();
+        assert_eq!(finished_pdu, finished_pdu_deserialized);
+    }
+
+    #[test]
+    fn test_deserialization_with_fs_responses() {
+        let entity_id_tlv = EntityIdTlv::new(TEST_DEST_ID.into());
+        let first_name = "first.txt";
+        let first_name_lv = Lv::new_from_str(first_name).unwrap();
+        let fs_response_0 = FilestoreResponseTlv::new_no_filestore_message(
+            crate::cfdp::tlv::FilestoreActionCode::CreateFile,
+            0,
+            first_name_lv,
+            None,
+        )
+        .unwrap();
+        let fs_response_1 = FilestoreResponseTlv::new_no_filestore_message(
+            crate::cfdp::tlv::FilestoreActionCode::DeleteFile,
+            0,
+            first_name_lv,
+            None,
+        )
+        .unwrap();
+        let fs_responses = &[fs_response_0, fs_response_1];
+
+        let pdu_header =
+            PduHeader::new_no_file_data(common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal), 0);
+        let finished_pdu = FinishedPduCreator::new_generic(
+            pdu_header,
+            ConditionCode::NakLimitReached,
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+            fs_responses,
+            Some(entity_id_tlv),
+        );
+        let finished_pdu_vec = finished_pdu.to_vec().unwrap();
+        let finished_pdu_deserialized = FinishedPduReader::from_bytes(&finished_pdu_vec).unwrap();
+        assert_eq!(finished_pdu_deserialized, finished_pdu);
+    }
+
+    #[test]
+    fn test_deserialization_with_fs_responses_and_fault_location() {
+        let first_name = "first.txt";
+        let first_name_lv = Lv::new_from_str(first_name).unwrap();
+        let fs_response_0 = FilestoreResponseTlv::new_no_filestore_message(
+            crate::cfdp::tlv::FilestoreActionCode::CreateFile,
+            0,
+            first_name_lv,
+            None,
+        )
+        .unwrap();
+        let fs_response_1 = FilestoreResponseTlv::new_no_filestore_message(
+            crate::cfdp::tlv::FilestoreActionCode::DeleteFile,
+            0,
+            first_name_lv,
+            None,
+        )
+        .unwrap();
+        let fs_responses = &[fs_response_0, fs_response_1];
+
+        let pdu_header =
+            PduHeader::new_no_file_data(common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal), 0);
+        let finished_pdu = FinishedPduCreator::new_generic(
+            pdu_header,
+            ConditionCode::NakLimitReached,
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+            fs_responses,
+            None,
+        );
+        let finished_pdu_vec = finished_pdu.to_vec().unwrap();
+        let finished_pdu_deserialized = FinishedPduReader::from_bytes(&finished_pdu_vec).unwrap();
+        assert_eq!(finished_pdu_deserialized, finished_pdu);
     }
 }

src/cfdp/pdu/metadata.rs

@@ -3,14 +3,16 @@ use crate::cfdp::pdu::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
     FileDirectiveType, PduError, PduHeader,
 };
-use crate::cfdp::tlv::Tlv;
-use crate::cfdp::{ChecksumType, CrcFlag, LargeFileFlag, PduType};
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::cfdp::tlv::{Tlv, WritableTlv};
+use crate::cfdp::{ChecksumType, CrcFlag, Direction, LargeFileFlag, PduType};
+use crate::ByteConversionError;
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::{CfdpPdu, WritablePduPacket};
+
 #[derive(Default, Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct MetadataGenericParams {
@@ -48,6 +50,160 @@ pub fn build_metadata_opts_from_vec(
     build_metadata_opts_from_slice(buf, tlvs.as_slice())
 }
 
+/// 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 [Tlv<'opts>],
+}
+
+impl<'src_name, 'dest_name, 'opts> MetadataPduCreator<'src_name, 'dest_name, 'opts> {
+    pub fn new_no_opts(
+        pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+    ) -> Self {
+        Self::new(
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            &[],
+        )
+    }
+
+    pub fn new_with_opts(
+        pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+        options: &'opts [Tlv<'opts>],
+    ) -> Self {
+        Self::new(
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            options,
+        )
+    }
+
+    pub fn new(
+        mut pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+        options: &'opts [Tlv<'opts>],
+    ) -> Self {
+        pdu_header.pdu_type = PduType::FileDirective;
+        pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
+        let mut pdu = Self {
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            options,
+        };
+        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
+        pdu
+    }
+
+    pub fn metadata_params(&self) -> &MetadataGenericParams {
+        &self.metadata_params
+    }
+
+    pub fn src_file_name(&self) -> Lv<'src_name> {
+        self.src_file_name
+    }
+
+    pub fn dest_file_name(&self) -> Lv<'dest_name> {
+        self.dest_file_name
+    }
+
+    pub fn options(&self) -> &'opts [Tlv<'opts>] {
+        self.options
+    }
+
+    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();
+        for tlv in self.options() {
+            len += tlv.len_full()
+        }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            len += 2;
+        }
+        len
+    }
+}
+
+impl CfdpPdu for MetadataPduCreator<'_, '_, '_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::MetadataPdu)
+    }
+}
+
+impl WritablePduPacket for MetadataPduCreator<'_, '_, '_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::MetadataPdu as u8;
+        current_idx += 1;
+        buf[current_idx] = ((self.metadata_params.closure_requested as u8) << 6)
+            | (self.metadata_params.checksum_type as u8);
+        current_idx += 1;
+        current_idx += write_fss_field(
+            self.pdu_header.common_pdu_conf().file_flag,
+            self.metadata_params.file_size,
+            &mut buf[current_idx..],
+        )?;
+        current_idx += self
+            .src_file_name
+            .write_to_be_bytes(&mut buf[current_idx..])?;
+        current_idx += self
+            .dest_file_name
+            .write_to_be_bytes(&mut buf[current_idx..])?;
+        for opt in self.options() {
+            opt.write_to_bytes(&mut buf[current_idx..current_idx + opt.len_full()])?;
+            current_idx += opt.len_full();
+        }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
 /// Helper structure to loop through all options of a metadata PDU. It should be noted that
 /// iterators in Rust are not fallible, but the TLV creation can fail, for example if the raw TLV
 /// data is invalid for some reason. In that case, the iterator will yield [None] because there
@@ -79,165 +235,28 @@ 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> {
+pub struct MetadataPduReader<'buf> {
     pdu_header: PduHeader,
     metadata_params: MetadataGenericParams,
     #[cfg_attr(feature = "serde", serde(borrow))]
-    src_file_name: Lv<'src_name>,
+    src_file_name: Lv<'buf>,
     #[cfg_attr(feature = "serde", serde(borrow))]
-    dest_file_name: Lv<'dest_name>,
-    options: Option<&'opts [u8]>,
+    dest_file_name: Lv<'buf>,
+    options: &'buf [u8],
 }
 
-impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
-    pub fn new_no_opts(
-        pdu_header: PduHeader,
-        metadata_params: MetadataGenericParams,
-        src_file_name: Lv<'src_name>,
-        dest_file_name: Lv<'dest_name>,
-    ) -> Self {
-        Self::new(
-            pdu_header,
-            metadata_params,
-            src_file_name,
-            dest_file_name,
-            None,
-        )
+impl<'raw> MetadataPduReader<'raw> {
+    pub fn new(buf: &'raw [u8]) -> Result<Self, PduError> {
+        Self::from_bytes(buf)
     }
 
-    pub fn new_with_opts(
-        pdu_header: PduHeader,
-        metadata_params: MetadataGenericParams,
-        src_file_name: Lv<'src_name>,
-        dest_file_name: Lv<'dest_name>,
-        options: &'opts [u8],
-    ) -> Self {
-        Self::new(
-            pdu_header,
-            metadata_params,
-            src_file_name,
-            dest_file_name,
-            Some(options),
-        )
-    }
-
-    pub fn new(
-        mut pdu_header: PduHeader,
-        metadata_params: MetadataGenericParams,
-        src_file_name: Lv<'src_name>,
-        dest_file_name: Lv<'dest_name>,
-        options: Option<&'opts [u8]>,
-    ) -> Self {
-        pdu_header.pdu_type = PduType::FileDirective;
-        let mut pdu = Self {
-            pdu_header,
-            metadata_params,
-            src_file_name,
-            dest_file_name,
-            options,
-        };
-        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
-        pdu
-    }
-
-    pub fn metadata_params(&self) -> &MetadataGenericParams {
-        &self.metadata_params
-    }
-
-    pub fn src_file_name(&self) -> Lv<'src_name> {
-        self.src_file_name
-    }
-
-    pub fn dest_file_name(&self) -> Lv<'dest_name> {
-        self.dest_file_name
-    }
-
-    pub fn options(&self) -> Option<&'opts [u8]> {
-        self.options
-    }
-
-    /// Yield an iterator which can be used to loop through all options. Returns [None] if the
-    /// options field is empty.
-    pub fn options_iter(&self) -> Option<OptionsIter<'opts>> {
-        self.options?;
-        Some(OptionsIter {
-            opt_buf: self.options.unwrap(),
-            current_idx: 0,
-        })
-    }
-
-    pub fn written_len(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
-    }
-
-    fn calc_pdu_datafield_len(&self) -> usize {
-        // One directve type octet and one byte of the directive parameter field.
-        let mut len = 2;
-        if self.pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
-            len += 8;
-        } else {
-            len += 4;
-        }
-        len += self.src_file_name.len_full();
-        len += self.dest_file_name.len_full();
-        if let Some(opts) = self.options {
-            len += opts.len();
-        }
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
-            len += 2;
-        }
-        len
-    }
-
-    pub fn pdu_header(&self) -> &PduHeader {
-        &self.pdu_header
-    }
-
-    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        let expected_len = self.written_len();
-        if buf.len() < expected_len {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: expected_len,
-            })
-            .into());
-        }
-
-        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
-        buf[current_idx] = FileDirectiveType::MetadataPdu as u8;
-        current_idx += 1;
-        buf[current_idx] = ((self.metadata_params.closure_requested as u8) << 7)
-            | (self.metadata_params.checksum_type as u8);
-        current_idx += 1;
-        current_idx += write_fss_field(
-            self.pdu_header.common_pdu_conf().file_flag,
-            self.metadata_params.file_size,
-            &mut buf[current_idx..],
-        )?;
-        current_idx += self
-            .src_file_name
-            .write_to_be_bytes(&mut buf[current_idx..])?;
-        current_idx += self
-            .dest_file_name
-            .write_to_be_bytes(&mut buf[current_idx..])?;
-        if let Some(opts) = self.options {
-            buf[current_idx..current_idx + opts.len()].copy_from_slice(opts);
-            current_idx += opts.len();
-        }
-        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
-            current_idx = add_pdu_crc(buf, current_idx);
-        }
-        Ok(current_idx)
-    }
-
-    pub fn from_bytes<'longest: 'src_name + 'dest_name + 'opts>(
-        buf: &'longest [u8],
-    ) -> Result<Self, PduError> {
+    pub fn from_bytes(buf: &'raw [u8]) -> Result<Self, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
         let is_large_file = pdu_header.pdu_conf.file_flag == LargeFileFlag::Large;
@@ -248,13 +267,16 @@ impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
         }
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::MetadataPdu))
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::MetadataPdu),
+            }
         })?;
         if directive_type != FileDirectiveType::MetadataPdu {
-            return Err(PduError::WrongDirectiveType((
-                directive_type,
-                FileDirectiveType::MetadataPdu,
-            )));
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::MetadataPdu,
+            });
         }
         current_idx += 1;
         let (fss_len, file_size) =
@@ -271,56 +293,95 @@ impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
         let dest_file_name = Lv::from_bytes(&buf[current_idx..])?;
         current_idx += dest_file_name.len_full();
         // All left-over bytes are options.
-        let mut options = None;
-        if current_idx < full_len_without_crc {
-            options = Some(&buf[current_idx..full_len_without_crc]);
-        }
         Ok(Self {
             pdu_header,
             metadata_params,
             src_file_name,
             dest_file_name,
-            options,
+            options: &buf[current_idx..full_len_without_crc],
         })
     }
+
+    /// Yield an iterator which can be used to loop through all options. Returns [None] if the
+    /// options field is empty.
+    pub fn options_iter(&self) -> Option<OptionsIter<'_>> {
+        Some(OptionsIter {
+            opt_buf: self.options,
+            current_idx: 0,
+        })
+    }
+
+    pub fn options(&self) -> &'raw [u8] {
+        self.options
+    }
+
+    pub fn metadata_params(&self) -> &MetadataGenericParams {
+        &self.metadata_params
+    }
+
+    pub fn src_file_name(&self) -> Lv {
+        self.src_file_name
+    }
+
+    pub fn dest_file_name(&self) -> Lv {
+        self.dest_file_name
+    }
+}
+
+impl CfdpPdu for MetadataPduReader<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::MetadataPdu)
+    }
 }
 
 #[cfg(test)]
 pub mod tests {
+    use alloc::string::ToString;
+
     use crate::cfdp::lv::Lv;
     use crate::cfdp::pdu::metadata::{
         build_metadata_opts_from_slice, build_metadata_opts_from_vec, MetadataGenericParams,
-        MetadataPdu,
+        MetadataPduCreator, MetadataPduReader,
     };
-    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use crate::cfdp::pdu::tests::{
+        common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID,
+    };
+    use crate::cfdp::pdu::{CfdpPdu, PduError, WritablePduPacket};
     use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
     use crate::cfdp::tlv::{Tlv, TlvType};
     use crate::cfdp::{
-        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>(
         crc_flag: CrcFlag,
+        checksum_type: ChecksumType,
+        closure_requested: bool,
         fss: LargeFileFlag,
-        opts: Option<&'opts [u8]>,
+        opts: &'opts [Tlv],
     ) -> (
         Lv<'static>,
         Lv<'static>,
-        MetadataPdu<'static, 'static, 'opts>,
+        MetadataPduCreator<'static, 'static, 'opts>,
     ) {
         let pdu_header = PduHeader::new_no_file_data(common_pdu_conf(crc_flag, fss), 0);
-        let metadata_params = MetadataGenericParams::new(false, ChecksumType::Crc32, 0x1010);
+        let metadata_params = MetadataGenericParams::new(closure_requested, checksum_type, 0x1010);
         let src_filename = Lv::new_from_str(SRC_FILENAME).expect("Generating string LV failed");
         let dest_filename =
             Lv::new_from_str(DEST_FILENAME).expect("Generating destination LV failed");
         (
             src_filename,
             dest_filename,
-            MetadataPdu::new(
+            MetadataPduCreator::new(
                 pdu_header,
                 metadata_params,
                 src_filename,
@@ -332,10 +393,15 @@ pub mod tests {
 
     #[test]
     fn test_basic() {
-        let (src_filename, dest_filename, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Normal,
+            &[],
+        );
         assert_eq!(
-            metadata_pdu.written_len(),
+            metadata_pdu.len_written(),
             metadata_pdu.pdu_header().header_len()
                 + 1
                 + 1
@@ -345,60 +411,169 @@ pub mod tests {
         );
         assert_eq!(metadata_pdu.src_file_name(), src_filename);
         assert_eq!(metadata_pdu.dest_file_name(), dest_filename);
-        assert_eq!(metadata_pdu.options(), None);
+        assert!(metadata_pdu.options().is_empty());
+        assert_eq!(metadata_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(metadata_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(metadata_pdu.pdu_type(), PduType::FileDirective);
+        assert!(!metadata_pdu.metadata_params().closure_requested);
+        assert_eq!(
+            metadata_pdu.metadata_params().checksum_type,
+            ChecksumType::Crc32
+        );
+        assert_eq!(
+            metadata_pdu.file_directive_type(),
+            Some(FileDirectiveType::MetadataPdu)
+        );
+        assert_eq!(
+            metadata_pdu.transmission_mode(),
+            TransmissionMode::Acknowledged
+        );
+        assert_eq!(metadata_pdu.direction(), Direction::TowardsReceiver);
+        assert_eq!(metadata_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(metadata_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(metadata_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
     }
 
-    #[test]
-    fn test_serialization() {
-        let (src_filename, dest_filename, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
-        let mut buf: [u8; 64] = [0; 64];
-        let res = metadata_pdu.write_to_bytes(&mut buf);
-        assert!(res.is_ok());
-        let written = res.unwrap();
+    fn check_metadata_raw_fields(
+        metadata_pdu: &MetadataPduCreator,
+        buf: &[u8],
+        written_bytes: usize,
+        checksum_type: ChecksumType,
+        closure_requested: bool,
+        expected_src_filename: &Lv,
+        expected_dest_filename: &Lv,
+    ) {
+        verify_raw_header(metadata_pdu.pdu_header(), buf);
         assert_eq!(
-            written,
+            written_bytes,
             metadata_pdu.pdu_header.header_len()
                 + 1
                 + 1
                 + 4
-                + src_filename.len_full()
-                + dest_filename.len_full()
+                + expected_src_filename.len_full()
+                + expected_dest_filename.len_full()
         );
-        verify_raw_header(metadata_pdu.pdu_header(), &buf);
         assert_eq!(buf[7], FileDirectiveType::MetadataPdu as u8);
-        assert_eq!(buf[8] >> 6, false as u8);
-        assert_eq!(buf[8] & 0b1111, ChecksumType::Crc32 as u8);
+        assert_eq!(buf[8] >> 6, closure_requested as u8);
+        assert_eq!(buf[8] & 0b1111, checksum_type as u8);
         assert_eq!(u32::from_be_bytes(buf[9..13].try_into().unwrap()), 0x1010);
         let mut current_idx = 13;
         let src_name_from_raw =
             Lv::from_bytes(&buf[current_idx..]).expect("Creating source name LV failed");
-        assert_eq!(src_name_from_raw, src_filename);
+        assert_eq!(src_name_from_raw, *expected_src_filename);
         current_idx += src_name_from_raw.len_full();
         let dest_name_from_raw =
             Lv::from_bytes(&buf[current_idx..]).expect("Creating dest name LV failed");
-        assert_eq!(dest_name_from_raw, dest_filename);
+        assert_eq!(dest_name_from_raw, *expected_dest_filename);
         current_idx += dest_name_from_raw.len_full();
         // No options, so no additional data here.
-        assert_eq!(current_idx, written);
+        assert_eq!(current_idx, written_bytes);
+    }
+
+    #[test]
+    fn test_serialization_0() {
+        let checksum_type = ChecksumType::Crc32;
+        let closure_requested = false;
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            checksum_type,
+            closure_requested,
+            LargeFileFlag::Normal,
+            &[],
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let res = metadata_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        check_metadata_raw_fields(
+            &metadata_pdu,
+            &buf,
+            written,
+            checksum_type,
+            closure_requested,
+            &src_filename,
+            &dest_filename,
+        );
+    }
+
+    #[test]
+    fn test_serialization_1() {
+        let checksum_type = ChecksumType::Modular;
+        let closure_requested = true;
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            checksum_type,
+            closure_requested,
+            LargeFileFlag::Normal,
+            &[],
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let res = metadata_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        check_metadata_raw_fields(
+            &metadata_pdu,
+            &buf,
+            written,
+            checksum_type,
+            closure_requested,
+            &src_filename,
+            &dest_filename,
+        );
+    }
+
+    #[test]
+    fn test_write_to_vec() {
+        let (_, _, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Normal,
+            &[],
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let pdu_vec = metadata_pdu.to_vec().unwrap();
+        let written = metadata_pdu.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(buf[0..written], pdu_vec);
+    }
+
+    fn compare_read_pdu_to_written_pdu(written: &MetadataPduCreator, read: &MetadataPduReader) {
+        assert_eq!(written.metadata_params(), read.metadata_params());
+        assert_eq!(written.src_file_name(), read.src_file_name());
+        assert_eq!(written.dest_file_name(), read.dest_file_name());
+        let opts = written.options();
+        for (tlv_written, tlv_read) in opts.iter().zip(read.options_iter().unwrap()) {
+            assert_eq!(tlv_written, &tlv_read);
+        }
     }
 
     #[test]
     fn test_deserialization() {
-        let (_, _, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
+        let (_, _, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            true,
+            LargeFileFlag::Normal,
+            &[],
+        );
         let mut buf: [u8; 64] = [0; 64];
         metadata_pdu.write_to_bytes(&mut buf).unwrap();
-        let pdu_read_back = MetadataPdu::from_bytes(&buf);
+        let pdu_read_back = MetadataPduReader::from_bytes(&buf);
         assert!(pdu_read_back.is_ok());
         let pdu_read_back = pdu_read_back.unwrap();
-        assert_eq!(pdu_read_back, metadata_pdu);
+        compare_read_pdu_to_written_pdu(&metadata_pdu, &pdu_read_back);
     }
 
     #[test]
     fn test_with_crc_flag() {
-        let (src_filename, dest_filename, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::WithCrc, LargeFileFlag::Normal, None);
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::WithCrc,
+            ChecksumType::Crc32,
+            true,
+            LargeFileFlag::Normal,
+            &[],
+        );
+        assert_eq!(metadata_pdu.crc_flag(), CrcFlag::WithCrc);
         let mut buf: [u8; 64] = [0; 64];
         let write_res = metadata_pdu.write_to_bytes(&mut buf);
         assert!(write_res.is_ok());
@@ -413,14 +588,20 @@ pub mod tests {
                 + dest_filename.len_full()
                 + 2
         );
-        let pdu_read_back = MetadataPdu::from_bytes(&buf).unwrap();
-        assert_eq!(pdu_read_back, metadata_pdu);
+        assert_eq!(written, metadata_pdu.len_written());
+        let pdu_read_back = MetadataPduReader::new(&buf).unwrap();
+        compare_read_pdu_to_written_pdu(&metadata_pdu, &pdu_read_back);
     }
 
     #[test]
     fn test_with_large_file_flag() {
-        let (src_filename, dest_filename, metadata_pdu) =
-            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Large, None);
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Large,
+            &[],
+        );
         let mut buf: [u8; 64] = [0; 64];
         let write_res = metadata_pdu.write_to_bytes(&mut buf);
         assert!(write_res.is_ok());
@@ -434,8 +615,8 @@ 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]
@@ -478,12 +659,13 @@ pub mod tests {
         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 opts_len = tlv1.len_full() + tlv2.len_full();
         let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
             CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
             LargeFileFlag::Normal,
-            Some(&opts_buf[..opts_len]),
+            &tlv_vec,
         );
         let mut buf: [u8; 128] = [0; 128];
         let write_res = metadata_pdu.write_to_bytes(&mut buf);
@@ -499,8 +681,8 @@ 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();
@@ -509,9 +691,60 @@ pub mod tests {
             assert_eq!(tlv_vec[idx], 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_invalid_directive_code() {
+        let (_, _, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            true,
+            LargeFileFlag::Large,
+            &[],
+        );
+        let mut metadata_vec = metadata_pdu.to_vec().unwrap();
+        metadata_vec[7] = 0xff;
+        let metadata_error = MetadataPduReader::from_bytes(&metadata_vec);
+        assert!(metadata_error.is_err());
+        let error = metadata_error.unwrap_err();
+        if let PduError::InvalidDirectiveType { found, expected } = error {
+            assert_eq!(found, 0xff);
+            assert_eq!(expected, Some(FileDirectiveType::MetadataPdu));
+            assert_eq!(
+                error.to_string(),
+                "invalid directive type value 255, expected Some(MetadataPdu)"
+            );
+        } else {
+            panic!("Expected InvalidDirectiveType error, got {:?}", error);
+        }
+    }
+
+    #[test]
+    fn test_wrong_directive_code() {
+        let (_, _, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Large,
+            &[],
+        );
+        let mut metadata_vec = metadata_pdu.to_vec().unwrap();
+        metadata_vec[7] = FileDirectiveType::EofPdu as u8;
+        let metadata_error = MetadataPduReader::from_bytes(&metadata_vec);
+        assert!(metadata_error.is_err());
+        let error = metadata_error.unwrap_err();
+        if let PduError::WrongDirectiveType { found, expected } = error {
+            assert_eq!(found, FileDirectiveType::EofPdu);
+            assert_eq!(expected, FileDirectiveType::MetadataPdu);
+            assert_eq!(
+                error.to_string(),
+                "found directive type EofPdu, expected MetadataPdu"
+            );
+        } else {
+            panic!("Expected InvalidDirectiveType error, got {:?}", error);
+        }
+    }
     #[test]
     fn test_corrects_pdu_header() {
         let pdu_header = PduHeader::new_for_file_data(
@@ -524,8 +757,12 @@ 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

@@ -1,16 +1,20 @@
 //! CFDP Packet Data Unit (PDU) support.
 use crate::cfdp::*;
 use crate::util::{UnsignedByteField, UnsignedByteFieldU8, UnsignedEnum};
+use crate::ByteConversionError;
 use crate::CRC_CCITT_FALSE;
-use crate::{ByteConversionError, SizeMissmatch};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 use core::fmt::{Display, Formatter};
 #[cfg(feature = "std")]
 use std::error::Error;
 
