tested basic frame parser

Reviewed-on: #111

.github/workflows/ci.yml

@@ -1,42 +1,39 @@
-on: [push]
-
 name: ci
+on: [push, pull_request]
 
 jobs:
   check:
-    name: Check
+    name: Check build
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-      - uses: actions-rs/cargo@v1
-        with:
-          command: check
-          args: --release
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - run: cargo check --release
 
-  msrv:
-    name: Check with MSRV
+  test:
+    name: Run Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          toolchain: 1.65.0
-          override: true
-          profile: minimal
-      - uses: actions-rs/cargo@v1
-        with:
-          command: check
-          args: --release
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - name: Install nextest
+        uses: taiki-e/install-action@nextest
+      - run: cargo nextest run --all-features
+      - run: cargo test --doc
+
+  msrv:
+    name: Check MSRV
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@1.70.0
+      - run: cargo check --release
 
   cross-check:
-    name: Check Cross
+    name: Check Cross-Compilation
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -44,70 +41,32 @@ jobs:
           - armv7-unknown-linux-gnueabihf
           - thumbv7em-none-eabihf
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
         with:
-          profile: minimal
-          toolchain: stable
-          target: ${{ matrix.target }}
-          override: true
-      - uses: actions-rs/cargo@v1
-        with:
-          use-cross: true
-          command: check
-          args: --release --target=${{ matrix.target }} --no-default-features
+          targets: "armv7-unknown-linux-gnueabihf, thumbv7em-none-eabihf"
+      - run: cargo check --release --target=${{matrix.target}} --no-default-features
 
   fmt:
-    name: Rustfmt
+    name: Check formatting
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-          override: true
-      - run: rustup component add rustfmt
-      - uses: actions-rs/cargo@v1
-        with:
-          command: fmt
-          args: --all -- --check
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - run: cargo fmt --all -- --check
 
-  check-doc:
+  docs:
     name: Check Documentation Build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          toolchain: nightly
-          override: true
-          profile: minimal
-      - uses: actions-rs/cargo@v1
-        with:
-          command: doc
-          args: --all-features
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@nightly
+      - run: RUSTDOCFLAGS="--cfg docsrs --generate-link-to-definition -Z unstable-options" cargo +nightly doc --all-features
 
   clippy:
     name: Clippy
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-      - run: rustup component add clippy
-      - uses: actions-rs/cargo@v1
-        with:
-          command: clippy
-          args: -- -D warnings
-
-  ci:
-      if: ${{ success() }}
-      # all new jobs must be added to this list
-      needs: [check, fmt, clippy]
-      runs-on: ubuntu-latest
-      steps:
-        - name: CI succeeded
-          run: exit 0
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - run: cargo clippy -- -D warnings

CHANGELOG.md

@@ -8,6 +8,62 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+# [v0.12.0] 2024-09-10
+
+- Bumped MSRV to 1.70.0
+
+## Added
+
+- Added new `cfdp::tlv::TlvOwned` type which erases the lifetime and is clonable.
+- Dedicated `cfdp::tlv::TlvLvDataTooLarge` error struct for APIs where this is the only possible
+  API error.
+- Added File Data PDU API which expects the expected file data size and then exposes the unwritten
+  file data field as a mutable slice. This allows to read data from the virtual file system
+  API to the file data buffer without an intermediate buffer.
+- Generic `EofPdu::new` constructor.
+- Added generic sequence counter module.
+- Added `MsgToUserTlv::to_tlv` converter which reduced the type and converts
+  it to a generic `Tlv`.
+- Implemented `From<MsgToUserTlv> for Tlv` converter trait.
+- Added CFDP maximum file segment length calculator method `calculate_max_file_seg_len_for_max_packet_len_and_pdu_header`
+
+## Added and Changed
+
+- Added new `ReadableTlv` to avoid some boilerplate code and have a common abstraction implemented
+  for both `Tlv` and `TlvOwned` to read the raw TLV data field and its length.
+- Replaced `cfdp::tlv::TlvLvError` by `cfdp::tlv::TlvLvDataTooLarge` where applicable.
+
+## Fixed
+
+- Fixed an error in the EOF writer which wrote the fault location to the wrong buffer position.
+- cfdp `ConditionCode::CheckLimitReached` previous had the wrong numerical value of `0b1001` (9)
+  and now has the correct value of `0b1010` (10).
+
+## Changed
+
+- Minor documentation build updates.
+- Increased delegate version range to v0.13
+
+# [v0.11.2] 2024-05-19
+
+- Bumped MSRV to 1.68.2
+
+## Fixed
+
+- Removed `defmt::Format` impl for `MetadataPduCreator` which seems to be problematic.
+
+# [v0.11.1] 2024-04-22
+
+## Fixed
+
+- The default data length for for `SpHeader` constructors where the data field length is not
+  specified is now 0.
+- The `SpHeader::new_from_fields` is public now.
+
+## Added
+
+- `SpHeader::to_vec` method.
+
 # [v0.11.0] 2024-04-16
 