+pub mod ack;
 pub mod eof;
 pub mod file_data;
 pub mod finished;
 pub mod metadata;
+pub mod nak;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
@@ -28,23 +32,30 @@ pub enum FileDirectiveType {
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum PduError {
-    ByteConversionError(ByteConversionError),
+    ByteConversion(ByteConversionError),
     /// Found version ID invalid, not equal to [CFDP_VERSION_2].
     CfdpVersionMissmatch(u8),
     /// Invalid length for the entity ID detected. Only the values 1, 2, 4 and 8 are supported.
     InvalidEntityLen(u8),
     /// Invalid length for the entity ID detected. Only the values 1, 2, 4 and 8 are supported.
     InvalidTransactionSeqNumLen(u8),
-    /// The first entry will be the source entity ID length, the second one the destination entity
-    /// ID length.
-    SourceDestIdLenMissmatch((usize, usize)),
-    /// The first tuple entry will be the found directive type, the second entry the expected entry
-    /// type.
-    WrongDirectiveType((FileDirectiveType, FileDirectiveType)),
-    /// The directive type field contained a value not in the range of permitted values.
-    /// The first tuple entry will be the found raw number, the second entry the expected entry
-    /// type.
-    InvalidDirectiveType((u8, FileDirectiveType)),
+    SourceDestIdLenMissmatch {
+        src_id_len: usize,
+        dest_id_len: usize,
+    },
+    /// Wrong directive type, for example when parsing the directive field for a file directive
+    /// PDU.
+    WrongDirectiveType {
+        found: FileDirectiveType,
+        expected: FileDirectiveType,
+    },
+    /// The directive type field contained a value not in the range of permitted values. This can
+    /// also happen if an invalid value is passed to the ACK PDU constructor.
+    InvalidDirectiveType {
+        found: u8,
+        expected: Option<FileDirectiveType>,
+    },
+    InvalidStartOrEndOfScopeValue,
     /// Invalid condition code. Contains the raw detected value.
     InvalidConditionCode(u8),
     /// Invalid checksum type which is not part of the checksums listed in the
@@ -65,9 +76,12 @@ impl Display for PduError {
             PduError::InvalidEntityLen(raw_id) => {
                 write!(
                     f,
-                    "Invalid PDU entity ID length {raw_id}, only [1, 2, 4, 8] are allowed"
+                    "invalid PDU entity ID length {raw_id}, only [1, 2, 4, 8] are allowed"
                 )
             }
+            PduError::InvalidStartOrEndOfScopeValue => {
+                write!(f, "invalid start or end of scope for NAK PDU")
+            }
             PduError::InvalidTransactionSeqNumLen(raw_id) => {
                 write!(
                     f,
@@ -80,29 +94,31 @@ impl Display for PduError {
                     "cfdp version missmatch, found {raw}, expected {CFDP_VERSION_2}"
                 )
             }
-            PduError::SourceDestIdLenMissmatch((src_len, dest_len)) => {
+            PduError::SourceDestIdLenMissmatch {
+                src_id_len,
+                dest_id_len,
+            } => {
                 write!(
                     f,
-                    "missmatch of PDU source length {src_len} and destination length {dest_len}"
+                    "missmatch of PDU source length {src_id_len} and destination length {dest_id_len}"
                 )
             }
-            PduError::ByteConversionError(e) => {
+            PduError::ByteConversion(e) => {
                 write!(f, "{}", e)
             }
             PduError::FileSizeTooLarge(value) => {
                 write!(f, "file size value {value} exceeds allowed 32 bit width")
             }
-            PduError::WrongDirectiveType((found, expected)) => {
+            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)) => {
+            PduError::InvalidDirectiveType { found, expected } => {
                 write!(
                     f,
-                    "invalid directive type value {found}, expected {expected:?} ({})",
-                    *expected as u8
+                    "invalid directive type value {found}, expected {expected:?}"
                 )
             }
             PduError::InvalidChecksumType(checksum_type) => {
@@ -125,7 +141,7 @@ impl Display for PduError {
 impl Error for PduError {
     fn source(&self) -> Option<&(dyn Error + 'static)> {
         match self {
-            PduError::ByteConversionError(e) => Some(e),
+            PduError::ByteConversion(e) => Some(e),
             PduError::TlvLvError(e) => Some(e),
             _ => None,
         }
@@ -134,7 +150,7 @@ impl Error for PduError {
 
 impl From<ByteConversionError> for PduError {
     fn from(value: ByteConversionError) -> Self {
-        Self::ByteConversionError(value)
+        Self::ByteConversion(value)
     }
 }
 
@@ -144,8 +160,65 @@ impl From<TlvLvError> for PduError {
     }
 }
 
+pub trait WritablePduPacket {
+    fn len_written(&self) -> usize;
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError>;
+    #[cfg(feature = "alloc")]
+    fn to_vec(&self) -> Result<Vec<u8>, PduError> {
+        // This is the correct way to do this. See
+        // [this issue](https://github.com/rust-lang/rust-clippy/issues/4483) for caveats of more
+        // "efficient" implementations.
+        let mut vec = alloc::vec![0; self.len_written()];
+        self.write_to_bytes(&mut vec)?;
+        Ok(vec)
+    }
+}
+
+/// Abstraction trait for fields and properties common for all PDUs.
+pub trait CfdpPdu {
+    fn pdu_header(&self) -> &PduHeader;
+
+    fn source_id(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().source_entity_id
+    }
+
+    fn dest_id(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().dest_entity_id
+    }
+
+    fn transaction_seq_num(&self) -> UnsignedByteField {
+        self.pdu_header().common_pdu_conf().transaction_seq_num
+    }
+
+    fn transmission_mode(&self) -> TransmissionMode {
+        self.pdu_header().common_pdu_conf().trans_mode
+    }
+    fn direction(&self) -> Direction {
+        self.pdu_header().common_pdu_conf().direction
+    }
+
+    fn crc_flag(&self) -> CrcFlag {
+        self.pdu_header().common_pdu_conf().crc_flag
+    }
+
+    fn file_flag(&self) -> LargeFileFlag {
+        self.pdu_header().common_pdu_conf().file_flag
+    }
+
+    fn pdu_type(&self) -> PduType {
+        self.pdu_header().pdu_type()
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType>;
+}
+
 /// Common configuration fields for a PDU.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+///
+/// Please note that this structure has a custom implementation of [PartialEq] which only
+/// compares the values for source entity ID, destination entity ID and transaction sequence
+/// number. This permits that those fields can have different widths, as long as the value is the
+/// same.
+#[derive(Debug, Copy, Clone, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct CommonPduConfig {
     source_entity_id: UnsignedByteField,
@@ -217,10 +290,10 @@ impl CommonPduConfig {
         let source_id = source_id.into();
         let dest_id = dest_id.into();
         if source_id.size() != dest_id.size() {
-            return Err(PduError::SourceDestIdLenMissmatch((
-                source_id.size(),
-                dest_id.size(),
-            )));
+            return Err(PduError::SourceDestIdLenMissmatch {
+                src_id_len: source_id.size(),
+                dest_id_len: dest_id.size(),
+            });
         }
         if source_id.size() != 1
             && source_id.size() != 2
@@ -266,6 +339,18 @@ impl Default for CommonPduConfig {
     }
 }
 
+impl PartialEq for CommonPduConfig {
+    fn eq(&self, other: &Self) -> bool {
+        self.source_entity_id.value() == other.source_entity_id.value()
+            && self.dest_entity_id.value() == other.dest_entity_id.value()
+            && self.transaction_seq_num.value() == other.transaction_seq_num.value()
+            && self.trans_mode == other.trans_mode
+            && self.file_flag == other.file_flag
+            && self.crc_flag == other.crc_flag
+            && self.direction == other.direction
+    }
+}
+
 pub const FIXED_HEADER_LEN: usize = 4;
 
 /// Abstraction for the PDU header common to all CFDP PDUs.
@@ -340,6 +425,10 @@ impl PduHeader {
             + self.pdu_conf.dest_entity_id.size()
     }
 
+    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.
     pub fn pdu_len(&self) -> usize {
@@ -350,20 +439,20 @@ impl PduHeader {
         // Internal note: There is currently no way to pass a PDU configuration like this, but
         // this check is still kept for defensive programming.
         if self.pdu_conf.source_entity_id.size() != self.pdu_conf.dest_entity_id.size() {
-            return Err(PduError::SourceDestIdLenMissmatch((
-                self.pdu_conf.source_entity_id.size(),
-                self.pdu_conf.dest_entity_id.size(),
-            )));
+            return Err(PduError::SourceDestIdLenMissmatch {
+                src_id_len: self.pdu_conf.source_entity_id.size(),
+                dest_id_len: self.pdu_conf.dest_entity_id.size(),
+            });
         }
         if buf.len()
             < FIXED_HEADER_LEN
                 + self.pdu_conf.source_entity_id.size()
                 + self.pdu_conf.transaction_seq_num.size()
         {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: FIXED_HEADER_LEN,
-            })
+            }
             .into());
         }
         let mut current_idx = 0;
@@ -404,10 +493,10 @@ impl PduHeader {
     /// flag is not set, it will simply return the PDU length.
     pub fn verify_length_and_checksum(&self, buf: &[u8]) -> Result<usize, PduError> {
         if buf.len() < self.pdu_len() {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: buf.len(),
                 expected: self.pdu_len(),
-            })
+            }
             .into());
         }
         if self.pdu_conf.crc_flag == CrcFlag::WithCrc {
@@ -433,11 +522,11 @@ impl PduHeader {
     /// function.
     pub fn from_bytes(buf: &[u8]) -> Result<(Self, usize), PduError> {
         if buf.len() < FIXED_HEADER_LEN {
-            return Err(PduError::ByteConversionError(
-                ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(PduError::ByteConversion(
+                ByteConversionError::FromSliceTooSmall {
                     found: buf.len(),
                     expected: FIXED_HEADER_LEN,
-                }),
+                },
             ));
         }
         let cfdp_version_raw = (buf[0] >> 5) & 0b111;
@@ -472,10 +561,10 @@ impl PduHeader {
             ));
         }
         if buf.len() < (4 + 2 * expected_len_entity_ids + expected_len_seq_num) {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: buf.len(),
                 expected: 4 + 2 * expected_len_entity_ids + expected_len_seq_num,
-            })
+            }
             .into());
         }
         let mut current_idx = 4;
@@ -571,17 +660,17 @@ pub(crate) fn generic_length_checks_pdu_deserialization(
 ) -> Result<(), ByteConversionError> {
     // Buffer too short to hold additional expected minimum datasize.
     if buf.len() < min_expected_len {
-        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+        return Err(ByteConversionError::FromSliceTooSmall {
             found: buf.len(),
             expected: min_expected_len,
-        }));
+        });
     }
     // This can happen if the PDU datafield length value is invalid.
     if full_len_without_crc < min_expected_len {
-        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+        return Err(ByteConversionError::FromSliceTooSmall {
             found: full_len_without_crc,
             expected: min_expected_len,
-        }));
+        });
     }
     Ok(())
 }
@@ -596,23 +685,26 @@ pub(crate) fn add_pdu_crc(buf: &mut [u8], mut current_idx: usize) -> usize {
 
 #[cfg(test)]
 mod tests {
+    use alloc::string::ToString;
+
     use crate::cfdp::pdu::{CommonPduConfig, PduError, PduHeader, FIXED_HEADER_LEN};
     use crate::cfdp::{
         CrcFlag, Direction, LargeFileFlag, PduType, SegmentMetadataFlag, SegmentationControl,
         TransmissionMode, CFDP_VERSION_2,
     };
     use crate::util::{
-        UbfU8, UnsignedByteField, UnsignedByteFieldU16, UnsignedByteFieldU8, UnsignedEnum,
+        UbfU16, UbfU8, UnsignedByteField, UnsignedByteFieldU16, UnsignedByteFieldU8, UnsignedEnum,
     };
     use crate::ByteConversionError;
     use std::format;
 
+    pub(crate) const TEST_SRC_ID: UbfU8 = UbfU8::new(5);
+    pub(crate) const TEST_DEST_ID: UbfU8 = UbfU8::new(10);
+    pub(crate) const TEST_SEQ_NUM: UbfU8 = UbfU8::new(20);
+
     pub(crate) fn common_pdu_conf(crc_flag: CrcFlag, fss: LargeFileFlag) -> CommonPduConfig {
-        let src_id = UbfU8::new(5);
-        let dest_id = UbfU8::new(10);
-        let transaction_seq_num = UbfU8::new(20);
         let mut pdu_conf =
-            CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_num)
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM)
                 .expect("Generating common PDU config");
         pdu_conf.crc_flag = crc_flag;
         pdu_conf.file_flag = fss;
@@ -623,7 +715,6 @@ mod tests {
         assert_eq!((buf[0] >> 5) & 0b111, CFDP_VERSION_2);
         // File directive
         assert_eq!((buf[0] >> 4) & 1, pdu_conf.pdu_type as u8);
-        // Towards receiver
         assert_eq!((buf[0] >> 3) & 1, pdu_conf.pdu_conf.direction as u8);
         // Acknowledged
         assert_eq!((buf[0] >> 2) & 1, pdu_conf.pdu_conf.trans_mode as u8);
@@ -669,7 +760,7 @@ mod tests {
                             .try_into()
                             .unwrap()
                     ),
-                    ubf.value() as u64
+                    ubf.value()
                 ),
                 _ => panic!("invalid entity ID length"),
             }
@@ -704,6 +795,17 @@ mod tests {
         assert_eq!(pdu_header.header_len(), 7);
     }
 
+    #[test]
+    fn test_common_pdu_conf_partial_eq() {
+        let common_pdu_cfg_0 =
+            CommonPduConfig::new_with_byte_fields(UbfU8::new(1), UbfU8::new(2), UbfU8::new(3))
+                .expect("common config creation failed");
+        let common_pdu_cfg_1 =
+            CommonPduConfig::new_with_byte_fields(UbfU16::new(1), UbfU16::new(2), UbfU16::new(3))
+                .expect("common config creation failed");
+        assert_eq!(common_pdu_cfg_0, common_pdu_cfg_1);
+    }
+
     #[test]
     fn test_basic_state_default() {
         let default_conf = CommonPduConfig::default();
@@ -718,6 +820,8 @@ mod tests {
         assert_eq!(default_conf.crc_flag, CrcFlag::NoCrc);
         assert_eq!(default_conf.file_flag, LargeFileFlag::Normal);
     }
+
+    #[test]
     fn test_pdu_header_setter() {
         let src_id = UnsignedByteFieldU8::new(1);
         let dest_id = UnsignedByteFieldU8::new(2);
@@ -747,6 +851,7 @@ mod tests {
         // 4 byte fixed header plus three bytes src, dest ID and transaction ID
         assert_eq!(res.unwrap(), 7);
         verify_raw_header(&pdu_header, &buf);
+        assert_eq!(pdu_header.pdu_datafield_len(), 5);
     }
 
     #[test]
@@ -840,6 +945,10 @@ mod tests {
         let error = res.unwrap_err();
         if let PduError::CfdpVersionMissmatch(raw_version) = error {
             assert_eq!(raw_version, CFDP_VERSION_2 + 1);
+            assert_eq!(
+                error.to_string(),
+                "cfdp version missmatch, found 2, expected 1"
+            );
         } else {
             panic!("invalid exception: {}", error);
         }
@@ -851,11 +960,13 @@ mod tests {
         let res = PduHeader::from_bytes(&buf);
         assert!(res.is_err());
         let error = res.unwrap_err();
-        if let PduError::ByteConversionError(ByteConversionError::FromSliceTooSmall(missmatch)) =
-            error
+        if let PduError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+            found,
+            expected,
+        }) = error
         {
-            assert_eq!(missmatch.found, 3);
-            assert_eq!(missmatch.expected, FIXED_HEADER_LEN);
+            assert_eq!(found, 3);
+            assert_eq!(expected, FIXED_HEADER_LEN);
         } else {
             panic!("invalid exception: {}", error);
         }
@@ -875,11 +986,17 @@ mod tests {
         let header = PduHeader::from_bytes(&buf[0..6]);
         assert!(header.is_err());
         let error = header.unwrap_err();
-        if let PduError::ByteConversionError(ByteConversionError::FromSliceTooSmall(missmatch)) =
-            error
+        if let PduError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+            found,
+            expected,
+        }) = error
         {
-            assert_eq!(missmatch.found, 6);
-            assert_eq!(missmatch.expected, 7);
+            assert_eq!(found, 6);
+            assert_eq!(expected, 7);
+            assert_eq!(
+                error.to_string(),
+                "source slice with size 6 too small, expected at least 7 bytes"
+            );
         }
     }
 
@@ -907,6 +1024,10 @@ mod tests {
         let error = pdu_conf_res.unwrap_err();
         if let PduError::InvalidEntityLen(len) = error {
             assert_eq!(len, 3);
+            assert_eq!(
+                error.to_string(),
+                "invalid PDU entity ID length 3, only [1, 2, 4, 8] are allowed"
+            );
         } else {
             panic!("Invalid exception: {}", error)
         }
@@ -920,9 +1041,17 @@ mod tests {
             CommonPduConfig::new_with_byte_fields(src_id, dest_id, transaction_seq_id);
         assert!(pdu_conf_res.is_err());
         let error = pdu_conf_res.unwrap_err();
-        if let PduError::SourceDestIdLenMissmatch((src_len, dest_len)) = error {
-            assert_eq!(src_len, 1);
-            assert_eq!(dest_len, 2);
+        if let PduError::SourceDestIdLenMissmatch {
+            src_id_len,
+            dest_id_len,
+        } = error
+        {
+            assert_eq!(src_id_len, 1);
+            assert_eq!(dest_id_len, 2);
+            assert_eq!(
+                error.to_string(),
+                "missmatch of PDU source length 1 and destination length 2"
+            );
         }
     }
 
@@ -973,4 +1102,20 @@ mod tests {
             panic!("invalid exception {:?}", error)
         }
     }
+
+    #[test]
+    fn test_pdu_error_clonable_and_comparable() {
+        let pdu_error = PduError::InvalidEntityLen(0);
+        let pdu_error_2 = pdu_error;
+        assert_eq!(pdu_error, pdu_error_2);
+    }
+
+    #[test]
+    fn test_pdu_config_clonable_and_comparable() {
+        let common_pdu_cfg_0 =
+            CommonPduConfig::new_with_byte_fields(UbfU8::new(1), UbfU8::new(2), UbfU8::new(3))
+                .expect("common config creation failed");
+        let common_pdu_cfg_1 = common_pdu_cfg_0;
+        assert_eq!(common_pdu_cfg_0, common_pdu_cfg_1);
+    }
 }