 ## Changed

Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "spacepackets"
-version = "0.11.0"
+version = "0.12.0"
 edition = "2021"
-rust-version = "1.65"
+rust-version = "1.70.0"
 authors = ["Robin Mueller <muellerr@irs.uni-stuttgart.de>"]
 description = "Generic implementations for various CCSDS and ECSS packet standards"
 homepage = "https://egit.irs.uni-stuttgart.de/rust/spacepackets"
@@ -14,7 +14,8 @@ categories = ["aerospace", "aerospace::space-protocols", "no-std", "hardware-sup
 
 [dependencies]
 crc = "3"
-delegate = ">=0.8, <0.11"
+delegate = ">=0.8, <=0.13"
+paste = "1"
 
 [dependencies.zerocopy]
 version = "0.7"
@@ -60,11 +61,11 @@ chrono = "0.4"
 default = ["std"]
 std = ["chrono/std", "chrono/clock", "alloc", "thiserror"]
 serde = ["dep:serde", "chrono/serde"]
-alloc = ["postcard/alloc", "chrono/alloc"]
+alloc = ["postcard/alloc", "chrono/alloc", "defmt/alloc", "serde/alloc"]
 chrono = ["dep:chrono"]
 timelib = ["dep:time"]
 defmt = ["dep:defmt"]
 
 [package.metadata.docs.rs]
 all-features = true
-rustdoc-args = ["--cfg", "docs_rs", "--generate-link-to-definition"]
+rustdoc-args = ["--generate-link-to-definition"]

README.md

@@ -61,3 +61,13 @@ cargo install grcov --locked
 
 After that, you can simply run `coverage.py` to test the project with coverage. You can optionally
 supply the `--open` flag to open the coverage report in your webbrowser.
+
+# Miri
+
+You can run the [`miri`](https://github.com/rust-lang/miri) tool on this library to check for
+undefined behaviour (UB). This library does not use use any `unsafe` code blocks, but `miri` could
+still catch UB from used libraries.
+
+```sh
+cargo +nightly miri nextest run --all-features
+```

automation/Jenkinsfile

@@ -21,7 +21,9 @@ pipeline {
     }
     stage('Docs') {
         steps {
-          sh 'cargo +nightly doc --all-features'
+          sh """
+            RUSTDOCFLAGS="--cfg docsrs --generate-link-to-definition -Z unstable-options" cargo +nightly doc --all-features
+          """
         }
     }
     stage('Rustfmt') {

release-checklist.md

@@ -4,7 +4,9 @@ Checklist for new releases
 # Pre-Release
 
 1. Make sure any new modules are documented sufficiently enough and check docs with
-   `cargo +nightly doc --all-features --config 'build.rustdocflags=["--cfg", "docs_rs"]' --open`.
+   `RUSTDOCFLAGS="--cfg docsrs --generate-link-to-definition -Z unstable-options" cargo +nightly doc --all-features --open`
+   or `cargo +nightly doc --all-features --config 'build.rustdocflags=["--cfg", "docsrs" --generate-link-to-definition"]' --open`
+   (was problematic on more recent nightly versions).
 2. Bump version specifier in `Cargo.toml`.
 3. Update `CHANGELOG.md`: Convert `unreleased` section into version section with date and add new
    `unreleased` section.

src/cfdp/lv.rs

@@ -1,5 +1,4 @@
 //! Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
-use crate::cfdp::TlvLvError;
 use crate::ByteConversionError;
 use core::str::Utf8Error;
 #[cfg(feature = "serde")]
@@ -7,6 +6,8 @@ use serde::{Deserialize, Serialize};
 #[cfg(feature = "std")]
 use std::string::String;
 
+use super::TlvLvDataTooLarge;
+
 pub const MIN_LV_LEN: usize = 1;
 
 /// Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
@@ -63,9 +64,9 @@ pub(crate) fn generic_len_check_deserialization(
 
 impl<'data> Lv<'data> {
     #[inline]
-    pub fn new(data: &[u8]) -> Result<Lv, TlvLvError> {
+    pub fn new(data: &[u8]) -> Result<Lv, TlvLvDataTooLarge> {
         if data.len() > u8::MAX as usize {
-            return Err(TlvLvError::DataTooLarge(data.len()));
+            return Err(TlvLvDataTooLarge(data.len()));
         }
         Ok(Lv {
             data,
@@ -85,7 +86,7 @@ impl<'data> Lv<'data> {
     /// Helper function to build a string LV. This is especially useful for the file or directory
     /// path LVs
     #[inline]
-    pub fn new_from_str(str_slice: &str) -> Result<Lv, TlvLvError> {
+    pub fn new_from_str(str_slice: &str) -> Result<Lv, TlvLvDataTooLarge> {
         Self::new(str_slice.as_bytes())
     }
 
@@ -93,7 +94,7 @@ impl<'data> Lv<'data> {
     /// path LVs
     #[cfg(feature = "std")]
     #[inline]
-    pub fn new_from_string(string: &'data String) -> Result<Lv<'data>, TlvLvError> {
+    pub fn new_from_string(string: &'data String) -> Result<Lv<'data>, TlvLvDataTooLarge> {
         Self::new(string.as_bytes())
     }
 
@@ -177,10 +178,10 @@ impl<'data> Lv<'data> {
 
 #[cfg(test)]
 pub mod tests {
-    use super::*;
     use alloc::string::ToString;
 
-    use crate::cfdp::TlvLvError;
+    use super::*;
+
     use crate::ByteConversionError;
     use std::string::String;
 
@@ -271,15 +272,11 @@ pub mod tests {
         let lv = Lv::new(&data_big);
         assert!(lv.is_err());
         let error = lv.unwrap_err();
-        if let TlvLvError::DataTooLarge(size) = error {
-            assert_eq!(size, u8::MAX as usize + 1);
-            assert_eq!(
-                error.to_string(),
-                "data with size 256 larger than allowed 255 bytes"
-            );
-        } else {
-            panic!("invalid exception {:?}", error)
-        }
+        assert_eq!(error.0, u8::MAX as usize + 1);
+        assert_eq!(
+            error.to_string(),
+            "data with size 256 larger than allowed 255 bytes"
+        );
     }
 
     #[test]

src/cfdp/mod.rs

@@ -116,7 +116,7 @@ pub enum ConditionCode {
     FileSizeError = 0b0110,
     NakLimitReached = 0b0111,
     InactivityDetected = 0b1000,
-    CheckLimitReached = 0b1001,
+    CheckLimitReached = 0b1010,
     UnsupportedChecksumType = 0b1011,
     /// Not an actual fault condition for which fault handler overrides can be specified
     SuspendRequestReceived = 0b1110,
@@ -176,11 +176,30 @@ impl Default for ChecksumType {
 
 pub const NULL_CHECKSUM_U32: [u8; 4] = [0; 4];
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct TlvLvDataTooLarge(pub usize);
+
+impl Display for TlvLvDataTooLarge {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        write!(
+            f,
+            "data with size {} larger than allowed {} bytes",
+            self.0,
+            u8::MAX
+        )
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for TlvLvDataTooLarge {}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum TlvLvError {
-    DataTooLarge(usize),
+    DataTooLarge(TlvLvDataTooLarge),
     ByteConversion(ByteConversionError),
     /// First value: Found value. Second value: Expected value if there is one.
     InvalidTlvTypeField {
@@ -197,6 +216,12 @@ pub enum TlvLvError {
     InvalidFilestoreActionCode(u8),
 }
 