src/cfdp/pdu/nak.rs

@@ -0,0 +1,803 @@
+use crate::{
+    cfdp::{CrcFlag, Direction, LargeFileFlag},
+    ByteConversionError,
+};
+use core::{marker::PhantomData, mem::size_of};
+
+use super::{
+    add_pdu_crc, generic_length_checks_pdu_deserialization, CfdpPdu, FileDirectiveType, PduError,
+    PduHeader, WritablePduPacket,
+};
+
+/// Helper type to encapsulate both normal file size segment requests and large file size segment
+/// requests.
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub enum SegmentRequests<'a> {
+    U32Pairs(&'a [(u32, u32)]),
+    U64Pairs(&'a [(u64, u64)]),
+}
+
+impl SegmentRequests<'_> {
+    pub fn is_empty(&self) -> bool {
+        match self {
+            SegmentRequests::U32Pairs(pairs) => pairs.is_empty(),
+            SegmentRequests::U64Pairs(pairs) => pairs.is_empty(),
+        }
+    }
+}
+
+/// NAK PDU abstraction specialized in the creation of NAK PDUs.
+///
+/// It exposes a specialized API which simplifies to generate these NAK PDUs with the
+/// format according to CFDP chapter 5.2.6.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct NakPduCreator<'seg_reqs> {
+    pdu_header: PduHeader,
+    start_of_scope: u64,
+    end_of_scope: u64,
+    segment_requests: Option<SegmentRequests<'seg_reqs>>,
+}
+
+impl<'seg_reqs> NakPduCreator<'seg_reqs> {
+    /// Please note that the start of scope and the end of scope need to be smaller or equal
+    /// to [u32::MAX] if the large file flag of the passed PDU configuration is
+    /// [LargeFileFlag::Normal].
+    ///
+    /// ## Errrors
+    ///
+    pub fn new_no_segment_requests(
+        pdu_header: PduHeader,
+        start_of_scope: u64,
+        end_of_scope: u64,
+    ) -> Result<NakPduCreator<'seg_reqs>, PduError> {
+        Self::new_generic(pdu_header, start_of_scope, end_of_scope, None)
+    }
+
+    /// Default constructor for normal file sizes.
+    pub fn new(
+        pdu_header: PduHeader,
+        start_of_scope: u32,
+        end_of_scope: u32,
+        segment_requests: &'seg_reqs [(u32, u32)],
+    ) -> Result<NakPduCreator, PduError> {
+        let mut passed_segment_requests = None;
+        if !segment_requests.is_empty() {
+            passed_segment_requests = Some(SegmentRequests::U32Pairs(segment_requests));
+        }
+        Self::new_generic(
+            pdu_header,
+            start_of_scope.into(),
+            end_of_scope.into(),
+            passed_segment_requests,
+        )
+    }
+
+    pub fn new_large_file_size(
+        pdu_header: PduHeader,
+        start_of_scope: u64,
+        end_of_scope: u64,
+        segment_requests: &'seg_reqs [(u64, u64)],
+    ) -> Result<NakPduCreator, PduError> {
+        let mut passed_segment_requests = None;
+        if !segment_requests.is_empty() {
+            passed_segment_requests = Some(SegmentRequests::U64Pairs(segment_requests));
+        }
+        Self::new_generic(
+            pdu_header,
+            start_of_scope,
+            end_of_scope,
+            passed_segment_requests,
+        )
+    }
+
+    fn new_generic(
+        mut pdu_header: PduHeader,
+        start_of_scope: u64,
+        end_of_scope: u64,
+        segment_requests: Option<SegmentRequests<'seg_reqs>>,
+    ) -> Result<NakPduCreator, PduError> {
+        // Force correct direction flag.
+        pdu_header.pdu_conf.direction = Direction::TowardsSender;
+        if let Some(ref segment_requests) = segment_requests {
+            match segment_requests {
+                SegmentRequests::U32Pairs(_) => {
+                    if start_of_scope > u32::MAX as u64 || end_of_scope > u32::MAX as u64 {
+                        return Err(PduError::InvalidStartOrEndOfScopeValue);
+                    }
+                    pdu_header.pdu_conf.file_flag = LargeFileFlag::Normal;
+                }
+                SegmentRequests::U64Pairs(_) => {
+                    pdu_header.pdu_conf.file_flag = LargeFileFlag::Large;
+                }
+            }
+        };
+        let mut nak_pdu = Self {
+            pdu_header,
+            start_of_scope,
+            end_of_scope,
+            segment_requests,
+        };
+        nak_pdu.pdu_header.pdu_datafield_len = nak_pdu.calc_pdu_datafield_len() as u16;
+        Ok(nak_pdu)
+    }
+
+    pub fn start_of_scope(&self) -> u64 {
+        self.start_of_scope
+    }
+
+    pub fn end_of_scope(&self) -> u64 {
+        self.end_of_scope
+    }
+
+    pub fn segment_requests(&self) -> Option<&SegmentRequests> {
+        self.segment_requests.as_ref()
+    }
+
+    pub fn num_segment_reqs(&self) -> usize {
+        match &self.segment_requests {
+            Some(seg_reqs) => match seg_reqs {
+                SegmentRequests::U32Pairs(pairs) => pairs.len(),
+                SegmentRequests::U64Pairs(pairs) => pairs.len(),
+            },
+            None => 0,
+        }
+    }
+
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        let mut datafield_len = 1;
+        if self.file_flag() == LargeFileFlag::Normal {
+            datafield_len += 8;
+            datafield_len += self.num_segment_reqs() * 8;
+        } else {
+            datafield_len += 16;
+            datafield_len += self.num_segment_reqs() * 16;
+        }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            datafield_len += 2;
+        }
+        datafield_len
+    }
+}
+
+impl CfdpPdu for NakPduCreator<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::NakPdu)
+    }
+}
+
+impl WritablePduPacket for NakPduCreator<'_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::NakPdu as u8;
+        current_idx += 1;
+
+        let mut write_start_end_of_scope_normal = || {
+            let start_of_scope = u32::try_from(self.start_of_scope).unwrap();
+            let end_of_scope = u32::try_from(self.end_of_scope).unwrap();
+            buf[current_idx..current_idx + 4].copy_from_slice(&start_of_scope.to_be_bytes());
+            current_idx += 4;
+            buf[current_idx..current_idx + 4].copy_from_slice(&end_of_scope.to_be_bytes());
+            current_idx += 4;
+        };
+        if let Some(ref seg_reqs) = self.segment_requests {
+            match seg_reqs {
+                SegmentRequests::U32Pairs(pairs) => {
+                    // Unwrap is okay here, the API should prevent invalid values which would trigger a
+                    // panic here.
+                    write_start_end_of_scope_normal();
+                    for (next_start_offset, next_end_offset) in *pairs {
+                        buf[current_idx..current_idx + 4]
+                            .copy_from_slice(&next_start_offset.to_be_bytes());
+                        current_idx += 4;
+                        buf[current_idx..current_idx + 4]
+                            .copy_from_slice(&next_end_offset.to_be_bytes());
+                        current_idx += 4;
+                    }
+                }
+                SegmentRequests::U64Pairs(pairs) => {
+                    buf[current_idx..current_idx + 8]
+                        .copy_from_slice(&self.start_of_scope.to_be_bytes());
+                    current_idx += 8;
+                    buf[current_idx..current_idx + 8]
+                        .copy_from_slice(&self.end_of_scope.to_be_bytes());
+                    current_idx += 8;
+                    for (next_start_offset, next_end_offset) in *pairs {
+                        buf[current_idx..current_idx + 8]
+                            .copy_from_slice(&next_start_offset.to_be_bytes());
+                        current_idx += 8;
+                        buf[current_idx..current_idx + 8]
+                            .copy_from_slice(&next_end_offset.to_be_bytes());
+                        current_idx += 8;
+                    }
+                }
+            }
+        } else {
+            write_start_end_of_scope_normal();
+        }
+
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+/// Special iterator type for the NAK PDU which allows to iterate over both normal and large file
+/// segment requests.
+#[derive(Debug)]
+pub struct SegmentRequestIter<'a, T> {
+    seq_req_raw: &'a [u8],
+    current_idx: usize,
+    phantom: core::marker::PhantomData<T>,
+}
+
+pub trait SegReqFromBytes {
+    fn from_bytes(bytes: &[u8]) -> Self;
+}
+
+impl SegReqFromBytes for u32 {
+    fn from_bytes(bytes: &[u8]) -> u32 {
+        u32::from_be_bytes(bytes.try_into().unwrap())
+    }
+}
+
+impl SegReqFromBytes for u64 {
+    fn from_bytes(bytes: &[u8]) -> u64 {
+        u64::from_be_bytes(bytes.try_into().unwrap())
+    }
+}
+
+impl<'a, T> Iterator for SegmentRequestIter<'a, T>
+where
+    T: SegReqFromBytes,
+{
+    type Item = (T, T);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let value = self.next_at_offset(self.current_idx);
+        self.current_idx += 2 * size_of::<T>();
+        value
+    }
+}
+
+impl<'a, 'b> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'b, u32> {
+    fn eq(&self, other: &SegmentRequests) -> bool {
+        match other {
+            SegmentRequests::U32Pairs(pairs) => self.compare_pairs(pairs),
+            SegmentRequests::U64Pairs(pairs) => {
+                if pairs.is_empty() && self.seq_req_raw.is_empty() {
+                    return true;
+                }
+                false
+            }
+        }
+    }
+}
+
+impl<'a, 'b> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'b, u64> {
+    fn eq(&self, other: &SegmentRequests) -> bool {
+        match other {
+            SegmentRequests::U32Pairs(pairs) => {
+                if pairs.is_empty() && self.seq_req_raw.is_empty() {
+                    return true;
+                }
+                false
+            }
+            SegmentRequests::U64Pairs(pairs) => self.compare_pairs(pairs),
+        }
+    }
+}
+
+impl<'a, T> SegmentRequestIter<'a, T>
+where
+    T: SegReqFromBytes + PartialEq,
+{
+    fn compare_pairs(&self, pairs: &[(T, T)]) -> bool {
+        if pairs.is_empty() && self.seq_req_raw.is_empty() {
+            return true;
+        }
+        let size = size_of::<T>();
+        if pairs.len() * 2 * size != self.seq_req_raw.len() {
+            return false;
+        }
+
+        for (i, pair) in pairs.iter().enumerate() {
+            let next_val = self.next_at_offset(i * 2 * size).unwrap();
+            if next_val != *pair {
+                return false;
+            }
+        }
+
+        true
+    }
+}
+
+impl<T: SegReqFromBytes> SegmentRequestIter<'_, T> {
+    fn next_at_offset(&self, mut offset: usize) -> Option<(T, T)> {
+        if offset + size_of::<T>() * 2 > self.seq_req_raw.len() {
+            return None;
+        }
+
+        let start_offset = T::from_bytes(&self.seq_req_raw[offset..offset + size_of::<T>()]);
+        offset += size_of::<T>();
+
+        let end_offset = T::from_bytes(&self.seq_req_raw[offset..offset + size_of::<T>()]);
+        Some((start_offset, end_offset))
+    }
+}
+
+/// NAK PDU abstraction specialized in the reading NAK PDUs from a raw bytestream.
+///
+/// This is a zero-copy class where the segment requests can be read using a special iterator
+/// API without the need to copy them.
+///
+/// The NAK format is expected to be conforming to CFDP chapter 5.2.6.
+#[derive(Debug, PartialEq, Eq)]
+pub struct NakPduReader<'seg_reqs> {
+    pdu_header: PduHeader,
+    start_of_scope: u64,
+    end_of_scope: u64,
+    seg_reqs_raw: &'seg_reqs [u8],
+}
+
+impl CfdpPdu for NakPduReader<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::NakPdu)
+    }
+}
+
+impl<'seg_reqs> NakPduReader<'seg_reqs> {
+    pub fn new(buf: &'seg_reqs [u8]) -> Result<NakPduReader, PduError> {
+        Self::from_bytes(buf)
+    }
+
+    pub fn from_bytes(buf: &'seg_reqs [u8]) -> Result<NakPduReader, PduError> {
+        let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
+        let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
+        // Minimum length of 9: 1 byte directive field and start and end of scope for normal file
+        // size.
+        generic_length_checks_pdu_deserialization(buf, 9, full_len_without_crc)?;
+        let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
+            PduError::InvalidDirectiveType {
+                found: buf[current_idx],
+                expected: Some(FileDirectiveType::NakPdu),
+            }
+        })?;
+        if directive_type != FileDirectiveType::NakPdu {
+            return Err(PduError::WrongDirectiveType {
+                found: directive_type,
+                expected: FileDirectiveType::AckPdu,
+            });
+        }
+        current_idx += 1;
+        let start_of_scope;
+        let end_of_scope;
+        if pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
+            if current_idx + 16 > buf.len() {
+                return Err(PduError::ByteConversion(
+                    ByteConversionError::FromSliceTooSmall {
+                        found: buf.len(),
+                        expected: current_idx + 16,
+                    },
+                ));
+            }
+            start_of_scope =
+                u64::from_be_bytes(buf[current_idx..current_idx + 8].try_into().unwrap());
+            current_idx += 8;
+            end_of_scope =
+                u64::from_be_bytes(buf[current_idx..current_idx + 8].try_into().unwrap());
+            current_idx += 8;
+        } else {
+            start_of_scope =
+                u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap()) as u64;
+            current_idx += 4;
+            end_of_scope =
+                u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap()) as u64;
+            current_idx += 4;
+        }
+        Ok(Self {
+            pdu_header,
+            start_of_scope,
+            end_of_scope,
+            seg_reqs_raw: &buf[current_idx..full_len_without_crc],
+        })
+    }
+
+    pub fn start_of_scope(&self) -> u64 {
+        self.start_of_scope
+    }
+
+    pub fn end_of_scope(&self) -> u64 {
+        self.end_of_scope
+    }
+
+    pub fn num_segment_reqs(&self) -> usize {
+        if self.seg_reqs_raw.is_empty() {
+            return 0;
+        }
+        if self.file_flag() == LargeFileFlag::Normal {
+            self.seg_reqs_raw.len() / 8
+        } else {
+            self.seg_reqs_raw.len() / 16
+        }
+    }
+
+    /// This function returns [None] if this NAK PDUs contains segment requests for a large file.
+    pub fn get_normal_segment_requests_iterator(&self) -> Option<SegmentRequestIter<'_, u32>> {
+        if self.file_flag() == LargeFileFlag::Large {
+            return None;
+        }
+        Some(SegmentRequestIter {
+            seq_req_raw: self.seg_reqs_raw,
+            current_idx: 0,
+            phantom: PhantomData,
+        })
+    }
+
+    /// This function returns [None] if this NAK PDUs contains segment requests for a normal file.
+    pub fn get_large_segment_requests_iterator(&self) -> Option<SegmentRequestIter<'_, u64>> {
+        if self.file_flag() == LargeFileFlag::Normal {
+            return None;
+        }
+        Some(SegmentRequestIter {
+            seq_req_raw: self.seg_reqs_raw,
+            current_idx: 0,
+            phantom: PhantomData,
+        })
+    }
+}
+
+impl<'a, 'b> PartialEq<NakPduCreator<'a>> for NakPduReader<'b> {
+    fn eq(&self, other: &NakPduCreator<'a>) -> bool {
+        if self.pdu_header() != other.pdu_header()
+            || self.end_of_scope() != other.end_of_scope()
+            || self.start_of_scope() != other.start_of_scope()
+        {
+            return false;
+        }
+
+        // Check if both segment requests are empty or None
+        match (self.seg_reqs_raw.is_empty(), other.segment_requests()) {
+            (true, None) => true,
+            (true, Some(seg_reqs)) => seg_reqs.is_empty(),
+            (false, None) => false,
+            _ => {
+                // Compare based on file_flag
+                if self.file_flag() == LargeFileFlag::Normal {
+                    let normal_iter = self.get_normal_segment_requests_iterator().unwrap();
+                    normal_iter == *other.segment_requests().unwrap()
+                } else {
+                    let large_iter = self.get_large_segment_requests_iterator().unwrap();
+                    large_iter == *other.segment_requests().unwrap()
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use alloc::string::ToString;
+
+    use crate::cfdp::{
+        pdu::tests::{common_pdu_conf, verify_raw_header, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID},
+        PduType, TransmissionMode,
+    };
+
+    use super::*;
+
+    fn check_generic_fields(nak_pdu: &impl CfdpPdu) {
+        assert_eq!(nak_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(nak_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(nak_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            nak_pdu.file_directive_type(),
+            Some(FileDirectiveType::NakPdu),
+        );
+        assert_eq!(nak_pdu.transmission_mode(), TransmissionMode::Acknowledged);
+        assert_eq!(nak_pdu.direction(), Direction::TowardsSender);
+        assert_eq!(nak_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(nak_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(nak_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
+    }
+
+    #[test]
+    fn test_seg_request_api() {
+        let seg_req = SegmentRequests::U32Pairs(&[]);
+        assert!(seg_req.is_empty());
+        let seg_req = SegmentRequests::U64Pairs(&[]);
+        assert!(seg_req.is_empty());
+    }
+
+    #[test]
+    fn test_basic_creator() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 0, 0)
+            .expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu.start_of_scope(), 0);
+        assert_eq!(nak_pdu.end_of_scope(), 0);
+        assert_eq!(nak_pdu.segment_requests(), None);
+        assert_eq!(nak_pdu.num_segment_reqs(), 0);
+        check_generic_fields(&nak_pdu);
+    }
+
+    #[test]
+    fn test_serialization_empty() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 100, 300)
+            .expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu.start_of_scope(), 100);
+        assert_eq!(nak_pdu.end_of_scope(), 300);
+        let mut buf: [u8; 64] = [0; 64];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        verify_raw_header(nak_pdu.pdu_header(), &buf);
+        let mut current_idx = nak_pdu.pdu_header().header_len();
+        assert_eq!(current_idx + 9, nak_pdu.len_written());
+        assert_eq!(buf[current_idx], FileDirectiveType::NakPdu as u8);
+        current_idx += 1;
+        let start_of_scope =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(start_of_scope, 100);
+        current_idx += 4;
+        let end_of_scope =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(end_of_scope, 300);
+        current_idx += 4;
+        assert_eq!(current_idx, nak_pdu.len_written());
+    }
+
+    #[test]
+    fn test_serialization_two_segments() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new(pdu_header, 100, 300, &[(0, 0), (32, 64)])
+            .expect("creating NAK PDU creator failed");
+        let mut buf: [u8; 64] = [0; 64];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        verify_raw_header(nak_pdu.pdu_header(), &buf);
+        let mut current_idx = nak_pdu.pdu_header().header_len();
+        assert_eq!(current_idx + 9 + 16, nak_pdu.len_written());
+        assert_eq!(buf[current_idx], FileDirectiveType::NakPdu as u8);
+        current_idx += 1;
+        let start_of_scope =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(start_of_scope, 100);
+        current_idx += 4;
+        let end_of_scope =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(end_of_scope, 300);
+        current_idx += 4;
+        let first_seg_start =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(first_seg_start, 0);
+        current_idx += 4;
+        let first_seg_end =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(first_seg_end, 0);
+        current_idx += 4;
+        let second_seg_start =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(second_seg_start, 32);
+        current_idx += 4;
+        let second_seg_end =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        assert_eq!(second_seg_end, 64);
+        current_idx += 4;
+        assert_eq!(current_idx, nak_pdu.len_written());
+    }
+
+    #[test]
+    fn test_deserialization_empty() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 100, 300)
+            .expect("creating NAK PDU creator failed");
+        let mut buf: [u8; 64] = [0; 64];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        let nak_pdu_deser = NakPduReader::from_bytes(&buf).expect("deserializing NAK PDU failed");
+        assert_eq!(nak_pdu_deser, nak_pdu);
+        check_generic_fields(&nak_pdu_deser);
+    }
+
+    #[test]
+    fn test_deserialization_large_segments() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Large);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu =
+            NakPduCreator::new_large_file_size(pdu_header, 100, 300, &[(50, 100), (200, 300)])
+                .expect("creating NAK PDU creator failed");
+        let mut buf: [u8; 128] = [0; 128];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        let nak_pdu_deser = NakPduReader::from_bytes(&buf).expect("deserializing NAK PDU failed");
+        assert_eq!(nak_pdu_deser, nak_pdu);
+        assert_eq!(nak_pdu_deser.start_of_scope(), 100);
+        assert_eq!(nak_pdu_deser.end_of_scope(), 300);
+        assert_eq!(nak_pdu_deser.num_segment_reqs(), 2);
+        assert!(nak_pdu_deser
+            .get_large_segment_requests_iterator()
+            .is_some());
+        assert!(nak_pdu_deser
+            .get_normal_segment_requests_iterator()
+            .is_none());
+        assert_eq!(
+            nak_pdu_deser
+                .get_large_segment_requests_iterator()
+                .unwrap()
+                .count(),
+            2
+        );
+        for (idx, large_segments) in nak_pdu_deser
+            .get_large_segment_requests_iterator()
+            .unwrap()
+            .enumerate()
+        {
+            if idx == 0 {
+                assert_eq!(large_segments.0, 50);
+                assert_eq!(large_segments.1, 100);
+            } else {
+                assert_eq!(large_segments.0, 200);
+                assert_eq!(large_segments.1, 300);
+            }
+        }
+    }
+
+    #[test]
+    fn test_deserialization_normal_segments() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new(pdu_header, 100, 300, &[(50, 100), (200, 300)])
+            .expect("creating NAK PDU creator failed");
+        let mut buf: [u8; 128] = [0; 128];
+        nak_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing NAK PDU to buffer failed");
+        let nak_pdu_deser = NakPduReader::from_bytes(&buf).expect("deserializing NAK PDU failed");
+        assert_eq!(nak_pdu_deser, nak_pdu);
+        assert_eq!(nak_pdu_deser.start_of_scope(), 100);
+        assert_eq!(nak_pdu_deser.end_of_scope(), 300);
+        assert_eq!(nak_pdu_deser.num_segment_reqs(), 2);
+        assert!(nak_pdu_deser
+            .get_normal_segment_requests_iterator()
+            .is_some());
+        assert!(nak_pdu_deser
+            .get_large_segment_requests_iterator()
+            .is_none());
+        assert_eq!(
+            nak_pdu_deser
+                .get_normal_segment_requests_iterator()
+                .unwrap()
+                .count(),
+            2
+        );
+        for (idx, large_segments) in nak_pdu_deser
+            .get_normal_segment_requests_iterator()
+            .unwrap()
+            .enumerate()
+        {
+            if idx == 0 {
+                assert_eq!(large_segments.0, 50);
+                assert_eq!(large_segments.1, 100);
+            } else {
+                assert_eq!(large_segments.0, 200);
+                assert_eq!(large_segments.1, 300);
+            }
+        }
+    }
+
+    #[test]
+    fn test_empty_is_empty() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu_0 =
+            NakPduCreator::new(pdu_header, 100, 300, &[]).expect("creating NAK PDU creator failed");
+        let nak_pdu_1 = NakPduCreator::new_no_segment_requests(pdu_header, 100, 300)
+            .expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu_0, nak_pdu_1);
+        // Assert the segment request is mapped to None.
+        assert!(nak_pdu_0.segment_requests().is_none());
+    }
+
+    #[test]
+    fn test_new_generic_invalid_input() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let u32_list = SegmentRequests::U32Pairs(&[(0, 50), (50, 100)]);
+        //let error = NakPduCreator::new_generic(pdu_header, 100, 300, Some(u32_list));
+        let error = NakPduCreator::new_generic(
+            pdu_header,
+            u32::MAX as u64 + 1,
+            u32::MAX as u64 + 2,
+            Some(u32_list),
+        );
+        assert!(error.is_err());
+        let error = error.unwrap_err();
+        if let PduError::InvalidStartOrEndOfScopeValue = error {
+            assert_eq!(
+                error.to_string(),
+                "invalid start or end of scope for NAK PDU"
+            );
+        } else {
+            panic!("unexpected error {error}");
+        }
+    }
+
+    #[test]
+    fn test_target_buf_too_small() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 100, 300)
+            .expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu.start_of_scope(), 100);
+        assert_eq!(nak_pdu.end_of_scope(), 300);
+        let mut buf: [u8; 5] = [0; 5];
+        let error = nak_pdu.write_to_bytes(&mut buf);
+        assert!(error.is_err());
+        let e = error.unwrap_err();
+        match e {
+            PduError::ByteConversion(conv_error) => match conv_error {
+                ByteConversionError::ToSliceTooSmall { found, expected } => {
+                    assert_eq!(expected, nak_pdu.len_written());
+                    assert_eq!(found, 5);
+                }
+                _ => panic!("unexpected error {conv_error}"),
+            },
+            _ => panic!("unexpected error {e}"),
+        }
+    }
+
+    #[test]
+    fn test_with_crc() {
+        let pdu_conf = common_pdu_conf(CrcFlag::WithCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu = NakPduCreator::new_no_segment_requests(pdu_header, 0, 0)
+            .expect("creating NAK PDU creator failed");
+        let mut nak_vec = nak_pdu.to_vec().expect("writing NAK to vector failed");
+        assert_eq!(nak_vec.len(), pdu_header.header_len() + 9 + 2);
+        assert_eq!(nak_vec.len(), nak_pdu.len_written());
+        let nak_pdu_deser = NakPduReader::new(&nak_vec).expect("reading NAK PDU failed");
+        assert_eq!(nak_pdu_deser, nak_pdu);
+        nak_vec[nak_pdu.len_written() - 1] -= 1;
+        let nak_pdu_deser = NakPduReader::new(&nak_vec);
+        assert!(nak_pdu_deser.is_err());
+        if let Err(PduError::ChecksumError(raw)) = nak_pdu_deser {
+            assert_eq!(
+                raw,
+                u16::from_be_bytes(nak_vec[nak_pdu.len_written() - 2..].try_into().unwrap())
+            );
+        }
+    }
+}

src/cfdp/tlv/msg_to_user.rs

@@ -0,0 +1,173 @@
+//! Abstractions for the Message to User CFDP TLV subtype.
+use super::{GenericTlv, Tlv, TlvLvError, TlvType, TlvTypeField, WritableTlv};
+use crate::ByteConversionError;
+use delegate::delegate;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct MsgToUserTlv<'data> {
+    pub tlv: Tlv<'data>,
+}
+
+impl<'data> MsgToUserTlv<'data> {
+    /// Create a new message to user TLV where the type field is set correctly.
+    pub fn new(value: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvError> {
+        Ok(Self {
+            tlv: Tlv::new(TlvType::MsgToUser, value)?,
+        })
+    }
+
+    delegate! {
+        to self.tlv {
+            pub fn value(&self) -> &[u8];
+            /// Helper method to retrieve the length of the value. Simply calls the [slice::len] method of
+            /// [Self::value]
+            pub fn len_value(&self) -> usize;
+            /// Returns the full raw length, including the length byte.
+            pub fn len_full(&self) -> usize;
+            /// Checks whether the value field is empty.
+            pub fn is_empty(&self) -> bool;
+            /// If the TLV was generated from a raw bytestream using [Self::from_bytes], the raw start
+            /// of the TLV can be retrieved with this method.
+            pub fn raw_data(&self) -> Option<&[u8]>;
+        }
+    }
+
+    pub fn is_standard_tlv(&self) -> bool {
+        true
+    }
+
+    pub fn tlv_type(&self) -> Option<TlvType> {
+        Some(TlvType::MsgToUser)
+    }
+
+    /// Check whether this message is a reserved CFDP message like a Proxy Operation Message.
+    pub fn is_reserved_cfdp_msg(&self) -> bool {
+        if self.value().len() < 4 {
+            return false;
+        }
+        let value = self.value();
+        if value[0] == b'c' && value[1] == b'f' && value[2] == b'd' && value[3] == b'p' {
+            return true;
+        }
+        false
+    }
+
+    /// This is a thin wrapper around [Tlv::from_bytes] with the additional type check.
+    pub fn from_bytes(buf: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvError> {
+        let msg_to_user = Self {
+            tlv: Tlv::from_bytes(buf)?,
+        };
+        match msg_to_user.tlv.tlv_type_field() {
+            TlvTypeField::Standard(tlv_type) => {
+                if tlv_type != TlvType::MsgToUser {
+                    return Err(TlvLvError::InvalidTlvTypeField {
+                        found: tlv_type as u8,
+                        expected: Some(TlvType::MsgToUser as u8),
+                    });
+                }
+            }
+            TlvTypeField::Custom(raw) => {
+                return Err(TlvLvError::InvalidTlvTypeField {
+                    found: raw,
+                    expected: Some(TlvType::MsgToUser as u8),
+                });
+            }
+        }
+        Ok(msg_to_user)
+    }
+}
+
+impl WritableTlv for MsgToUserTlv<'_> {
+    fn len_written(&self) -> usize {
+        self.len_full()
+    }
+
+    delegate!(
+        to self.tlv {
+            fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
+        }
+    );
+}
+
+impl GenericTlv for MsgToUserTlv<'_> {
+    fn tlv_type_field(&self) -> TlvTypeField {
+        self.tlv.tlv_type_field()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_basic() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value);
+        assert!(msg_to_user.is_ok());
+        let msg_to_user = msg_to_user.unwrap();
+        assert!(msg_to_user.is_standard_tlv());
+        assert_eq!(msg_to_user.tlv_type().unwrap(), TlvType::MsgToUser);
+        assert_eq!(
+            msg_to_user.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::MsgToUser)
+        );
+        assert_eq!(msg_to_user.value(), custom_value);
+        assert_eq!(msg_to_user.value().len(), 4);
+        assert_eq!(msg_to_user.len_value(), 4);
+        assert_eq!(msg_to_user.len_full(), 6);
+        assert!(!msg_to_user.is_empty());
+        assert!(msg_to_user.raw_data().is_none());
+        assert!(!msg_to_user.is_reserved_cfdp_msg());
+    }
+
+    #[test]
+    fn test_reserved_msg_serialization() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let mut buf: [u8; 6] = [0; 6];
+        msg_to_user.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(
+            buf,
+            [
+                TlvType::MsgToUser as u8,
+                custom_value.len() as u8,
+                1,
+                2,
+                3,
+                4
+            ]
+        );
+    }
+
+    #[test]
+    fn test_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 { found, expected } = error {
+            assert_eq!(found, TlvType::FlowLabel as u8);
+            assert_eq!(expected, Some(TlvType::MsgToUser as u8));
+        } else {
+            panic!("Wrong error type returned: {:?}", error);
+        }
+    }
+
+    #[test]
+    fn test_reserved_msg() {
+        let reserved_str = "cfdp";
+        let msg_to_user = MsgToUserTlv::new(reserved_str.as_bytes());
+        assert!(msg_to_user.is_ok());
+        let msg_to_user = msg_to_user.unwrap();
+        assert!(msg_to_user.is_reserved_cfdp_msg());
+    }
+}

src/ecss/hk.rs

@@ -29,3 +29,33 @@ pub enum Subservice {
     TcGenerateOneShotDiag = 28,
     TcModifyDiagCollectionInterval = 32,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_try_from_u8() {
+        let hk_report_subservice_raw = 25;
+        let hk_report: Subservice = Subservice::try_from(hk_report_subservice_raw).unwrap();
+        assert_eq!(hk_report, Subservice::TmHkPacket);
+    }
+
+    #[test]
+    fn test_into_u8() {
+        let hk_report_raw: u8 = Subservice::TmHkPacket.into();
+        assert_eq!(hk_report_raw, 25);
+    }
+
+    #[test]
+    fn test_partial_eq() {
+        let hk_report_raw = Subservice::TmHkPacket;
+        assert_ne!(hk_report_raw, Subservice::TcGenerateOneShotHk);
+        assert_eq!(hk_report_raw, Subservice::TmHkPacket);
+    }
+    #[test]
+    fn test_copy_clone() {
+        let hk_report = Subservice::TmHkPacket;
+        let hk_report_copy = hk_report;
+        assert_eq!(hk_report, hk_report_copy);
+    }
+}

src/ecss/mod.rs

@@ -4,6 +4,8 @@
 //! 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};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 use core::fmt::{Debug, Display, Formatter};
 use core::mem::size_of;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
@@ -72,6 +74,7 @@ pub enum PusServiceId {
 /// All PUS versions. Only PUS C is supported by this library.
 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[non_exhaustive]
 pub enum PusVersion {
     EsaPus = 0,
     PusA = 1,
@@ -93,8 +96,9 @@ impl TryFrom<u8> for PusVersion {
 }
 