+impl From<TlvLvDataTooLarge> for TlvLvError {
+    fn from(value: TlvLvDataTooLarge) -> Self {
+        Self::DataTooLarge(value)
+    }
+}
+
 impl From<ByteConversionError> for TlvLvError {
     fn from(value: ByteConversionError) -> Self {
         Self::ByteConversion(value)
@@ -206,13 +231,8 @@ impl From<ByteConversionError> for TlvLvError {
 impl Display for TlvLvError {
     fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
         match self {
-            TlvLvError::DataTooLarge(data_len) => {
-                write!(
-                    f,
-                    "data with size {} larger than allowed {} bytes",
-                    data_len,
-                    u8::MAX
-                )
+            TlvLvError::DataTooLarge(e) => {
+                write!(f, "{}", e)
             }
             TlvLvError::ByteConversion(e) => {
                 write!(f, "tlv or lv byte conversion: {}", e)
@@ -240,6 +260,7 @@ impl Display for TlvLvError {
 impl Error for TlvLvError {
     fn source(&self) -> Option<&(dyn Error + 'static)> {
         match self {
+            TlvLvError::DataTooLarge(e) => Some(e),
             TlvLvError::ByteConversion(e) => Some(e),
             _ => None,
         }

src/cfdp/pdu/eof.rs

@@ -25,20 +25,36 @@ pub struct EofPdu {
 }
 
 impl EofPdu {
-    pub fn new_no_error(mut pdu_header: PduHeader, file_checksum: u32, file_size: u64) -> Self {
+    pub fn new(
+        mut pdu_header: PduHeader,
+        condition_code: ConditionCode,
+        file_checksum: u32,
+        file_size: u64,
+        fault_location: Option<EntityIdTlv>,
+    ) -> Self {
         // Force correct direction flag.
         pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
         let mut eof_pdu = Self {
             pdu_header,
-            condition_code: ConditionCode::NoError,
+            condition_code,
             file_checksum,
             file_size,
-            fault_location: None,
+            fault_location,
         };
         eof_pdu.pdu_header.pdu_datafield_len = eof_pdu.calc_pdu_datafield_len() as u16;
         eof_pdu
     }
 
+    pub fn new_no_error(pdu_header: PduHeader, file_checksum: u32, file_size: u64) -> Self {
+        Self::new(
+            pdu_header,
+            ConditionCode::NoError,
+            file_checksum,
+            file_size,
+            None,
+        )
+    }
+
     pub fn pdu_header(&self) -> &PduHeader {
         &self.pdu_header
     }
@@ -148,7 +164,7 @@ impl WritablePduPacket for EofPdu {
             &mut buf[current_idx..],
         )?;
         if let Some(fault_location) = self.fault_location {
-            current_idx += fault_location.write_to_bytes(buf)?;
+            current_idx += fault_location.write_to_bytes(&mut buf[current_idx..])?;
         }
         if self.crc_flag() == CrcFlag::WithCrc {
             current_idx = add_pdu_crc(buf, current_idx);
@@ -171,13 +187,23 @@ mod tests {
     use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag, PduType, TransmissionMode};
     #[cfg(feature = "serde")]
     use crate::tests::generic_serde_test;
+    use crate::util::{UnsignedByteFieldU16, UnsignedEnum};
 
-    fn verify_state(&eof_pdu: &EofPdu, file_flag: LargeFileFlag) {
+    fn verify_state_no_error_no_crc(eof_pdu: &EofPdu, file_flag: LargeFileFlag) {
+        verify_state(eof_pdu, CrcFlag::NoCrc, file_flag, ConditionCode::NoError);
+    }
+
+    fn verify_state(
+        eof_pdu: &EofPdu,
+        crc_flag: CrcFlag,
+        file_flag: LargeFileFlag,
+        cond_code: ConditionCode,
+    ) {
         assert_eq!(eof_pdu.file_checksum(), 0x01020304);
         assert_eq!(eof_pdu.file_size(), 12);
-        assert_eq!(eof_pdu.condition_code(), ConditionCode::NoError);
+        assert_eq!(eof_pdu.condition_code(), cond_code);
 