 /// ECSS Packet Type Codes (PTC)s.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
 pub enum PacketTypeCodes {
     Boolean = 1,
     Enumerated = 2,
@@ -113,9 +117,10 @@ pub enum PacketTypeCodes {
 pub type Ptc = PacketTypeCodes;
 
 /// ECSS Packet Field Codes (PFC)s for the unsigned [Ptc].
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub enum UnsignedPfc {
+#[repr(u8)]
+pub enum PfcUnsigned {
     OneByte = 4,
     TwelveBits = 8,
     TwoBytes = 12,
@@ -129,9 +134,10 @@ pub enum UnsignedPfc {
 }
 
 /// ECSS Packet Field Codes (PFC)s for the real (floating point) [Ptc].
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub enum RealPfc {
+#[repr(u8)]
+pub enum PfcReal {
     /// 4 octets simple precision format (IEEE)
     Float = 1,
     /// 8 octets simple precision format (IEEE)
@@ -146,9 +152,7 @@ pub enum RealPfc {
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum PusError {
     VersionNotSupported(PusVersion),
-    IncorrectCrc(u16),
-    RawDataTooShort(usize),
-    NoRawData,
+    ChecksumFailure(u16),
     /// CRC16 needs to be calculated first
     CrcCalculationMissing,
     ByteConversion(ByteConversionError),
@@ -160,23 +164,14 @@ impl Display for PusError {
             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::ChecksumFailure(crc) => {
+                write!(f, "checksum verification for crc16 {crc:#06x} failed")
             }
             PusError::CrcCalculationMissing => {
                 write!(f, "crc16 was not calculated")
             }
             PusError::ByteConversion(e) => {
-                write!(f, "low level byte conversion error: {e}")
+                write!(f, "pus error: {e}")
             }
         }
     }
@@ -212,7 +207,11 @@ pub trait PusPacket: CcsdsPacket {
 
 pub(crate) fn crc_from_raw_data(raw_data: &[u8]) -> Result<u16, PusError> {
     if raw_data.len() < 2 {
-        return Err(PusError::RawDataTooShort(raw_data.len()));
+        return Err(ByteConversionError::FromSliceTooSmall {
+            found: raw_data.len(),
+            expected: 2,
+        }
+        .into());
     }
     Ok(u16::from_be_bytes(
         raw_data[raw_data.len() - 2..raw_data.len()]
@@ -248,11 +247,14 @@ pub(crate) fn crc_procedure(
 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)),
+        _ if current_idx > total_len - 2 => Err(ByteConversionError::FromSliceTooSmall {
+            found: total_len - 2,
+            expected: current_idx,
+        }
+        .into()),
         _ => Ok(&slice[current_idx..total_len - 2]),
     }
 }
@@ -263,7 +265,7 @@ pub(crate) fn verify_crc16_ccitt_false_from_raw_to_pus_error(
 ) -> Result<(), PusError> {
     verify_crc16_ccitt_false_from_raw(raw_data)
         .then(|| ())
-        .ok_or(PusError::IncorrectCrc(crc16))
+        .ok_or(PusError::ChecksumFailure(crc16))
 }
 
 pub(crate) fn verify_crc16_ccitt_false_from_raw(raw_data: &[u8]) -> bool {
@@ -313,15 +315,19 @@ pub trait EcssEnumerationExt: EcssEnumeration + Debug + Copy + Clone + PartialEq
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct GenericEcssEnumWrapper<TYPE> {
+pub struct GenericEcssEnumWrapper<TYPE: Copy + Into<u64>> {
     field: GenericUnsignedByteField<TYPE>,
 }
 
-impl<TYPE> GenericEcssEnumWrapper<TYPE> {
+impl<TYPE: Copy + Into<u64>> GenericEcssEnumWrapper<TYPE> {
     pub const fn ptc() -> PacketTypeCodes {
         PacketTypeCodes::Enumerated
     }
 
+    pub const fn value_typed(&self) -> TYPE {
+        self.field.value_typed()
+    }
+
     pub fn new(val: TYPE) -> Self {
         Self {
             field: GenericUnsignedByteField::new(val),
@@ -329,7 +335,7 @@ impl<TYPE> GenericEcssEnumWrapper<TYPE> {
     }
 }
 
-impl<TYPE: ToBeBytes> UnsignedEnum for GenericEcssEnumWrapper<TYPE> {
+impl<TYPE: Copy + ToBeBytes + Into<u64>> UnsignedEnum for GenericEcssEnumWrapper<TYPE> {
     fn size(&self) -> usize {
         (self.pfc() / 8) as usize
     }
@@ -337,45 +343,89 @@ impl<TYPE: ToBeBytes> UnsignedEnum for GenericEcssEnumWrapper<TYPE> {
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         self.field.write_to_be_bytes(buf)
     }
+
+    fn value(&self) -> u64 {
+        self.field.value()
+    }
 }
 
-impl<TYPE: ToBeBytes> EcssEnumeration for GenericEcssEnumWrapper<TYPE> {
+impl<TYPE: Copy + ToBeBytes + Into<u64>> EcssEnumeration for GenericEcssEnumWrapper<TYPE> {
     fn pfc(&self) -> u8 {
         size_of::<TYPE>() as u8 * 8_u8
     }
 }
 
-impl<TYPE: Debug + Copy + Clone + PartialEq + Eq + ToBeBytes> EcssEnumerationExt
+impl<TYPE: Debug + Copy + Clone + PartialEq + Eq + ToBeBytes + Into<u64>> EcssEnumerationExt
     for GenericEcssEnumWrapper<TYPE>
 {
 }
 
-pub type EcssEnumU8 = GenericEcssEnumWrapper<u8>;
-pub type EcssEnumU16 = GenericEcssEnumWrapper<u16>;
-pub type EcssEnumU32 = GenericEcssEnumWrapper<u32>;
-pub type EcssEnumU64 = GenericEcssEnumWrapper<u64>;
+macro_rules! generic_ecss_enum_typedefs_and_from_impls {
+    ($($ty:ty => $Enum:ident),*) => {
+        $(
+            pub type $Enum = GenericEcssEnumWrapper<$ty>;
+
+            impl From<$ty> for $Enum {
+                fn from(value: $ty) -> Self {
+                    Self::new(value)
+                }
+            }
+        )*
+    };
+}
+
+// Generates EcssEnum<$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;
+pub trait WritablePusPacket {
+    fn len_written(&self) -> usize;
     fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError>;
+    #[cfg(feature = "alloc")]
+    fn to_vec(&self) -> Result<Vec<u8>, PusError> {
+        // This is the correct way to do this. See
+        // [this issue](https://github.com/rust-lang/rust-clippy/issues/4483) for caveats of more
+        // "efficient" implementations.
+        let mut vec = alloc::vec![0; self.len_written()];
+        self.write_to_bytes(&mut vec)?;
+        Ok(vec)
+    }
 }
 
 #[cfg(test)]
 mod tests {
+    use alloc::string::ToString;
+
     use crate::ecss::{EcssEnumU16, EcssEnumU32, EcssEnumU8, UnsignedEnum};
     use crate::ByteConversionError;
 
+    use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
+
     #[test]
     fn test_enum_u8() {
         let mut buf = [0, 0, 0];
         let my_enum = EcssEnumU8::new(1);
+        assert_eq!(EcssEnumU8::ptc(), Ptc::Enumerated);
+        assert_eq!(my_enum.size(), 1);
+        assert_eq!(my_enum.pfc(), 8);
         my_enum
             .write_to_be_bytes(&mut buf[1..2])
             .expect("To byte conversion of u8 failed");
         assert_eq!(buf[1], 1);
+        assert_eq!(my_enum.value(), 1);
+        assert_eq!(my_enum.value_typed(), 1);
+        let vec = my_enum.to_vec();
+        assert_eq!(vec, buf[1..2]);
     }
 
     #[test]
@@ -385,8 +435,14 @@ mod tests {
         my_enum
             .write_to_be_bytes(&mut buf[1..3])
             .expect("To byte conversion of u8 failed");
+        assert_eq!(my_enum.size(), 2);
+        assert_eq!(my_enum.pfc(), 16);
         assert_eq!(buf[1], 0x1f);
         assert_eq!(buf[2], 0x2f);
+        assert_eq!(my_enum.value(), 0x1f2f);
+        assert_eq!(my_enum.value_typed(), 0x1f2f);
+        let vec = my_enum.to_vec();
+        assert_eq!(vec, buf[1..3]);
     }
 
     #[test]
@@ -397,9 +453,9 @@ mod tests {
         assert!(res.is_err());
         let error = res.unwrap_err();
         match error {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.expected, 2);
-                assert_eq!(missmatch.found, 1);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(expected, 2);
+                assert_eq!(found, 1);
             }
             _ => {
                 panic!("Unexpected error {:?}", error);
@@ -418,6 +474,10 @@ mod tests {
         assert_eq!(buf[2], 0x2f);
         assert_eq!(buf[3], 0x3f);
         assert_eq!(buf[4], 0x4f);
+        assert_eq!(my_enum.value(), 0x1f2f3f4f);
+        assert_eq!(my_enum.value_typed(), 0x1f2f3f4f);
+        let vec = my_enum.to_vec();
+        assert_eq!(vec, buf[1..5]);
     }
 
     #[test]
@@ -428,13 +488,106 @@ mod tests {
         assert!(res.is_err());
         let error = res.unwrap_err();
         match error {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.expected, 4);
-                assert_eq!(missmatch.found, 3);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(expected, 4);
+                assert_eq!(found, 3);
             }
             _ => {
                 panic!("Unexpected error {:?}", error);
             }
         }
     }
+
+    #[test]
+    fn test_enum_u64() {
+        let mut buf = [0; 8];
+        let my_enum = EcssEnumU64::new(0x1f2f3f4f5f);
+        my_enum
+            .write_to_be_bytes(&mut buf)
+            .expect("To byte conversion of u64 failed");
+        assert_eq!(buf[3], 0x1f);
+        assert_eq!(buf[4], 0x2f);
+        assert_eq!(buf[5], 0x3f);
+        assert_eq!(buf[6], 0x4f);
+        assert_eq!(buf[7], 0x5f);
+        assert_eq!(my_enum.value(), 0x1f2f3f4f5f);
+        assert_eq!(my_enum.value_typed(), 0x1f2f3f4f5f);
+        assert_eq!(u64::from_be_bytes(buf), 0x1f2f3f4f5f);
+        let vec = my_enum.to_vec();
+        assert_eq!(vec, buf);
+    }
+
+    #[test]
+    fn test_pus_error_display() {
+        let unsupport_version = PusError::VersionNotSupported(super::PusVersion::EsaPus);
+        let write_str = unsupport_version.to_string();
+        assert_eq!(write_str, "PUS version EsaPus not supported")
+    }
+
+    #[test]
+    fn test_service_id_from_u8() {
+        let verification_id_raw = 1;
+        let verification_id = PusServiceId::try_from(verification_id_raw).unwrap();
+        assert_eq!(verification_id, PusServiceId::Verification);
+    }
+
+    #[test]
+    fn test_ptc_from_u8() {
+        let ptc_raw = Ptc::AbsoluteTime as u8;
+        let ptc = Ptc::try_from(ptc_raw).unwrap();
+        assert_eq!(ptc, Ptc::AbsoluteTime);
+    }
+
+    #[test]
+    fn test_unsigned_pfc_from_u8() {
+        let pfc_raw = PfcUnsigned::OneByte as u8;
+        let pfc = PfcUnsigned::try_from(pfc_raw).unwrap();
+        assert_eq!(pfc, PfcUnsigned::OneByte);
+    }
+
+    #[test]
+    fn test_real_pfc_from_u8() {
+        let pfc_raw = PfcReal::Double as u8;
+        let pfc = PfcReal::try_from(pfc_raw).unwrap();
+        assert_eq!(pfc, PfcReal::Double);
+    }
+
+    #[test]
+    fn test_pus_error_eq_impl() {
+        assert_eq!(
+            PusError::VersionNotSupported(PusVersion::EsaPus),
+            PusError::VersionNotSupported(PusVersion::EsaPus)
+        );
+    }
+
+    #[test]
+    fn test_pus_error_clonable() {
+        let pus_error = PusError::ChecksumFailure(0x0101);
+        let cloned = pus_error;
+        assert_eq!(pus_error, cloned);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_pus_service_id() {
+        generic_serde_test(PusServiceId::Verification);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_ptc() {
+        generic_serde_test(Ptc::AbsoluteTime);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_pfc_unsigned() {
+        generic_serde_test(PfcUnsigned::EightBytes);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_pfc_real() {
+        generic_serde_test(PfcReal::Double);
+    }
 }

src/ecss/scheduling.rs

@@ -76,6 +76,8 @@ pub enum TimeWindowType {
 #[cfg(test)]
 mod tests {
     use super::*;
+    #[cfg(feature = "serde")]
+    use crate::tests::generic_serde_test;
 
     #[test]
     fn test_bool_conv_0() {
@@ -102,4 +104,22 @@ mod tests {
         let subservice: Subservice = 22u8.try_into().unwrap();
         assert_eq!(subservice, Subservice::TcCreateScheduleGroup);
     }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_subservice_id() {
+        generic_serde_test(Subservice::TcEnableScheduling);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_sched_status() {
+        generic_serde_test(SchedStatus::Enabled);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serde_time_window_type() {
+        generic_serde_test(TimeWindowType::SelectAll);
+    }
 }

src/ecss/tc.rs

@@ -5,13 +5,13 @@
 //!
 //! ```rust
 //! use spacepackets::{CcsdsPacket, SpHeader};
-//! use spacepackets::ecss::{PusPacket, SerializablePusPacket};
+//! use spacepackets::ecss::{PusPacket, WritablePusPacket};
 //! use spacepackets::ecss::tc::{PusTcCreator, PusTcReader, PusTcSecondaryHeader};
 //!
 //! // Create a ping telecommand with no user application data
 //! let mut sph = SpHeader::tc_unseg(0x02, 0x34, 0).unwrap();
 //! let tc_header = PusTcSecondaryHeader::new_simple(17, 1);
-//! let pus_tc = PusTcCreator::new(&mut sph, tc_header, None, true);
+//! let pus_tc = PusTcCreator::new_no_app_data(&mut sph, tc_header, true);
 //! println!("{:?}", pus_tc);
 //! assert_eq!(pus_tc.service(), 17);
 //! assert_eq!(pus_tc.subservice(), 1);
@@ -34,14 +34,13 @@
 use crate::ecss::{
     ccsds_impl, crc_from_raw_data, sp_header_impls, user_data_from_raw,
     verify_crc16_ccitt_false_from_raw_to_pus_error, CrcType, PusError, PusPacket, PusVersion,
-    SerializablePusPacket,
-};
-use crate::{
-    ByteConversionError, CcsdsPacket, PacketType, SequenceFlags, SizeMissmatch, CCSDS_HEADER_LEN,
+    WritablePusPacket,
 };
+use crate::{ByteConversionError, CcsdsPacket, PacketType, SequenceFlags, CCSDS_HEADER_LEN};
 use crate::{SpHeader, CRC_CCITT_FALSE};
 use core::mem::size_of;
 use delegate::delegate;
+use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 use zerocopy::AsBytes;
@@ -60,7 +59,9 @@ const PUS_VERSION: PusVersion = PusVersion::PusC;
 /// Marker trait for PUS telecommand structures.
 pub trait IsPusTelecommand {}
 
-#[derive(Copy, Clone, PartialEq, Debug)]
+#[derive(Debug, Eq, PartialEq, Copy, Clone, IntoPrimitive, TryFromPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
 enum AckOpts {
     Acceptance = 0b1000,
     Start = 0b0100,
@@ -84,9 +85,9 @@ pub trait GenericPusTcSecondaryHeader {
 pub mod zc {
     use crate::ecss::tc::GenericPusTcSecondaryHeader;
     use crate::ecss::{PusError, PusVersion};
-    use zerocopy::{AsBytes, FromBytes, NetworkEndian, Unaligned, U16};
+    use zerocopy::{AsBytes, FromBytes, FromZeroes, NetworkEndian, Unaligned, U16};
 
-    #[derive(FromBytes, AsBytes, Unaligned)]
+    #[derive(FromZeroes, FromBytes, AsBytes, Unaligned)]
     #[repr(C)]
     pub struct PusTcSecondaryHeader {
         version_ack: u8,
@@ -218,14 +219,12 @@ pub mod legacy_tc {
     };
     use crate::ecss::{
         ccsds_impl, crc_from_raw_data, crc_procedure, sp_header_impls,
-        verify_crc16_ccitt_false_from_raw_to_pus_error, PusError, PusPacket, SerializablePusPacket,
+        verify_crc16_ccitt_false_from_raw_to_pus_error, PusError, PusPacket, WritablePusPacket,
         CCSDS_HEADER_LEN,
     };
     use crate::ecss::{user_data_from_raw, PusVersion};
     use crate::SequenceFlags;
-    use crate::{
-        ByteConversionError, CcsdsPacket, PacketType, SizeMissmatch, SpHeader, CRC_CCITT_FALSE,
-    };
+    use crate::{ByteConversionError, CcsdsPacket, PacketType, SpHeader, CRC_CCITT_FALSE};
     use core::mem::size_of;
     use delegate::delegate;
     use zerocopy::AsBytes;
@@ -351,7 +350,7 @@ pub mod legacy_tc {
         /// is set correctly.
         pub fn update_ccsds_data_len(&mut self) {
             self.sp_header.data_len =
-                self.len_packed() as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
+                self.len_written() as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
         }
 
         /// This function should be called before the TC packet is serialized if
@@ -409,14 +408,22 @@ pub mod legacy_tc {
         pub fn from_bytes(slice: &'raw_data [u8]) -> Result<(Self, usize), PusError> {
             let raw_data_len = slice.len();
             if raw_data_len < PUS_TC_MIN_LEN_WITHOUT_APP_DATA {
-                return Err(PusError::RawDataTooShort(raw_data_len));
+                return Err(ByteConversionError::FromSliceTooSmall {
+                    found: raw_data_len,
+                    expected: PUS_TC_MIN_LEN_WITHOUT_APP_DATA,
+                }
+                .into());
             }
             let mut current_idx = 0;
             let (sp_header, _) = SpHeader::from_be_bytes(&slice[0..CCSDS_HEADER_LEN])?;
             current_idx += CCSDS_HEADER_LEN;
             let total_len = sp_header.total_len();
             if raw_data_len < total_len || total_len < PUS_TC_MIN_LEN_WITHOUT_APP_DATA {
-                return Err(PusError::RawDataTooShort(raw_data_len));
+                return Err(ByteConversionError::FromSliceTooSmall {
+                    found: raw_data_len,
+                    expected: total_len,
+                }
+                .into());
             }
             let sec_header = zc::PusTcSecondaryHeader::from_bytes(
                 &slice[current_idx..current_idx + PUC_TC_SECONDARY_HEADER_LEN],
@@ -428,7 +435,7 @@ pub mod legacy_tc {
                 sp_header,
                 sec_header: PusTcSecondaryHeader::try_from(sec_header).unwrap(),
                 raw_data: Some(raw_data),
-                app_data: user_data_from_raw(current_idx, total_len, raw_data_len, slice)?,
+                app_data: user_data_from_raw(current_idx, total_len, slice)?,
                 calc_crc_on_serialization: false,
                 crc16: Some(crc_from_raw_data(raw_data)?),
             };
@@ -451,8 +458,8 @@ pub mod legacy_tc {
         }
     }
 
-    impl SerializablePusPacket for PusTc<'_> {
-        fn len_packed(&self) -> usize {
+    impl WritablePusPacket for PusTc<'_> {
+        fn len_written(&self) -> usize {
             PUS_TC_MIN_LEN_WITHOUT_APP_DATA + self.app_data.len()
         }
 
@@ -460,12 +467,12 @@ pub mod legacy_tc {
         fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
             let mut curr_idx = 0;
             let tc_header_len = size_of::<zc::PusTcSecondaryHeader>();
-            let total_size = self.len_packed();
+            let total_size = self.len_written();
             if total_size > slice.len() {
-                return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                return Err(ByteConversionError::ToSliceTooSmall {
                     found: slice.len(),
                     expected: total_size,
-                })
+                }
                 .into());
             }
             self.sp_header.write_to_be_bytes(slice)?;
@@ -564,14 +571,14 @@ impl<'raw_data> PusTcCreator<'raw_data> {
     pub fn new(
         sp_header: &mut SpHeader,
         sec_header: PusTcSecondaryHeader,
-        app_data: Option<&'raw_data [u8]>,
+        app_data: &'raw_data [u8],
         set_ccsds_len: bool,
     ) -> Self {
         sp_header.set_packet_type(PacketType::Tc);
         sp_header.set_sec_header_flag();
         let mut pus_tc = Self {
             sp_header: *sp_header,
-            app_data: app_data.unwrap_or(&[]),
+            app_data,
             sec_header,
         };
         if set_ccsds_len {
@@ -592,11 +599,19 @@ impl<'raw_data> PusTcCreator<'raw_data> {
         Self::new(
             sph,
             PusTcSecondaryHeader::new(service, subservice, ACK_ALL, 0),
-            app_data,
+            app_data.unwrap_or(&[]),
             set_ccsds_len,
         )
     }
 
+    pub fn new_no_app_data(
+        sp_header: &mut SpHeader,
+        sec_header: PusTcSecondaryHeader,
+        set_ccsds_len: bool,
+    ) -> Self {
+        Self::new(sp_header, sec_header, &[], set_ccsds_len)
+    }
+
     pub fn sp_header(&self) -> &SpHeader {
         &self.sp_header
     }
@@ -623,7 +638,7 @@ impl<'raw_data> PusTcCreator<'raw_data> {
     /// is set correctly.
     pub fn update_ccsds_data_len(&mut self) {
         self.sp_header.data_len =
-            self.len_packed() as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
+            self.len_written() as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
     }
 
     /// This function should be called before the TC packet is serialized if
@@ -657,8 +672,8 @@ impl<'raw_data> PusTcCreator<'raw_data> {
     }
 }
 
-impl SerializablePusPacket for PusTcCreator<'_> {
-    fn len_packed(&self) -> usize {
+impl WritablePusPacket for PusTcCreator<'_> {
+    fn len_written(&self) -> usize {
         PUS_TC_MIN_LEN_WITHOUT_APP_DATA + self.app_data.len()
     }
 
@@ -666,12 +681,12 @@ impl SerializablePusPacket for PusTcCreator<'_> {
     fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
         let mut curr_idx = 0;
         let tc_header_len = size_of::<zc::PusTcSecondaryHeader>();
-        let total_size = self.len_packed();
+        let total_size = self.len_written();
         if total_size > slice.len() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: slice.len(),
                 expected: total_size,
-            })
+            }
             .into());
         }
         self.sp_header.write_to_be_bytes(slice)?;
@@ -752,14 +767,29 @@ impl<'raw_data> PusTcReader<'raw_data> {
     pub fn new(slice: &'raw_data [u8]) -> Result<(Self, usize), PusError> {
         let raw_data_len = slice.len();
         if raw_data_len < PUS_TC_MIN_LEN_WITHOUT_APP_DATA {
-            return Err(PusError::RawDataTooShort(raw_data_len));
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: raw_data_len,
+                expected: PUS_TC_MIN_LEN_WITHOUT_APP_DATA,
+            }
+            .into());
         }
         let mut current_idx = 0;
         let (sp_header, _) = SpHeader::from_be_bytes(&slice[0..CCSDS_HEADER_LEN])?;
         current_idx += CCSDS_HEADER_LEN;
         let total_len = sp_header.total_len();
-        if raw_data_len < total_len || total_len < PUS_TC_MIN_LEN_WITHOUT_APP_DATA {
-            return Err(PusError::RawDataTooShort(raw_data_len));
+        if raw_data_len < total_len {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: raw_data_len,
+                expected: total_len,
+            }
+            .into());
+        }
+        if total_len < PUS_TC_MIN_LEN_WITHOUT_APP_DATA {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: total_len,
+                expected: PUS_TC_MIN_LEN_WITHOUT_APP_DATA,
+            }
+            .into());
         }
         let sec_header = zc::PusTcSecondaryHeader::from_bytes(
             &slice[current_idx..current_idx + PUC_TC_SECONDARY_HEADER_LEN],
@@ -771,7 +801,7 @@ impl<'raw_data> PusTcReader<'raw_data> {
             sp_header,
             sec_header: PusTcSecondaryHeader::try_from(sec_header).unwrap(),
             raw_data,
-            app_data: user_data_from_raw(current_idx, total_len, raw_data_len, slice)?,
+            app_data: user_data_from_raw(current_idx, total_len, slice)?,
             crc16: crc_from_raw_data(raw_data)?,
         };
         verify_crc16_ccitt_false_from_raw_to_pus_error(raw_data, pus_tc.crc16)?;
@@ -851,19 +881,22 @@ impl PartialEq<PusTcReader<'_>> for PusTcCreator<'_> {
 
 #[cfg(all(test, feature = "std"))]
 mod tests {
-    use crate::ecss::tc::{
-        GenericPusTcSecondaryHeader, PusTcCreator, PusTcReader, PusTcSecondaryHeader, ACK_ALL,
-    };
+    use std::error::Error;
+
+    use super::*;
     use crate::ecss::PusVersion::PusC;
-    use crate::ecss::{PusError, PusPacket, SerializablePusPacket};
+    use crate::ecss::{PusError, PusPacket, WritablePusPacket};
     use crate::{ByteConversionError, SpHeader};
     use crate::{CcsdsPacket, SequenceFlags};
+    use alloc::string::ToString;
     use alloc::vec::Vec;
+    #[cfg(feature = "serde")]
+    use postcard::{from_bytes, to_allocvec};
 
     fn base_ping_tc_full_ctor() -> PusTcCreator<'static> {
         let mut sph = SpHeader::tc_unseg(0x02, 0x34, 0).unwrap();
         let tc_header = PusTcSecondaryHeader::new_simple(17, 1);
-        PusTcCreator::new(&mut sph, tc_header, None, true)
+        PusTcCreator::new_no_app_data(&mut sph, tc_header, true)
     }
 
     fn base_ping_tc_simple_ctor() -> PusTcCreator<'static> {
@@ -890,6 +923,10 @@ mod tests {
             .write_to_bytes(test_buf.as_mut_slice())
             .expect("Error writing TC to buffer");
         assert_eq!(size, 13);
+        assert_eq!(
+            pus_tc.crc16().unwrap(),
+            u16::from_be_bytes(test_buf[size - 2..size].try_into().unwrap())
+        );
     }
 
     #[test]
@@ -909,6 +946,20 @@ mod tests {
         verify_crc_no_app_data(&test_buf);
     }
 
+    #[test]
+    fn test_writing_into_vec() {
+        let pus_tc = base_ping_tc_simple_ctor();
+        let tc_vec = pus_tc.to_vec().expect("Error writing TC to buffer");
+        assert_eq!(tc_vec.len(), 13);
+        let (tc_from_raw, size) = PusTcReader::new(tc_vec.as_slice())
+            .expect("Creating PUS TC struct from raw buffer failed");
+        assert_eq!(size, 13);
+        verify_test_tc_with_reader(&tc_from_raw, false, 13);
+        assert!(tc_from_raw.user_data().is_empty());
+        verify_test_tc_raw(&tc_vec);
+        verify_crc_no_app_data(&tc_vec);
+    }
+
     #[test]
     fn test_update_func() {
         let mut sph = SpHeader::tc_unseg(0x02, 0x34, 0).unwrap();
@@ -930,11 +981,31 @@ mod tests {
         assert_eq!(size, 16);
         verify_test_tc_with_reader(&tc_from_raw, true, 16);
         let user_data = tc_from_raw.user_data();
+        assert_eq!(tc_from_raw.user_data(), tc_from_raw.app_data());
+        assert_eq!(tc_from_raw.raw_data(), &test_buf[..size]);
+        assert_eq!(
+            tc_from_raw.crc16().unwrap(),
+            u16::from_be_bytes(test_buf[size - 2..size].try_into().unwrap())
+        );
         assert_eq!(user_data[0], 1);
         assert_eq!(user_data[1], 2);
         assert_eq!(user_data[2], 3);
     }
 
+    #[test]
+    fn test_reader_eq() {
+        let pus_tc = base_ping_tc_simple_ctor_with_app_data(&[1, 2, 3]);
+        let mut test_buf: [u8; 32] = [0; 32];
+        pus_tc
+            .write_to_bytes(test_buf.as_mut_slice())
+            .expect("Error writing TC to buffer");
+        let (tc_from_raw_0, _) =
+            PusTcReader::new(&test_buf).expect("Creating PUS TC struct from raw buffer failed");
+        let (tc_from_raw_1, _) =
+            PusTcReader::new(&test_buf).expect("Creating PUS TC struct from raw buffer failed");
+        assert_eq!(tc_from_raw_0, tc_from_raw_1);
+    }
+
     #[test]
     fn test_vec_ser_deser() {
         let pus_tc = base_ping_tc_simple_ctor();
@@ -955,10 +1026,19 @@ mod tests {
             .write_to_bytes(test_buf.as_mut_slice())
             .expect("Error writing TC to buffer");
         test_buf[12] = 0;
+        test_buf[11] = 0;
         let res = PusTcReader::new(&test_buf);
         assert!(res.is_err());
         let err = res.unwrap_err();
-        assert!(matches!(err, PusError::IncorrectCrc { .. }));
+        if let PusError::ChecksumFailure(crc) = err {
+            assert_eq!(crc, 0);
+            assert_eq!(
+                err.to_string(),
+                "checksum verification for crc16 0x0000 failed"
+            );
+        } else {
+            panic!("unexpected error {err}");
+        }
     }
 
     #[test]
@@ -994,15 +1074,21 @@ mod tests {
         let res = pus_tc.write_to_bytes(test_buf.as_mut_slice());
         assert!(res.is_err());
         let err = res.unwrap_err();
-        match err {
-            PusError::ByteConversion(err) => match err {
-                ByteConversionError::ToSliceTooSmall(missmatch) => {
-                    assert_eq!(missmatch.expected, pus_tc.len_packed());
-                    assert_eq!(missmatch.found, 12);
+        if let PusError::ByteConversion(e) = err {
+            assert_eq!(
+                e,
+                ByteConversionError::ToSliceTooSmall {
+                    found: 12,
+                    expected: 13
                 }
-                _ => panic!("Unexpected error"),
-            },
-            _ => panic!("Unexpected error"),
+            );
+            assert_eq!(
+                err.to_string(),
+                "pus error: target slice with size 12 is too small, expected size of at least 13"
+            );
+            assert_eq!(err.source().unwrap().to_string(), e.to_string());
+        } else {
+            panic!("unexpected error {err}");
         }
     }
 
@@ -1071,13 +1157,20 @@ mod tests {
 
     fn verify_test_tc_generic(tc: &(impl CcsdsPacket + PusPacket + GenericPusTcSecondaryHeader)) {
         assert_eq!(PusPacket::service(tc), 17);
+        assert_eq!(GenericPusTcSecondaryHeader::service(tc), 17);
         assert_eq!(PusPacket::subservice(tc), 1);
+        assert_eq!(GenericPusTcSecondaryHeader::subservice(tc), 1);
         assert!(tc.sec_header_flag());
         assert_eq!(PusPacket::pus_version(tc), PusC);
         assert_eq!(tc.seq_count(), 0x34);
         assert_eq!(tc.source_id(), 0);
         assert_eq!(tc.apid(), 0x02);
         assert_eq!(tc.ack_flags(), ACK_ALL);
+        assert_eq!(PusPacket::pus_version(tc), PusVersion::PusC);
+        assert_eq!(
+            GenericPusTcSecondaryHeader::pus_version(tc),
+            PusVersion::PusC
+        );
     }
     fn verify_test_tc_raw(slice: &impl AsRef<[u8]>) {
         // Reference comparison implementation:
@@ -1129,4 +1222,59 @@ mod tests {
         assert_eq!(pus_tc, PusTcReader::new(&buf).unwrap().0);
         assert_eq!(PusTcReader::new(&buf).unwrap().0, pus_tc);
     }
+
+    #[test]
+    fn test_ack_opts_from_raw() {
+        let ack_opts_raw = AckOpts::Start as u8;
+        let ack_opts = AckOpts::try_from(ack_opts_raw).unwrap();
+        assert_eq!(ack_opts, AckOpts::Start);
+    }
+
+    #[test]
+    fn test_reader_buf_too_small() {
+        let app_data = &[1, 2, 3, 4];
+        let pus_tc = base_ping_tc_simple_ctor_with_app_data(app_data);
+        let mut buf = [0; 32];
+        let written_len = pus_tc.write_to_bytes(&mut buf).unwrap();
+        let error = PusTcReader::new(&buf[0..PUS_TC_MIN_LEN_WITHOUT_APP_DATA + 1]);
+        assert!(error.is_err());
+        let error = error.unwrap_err();
+        if let PusError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+            found,
+            expected,
+        }) = error
+        {
+            assert_eq!(found, PUS_TC_MIN_LEN_WITHOUT_APP_DATA + 1);
+            assert_eq!(expected, written_len);
+        } else {
+            panic!("unexpected error {error}")
+        }
+    }
+
+    #[test]
+    fn test_reader_input_too_small() {
+        let buf: [u8; 5] = [0; 5];
+        let error = PusTcReader::new(&buf);
+        assert!(error.is_err());
+        let error = error.unwrap_err();
+        if let PusError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+            found,
+            expected,
+        }) = error
+        {
+            assert_eq!(found, 5);
+            assert_eq!(expected, PUS_TC_MIN_LEN_WITHOUT_APP_DATA);
+        } else {
+            panic!("unexpected error {error}")
+        }
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serialization_tc_serde() {
+        let pus_tc = base_ping_tc_simple_ctor();
+        let output = to_allocvec(&pus_tc).unwrap();
+        let output_converted_back: PusTcCreator = from_bytes(&output).unwrap();
+        assert_eq!(output_converted_back, pus_tc);
+    }
 }

src/ecss/tm.rs

@@ -3,11 +3,11 @@
 use crate::ecss::{
     calc_pus_crc16, ccsds_impl, crc_from_raw_data, sp_header_impls, user_data_from_raw,
     verify_crc16_ccitt_false_from_raw_to_pus_error, CrcType, PusError, PusPacket, PusVersion,
-    SerializablePusPacket,
+    WritablePusPacket,
 };
 use crate::{
-    ByteConversionError, CcsdsPacket, PacketType, SequenceFlags, SizeMissmatch, SpHeader,
-    CCSDS_HEADER_LEN, CRC_CCITT_FALSE, MAX_APID, MAX_SEQ_COUNT,
+    ByteConversionError, CcsdsPacket, PacketType, SequenceFlags, SpHeader, CCSDS_HEADER_LEN,
+    CRC_CCITT_FALSE, MAX_APID, MAX_SEQ_COUNT,
 };
 use core::mem::size_of;
 #[cfg(feature = "serde")]
@@ -21,12 +21,14 @@ use delegate::delegate;
 use crate::time::{TimeWriter, TimestampError};
 pub use legacy_tm::*;
 
+use self::zc::PusTmSecHeaderWithoutTimestamp;
+
 pub trait IsPusTelemetry {}
 
 /// Length without timestamp
-pub const PUC_TM_MIN_SEC_HEADER_LEN: usize = 7;
+pub const PUS_TM_MIN_SEC_HEADER_LEN: usize = 7;
 pub const PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA: usize =
-    CCSDS_HEADER_LEN + PUC_TM_MIN_SEC_HEADER_LEN + size_of::<CrcType>();
+    CCSDS_HEADER_LEN + PUS_TM_MIN_SEC_HEADER_LEN + size_of::<CrcType>();
 
 pub trait GenericPusTmSecondaryHeader {
     fn pus_version(&self) -> PusVersion;
@@ -40,9 +42,9 @@ pub trait GenericPusTmSecondaryHeader {
 pub mod zc {
     use super::GenericPusTmSecondaryHeader;
     use crate::ecss::{PusError, PusVersion};
-    use zerocopy::{AsBytes, FromBytes, NetworkEndian, Unaligned, U16};
+    use zerocopy::{AsBytes, FromBytes, FromZeroes, NetworkEndian, Unaligned, U16};
 
-    #[derive(FromBytes, AsBytes, Unaligned)]
+    #[derive(FromBytes, FromZeroes, AsBytes, Unaligned)]
     #[repr(C)]
     pub struct PusTmSecHeaderWithoutTimestamp {
         pus_version_and_sc_time_ref_status: u8,
@@ -198,18 +200,16 @@ impl<'slice> TryFrom<zc::PusTmSecHeader<'slice>> for PusTmSecondaryHeader<'slice
 pub mod legacy_tm {
     use crate::ecss::tm::{
         zc, GenericPusTmSecondaryHeader, IsPusTelemetry, PusTmSecondaryHeader,
-        PUC_TM_MIN_SEC_HEADER_LEN, PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA,
+        PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA, PUS_TM_MIN_SEC_HEADER_LEN,
     };
     use crate::ecss::PusVersion;
     use crate::ecss::{
         ccsds_impl, crc_from_raw_data, crc_procedure, sp_header_impls, user_data_from_raw,
-        verify_crc16_ccitt_false_from_raw_to_pus_error, PusError, PusPacket, SerializablePusPacket,
+        verify_crc16_ccitt_false_from_raw_to_pus_error, PusError, PusPacket, WritablePusPacket,
         CCSDS_HEADER_LEN,
     };
     use crate::SequenceFlags;
-    use crate::{
-        ByteConversionError, CcsdsPacket, PacketType, SizeMissmatch, SpHeader, CRC_CCITT_FALSE,
-    };
+    use crate::{ByteConversionError, CcsdsPacket, PacketType, SpHeader, CRC_CCITT_FALSE};
     use core::mem::size_of;
     use zerocopy::AsBytes;
 
@@ -316,7 +316,7 @@ pub mod legacy_tm {
         /// is set correctly
         pub fn update_ccsds_data_len(&mut self) {
             self.sp_header.data_len =
-                self.len_packed() as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
+                self.len_written() as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
         }
 
         /// This function should be called before the TM packet is serialized if
@@ -383,20 +383,35 @@ pub mod legacy_tm {
         ) -> Result<(Self, usize), PusError> {
             let raw_data_len = slice.len();
             if raw_data_len < PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA {
-                return Err(PusError::RawDataTooShort(raw_data_len));
+                return Err(ByteConversionError::FromSliceTooSmall {
+                    found: raw_data_len,
+                    expected: PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA,
+                }
+                .into());
             }
             let mut current_idx = 0;
             let (sp_header, _) = SpHeader::from_be_bytes(&slice[0..CCSDS_HEADER_LEN])?;
             current_idx += 6;
             let total_len = sp_header.total_len();
-            if raw_data_len < total_len || total_len < PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA {
-                return Err(PusError::RawDataTooShort(raw_data_len));
+            if raw_data_len < total_len {
+                return Err(ByteConversionError::FromSliceTooSmall {
+                    found: raw_data_len,
+                    expected: PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA,
+                }
+                .into());
+            }
+            if total_len < PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA {
+                return Err(ByteConversionError::FromSliceTooSmall {
+                    found: total_len,
+                    expected: PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA,
+                }
+                .into());
             }
             let sec_header_zc = zc::PusTmSecHeaderWithoutTimestamp::from_bytes(
-                &slice[current_idx..current_idx + PUC_TM_MIN_SEC_HEADER_LEN],
+                &slice[current_idx..current_idx + PUS_TM_MIN_SEC_HEADER_LEN],
             )
             .ok_or(ByteConversionError::ZeroCopyFromError)?;
-            current_idx += PUC_TM_MIN_SEC_HEADER_LEN;
+            current_idx += PUS_TM_MIN_SEC_HEADER_LEN;
             let zc_sec_header_wrapper = zc::PusTmSecHeader {
                 zc_header: sec_header_zc,
                 timestamp: &slice[current_idx..current_idx + timestamp_len],
@@ -407,7 +422,7 @@ pub mod legacy_tm {
                 sp_header,
                 sec_header: PusTmSecondaryHeader::try_from(zc_sec_header_wrapper).unwrap(),
                 raw_data: Some(&slice[0..total_len]),
-                source_data: user_data_from_raw(current_idx, total_len, raw_data_len, slice)?,
+                source_data: user_data_from_raw(current_idx, total_len, slice)?,
                 calc_crc_on_serialization: false,
                 crc16: Some(crc_from_raw_data(raw_data)?),
             };
@@ -425,8 +440,8 @@ pub mod legacy_tm {
         }
     }
 
-    impl SerializablePusPacket for PusTm<'_> {
-        fn len_packed(&self) -> usize {
+    impl WritablePusPacket for PusTm<'_> {
+        fn len_written(&self) -> usize {
             PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA
                 + self.sec_header.timestamp.len()
                 + self.source_data.len()
@@ -434,12 +449,12 @@ pub mod legacy_tm {
         /// Write the raw PUS byte representation to a provided buffer.
         fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
             let mut curr_idx = 0;
-            let total_size = self.len_packed();
+            let total_size = self.len_written();
             if total_size > slice.len() {
-                return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                return Err(ByteConversionError::ToSliceTooSmall {
                     found: slice.len(),
                     expected: total_size,
-                })
+                }
                 .into());
             }
             self.sp_header
@@ -543,21 +558,21 @@ impl<'raw_data> PusTmCreator<'raw_data> {
     ///     automatically
     /// * `sec_header` - Information contained in the secondary header, including the service
     ///     and subservice type
-    /// * `app_data` - Custom application data
+    /// * `source_data` - Custom application data
     /// * `set_ccsds_len` - Can be used to automatically update the CCSDS space packet data length
     ///     field. If this is not set to true, [PusTm::update_ccsds_data_len] can be called to set
     ///     the correct value to this field manually
     pub fn new(
         sp_header: &mut SpHeader,
         sec_header: PusTmSecondaryHeader<'raw_data>,
-        source_data: Option<&'raw_data [u8]>,
+        source_data: &'raw_data [u8],
         set_ccsds_len: bool,
     ) -> Self {
         sp_header.set_packet_type(PacketType::Tm);
         sp_header.set_sec_header_flag();
         let mut pus_tm = Self {
             sp_header: *sp_header,
-            source_data: source_data.unwrap_or(&[]),
+            source_data,
             sec_header,
             calc_crc_on_serialization: true,
         };
@@ -579,8 +594,22 @@ impl<'raw_data> PusTmCreator<'raw_data> {
         let stamp_size = time_provider.write_to_bytes(stamp_buf)?;
         let sec_header =
             PusTmSecondaryHeader::new_simple(service, subservice, &stamp_buf[0..stamp_size]);
-        Ok(Self::new(sp_header, sec_header, source_data, set_ccsds_len))
+        Ok(Self::new(
+            sp_header,
+            sec_header,
+            source_data.unwrap_or(&[]),
+            set_ccsds_len,
+        ))
     }
+
+    pub fn new_no_source_data(
+        sp_header: &mut SpHeader,
+        sec_header: PusTmSecondaryHeader<'raw_data>,
+        set_ccsds_len: bool,
+    ) -> Self {
+        Self::new(sp_header, sec_header, &[], set_ccsds_len)
+    }
+
     pub fn timestamp(&self) -> &[u8] {
         self.sec_header.timestamp
     }
@@ -610,7 +639,7 @@ impl<'raw_data> PusTmCreator<'raw_data> {
     /// is set correctly
     pub fn update_ccsds_data_len(&mut self) {
         self.sp_header.data_len =
-            self.len_packed() as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
+            self.len_written() as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
     }
 
     /// This function should be called before the TM packet is serialized if
@@ -652,8 +681,8 @@ impl<'raw_data> PusTmCreator<'raw_data> {
     }
 }
 
-impl SerializablePusPacket for PusTmCreator<'_> {
-    fn len_packed(&self) -> usize {
+impl WritablePusPacket for PusTmCreator<'_> {
+    fn len_written(&self) -> usize {
         PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA
             + self.sec_header.timestamp.len()
             + self.source_data.len()
@@ -661,12 +690,12 @@ impl SerializablePusPacket for PusTmCreator<'_> {
     /// Write the raw PUS byte representation to a provided buffer.
     fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
         let mut curr_idx = 0;
-        let total_size = self.len_packed();
+        let total_size = self.len_written();
         if total_size > slice.len() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: slice.len(),
                 expected: total_size,
-            })
+            }
             .into());
         }
         self.sp_header
@@ -762,20 +791,35 @@ impl<'raw_data> PusTmReader<'raw_data> {
     pub fn new(slice: &'raw_data [u8], timestamp_len: usize) -> Result<(Self, usize), PusError> {
         let raw_data_len = slice.len();
         if raw_data_len < PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA {
-            return Err(PusError::RawDataTooShort(raw_data_len));
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: raw_data_len,
+                expected: PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA,
+            }
+            .into());
         }
         let mut current_idx = 0;
         let (sp_header, _) = SpHeader::from_be_bytes(&slice[0..CCSDS_HEADER_LEN])?;
         current_idx += 6;
         let total_len = sp_header.total_len();
-        if raw_data_len < total_len || total_len < PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA {
-            return Err(PusError::RawDataTooShort(raw_data_len));
+        if raw_data_len < total_len {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: raw_data_len,
+                expected: total_len,
+            }
+            .into());
+        }
+        if total_len < PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: total_len,
+                expected: PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA,
+            }
+            .into());
         }
         let sec_header_zc = zc::PusTmSecHeaderWithoutTimestamp::from_bytes(
-            &slice[current_idx..current_idx + PUC_TM_MIN_SEC_HEADER_LEN],
+            &slice[current_idx..current_idx + PUS_TM_MIN_SEC_HEADER_LEN],
         )
         .ok_or(ByteConversionError::ZeroCopyFromError)?;
-        current_idx += PUC_TM_MIN_SEC_HEADER_LEN;
+        current_idx += PUS_TM_MIN_SEC_HEADER_LEN;
         let zc_sec_header_wrapper = zc::PusTmSecHeader {
             zc_header: sec_header_zc,
             timestamp: &slice[current_idx..current_idx + timestamp_len],
@@ -786,7 +830,7 @@ impl<'raw_data> PusTmReader<'raw_data> {
             sp_header,
             sec_header: PusTmSecondaryHeader::try_from(zc_sec_header_wrapper).unwrap(),
             raw_data: &slice[0..total_len],
-            source_data: user_data_from_raw(current_idx, total_len, raw_data_len, slice)?,
+            source_data: user_data_from_raw(current_idx, total_len, slice)?,
             crc16: crc_from_raw_data(raw_data)?,
         };
         verify_crc16_ccitt_false_from_raw_to_pus_error(raw_data, pus_tm.crc16)?;
@@ -813,7 +857,10 @@ impl<'raw_data> PusTmReader<'raw_data> {
 
 impl PartialEq for PusTmReader<'_> {
     fn eq(&self, other: &Self) -> bool {
-        self.raw_data == other.raw_data
+        self.sec_header == other.sec_header
+            && self.source_data == other.source_data
+            && self.sp_header == other.sp_header
+            && self.crc16 == other.crc16
     }
 }
 