-        assert_eq!(eof_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(eof_pdu.crc_flag(), crc_flag);
         assert_eq!(eof_pdu.file_flag(), file_flag);
         assert_eq!(eof_pdu.pdu_type(), PduType::FileDirective);
         assert_eq!(
@@ -197,7 +223,7 @@ mod tests {
         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.len_written(), pdu_header.header_len() + 2 + 4 + 4);
-        verify_state(&eof_pdu, LargeFileFlag::Normal);
+        verify_state_no_error_no_crc(&eof_pdu, LargeFileFlag::Normal);
     }
 
     #[test]
@@ -283,7 +309,7 @@ mod tests {
         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);
+        verify_state_no_error_no_crc(&eof_pdu, LargeFileFlag::Large);
         assert_eq!(eof_pdu.len_written(), pdu_header.header_len() + 2 + 8 + 4);
     }
 
@@ -295,4 +321,48 @@ mod tests {
         let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
         generic_serde_test(eof_pdu);
     }
+
+    fn generic_test_with_fault_location_and_error(crc: CrcFlag) {
+        let pdu_conf = common_pdu_conf(crc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new(
+            pdu_header,
+            ConditionCode::FileChecksumFailure,
+            0x01020304,
+            12,
+            Some(EntityIdTlv::new(UnsignedByteFieldU16::new(5).into())),
+        );
+        let mut expected_len = pdu_header.header_len() + 2 + 4 + 4 + 4;
+        if crc == CrcFlag::WithCrc {
+            expected_len += 2;
+        }
+        // Entity ID TLV increaes length by 4.
+        assert_eq!(eof_pdu.len_written(), expected_len);
+        verify_state(
+            &eof_pdu,
+            crc,
+            LargeFileFlag::Normal,
+            ConditionCode::FileChecksumFailure,
+        );
+        let eof_vec = eof_pdu.to_vec().unwrap();
+        let eof_read_back = EofPdu::from_bytes(&eof_vec);
+        if let Err(e) = eof_read_back {
+            panic!("deserialization failed with: {e}")
+        }
+        let eof_read_back = eof_read_back.unwrap();
+        assert_eq!(eof_read_back, eof_pdu);
+        assert!(eof_read_back.fault_location.is_some());
+        assert_eq!(eof_read_back.fault_location.unwrap().entity_id().value(), 5);
+        assert_eq!(eof_read_back.fault_location.unwrap().entity_id().size(), 2);
+    }
+
+    #[test]
+    fn test_with_fault_location_and_error() {
+        generic_test_with_fault_location_and_error(CrcFlag::NoCrc);
+    }
+
+    #[test]
+    fn test_with_fault_location_and_error_and_crc() {
+        generic_test_with_fault_location_and_error(CrcFlag::WithCrc);
+    }
 }

src/cfdp/pdu/file_data.rs

@@ -92,16 +92,67 @@ impl<'seg_meta> SegmentMetadata<'seg_meta> {
     }
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+struct FdPduBase<'seg_meta> {
+    pdu_header: PduHeader,
+    #[cfg_attr(feature = "serde", serde(borrow))]
+    segment_metadata: Option<SegmentMetadata<'seg_meta>>,
+    offset: u64,
+}
+
+impl CfdpPdu for FdPduBase<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        None
+    }
+}
+
+impl FdPduBase<'_> {
+    fn calc_pdu_datafield_len(&self, file_data_len: u64) -> usize {
+        let mut len = core::mem::size_of::<u32>();
+        if self.pdu_header.pdu_conf.file_flag == LargeFileFlag::Large {
+            len += 4;
+        }
+        if self.segment_metadata.is_some() {
+            len += self.segment_metadata.as_ref().unwrap().written_len()
+        }
+        len += file_data_len as usize;
+        if self.crc_flag() == CrcFlag::WithCrc {
+            len += 2;
+        }
+        len
+    }
+
+    fn write_common_fields_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        if self.segment_metadata.is_some() {
+            current_idx += self
+                .segment_metadata
+                .as_ref()
+                .unwrap()
+                .write_to_bytes(&mut buf[current_idx..])?;
+        }
+        current_idx += write_fss_field(
+            self.pdu_header.common_pdu_conf().file_flag,
+            self.offset,
+            &mut buf[current_idx..],
+        )?;
+        Ok(current_idx)
+    }
+}
+
 /// File Data PDU abstraction.
 ///
 /// For more information, refer to CFDP chapter 5.3.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct FileDataPdu<'seg_meta, 'file_data> {
-    pdu_header: PduHeader,
     #[cfg_attr(feature = "serde", serde(borrow))]
-    segment_metadata: Option<SegmentMetadata<'seg_meta>>,
-    offset: u64,
+    common: FdPduBase<'seg_meta>,
     file_data: &'file_data [u8],
 }
 