@@ -867,36 +914,40 @@ impl PartialEq<PusTmReader<'_>> for PusTmCreator<'_> {
 }
 
 /// This is a helper class to update certain fields in a raw PUS telemetry packet directly in place.
-/// This can be more efficient than creating a full [PusTm], modifying the fields and then writing
-/// it back to another buffer.
+/// This can be more efficient than creating a full [PusTmReader], modifying the fields and then
+/// writing it back to another buffer.
 ///
 /// Please note that the [Self::finish] method has to be called for the PUS TM CRC16 to be valid
 /// after changing fields of the TM packet. Furthermore, the constructor of this class will not
-/// do any checks except a length check to ensure that all relevant fields can be updated without
-/// a panic. If a full validity check of the PUS TM packet is required, it is recommended
-/// to construct a full [PusTm] object from the raw bytestream first.
+/// do any checks except basic length checks to ensure that all relevant fields can be updated and
+/// all methods can be called without a panic. If a full validity check of the PUS TM packet is
+/// required, it is recommended to construct a full [PusTmReader] object from the raw bytestream
+/// first.
 pub struct PusTmZeroCopyWriter<'raw> {
     raw_tm: &'raw mut [u8],
+    timestamp_len: usize,
 }
 
 impl<'raw> PusTmZeroCopyWriter<'raw> {
     /// This function will not do any other checks on the raw data other than a length check
-    /// for all internal fields which can be updated. It is the responsibility of the user to ensure
-    /// the raw slice contains a valid telemetry packet. The slice should have the exact length
-    /// of the telemetry packet for this class to work properly.
-    pub fn new(raw_tm: &'raw mut [u8]) -> Option<Self> {
-        if raw_tm.len() < 13 {
+    /// for all internal fields which can be updated.
+    ///
+    /// It is the responsibility of the user to ensure the raw slice contains a valid telemetry
+    /// packet.
+    pub fn new(raw_tm: &'raw mut [u8], timestamp_len: usize) -> Option<Self> {
+        let raw_tm_len = raw_tm.len();
+        if raw_tm_len < CCSDS_HEADER_LEN + PUS_TM_MIN_SEC_HEADER_LEN + timestamp_len {
             return None;
         }
-        Some(Self { raw_tm })
-    }
-
-    pub fn service(&self) -> u8 {
-        self.raw_tm[7]
-    }
-
-    pub fn subservice(&self) -> u8 {
-        self.raw_tm[8]
+        let sp_header = crate::zc::SpHeader::from_bytes(&raw_tm[0..CCSDS_HEADER_LEN]).unwrap();
+        if raw_tm_len < sp_header.total_len() {
+            return None;
+        }
+        let writer = Self {
+            raw_tm: &mut raw_tm[..sp_header.total_len()],
+            timestamp_len,
+        };
+        Some(writer)
     }
 
     /// Set the sequence count. Returns false and does not update the value if the passed value
@@ -922,6 +973,24 @@ impl<'raw> PusTmZeroCopyWriter<'raw> {
         self.raw_tm[11..13].copy_from_slice(&dest_id.to_be_bytes())
     }
 
+    /// Helper API to generate the space packet header portion of the PUS TM from the raw memory.
+    #[inline]
+    pub fn sp_header(&self) -> crate::zc::SpHeader {
+        // Valid minimum length of packet was checked before.
+        crate::zc::SpHeader::from_bytes(&self.raw_tm[0..CCSDS_HEADER_LEN]).unwrap()
+    }
+
+    /// Helper API to generate the portion of the secondary header without a timestamp from the
+    /// raw memory.
+    #[inline]
+    pub fn sec_header_without_timestamp(&self) -> PusTmSecHeaderWithoutTimestamp {
+        // Valid minimum length of packet was checked before.
+        PusTmSecHeaderWithoutTimestamp::from_bytes(
+            &self.raw_tm[CCSDS_HEADER_LEN..CCSDS_HEADER_LEN + PUS_TM_MIN_SEC_HEADER_LEN],
+        )
+        .unwrap()
+    }
+
     /// Set the sequence count. Returns false and does not update the value if the passed value
     /// exceeds [MAX_SEQ_COUNT].
     pub fn set_seq_count(&mut self, seq_count: u16) -> bool {
@@ -943,45 +1012,148 @@ impl<'raw> PusTmZeroCopyWriter<'raw> {
     }
 }
 
+impl CcsdsPacket for PusTmZeroCopyWriter<'_> {
+    #[inline]
+    fn ccsds_version(&self) -> u8 {
+        self.sp_header().ccsds_version()
+    }
+
+    #[inline]
+    fn packet_id(&self) -> crate::PacketId {
+        self.sp_header().packet_id()
+    }
+
+    #[inline]
+    fn psc(&self) -> crate::PacketSequenceCtrl {
+        self.sp_header().psc()
+    }
+
+    #[inline]
+    fn data_len(&self) -> u16 {
+        self.sp_header().data_len()
+    }
+}
+
+impl PusPacket for PusTmZeroCopyWriter<'_> {
+    #[inline]
+    fn pus_version(&self) -> PusVersion {
+        self.sec_header_without_timestamp().pus_version()
+    }
+
+    #[inline]
+    fn service(&self) -> u8 {
+        self.raw_tm[7]
+    }
+
+    #[inline]
+    fn subservice(&self) -> u8 {
+        self.raw_tm[8]
+    }
+
+    #[inline]
+    fn user_data(&self) -> &[u8] {
+        &self.raw_tm[CCSDS_HEADER_LEN + PUS_TM_MIN_SEC_HEADER_LEN + self.timestamp_len
+            ..self.sp_header().total_len() - 2]
+    }
+
+    #[inline]
+    fn crc16(&self) -> Option<u16> {
+        Some(u16::from_be_bytes(
+            self.raw_tm[self.sp_header().total_len() - 2..self.sp_header().total_len()]
+                .try_into()
+                .unwrap(),
+        ))
+    }
+}
+
+impl GenericPusTmSecondaryHeader for PusTmZeroCopyWriter<'_> {
+    delegate! {
+        to self.sec_header_without_timestamp() {
+            #[inline]
+            fn pus_version(&self) -> PusVersion;
+            #[inline]
+            fn sc_time_ref_status(&self) -> u8;
+            #[inline]
+            fn msg_counter(&self) -> u16;
+            #[inline]
+            fn dest_id(&self) -> u16;
+        }
+    }
+
+    #[inline]
+    fn service(&self) -> u8 {
+        PusPacket::service(self)
+    }
+
+    #[inline]
+    fn subservice(&self) -> u8 {
+        PusPacket::subservice(self)
+    }
+}
+
 #[cfg(test)]
 mod tests {
+    use alloc::string::ToString;
+
     use super::*;
     use crate::ecss::PusVersion::PusC;
+    use crate::time::cds::TimeProvider;
+    #[cfg(feature = "serde")]
+    use crate::time::CcsdsTimeProvider;
     use crate::SpHeader;
+    #[cfg(feature = "serde")]
+    use postcard::{from_bytes, to_allocvec};
+
+    const DUMMY_DATA: &[u8] = &[0, 1, 2];
 
     fn base_ping_reply_full_ctor(timestamp: &[u8]) -> PusTmCreator {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
-        let tm_header = PusTmSecondaryHeader::new_simple(17, 2, &timestamp);
-        PusTmCreator::new(&mut sph, tm_header, None, true)
+        let tm_header = PusTmSecondaryHeader::new_simple(17, 2, timestamp);
+        PusTmCreator::new_no_source_data(&mut sph, tm_header, true)
+    }
+    fn ping_reply_with_data(timestamp: &[u8]) -> PusTmCreator {
+        let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
+        let tm_header = PusTmSecondaryHeader::new_simple(17, 2, timestamp);
+        PusTmCreator::new(&mut sph, tm_header, DUMMY_DATA, true)
     }
 
     fn base_hk_reply<'a>(timestamp: &'a [u8], src_data: &'a [u8]) -> PusTmCreator<'a> {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
-        let tc_header = PusTmSecondaryHeader::new_simple(3, 5, &timestamp);
-        PusTmCreator::new(&mut sph, tc_header, Some(src_data), true)
+        let tc_header = PusTmSecondaryHeader::new_simple(3, 5, timestamp);
+        PusTmCreator::new(&mut sph, tc_header, src_data, true)
     }
 
     fn dummy_timestamp() -> &'static [u8] {
-        return &[0, 1, 2, 3, 4, 5, 6];
+        &[0, 1, 2, 3, 4, 5, 6]
     }
 
     #[test]
     fn test_basic() {
         let timestamp = dummy_timestamp();
-        let pus_tm = base_ping_reply_full_ctor(&timestamp);
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
         verify_ping_reply(&pus_tm, false, 22, dummy_timestamp());
     }
+    #[test]
+    fn test_basic_simple_api() {
+        let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
+        let time_provider = TimeProvider::new_with_u16_days(0, 0);
+        let mut stamp_buf: [u8; 8] = [0; 8];
+        let pus_tm =
+            PusTmCreator::new_simple(&mut sph, 17, 2, &time_provider, &mut stamp_buf, None, true)
+                .unwrap();
+        verify_ping_reply(&pus_tm, false, 22, &[64, 0, 0, 0, 0, 0, 0]);
+    }
 
     #[test]
     fn test_serialization_no_source_data() {
         let timestamp = dummy_timestamp();
-        let pus_tm = base_ping_reply_full_ctor(&timestamp);
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
         let mut buf: [u8; 32] = [0; 32];
         let ser_len = pus_tm
             .write_to_bytes(&mut buf)
             .expect("Serialization failed");
         assert_eq!(ser_len, 22);
-        verify_raw_ping_reply(&buf);
+        verify_raw_ping_reply(pus_tm.crc16().unwrap(), &buf);
     }
 
     #[test]
@@ -1001,7 +1173,7 @@ mod tests {
     #[test]
     fn test_setters() {
         let timestamp = dummy_timestamp();
-        let mut pus_tm = base_ping_reply_full_ctor(&timestamp);
+        let mut pus_tm = base_ping_reply_full_ctor(timestamp);
         pus_tm.set_sc_time_ref_status(0b1010);
         pus_tm.set_dest_id(0x7fff);
         pus_tm.set_msg_counter(0x1f1f);
@@ -1012,10 +1184,21 @@ mod tests {
         assert_eq!(pus_tm.apid(), 0x7ff);
     }
 
+    #[test]
+    fn test_write_into_vec() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let tm_vec = pus_tm.to_vec().expect("Serialization failed");
+        assert_eq!(tm_vec.len(), 22);
+        let (tm_deserialized, size) =
+            PusTmReader::new(tm_vec.as_slice(), 7).expect("Deserialization failed");
+        assert_eq!(tm_vec.len(), size);
+        verify_ping_reply_with_reader(&tm_deserialized, false, 22, dummy_timestamp());
+    }
     #[test]
     fn test_deserialization_no_source_data() {
         let timestamp = dummy_timestamp();
-        let pus_tm = base_ping_reply_full_ctor(&timestamp);
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
         let mut buf: [u8; 32] = [0; 32];
         let ser_len = pus_tm
             .write_to_bytes(&mut buf)
@@ -1023,14 +1206,39 @@ mod tests {
         assert_eq!(ser_len, 22);
         let (tm_deserialized, size) = PusTmReader::new(&buf, 7).expect("Deserialization failed");
         assert_eq!(ser_len, size);
+        assert_eq!(tm_deserialized.user_data(), tm_deserialized.source_data());
+        assert_eq!(tm_deserialized.raw_data(), &buf[..ser_len]);
+        assert_eq!(tm_deserialized.crc16().unwrap(), pus_tm.crc16().unwrap());
         verify_ping_reply_with_reader(&tm_deserialized, false, 22, dummy_timestamp());
     }
+    #[test]
+    fn test_deserialization_faulty_crc() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let mut buf: [u8; 32] = [0; 32];
+        let ser_len = pus_tm
+            .write_to_bytes(&mut buf)
+            .expect("Serialization failed");
+        assert_eq!(ser_len, 22);
+        buf[ser_len - 2] = 0;
+        buf[ser_len - 1] = 0;
+        let tm_error = PusTmReader::new(&buf, 7);
+        assert!(tm_error.is_err());
+        let tm_error = tm_error.unwrap_err();
+        if let PusError::ChecksumFailure(crc) = tm_error {
+            assert_eq!(crc, 0);
+            assert_eq!(
+                tm_error.to_string(),
+                "checksum verification for crc16 0x0000 failed"
+            );
+        }
+    }
 
     #[test]
     fn test_manual_field_update() {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
         let tc_header = PusTmSecondaryHeader::new_simple(17, 2, dummy_timestamp());
-        let mut tm = PusTmCreator::new(&mut sph, tc_header, None, false);
+        let mut tm = PusTmCreator::new_no_source_data(&mut sph, tc_header, false);
         tm.calc_crc_on_serialization = false;
         assert_eq!(tm.data_len(), 0x00);
         let mut buf: [u8; 32] = [0; 32];
@@ -1047,7 +1255,7 @@ mod tests {
     #[test]
     fn test_target_buf_too_small() {
         let timestamp = dummy_timestamp();
-        let pus_tm = base_ping_reply_full_ctor(&timestamp);
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
         let mut buf: [u8; 16] = [0; 16];
         let res = pus_tm.write_to_bytes(&mut buf);
         assert!(res.is_err());
@@ -1055,9 +1263,9 @@ mod tests {
         assert!(matches!(error, PusError::ByteConversion { .. }));
         match error {
             PusError::ByteConversion(err) => match err {
-                ByteConversionError::ToSliceTooSmall(size_missmatch) => {
-                    assert_eq!(size_missmatch.expected, 22);
-                    assert_eq!(size_missmatch.found, 16);
+                ByteConversionError::ToSliceTooSmall { found, expected } => {
+                    assert_eq!(expected, 22);
+                    assert_eq!(found, 16);
                 }
                 _ => panic!("Invalid PUS error {:?}", err),
             },
@@ -1071,12 +1279,12 @@ mod tests {
     #[cfg(feature = "alloc")]
     fn test_append_to_vec() {
         let timestamp = dummy_timestamp();
-        let pus_tm = base_ping_reply_full_ctor(&timestamp);
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
         let mut vec = Vec::new();
         let res = pus_tm.append_to_vec(&mut vec);
         assert!(res.is_ok());
         assert_eq!(res.unwrap(), 22);
-        verify_raw_ping_reply(vec.as_slice());
+        verify_raw_ping_reply(pus_tm.crc16().unwrap(), vec.as_slice());
     }
 
     #[test]
@@ -1092,7 +1300,7 @@ mod tests {
         assert_eq!(vec.len(), 26);
     }
 
-    fn verify_raw_ping_reply(buf: &[u8]) {
+    fn verify_raw_ping_reply(crc16: u16, buf: &[u8]) {
         // Secondary header is set -> 0b0000_1001 , APID occupies last bit of first byte
         assert_eq!(buf[0], 0x09);
         // Rest of APID 0x123
@@ -1115,9 +1323,10 @@ mod tests {
         assert_eq!(&buf[13..20], dummy_timestamp());
         let mut digest = CRC_CCITT_FALSE.digest();
         digest.update(&buf[0..20]);
-        let crc16 = digest.finalize();
+        let crc16_calced = digest.finalize();
         assert_eq!(((crc16 >> 8) & 0xff) as u8, buf[20]);
         assert_eq!((crc16 & 0xff) as u8, buf[21]);
+        assert_eq!(crc16, crc16_calced);
     }
 
     fn verify_ping_reply(
@@ -1126,8 +1335,9 @@ mod tests {
         exp_full_len: usize,
         exp_timestamp: &[u8],
     ) {
-        assert_eq!(tm.len_packed(), exp_full_len);
+        assert_eq!(tm.len_written(), exp_full_len);
         assert_eq!(tm.timestamp(), exp_timestamp);
+        assert_eq!(tm.source_data(), tm.user_data());
         verify_ping_reply_generic(tm, has_user_data, exp_full_len);
     }
 
@@ -1149,7 +1359,9 @@ mod tests {
     ) {
         assert!(tm.is_tm());
         assert_eq!(PusPacket::service(tm), 17);
+        assert_eq!(GenericPusTmSecondaryHeader::service(tm), 17);
         assert_eq!(PusPacket::subservice(tm), 2);
+        assert_eq!(GenericPusTmSecondaryHeader::subservice(tm), 2);
         assert!(tm.sec_header_flag());
         if has_user_data {
             assert!(!tm.user_data().is_empty());
@@ -1157,6 +1369,11 @@ mod tests {
         assert_eq!(PusPacket::pus_version(tm), PusC);
         assert_eq!(tm.apid(), 0x123);
         assert_eq!(tm.seq_count(), 0x234);
+        assert_eq!(PusPacket::pus_version(tm), PusVersion::PusC);
+        assert_eq!(
+            GenericPusTmSecondaryHeader::pus_version(tm),
+            PusVersion::PusC
+        );
         assert_eq!(tm.data_len(), exp_full_len as u16 - 7);
         assert_eq!(tm.dest_id(), 0x0000);
         assert_eq!(tm.msg_counter(), 0x0000);
@@ -1187,12 +1404,14 @@ mod tests {
         let tm_size = ping_tm
             .write_to_bytes(&mut buf)
             .expect("writing PUS ping TM failed");
-        let mut writer = PusTmZeroCopyWriter::new(&mut buf[..tm_size])
+        let mut writer = PusTmZeroCopyWriter::new(&mut buf[..tm_size], 7)
             .expect("Creating zero copy writer failed");
         writer.set_destination_id(55);
         writer.set_msg_count(100);
         writer.set_seq_count(MAX_SEQ_COUNT);
         writer.set_apid(MAX_APID);
+        assert!(!writer.set_apid(MAX_APID + 1));
+        assert!(!writer.set_apid(MAX_SEQ_COUNT + 1));
         writer.finish();
         // This performs all necessary checks, including the CRC check.
         let (tm_read_back, tm_size_read_back) =
@@ -1203,4 +1422,142 @@ mod tests {
         assert_eq!(tm_read_back.seq_count(), MAX_SEQ_COUNT);
         assert_eq!(tm_read_back.apid(), MAX_APID);
     }
+
+    #[test]
+    fn test_zero_copy_writer_ccsds_api() {
+        let ping_tm = base_ping_reply_full_ctor(dummy_timestamp());
+        let mut buf: [u8; 64] = [0; 64];
+        let tm_size = ping_tm
+            .write_to_bytes(&mut buf)
+            .expect("writing PUS ping TM failed");
+        let mut writer = PusTmZeroCopyWriter::new(&mut buf[..tm_size], 7)
+            .expect("Creating zero copy writer failed");
+        writer.set_destination_id(55);
+        writer.set_msg_count(100);
+        writer.set_seq_count(MAX_SEQ_COUNT);
+        writer.set_apid(MAX_APID);
+        assert_eq!(PusPacket::service(&writer), 17);
+        assert_eq!(PusPacket::subservice(&writer), 2);
+        assert_eq!(writer.apid(), MAX_APID);
+        assert_eq!(writer.seq_count(), MAX_SEQ_COUNT);
+    }
+
+    #[test]
+    fn test_zero_copy_pus_api() {
+        let ping_tm = ping_reply_with_data(dummy_timestamp());
+        let mut buf: [u8; 64] = [0; 64];
+        let tm_size = ping_tm
+            .write_to_bytes(&mut buf)
+            .expect("writing PUS ping TM failed");
+        let crc16_raw = u16::from_be_bytes(buf[tm_size - 2..tm_size].try_into().unwrap());
+        let mut writer = PusTmZeroCopyWriter::new(&mut buf[..tm_size], 7)
+            .expect("Creating zero copy writer failed");
+        writer.set_destination_id(55);
+        writer.set_msg_count(100);
+        writer.set_seq_count(MAX_SEQ_COUNT);
+        writer.set_apid(MAX_APID);
+        assert_eq!(PusPacket::service(&writer), 17);
+        assert_eq!(PusPacket::subservice(&writer), 2);
+        assert_eq!(writer.dest_id(), 55);
+        assert_eq!(writer.msg_counter(), 100);
+        assert_eq!(writer.sec_header_without_timestamp().dest_id(), 55);
+        assert_eq!(writer.sec_header_without_timestamp().msg_counter(), 100);
+        assert_eq!(writer.user_data(), DUMMY_DATA);
+        // Need to check crc16 before finish, because finish will update the CRC.
+        let crc16 = writer.crc16();
+        assert!(crc16.is_some());
+        assert_eq!(crc16.unwrap(), crc16_raw);
+        writer.finish();
+    }
+
+    #[test]
+    fn test_sec_header_without_stamp() {
+        let sec_header = PusTmSecondaryHeader::new_simple_no_timestamp(17, 1);
+        assert_eq!(sec_header.timestamp, &[]);
+    }
+
+    #[test]
+    fn test_reader_partial_eq() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let mut buf = [0; 32];
+        pus_tm.write_to_bytes(&mut buf).unwrap();
+        let (tm_0, _) = PusTmReader::new(&buf, timestamp.len()).unwrap();
+        let (tm_1, _) = PusTmReader::new(&buf, timestamp.len()).unwrap();
+        assert_eq!(tm_0, tm_1);
+    }
+    #[test]
+    fn test_reader_buf_too_small_2() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let mut buf = [0; 32];
+        let written = pus_tm.write_to_bytes(&mut buf).unwrap();
+        let tm_error = PusTmReader::new(
+            &buf[0..PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA + 1],
+            timestamp.len(),
+        );
+        assert!(tm_error.is_err());
+        let tm_error = tm_error.unwrap_err();
+        if let PusError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+            found,
+            expected,
+        }) = tm_error
+        {
+            assert_eq!(found, PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA + 1);
+            assert_eq!(expected, written);
+        } else {
+            panic!("unexpected error {tm_error}")
+        }
+    }
+    #[test]
+    fn test_reader_buf_too_small() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let mut buf = [0; 32];
+        pus_tm.write_to_bytes(&mut buf).unwrap();
+        let tm_error = PusTmReader::new(&buf[0..5], timestamp.len());
+        assert!(tm_error.is_err());
+        let tm_error = tm_error.unwrap_err();
+        if let PusError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+            found,
+            expected,
+        }) = tm_error
+        {
+            assert_eq!(found, 5);
+            assert_eq!(expected, PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA);
+        } else {
+            panic!("unexpected error {tm_error}")
+        }
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serialization_creator_serde() {
+        let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
+        let time_provider = TimeProvider::new_with_u16_days(0, 0);
+        let mut stamp_buf: [u8; 8] = [0; 8];
+        let pus_tm =
+            PusTmCreator::new_simple(&mut sph, 17, 2, &time_provider, &mut stamp_buf, None, true)
+                .unwrap();
+
+        let output = to_allocvec(&pus_tm).unwrap();
+        let output_converted_back: PusTmCreator = from_bytes(&output).unwrap();
+        assert_eq!(output_converted_back, pus_tm);
+    }
+
+    #[test]
+    #[cfg(feature = "serde")]
+    fn test_serialization_reader_serde() {
+        let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
+        let time_provider = TimeProvider::new_with_u16_days(0, 0);
+        let mut stamp_buf: [u8; 8] = [0; 8];
+        let pus_tm =
+            PusTmCreator::new_simple(&mut sph, 17, 2, &time_provider, &mut stamp_buf, None, true)
+                .unwrap();
+        let pus_tm_vec = pus_tm.to_vec().unwrap();
+        let (tm_reader, _) = PusTmReader::new(&pus_tm_vec, time_provider.len_as_bytes()).unwrap();
+        let output = to_allocvec(&tm_reader).unwrap();
+        let output_converted_back: PusTmReader = from_bytes(&output).unwrap();
+        assert_eq!(output_converted_back, tm_reader);
+    }
 }

src/lib.rs

@@ -62,7 +62,10 @@ extern crate alloc;
 extern crate std;
 
 use crate::ecss::CCSDS_HEADER_LEN;
-use core::fmt::{Debug, Display, Formatter};
+use core::{
+    fmt::{Debug, Display, Formatter},
+    hash::Hash,
+};
 use crc::{Crc, CRC_16_IBM_3740};
 use delegate::delegate;
 
@@ -87,20 +90,20 @@ pub const CRC_CCITT_FALSE: Crc<u16> = Crc::<u16>::new(&CRC_16_IBM_3740);
 pub const MAX_APID: u16 = 2u16.pow(11) - 1;
 pub const MAX_SEQ_COUNT: u16 = 2u16.pow(14) - 1;
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct SizeMissmatch {
-    pub found: usize,
-    pub expected: usize,
-}
-
+/// Generic error type when converting to and from raw byte slices.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum ByteConversionError {
     /// The passed slice is too small. Returns the passed slice length and expected minimum size
-    ToSliceTooSmall(SizeMissmatch),
+    ToSliceTooSmall {
+        found: usize,
+        expected: usize,
+    },
     /// The provider buffer is too small. Returns the passed slice length and expected minimum size
-    FromSliceTooSmall(SizeMissmatch),
+    FromSliceTooSmall {
+        found: usize,
+        expected: usize,
+    },
     /// The [zerocopy] library failed to write to bytes
     ZeroCopyToError,
     ZeroCopyFromError,
@@ -109,18 +112,18 @@ pub enum ByteConversionError {
 impl Display for ByteConversionError {
     fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
         match self {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
                 write!(
                     f,
                     "target slice with size {} is too small, expected size of at least {}",
-                    missmatch.found, missmatch.expected
+                    found, expected
                 )
             }
-            ByteConversionError::FromSliceTooSmall(missmatch) => {
+            ByteConversionError::FromSliceTooSmall { found, expected } => {
                 write!(
                     f,
                     "source slice with size {} too small, expected at least {} bytes",
-                    missmatch.found, missmatch.expected
+                    found, expected
                 )
             }
             ByteConversionError::ZeroCopyToError => {
@@ -187,7 +190,7 @@ impl TryFrom<u8> for SequenceFlags {
 
 /// Abstraction for the CCSDS Packet ID, which forms the last thirteen bits
 /// of the first two bytes in the CCSDS primary header.
-#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+#[derive(Debug, Eq, Copy, Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct PacketId {
     pub ptype: PacketType,
@@ -195,6 +198,31 @@ pub struct PacketId {
     apid: u16,
 }
 
+impl PartialEq for PacketId {
+    fn eq(&self, other: &Self) -> bool {
+        self.raw().eq(&other.raw())
+    }
+}
+
+impl PartialOrd for PacketId {
+    fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for PacketId {
+    fn cmp(&self, other: &Self) -> core::cmp::Ordering {
+        self.raw().cmp(&other.raw())
+    }
+}
+
+impl Hash for PacketId {
+    fn hash<H: core::hash::Hasher>(&self, state: &mut H) {
+        let raw = self.raw();
+        raw.hash(state);
+    }
+}
+
 impl Default for PacketId {
     fn default() -> Self {
         PacketId {
@@ -255,6 +283,7 @@ impl PacketId {
         self.apid
     }
 
+    #[inline]
     pub fn raw(&self) -> u16 {
         ((self.ptype as u16) << 12) | ((self.sec_header_flag as u16) << 11) | self.apid
     }
@@ -282,7 +311,7 @@ pub struct PacketSequenceCtrl {
 impl PacketSequenceCtrl {
     /// const variant of [PacketSequenceCtrl::new], but panics if the sequence count exceeds
     /// [MAX_SEQ_COUNT].
-    const fn const_new(seq_flags: SequenceFlags, seq_count: u16) -> PacketSequenceCtrl {
+    pub const fn const_new(seq_flags: SequenceFlags, seq_count: u16) -> PacketSequenceCtrl {
         if seq_count > MAX_SEQ_COUNT {
             panic!("Sequence count too large");
         }
@@ -564,10 +593,10 @@ impl SpHeader {
     /// CCSDS header.
     pub fn from_be_bytes(buf: &[u8]) -> Result<(Self, &[u8]), ByteConversionError> {
         if buf.len() < CCSDS_HEADER_LEN {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: buf.len(),
                 expected: CCSDS_HEADER_LEN,
-            }));
+            });
         }
         let zc_header = zc::SpHeader::from_bytes(&buf[0..CCSDS_HEADER_LEN])
             .ok_or(ByteConversionError::ZeroCopyFromError)?;
@@ -581,10 +610,10 @@ impl SpHeader {
         buf: &'a mut [u8],
     ) -> Result<&'a mut [u8], ByteConversionError> {
         if buf.len() < CCSDS_HEADER_LEN {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 found: buf.len(),
                 expected: CCSDS_HEADER_LEN,
-            }));
+            });
         }
         let zc_header: zc::SpHeader = zc::SpHeader::from(*self);
         zc_header
@@ -641,9 +670,9 @@ sph_from_other!(SpHeader, crate::zc::SpHeader);
 pub mod zc {
     use crate::{CcsdsPacket, CcsdsPrimaryHeader, PacketId, PacketSequenceCtrl, VERSION_MASK};
     use zerocopy::byteorder::NetworkEndian;
-    use zerocopy::{AsBytes, FromBytes, Unaligned, U16};
+    use zerocopy::{AsBytes, FromBytes, FromZeroes, Unaligned, U16};
 
-    #[derive(FromBytes, AsBytes, Unaligned, Debug)]
+    #[derive(FromBytes, FromZeroes, AsBytes, Unaligned, Debug)]
     #[repr(C)]
     pub struct SpHeader {
         version_packet_id: U16<NetworkEndian>,
@@ -720,7 +749,9 @@ pub mod zc {
 }
 
 #[cfg(all(test, feature = "std"))]
-mod tests {
+pub(crate) mod tests {
+    use std::collections::HashSet;
+
     #[cfg(feature = "serde")]
     use crate::CcsdsPrimaryHeader;
     use crate::{
@@ -728,9 +759,13 @@ mod tests {
     };
     use crate::{SequenceFlags, SpHeader};
     use alloc::vec;
+    #[cfg(feature = "serde")]
+    use core::fmt::Debug;
     use num_traits::pow;
     #[cfg(feature = "serde")]
     use postcard::{from_bytes, to_allocvec};
+    #[cfg(feature = "serde")]
+    use serde::{de::DeserializeOwned, Serialize};
 
     const CONST_SP: SpHeader = SpHeader::new(
         PacketId::const_tc(true, 0x36),
@@ -740,10 +775,19 @@ mod tests {
 
     const PACKET_ID_TM: PacketId = PacketId::const_tm(true, 0x22);
 
+    #[cfg(feature = "serde")]
+    pub(crate) fn generic_serde_test<T: Serialize + DeserializeOwned + PartialEq + Debug>(
+        value: T,
+    ) {
+        let output: alloc::vec::Vec<u8> = to_allocvec(&value).unwrap();
+        let output_converted_back: T = from_bytes(&output).unwrap();
+        assert_eq!(output_converted_back, value);
+    }
+
     #[test]
     fn verify_const_packet_id() {
         assert_eq!(PACKET_ID_TM.apid(), 0x22);
-        assert_eq!(PACKET_ID_TM.sec_header_flag, true);
+        assert!(PACKET_ID_TM.sec_header_flag);
         assert_eq!(PACKET_ID_TM.ptype, PacketType::Tm);
         let const_tc_id = PacketId::const_tc(true, 0x23);
         assert_eq!(const_tc_id.ptype, PacketType::Tc);
@@ -849,6 +893,7 @@ mod tests {
     fn test_invalid_seq_count() {
         let mut psc = PacketSequenceCtrl::new(SequenceFlags::ContinuationSegment, 77)
             .expect("PSC creation failed");
+        assert_eq!(psc.seq_count(), 77);
         assert!(!psc.set_seq_count(0xffff));
     }
 
@@ -1034,4 +1079,22 @@ mod tests {
         assert_eq!(sp_header.ptype(), PacketType::Tc);
         assert_eq!(sp_header.data_len(), 0);
     }
+
+    #[test]
+    fn packet_id_ord_partial_ord() {
+        let packet_id_small = PacketId::from(1_u16);
+        let packet_id_larger = PacketId::from(2_u16);
+        assert!(packet_id_small < packet_id_larger);
+        assert!(packet_id_larger > packet_id_small);
+        assert_eq!(
+            packet_id_small.cmp(&packet_id_larger),
+            core::cmp::Ordering::Less
+        );
+    }
+
+    #[test]
+    fn packet_id_hashable() {
+        let mut id_set = HashSet::new();
+        id_set.insert(PacketId::from(1_u16));
+    }
 }

src/time/cuc.rs

@@ -7,6 +7,7 @@ use chrono::Datelike;
 use core::fmt::Debug;
 use core::ops::{Add, AddAssign};
 use core::time::Duration;
+use core::u64;
 
 const MIN_CUC_LEN: usize = 2;
 
@@ -93,10 +94,15 @@ pub fn fractional_part_from_subsec_ns(
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum CucError {
     InvalidCounterWidth(u8),
-    InvalidFractionResolution(FractionalResolution),
     /// Invalid counter supplied.
-    InvalidCounter(u8, u64),
-    InvalidFractions(FractionalResolution, u64),
+    InvalidCounter {
+        width: u8,
+        counter: u64,
+    },
+    InvalidFractions {
+        resolution: FractionalResolution,
+        value: u64,
+    },
 }
 
 impl Display for CucError {
@@ -105,14 +111,14 @@ impl Display for CucError {
             CucError::InvalidCounterWidth(w) => {
                 write!(f, "invalid cuc counter byte width {w}")
             }
-            CucError::InvalidFractionResolution(w) => {
-                write!(f, "invalid cuc fractional part byte width {w:?}")
+            CucError::InvalidCounter { width, counter } => {
+                write!(f, "invalid cuc counter {counter} for width {width}")
             }
-            CucError::InvalidCounter(w, c) => {
-                write!(f, "invalid cuc counter {c} for width {w}")
-            }
-            CucError::InvalidFractions(w, c) => {
-                write!(f, "invalid cuc fractional part {c} for width {w:?}")
+            CucError::InvalidFractions { resolution, value } => {
+                write!(
+                    f,
+                    "invalid cuc fractional part {value} for resolution {resolution:?}"
+                )
             }
         }
     }
@@ -278,6 +284,8 @@ impl TimeProviderCcsdsEpoch {
         .map_err(|e| e.into())
     }
 
+    /// Generates a CUC timestamp from a UNIX timestamp with a width of 4. This width is able
+    /// to accomodate all possible UNIX timestamp values.
     pub fn from_unix_stamp(
         unix_stamp: &UnixTimestamp,
         res: FractionalResolution,
@@ -289,13 +297,10 @@ impl TimeProviderCcsdsEpoch {
                 unix_stamp.as_date_time().unwrap(),
             ));
         }
-        if ccsds_epoch > u32::MAX as i64 {
-            return Err(CucError::InvalidCounter(4, ccsds_epoch as u64).into());
-        }
-        let mut fractions = None;
-        if let Some(subsec_millis) = unix_stamp.subsecond_millis {
-            fractions = fractional_part_from_subsec_ns(res, subsec_millis as u64 * 10_u64.pow(6));
-        }
+        let fractions = fractional_part_from_subsec_ns(
+            res,
+            unix_stamp.subsecond_millis() as u64 * 10_u64.pow(6),
+        );
         Self::new_generic(WidthCounterPair(4, ccsds_epoch as u32), fractions).map_err(|e| e.into())
     }
 
@@ -308,12 +313,19 @@ impl TimeProviderCcsdsEpoch {
         self.counter
     }
 
+    pub fn width(&self) -> u8 {
+        self.counter.0
+    }
+
+    pub fn counter(&self) -> u32 {
+        self.counter.1
+    }
+
     pub fn width_fractions_pair(&self) -> Option<FractionalPart> {
         self.fractions
     }
 
     pub fn set_fractions(&mut self, fractions: FractionalPart) -> Result<(), CucError> {
-        Self::verify_fractions_width(fractions.0)?;
         Self::verify_fractions_value(fractions)?;
         self.fractions = Some(fractions);
         self.update_p_field_fractions();
@@ -343,10 +355,12 @@ impl TimeProviderCcsdsEpoch {
     ) -> Result<Self, CucError> {
         Self::verify_counter_width(counter.0)?;
         if counter.1 > (2u64.pow(counter.0 as u32 * 8) - 1) as u32 {
-            return Err(CucError::InvalidCounter(counter.0, counter.1 as u64));
+            return Err(CucError::InvalidCounter {
+                width: counter.0,
+                counter: counter.1 as u64,
+            });
         }
         if let Some(fractions) = fractions {
-            Self::verify_fractions_width(fractions.0)?;
             Self::verify_fractions_value(fractions)?;
         }
         Ok(Self {
@@ -432,16 +446,12 @@ impl TimeProviderCcsdsEpoch {
         Ok(())
     }
 
-    fn verify_fractions_width(width: FractionalResolution) -> Result<(), CucError> {
-        if width as u8 > 3 {
-            return Err(CucError::InvalidFractionResolution(width));
-        }
-        Ok(())
-    }
-
     fn verify_fractions_value(val: FractionalPart) -> Result<(), CucError> {
         if val.1 > 2u32.pow((val.0 as u32) * 8) - 1 {
-            return Err(CucError::InvalidFractions(val.0, val.1 as u64));
+            return Err(CucError::InvalidFractions {
+                resolution: val.0,
+                value: val.1 as u64,
+            });
         }
         Ok(())
     }
@@ -454,36 +464,36 @@ impl TimeReader for TimeProviderCcsdsEpoch {
     {
         if buf.len() < MIN_CUC_LEN {
             return Err(TimestampError::ByteConversion(
-                ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+                ByteConversionError::FromSliceTooSmall {
                     expected: MIN_CUC_LEN,
                     found: buf.len(),
-                }),
+                },
             ));
         }
         match ccsds_time_code_from_p_field(buf[0]) {
             Ok(code) => {
                 if code != CcsdsTimeCodes::CucCcsdsEpoch {
-                    return Err(TimestampError::InvalidTimeCode(
-                        CcsdsTimeCodes::CucCcsdsEpoch,
-                        code as u8,
-                    ));
+                    return Err(TimestampError::InvalidTimeCode {
+                        expected: CcsdsTimeCodes::CucCcsdsEpoch,
+                        found: code as u8,
+                    });
                 }
             }
             Err(raw) => {
-                return Err(TimestampError::InvalidTimeCode(
-                    CcsdsTimeCodes::CucCcsdsEpoch,
-                    raw,
-                ))
+                return Err(TimestampError::InvalidTimeCode {
+                    expected: CcsdsTimeCodes::CucCcsdsEpoch,
+                    found: raw,
+                });
             }
         }
         let (cntr_len, fractions_len, total_len) =
             Self::len_components_and_total_from_pfield(buf[0]);
         if buf.len() < total_len {
             return Err(TimestampError::ByteConversion(
-                ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+                ByteConversionError::FromSliceTooSmall {
                     expected: total_len,
                     found: buf.len(),
-                }),
+                },
             ));
         }
         let mut current_idx = 1;
@@ -536,10 +546,10 @@ impl TimeWriter for TimeProviderCcsdsEpoch {
         // Cross check the sizes of the counters against byte widths in the ctor
         if bytes.len() < self.len_as_bytes() {
             return Err(TimestampError::ByteConversion(
-                ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                ByteConversionError::ToSliceTooSmall {
                     found: bytes.len(),
                     expected: self.len_as_bytes(),
-                }),
+                },
             ));
         }
         bytes[0] = self.pfield;
@@ -577,6 +587,10 @@ impl TimeWriter for TimeProviderCcsdsEpoch {
         }
         Ok(current_idx)
     }
+
+    fn len_written(&self) -> usize {
+        self.len_as_bytes()
+    }
 }
 
 impl CcsdsTimeProvider for TimeProviderCcsdsEpoch {
@@ -596,15 +610,15 @@ impl CcsdsTimeProvider for TimeProviderCcsdsEpoch {
         self.unix_seconds()
     }
 
-    fn subsecond_millis(&self) -> Option<u16> {
+    fn subsecond_millis(&self) -> u16 {
         if let Some(fractions) = self.fractions {
             if fractions.0 == FractionalResolution::Seconds {
-                return None;
+                return 0;
             }
             // Rounding down here is the correct approach.
-            return Some((convert_fractional_part_to_ns(fractions) / 10_u32.pow(6) as u64) as u16);
+            return (convert_fractional_part_to_ns(fractions) / 10_u32.pow(6) as u64) as u16;
         }
-        None
+        0
     }
 
     fn date_time(&self) -> Option<DateTime<Utc>> {
@@ -713,6 +727,7 @@ impl Add<Duration> for &TimeProviderCcsdsEpoch {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use alloc::string::ToString;
     use chrono::{Datelike, Timelike};
     #[allow(unused_imports)]
     use std::println;
@@ -721,6 +736,8 @@ mod tests {
     fn test_basic_zero_epoch() {
         let zero_cuc = TimeProviderCcsdsEpoch::new(0);
         assert_eq!(zero_cuc.len_as_bytes(), 5);
+        assert_eq!(zero_cuc.width(), zero_cuc.width_counter_pair().0);
+        assert_eq!(zero_cuc.counter(), zero_cuc.width_counter_pair().1);
         assert_eq!(zero_cuc.ccdsd_time_code(), CcsdsTimeCodes::CucCcsdsEpoch);
         let counter = zero_cuc.width_counter_pair();
         assert_eq!(counter.0, 4);
@@ -746,7 +763,7 @@ mod tests {
         let zero_cuc = zero_cuc.unwrap();
         let res = zero_cuc.write_to_bytes(&mut buf);
         assert!(res.is_ok());
-        assert!(zero_cuc.subsecond_millis().is_none());
+        assert_eq!(zero_cuc.subsecond_millis(), 0);
         assert_eq!(zero_cuc.len_as_bytes(), 5);
         assert_eq!(pfield_len(buf[0]), 1);
         let written = res.unwrap();
@@ -797,9 +814,13 @@ mod tests {
             let res = TimeProviderCcsdsEpoch::from_bytes(&buf[0..i]);
             assert!(res.is_err());
             let err = res.unwrap_err();
-            if let TimestampError::ByteConversion(ByteConversionError::FromSliceTooSmall(e)) = err {
-                assert_eq!(e.found, i);
-                assert_eq!(e.expected, 2);
+            if let TimestampError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+                found,
+                expected,
+            }) = err
+            {
+                assert_eq!(found, i);
+                assert_eq!(expected, 2);
             }
         }
         let large_stamp = TimeProviderCcsdsEpoch::new_with_fine_fractions(22, 300).unwrap();
@@ -808,9 +829,13 @@ mod tests {
             let res = TimeProviderCcsdsEpoch::from_bytes(&buf[0..i]);
             assert!(res.is_err());
             let err = res.unwrap_err();
-            if let TimestampError::ByteConversion(ByteConversionError::FromSliceTooSmall(e)) = err {
-                assert_eq!(e.found, i);
-                assert_eq!(e.expected, large_stamp.len_as_bytes());
+            if let TimestampError::ByteConversion(ByteConversionError::FromSliceTooSmall {
+                found,
+                expected,
+            }) = err
+            {
+                assert_eq!(found, i);
+                assert_eq!(expected, large_stamp.len_as_bytes());
             }
         }
     }
@@ -853,6 +878,7 @@ mod tests {
 
     #[test]
     fn invalid_buf_len_for_read() {}
+
     #[test]
     fn write_read_three_byte_cntr_stamp() {
         let mut buf = [0; 4];
@@ -882,9 +908,13 @@ mod tests {
             let err = cuc.write_to_bytes(&mut buf[0..i]);
             assert!(err.is_err());
             let err = err.unwrap_err();
-            if let TimestampError::ByteConversion(ByteConversionError::ToSliceTooSmall(e)) = err {
-                assert_eq!(e.expected, cuc.len_as_bytes());
-                assert_eq!(e.found, i);
+            if let TimestampError::ByteConversion(ByteConversionError::ToSliceTooSmall {
+                found,
+                expected,
+            }) = err
+            {
+                assert_eq!(expected, cuc.len_as_bytes());
+                assert_eq!(found, i);
             } else {
                 panic!("unexpected error: {}", err);
             }
@@ -897,9 +927,9 @@ mod tests {
         let res = TimeProviderCcsdsEpoch::from_bytes(&buf);
         assert!(res.is_err());
         let err = res.unwrap_err();
-        if let TimestampError::InvalidTimeCode(code, raw) = err {
-            assert_eq!(code, CcsdsTimeCodes::CucCcsdsEpoch);
-            assert_eq!(raw, CcsdsTimeCodes::CucAgencyEpoch as u8);
+        if let TimestampError::InvalidTimeCode { expected, found } = err {
+            assert_eq!(expected, CcsdsTimeCodes::CucCcsdsEpoch);
+            assert_eq!(found, CcsdsTimeCodes::CucAgencyEpoch as u8);
         } else {
             panic!("unexpected error: {}", err);
         }
@@ -1090,12 +1120,7 @@ mod tests {
         assert_eq!(fractions.1, 2_u32.pow(3 * 8) - 2);
     }
 
-    #[test]
-    fn add_duration_basic() {
-        let mut cuc_stamp = TimeProviderCcsdsEpoch::new(200);
-        cuc_stamp.set_fractional_resolution(FractionalResolution::FifteenUs);
-        let duration = Duration::from_millis(2500);
-        cuc_stamp += duration;
+    fn check_stamp_after_addition(cuc_stamp: &TimeProviderCcsdsEpoch) {
         assert_eq!(cuc_stamp.width_counter_pair().1, 202);
         let fractions = cuc_stamp.width_fractions_pair().unwrap().1;
         let expected_val =
@@ -1105,9 +1130,44 @@ mod tests {
         // What I would roughly expect
         assert_eq!(cuc_stamp2.counter.1, 203);
         assert!(cuc_stamp2.fractions.unwrap().1 < 100);
-        assert!(cuc_stamp2.subsecond_millis().unwrap() <= 1);
+        assert!(cuc_stamp2.subsecond_millis() <= 1);
     }
 
+    #[test]
+    fn add_duration_basic() {
+        let mut cuc_stamp = TimeProviderCcsdsEpoch::new(200);
+        cuc_stamp.set_fractional_resolution(FractionalResolution::FifteenUs);
+        let duration = Duration::from_millis(2500);
+        cuc_stamp += duration;
+        check_stamp_after_addition(&cuc_stamp);
+    }
+
+    #[test]
+    fn add_duration_basic_on_ref() {
+        let mut cuc_stamp = TimeProviderCcsdsEpoch::new(200);
+        cuc_stamp.set_fractional_resolution(FractionalResolution::FifteenUs);
+        let duration = Duration::from_millis(2500);
+        let new_stamp = cuc_stamp + duration;
+        check_stamp_after_addition(&new_stamp);
+    }
+
+    #[test]
+    fn add_duration_basic_no_fractions() {
+        let mut cuc_stamp = TimeProviderCcsdsEpoch::new(200);
+        let duration = Duration::from_millis(2000);
+        cuc_stamp += duration;
+        assert_eq!(cuc_stamp.counter(), 202);
+        assert_eq!(cuc_stamp.width_fractions_pair(), None);
+    }
+
+    #[test]
+    fn add_duration_basic_on_ref_no_fractions() {
+        let cuc_stamp = TimeProviderCcsdsEpoch::new(200);
+        let duration = Duration::from_millis(2000);
+        let new_stamp = cuc_stamp + duration;
+        assert_eq!(new_stamp.counter(), 202);
+        assert_eq!(new_stamp.width_fractions_pair(), None);
+    }
     #[test]
     fn add_duration_overflow() {
         let mut cuc_stamp =
@@ -1116,4 +1176,67 @@ mod tests {
         cuc_stamp += duration;
         assert_eq!(cuc_stamp.counter.1, 10);
     }
+
+    #[test]
+    fn test_invalid_width_param() {
+        let error = TimeProviderCcsdsEpoch::new_generic(WidthCounterPair(8, 0), None);
+        assert!(error.is_err());
+        let error = error.unwrap_err();
+        if let CucError::InvalidCounterWidth(width) = error {
+            assert_eq!(width, 8);
+            assert_eq!(error.to_string(), "invalid cuc counter byte width 8");
+        } else {
+            panic!("unexpected error: {}", error);
+        }
+    }
+
+    #[test]
+    fn test_from_dt() {
+        let dt = Utc.with_ymd_and_hms(2021, 1, 1, 0, 0, 0).unwrap();
+        let cuc =
+            TimeProviderCcsdsEpoch::from_date_time(&dt, FractionalResolution::Seconds).unwrap();
+        assert_eq!(cuc.counter(), dt.timestamp() as u32);
+    }
+
+    #[test]
+    fn test_new_u16_width() {
+        let cuc = TimeProviderCcsdsEpoch::new_u16_counter(0);
+        assert_eq!(cuc.width(), 2);
+        assert_eq!(cuc.counter(), 0);
+    }
+
+    #[test]
+    fn from_unix_stamp() {
+        let unix_stamp = UnixTimestamp::new(0, 0).unwrap();
+        let cuc =
+            TimeProviderCcsdsEpoch::from_unix_stamp(&unix_stamp, FractionalResolution::Seconds)
+                .expect("failed to create cuc from unix stamp");
+        assert_eq!(
+            cuc.counter(),
+            (-DAYS_CCSDS_TO_UNIX * SECONDS_PER_DAY as i32) as u32
+        );
+    }
+
+    #[test]
+    fn test_invalid_counter() {
+        let cuc_error = TimeProviderCcsdsEpoch::new_generic(WidthCounterPair(1, 256), None);
+        assert!(cuc_error.is_err());
+        let cuc_error = cuc_error.unwrap_err();
+        if let CucError::InvalidCounter { width, counter } = cuc_error {
+            assert_eq!(width, 1);
+            assert_eq!(counter, 256);
+            assert_eq!(cuc_error.to_string(), "invalid cuc counter 256 for width 1");
+        } else {
+            panic!("unexpected error: {}", cuc_error);
+        }
+    }
+
+    #[test]
+    fn test_stamp_to_vec() {
+        let stamp = TimeProviderCcsdsEpoch::new_u16_counter(100);
+        let stamp_vec = stamp.to_vec().unwrap();
+        let mut buf: [u8; 16] = [0; 16];
+        stamp.write_to_bytes(&mut buf).unwrap();
+        assert_eq!(stamp_vec, buf[..stamp.len_written()]);
+    }
 }

src/time/mod.rs

@@ -1,10 +1,11 @@
 //! CCSDS Time Code Formats according to [CCSDS 301.0-B-4](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::ByteConversionError;
 use chrono::{DateTime, LocalResult, 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"))]
@@ -63,9 +64,7 @@ pub fn ccsds_time_code_from_p_field(pfield: u8) -> Result<CcsdsTimeCodes, u8> {
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[non_exhaustive]
 pub enum TimestampError {
-    /// Contains tuple where first value is the expected time code and the second
-    /// value is the found raw value
-    InvalidTimeCode(CcsdsTimeCodes, u8),
+    InvalidTimeCode { expected: CcsdsTimeCodes, found: u8 },
     ByteConversion(ByteConversionError),
     Cds(cds::CdsError),
     Cuc(cuc::CucError),
@@ -76,20 +75,20 @@ pub enum TimestampError {
 impl Display for TimestampError {
     fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
         match self {
-            TimestampError::InvalidTimeCode(time_code, raw_val) => {
+            TimestampError::InvalidTimeCode { expected, found } => {
                 write!(
                     f,
-                    "invalid raw time code value {raw_val} for time code {time_code:?}"
+                    "invalid raw time code value {found} for time code {expected:?}"
                 )
             }
             TimestampError::Cds(e) => {
-                write!(f, "cds error {e}")
+                write!(f, "cds error: {e}")
             }
             TimestampError::Cuc(e) => {
-                write!(f, "cuc error {e}")
+                write!(f, "cuc error: {e}")
             }
             TimestampError::ByteConversion(e) => {
-                write!(f, "byte conversion error {e}")
+                write!(f, "time stamp: {e}")
             }
             TimestampError::DateBeforeCcsdsEpoch(e) => {
                 write!(f, "datetime with date before ccsds epoch: {e}")
@@ -190,9 +189,19 @@ pub fn ms_of_day(seconds_since_epoch: f64) -> u32 {
 }
 
 pub trait TimeWriter {
+    fn len_written(&self) -> usize;
+
     /// Generic function to convert write a timestamp into a raw buffer.
     /// Returns the number of written bytes on success.
     fn write_to_bytes(&self, bytes: &mut [u8]) -> Result<usize, TimestampError>;
+
+    #[cfg(feature = "alloc")]
+    #[cfg_attr(doc_cfg, doc(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 {
@@ -216,12 +225,9 @@ pub trait CcsdsTimeProvider {
     fn ccdsd_time_code(&self) -> CcsdsTimeCodes;
 
     fn unix_seconds(&self) -> i64;
-    fn subsecond_millis(&self) -> Option<u16>;
+    fn subsecond_millis(&self) -> 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())
+        UnixTimestamp::const_new(self.unix_seconds(), self.subsecond_millis())
     }
 
     fn date_time(&self) -> Option<DateTime<Utc>>;
@@ -229,18 +235,16 @@ pub trait CcsdsTimeProvider {
 
 /// UNIX timestamp: Elapsed seconds since 1970-01-01T00:00:00+00:00.
 ///
-/// Also can optionally include subsecond millisecond for greater accuracy. Please note that a
-/// subsecond millisecond value of 0 gets converted to [None].
+/// Also can optionally include subsecond millisecond for greater accuracy.
 #[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>,
+    subsecond_millis: u16,
 }
 
 impl UnixTimestamp {
-    /// Returns none if the subsecond millisecond value is larger than 999. 0 is converted to
-    /// a [None] value.
+    /// Returns [None] if the subsecond millisecond value is larger than 999.
     pub fn new(unix_seconds: i64, subsec_millis: u16) -> Option<Self> {
         if subsec_millis > 999 {
             return None;
@@ -249,15 +253,10 @@ impl UnixTimestamp {
     }
 
     /// 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 {
+    pub const fn const_new(unix_seconds: i64, subsecond_millis: u16) -> Self {
+        if subsecond_millis > 999 {
             panic!("subsec milliseconds exceeds 999");
         }
-        let subsecond_millis = if subsec_millis == 0 {
-            None
-        } else {
-            Some(subsec_millis)
-        };
         Self {
             unix_seconds,
             subsecond_millis,
@@ -267,11 +266,11 @@ impl UnixTimestamp {
     pub fn new_only_seconds(unix_seconds: i64) -> Self {
         Self {
             unix_seconds,
-            subsecond_millis: None,
+            subsecond_millis: 0,
         }
     }
 
-    pub fn subsecond_millis(&self) -> Option<u16> {
+    pub fn subsecond_millis(&self) -> u16 {
         self.subsecond_millis
     }
 
@@ -285,19 +284,28 @@ impl UnixTimestamp {
 
     #[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
+        self.unix_seconds as f64 + (self.subsecond_millis as f64 / 1000.0)
     }
 
     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),
+            self.subsecond_millis as u32 * 10_u32.pow(6),
         )
     }
+
+    // Calculate the difference in milliseconds between two UnixTimestamps
+    pub fn difference_in_millis(&self, other: &UnixTimestamp) -> i64 {
+        let seconds_difference = self.unix_seconds - other.unix_seconds;
+        // Convert seconds difference to milliseconds
+        let milliseconds_difference = seconds_difference * 1000;
+
+        // Calculate the difference in subsecond milliseconds directly
+        let subsecond_difference = self.subsecond_millis as i64 - other.subsecond_millis as i64;
+
+        // Combine the differences
+        milliseconds_difference + subsecond_difference
+    }
 }
 
 impl From<DateTime<Utc>> for UnixTimestamp {
@@ -308,43 +316,66 @@ impl From<DateTime<Utc>> for UnixTimestamp {
 
 impl PartialOrd for UnixTimestamp {
     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        if self == other {
-            return Some(Ordering::Equal);
-        }
-        match self.unix_seconds.cmp(&other.unix_seconds) {
-            Ordering::Less => return Some(Ordering::Less),
-            Ordering::Greater => return Some(Ordering::Greater),
-            _ => (),
-        }
-
-        match self
-            .subsecond_millis()
-            .unwrap_or(0)
-            .cmp(&other.subsecond_millis().unwrap_or(0))
-        {
-            Ordering::Less => {
-                return if self.unix_seconds < 0 {
-                    Some(Ordering::Greater)
-                } else {
-                    Some(Ordering::Less)
-                }
-            }
-            Ordering::Greater => {
-                return if self.unix_seconds < 0 {
-                    Some(Ordering::Less)
-                } else {
-                    Some(Ordering::Greater)
-                }
-            }
-            Ordering::Equal => (),
-        }
-        Some(Ordering::Equal)
+        Some(self.cmp(other))
     }
 }
 
 impl Ord for UnixTimestamp {
     fn cmp(&self, other: &Self) -> Ordering {
-        PartialOrd::partial_cmp(self, other).unwrap()
+        if self == other {
+            return Ordering::Equal;
+        }
+        match self.unix_seconds.cmp(&other.unix_seconds) {
+            Ordering::Less => return Ordering::Less,
+            Ordering::Greater => return Ordering::Greater,
+            _ => (),
+        }
+
+        match self.subsecond_millis().cmp(&other.subsecond_millis()) {
+            Ordering::Less => {
+                return if self.unix_seconds < 0 {
+                    Ordering::Greater
+                } else {
+                    Ordering::Less
+                }
+            }
+            Ordering::Greater => {
+                return if self.unix_seconds < 0 {
+                    Ordering::Less
+                } else {
+                    Ordering::Greater
+                }
+            }
+            Ordering::Equal => (),
+        }
+        Ordering::Equal
+    }
+}
+
+/// Difference between two UNIX timestamps. The [Duration] type can not contain negative durations,
+/// so the sign information is supplied separately.
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct StampDiff {
+    pub positive_duration: bool,
+    pub duration_absolute: Duration,
+}
+
+impl Sub for UnixTimestamp {
+    type Output = StampDiff;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        let difference = self.difference_in_millis(&rhs);
+        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),
+            }
+        }
     }
 }
 
@@ -352,8 +383,7 @@ 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_subsec_millis = current_stamp.subsecond_millis() + duration.subsec_millis() as u16;
     let mut new_unix_seconds = current_stamp.unix_seconds;
     let mut increment_seconds = |value: u32| {
         if new_unix_seconds < 0 {
@@ -413,7 +443,11 @@ 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;
+
+    use super::{cuc::CucError, *};
 
     #[test]
     fn test_days_conversion() {
@@ -427,6 +461,14 @@ mod tests {
         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]
     fn test_ccsds_epoch() {
         let now = SystemTime::now()
@@ -444,18 +486,17 @@ mod tests {
     fn basic_unix_stamp_test() {
         let stamp = UnixTimestamp::new_only_seconds(-200);
         assert_eq!(stamp.unix_seconds, -200);
-        assert!(stamp.subsecond_millis().is_none());
+        assert_eq!(stamp.subsecond_millis(), 0);
         let stamp = UnixTimestamp::new_only_seconds(250);
         assert_eq!(stamp.unix_seconds, 250);
-        assert!(stamp.subsecond_millis().is_none());
+        assert_eq!(stamp.subsecond_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 subsec_millis = stamp.subsecond_millis();
         assert_eq!(subsec_millis, 600);
         assert!((500.6 - stamp.unix_seconds_f64()).abs() < 0.0001);
     }
@@ -504,6 +545,7 @@ mod tests {
         assert!(stamp2 <= stamp1);
     }
 
+    #[allow(clippy::nonminimal_bool)]
     #[test]
     fn test_eq() {
         let stamp0 = UnixTimestamp::new(5, 0).unwrap();
@@ -520,11 +562,10 @@ mod tests {
         let mut stamp0 = UnixTimestamp::new_only_seconds(1);
         stamp0 += Duration::from_secs(5);
         assert_eq!(stamp0.unix_seconds, 6);
-        assert!(stamp0.subsecond_millis().is_none());
+        assert_eq!(stamp0.subsecond_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.subsecond_millis(), 500);
     }
 
     #[test]
@@ -532,7 +573,61 @@ mod tests {
         let stamp0 = &UnixTimestamp::new(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.subsecond_millis(), 0);
+    }
+
+    #[test]
+    fn test_as_dt() {
+        let stamp = UnixTimestamp::new_only_seconds(0);
+        let dt = stamp.as_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]
+    fn test_from_now() {
+        let stamp_now = UnixTimestamp::from_now().unwrap();
+        let dt_now = stamp_now.as_date_time().unwrap();
+        assert!(dt_now.year() >= 2020);
+    }
+
+    #[test]
+    fn test_stamp_diff_positive_0() {
+        let stamp_later = UnixTimestamp::new(2, 0).unwrap();
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = stamp_later - UnixTimestamp::new(1, 0).unwrap();
+        assert!(positive_duration);
+        assert_eq!(duration_absolute, Duration::from_secs(1));
+    }
+
+    #[test]
+    fn test_stamp_diff_positive_1() {
+        let stamp_later = UnixTimestamp::new(3, 800).unwrap();
+        let stamp_earlier = UnixTimestamp::new(1, 900).unwrap();
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = stamp_later - stamp_earlier;
+        assert!(positive_duration);
+        assert_eq!(duration_absolute, Duration::from_millis(1900));
+    }
+
+    #[test]
+    fn test_stamp_diff_negative() {
+        let stamp_later = UnixTimestamp::new(3, 800).unwrap();
+        let stamp_earlier = UnixTimestamp::new(1, 900).unwrap();
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = stamp_earlier - stamp_later;
+        assert!(!positive_duration);
+        assert_eq!(duration_absolute, Duration::from_millis(1900));
     }
 
     #[test]
@@ -540,9 +635,16 @@ mod tests {
         let mut stamp0 = UnixTimestamp::new(1, 900).unwrap();
         stamp0 += Duration::from_millis(100);
         assert_eq!(stamp0.unix_seconds, 2);
-        assert!(stamp0.subsecond_millis().is_none());
+        assert_eq!(stamp0.subsecond_millis(), 0);
         stamp0 += Duration::from_millis(1100);
         assert_eq!(stamp0.unix_seconds, 3);
-        assert_eq!(stamp0.subsecond_millis().unwrap(), 100);
+        assert_eq!(stamp0.subsecond_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}"));
     }
 }

src/util.rs

@@ -1,4 +1,4 @@
-use crate::{ByteConversionError, SizeMissmatch};
+use crate::ByteConversionError;
 use core::fmt::{Debug, Display, Formatter};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -73,6 +73,16 @@ pub trait UnsignedEnum {
     fn size(&self) -> usize;
     /// Write the unsigned enumeration to a raw buffer. Returns the written size on success.
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
+
+    fn value(&self) -> u64;
+
+    #[cfg(feature = "alloc")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
+    fn to_vec(&self) -> alloc::vec::Vec<u8> {
+        let mut buf = alloc::vec![0; self.size()];
+        self.write_to_be_bytes(&mut buf).unwrap();
+        buf
+    }
 }
 
 pub trait UnsignedEnumExt: UnsignedEnum + Debug + Copy + Clone + PartialEq + Eq {}
@@ -80,12 +90,17 @@ pub trait UnsignedEnumExt: UnsignedEnum + Debug + Copy + Clone + PartialEq + Eq
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum UnsignedByteFieldError {
-    /// Value is too large for specified width of byte field. The first value contains the width,
-    /// the second value contains the detected value.
-    ValueTooLargeForWidth((usize, u64)),
+    /// Value is too large for specified width of byte field.
+    ValueTooLargeForWidth {
+        width: usize,
+        value: u64,
+    },
     /// Only 1, 2, 4 and 8 are allow width values. Optionally contains the expected width if
     /// applicable, for example for conversions.
-    InvalidWidth(usize, Option<usize>),
+    InvalidWidth {
+        found: usize,
+        expected: Option<usize>,
+    },
     ByteConversionError(ByteConversionError),
 }
 
@@ -101,10 +116,10 @@ impl Display for UnsignedByteFieldError {
             Self::ByteConversionError(e) => {
                 write!(f, "low level byte conversion error: {e}")
             }
-            Self::InvalidWidth(val, _) => {
-                write!(f, "invalid width {val}, only 1, 2, 4 and 8 are allowed.")
+            Self::InvalidWidth { found, .. } => {
+                write!(f, "invalid width {found}, only 1, 2, 4 and 8 are allowed.")
             }
-            Self::ValueTooLargeForWidth((width, value)) => {
+            Self::ValueTooLargeForWidth { width, value } => {
                 write!(f, "value {value} too large for width {width}")
             }
         }
@@ -123,20 +138,20 @@ pub struct UnsignedByteField {
 }
 
 impl UnsignedByteField {
-    pub fn new(width: usize, value: u64) -> Self {
+    pub const fn new(width: usize, value: u64) -> Self {
         Self { width, value }
     }
 
-    pub fn value(&self) -> u64 {
+    pub const fn value_const(&self) -> u64 {
         self.value
     }
 
     pub fn new_from_be_bytes(width: usize, buf: &[u8]) -> Result<Self, UnsignedByteFieldError> {
         if width > buf.len() {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::FromSliceTooSmall {
                 expected: width,
                 found: buf.len(),
-            })
+            }
             .into());
         }
         match width {
@@ -154,7 +169,10 @@ impl UnsignedByteField {
                 width,
                 u64::from_be_bytes(buf[0..8].try_into().unwrap()),
             )),
-            _ => Err(UnsignedByteFieldError::InvalidWidth(width, None)),
+            _ => Err(UnsignedByteFieldError::InvalidWidth {
+                found: width,
+                expected: None,
+            }),
         }
     }
 }
@@ -164,12 +182,16 @@ impl UnsignedEnum for UnsignedByteField {
         self.width
     }
 
+    fn value(&self) -> u64 {
+        self.value_const()
+    }
+
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         if buf.len() < self.size() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 expected: self.size(),
                 found: buf.len(),
-            }));
+            });
         }
         match self.size() {
             0 => Ok(0),
@@ -199,31 +221,39 @@ impl UnsignedEnum for UnsignedByteField {
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct GenericUnsignedByteField<TYPE> {
+pub struct GenericUnsignedByteField<TYPE: Copy + Into<u64>> {
     value: TYPE,
 }
 
-impl<TYPE> GenericUnsignedByteField<TYPE> {
-    pub fn new(val: TYPE) -> Self {
+impl<TYPE: Copy + Into<u64>> GenericUnsignedByteField<TYPE> {
+    pub const fn new(val: TYPE) -> Self {
         Self { value: val }
     }
+
+    pub const fn value_typed(&self) -> TYPE {
+        self.value
+    }
 }
 
-impl<TYPE: ToBeBytes> UnsignedEnum for GenericUnsignedByteField<TYPE> {
+impl<TYPE: Copy + ToBeBytes + Into<u64>> UnsignedEnum for GenericUnsignedByteField<TYPE> {
     fn size(&self) -> usize {
         self.value.written_len()
     }
 
     fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
         if buf.len() < self.size() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
                 expected: self.size(),
-            }));
+            });
         }
-        buf[0..self.size()].copy_from_slice(self.value.to_be_bytes().as_ref());
+        buf[..self.size()].copy_from_slice(self.value.to_be_bytes().as_ref());
         Ok(self.value.written_len())
     }
+
+    fn value(&self) -> u64 {
+        self.value_typed().into()
+    }
 }
 
 pub type UnsignedByteFieldEmpty = GenericUnsignedByteField<()>;
@@ -248,7 +278,10 @@ impl TryFrom<UnsignedByteField> for UnsignedByteFieldU8 {
 
     fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
         if value.width != 1 {
-            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(1)));
+            return Err(UnsignedByteFieldError::InvalidWidth {
+                found: value.width,
+                expected: Some(1),
+            });
         }
         Ok(Self::new(value.value as u8))
     }
@@ -265,7 +298,10 @@ impl TryFrom<UnsignedByteField> for UnsignedByteFieldU16 {
 
     fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
         if value.width != 2 {
-            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(2)));
+            return Err(UnsignedByteFieldError::InvalidWidth {
+                found: value.width,
+                expected: Some(2),
+            });
         }
         Ok(Self::new(value.value as u16))
     }
@@ -282,7 +318,10 @@ impl TryFrom<UnsignedByteField> for UnsignedByteFieldU32 {
 
     fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
         if value.width != 4 {
-            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(4)));
+            return Err(UnsignedByteFieldError::InvalidWidth {
+                found: value.width,
+                expected: Some(4),
+            });
         }
         Ok(Self::new(value.value as u32))
     }
@@ -299,7 +338,10 @@ impl TryFrom<UnsignedByteField> for UnsignedByteFieldU64 {
 
     fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
         if value.width != 8 {
-            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(8)));
+            return Err(UnsignedByteFieldError::InvalidWidth {
+                found: value.width,
+                expected: Some(8),
+            });
         }
         Ok(Self::new(value.value))
     }
@@ -324,9 +366,11 @@ pub mod tests {
             .expect("writing to raw buffer failed");
         assert_eq!(len, 1);
         assert_eq!(buf[0], 5);
-        for i in 1..8 {
-            assert_eq!(buf[i], 0);
+        for val in buf.iter().skip(1) {
+            assert_eq!(*val, 0);
         }
+        assert_eq!(u8.value_typed(), 5);
+        assert_eq!(u8.value(), 5);
     }
 
     #[test]
@@ -340,9 +384,11 @@ pub mod tests {
         assert_eq!(len, 2);
         let raw_val = u16::from_be_bytes(buf[0..2].try_into().unwrap());
         assert_eq!(raw_val, 3823);
-        for i in 2..8 {
-            assert_eq!(buf[i], 0);
+        for val in buf.iter().skip(2) {
+            assert_eq!(*val, 0);
         }
+        assert_eq!(u16.value_typed(), 3823);
+        assert_eq!(u16.value(), 3823);
     }
 
     #[test]
@@ -356,9 +402,11 @@ pub mod tests {
         assert_eq!(len, 4);
         let raw_val = u32::from_be_bytes(buf[0..4].try_into().unwrap());
         assert_eq!(raw_val, 80932);
-        for i in 4..8 {
+        (4..8).for_each(|i| {
             assert_eq!(buf[i], 0);
-        }
+        });
+        assert_eq!(u32.value_typed(), 80932);
+        assert_eq!(u32.value(), 80932);
     }
 
     #[test]
@@ -372,6 +420,8 @@ pub mod tests {
         assert_eq!(len, 8);
         let raw_val = u64::from_be_bytes(buf[0..8].try_into().unwrap());
         assert_eq!(raw_val, 5999999);
+        assert_eq!(u64.value_typed(), 5999999);
+        assert_eq!(u64.value(), 5999999);
     }
 
     #[test]
@@ -393,8 +443,11 @@ pub mod tests {
         assert!(conv_fails.is_err());
         let err = conv_fails.unwrap_err();
         match err {
-            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
-                assert_eq!(width, 2);
+            UnsignedByteFieldError::InvalidWidth {
+                found,
+                expected: Some(expected),
+            } => {
+                assert_eq!(found, 2);
                 assert_eq!(expected, 1);
             }
             _ => {
@@ -422,8 +475,11 @@ pub mod tests {
         assert!(conv_fails.is_err());
         let err = conv_fails.unwrap_err();
         match err {
-            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
-                assert_eq!(width, 4);
+            UnsignedByteFieldError::InvalidWidth {
+                found,
+                expected: Some(expected),
+            } => {
+                assert_eq!(found, 4);
                 assert_eq!(expected, 2);
             }
             _ => {
@@ -451,8 +507,11 @@ pub mod tests {
         assert!(conv_fails.is_err());
         let err = conv_fails.unwrap_err();
         match err {
-            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
-                assert_eq!(width, 8);
+            UnsignedByteFieldError::InvalidWidth {
+                found,
+                expected: Some(expected),
+            } => {
+                assert_eq!(found, 8);
                 assert_eq!(expected, 4);
             }
             _ => {
@@ -480,8 +539,11 @@ pub mod tests {
         assert!(conv_fails.is_err());
         let err = conv_fails.unwrap_err();
         match err {
-            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
-                assert_eq!(width, 4);
+            UnsignedByteFieldError::InvalidWidth {
+                found,
+                expected: Some(expected),
+            } => {
+                assert_eq!(found, 4);
                 assert_eq!(expected, 8);
             }
             _ => {
@@ -498,9 +560,9 @@ pub mod tests {
         u8.write_to_be_bytes(&mut buf)
             .expect("writing to raw buffer failed");
         assert_eq!(buf[0], 5);
-        for i in 1..8 {
+        (1..8).for_each(|i| {
             assert_eq!(buf[i], 0);
-        }
+        });
     }
 
     #[test]
@@ -512,8 +574,8 @@ pub mod tests {
             .expect("writing to raw buffer failed");
         let raw_val = u16::from_be_bytes(buf[0..2].try_into().unwrap());
         assert_eq!(raw_val, 3823);
-        for i in 2..8 {
-            assert_eq!(buf[i], 0);
+        for val in buf.iter().skip(2) {
+            assert_eq!(*val, 0);
         }
     }
 
@@ -526,9 +588,9 @@ pub mod tests {
             .expect("writing to raw buffer failed");
         let raw_val = u32::from_be_bytes(buf[0..4].try_into().unwrap());
         assert_eq!(raw_val, 80932);
-        for i in 4..8 {
+        (4..8).for_each(|i| {
             assert_eq!(buf[i], 0);
-        }
+        });
     }
 
     #[test]
@@ -582,9 +644,9 @@ pub mod tests {
         assert!(res.is_err());
         let err = res.unwrap_err();
         match err {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.found, 1);
-                assert_eq!(missmatch.expected, 2);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(found, 1);
+                assert_eq!(expected, 2);
             }
             _ => {
                 panic!("invalid exception")
@@ -600,9 +662,9 @@ pub mod tests {
         assert!(res.is_err());
         let err = res.unwrap_err();
         match err {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.found, 1);
-                assert_eq!(missmatch.expected, 2);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(found, 1);
+                assert_eq!(expected, 2);
             }
             _ => {
                 panic!("invalid exception {}", err)
@@ -612,11 +674,11 @@ pub mod tests {
         assert!(u16.is_err());
         let err = u16.unwrap_err();
         if let UnsignedByteFieldError::ByteConversionError(
-            ByteConversionError::FromSliceTooSmall(missmatch),
+            ByteConversionError::FromSliceTooSmall { found, expected },
         ) = err
         {
-            assert_eq!(missmatch.expected, 2);
-            assert_eq!(missmatch.found, 1);
+            assert_eq!(expected, 2);
+            assert_eq!(found, 1);
         } else {
             panic!("unexpected exception {}", err);
         }
@@ -630,9 +692,9 @@ pub mod tests {
         assert!(res.is_err());
         let err = res.unwrap_err();
         match err {
-            ByteConversionError::ToSliceTooSmall(missmatch) => {
-                assert_eq!(missmatch.found, 3);
-                assert_eq!(missmatch.expected, 4);
+            ByteConversionError::ToSliceTooSmall { found, expected } => {
+                assert_eq!(found, 3);
+                assert_eq!(expected, 4);
             }
             _ => {
                 panic!("invalid exception")