@@ -134,42 +185,34 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
             pdu_header.seg_metadata_flag = SegmentMetadataFlag::Present;
         }
         let mut pdu = Self {
-            pdu_header,
-            segment_metadata,
-            offset,
+            common: FdPduBase {
+                pdu_header,
+                segment_metadata,
+                offset,
+            },
             file_data,
         };
-        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
+        pdu.common.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
         pdu
     }
 
     fn calc_pdu_datafield_len(&self) -> usize {
-        let mut len = core::mem::size_of::<u32>();
-        if self.pdu_header.pdu_conf.file_flag == LargeFileFlag::Large {
-            len += 4;
-        }
-        if self.segment_metadata.is_some() {
-            len += self.segment_metadata.as_ref().unwrap().written_len()
-        }
-        len += self.file_data.len();
-        if self.crc_flag() == CrcFlag::WithCrc {
-            len += 2;
-        }
-        len
+        self.common
+            .calc_pdu_datafield_len(self.file_data.len() as u64)
+    }
+
+    pub fn segment_metadata(&self) -> Option<&SegmentMetadata> {
+        self.common.segment_metadata.as_ref()
     }
 
     pub fn offset(&self) -> u64 {
-        self.offset
+        self.common.offset
     }
 
     pub fn file_data(&self) -> &'file_data [u8] {
         self.file_data
     }
 
-    pub fn segment_metadata(&self) -> Option<&SegmentMetadata> {
-        self.segment_metadata.as_ref()
-    }
-
     pub fn 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)?;
@@ -190,16 +233,18 @@ impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
             .into());
         }
         Ok(Self {
-            pdu_header,
-            segment_metadata,
-            offset,
+            common: FdPduBase {
+                pdu_header,
+                segment_metadata,
+                offset,
+            },
             file_data: &buf[current_idx..full_len_without_crc],
         })
     }
 }
 impl CfdpPdu for FileDataPdu<'_, '_> {
     fn pdu_header(&self) -> &PduHeader {
-        &self.pdu_header
+        &self.common.pdu_header
     }
 
     fn file_directive_type(&self) -> Option<FileDirectiveType> {
@@ -216,19 +261,8 @@ impl WritablePduPacket for FileDataPdu<'_, '_> {
             }
             .into());
         }
-        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
-        if self.segment_metadata.is_some() {
-            current_idx += self
-                .segment_metadata
-                .as_ref()
-                .unwrap()
-                .write_to_bytes(&mut buf[current_idx..])?;
-        }
-        current_idx += write_fss_field(
-            self.pdu_header.common_pdu_conf().file_flag,
-            self.offset,
-            &mut buf[current_idx..],
-        )?;
+
+        let mut current_idx = self.common.write_common_fields_to_bytes(buf)?;
         buf[current_idx..current_idx + self.file_data.len()].copy_from_slice(self.file_data);
         current_idx += self.file_data.len();
         if self.crc_flag() == CrcFlag::WithCrc {
@@ -238,10 +272,167 @@ impl WritablePduPacket for FileDataPdu<'_, '_> {
     }
 
     fn len_written(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+        self.common.pdu_header.header_len() + self.calc_pdu_datafield_len()
     }
 }
 
+/// File Data PDU creator abstraction.
+///
+/// This special creator object allows to read into the file data buffer directly. This avoids
+/// the need of an additional buffer to create a file data PDU. This structure therefore
+/// does not implement the regular [WritablePduPacket] trait.
+///
+/// For more information, refer to CFDP chapter 5.3.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct FileDataPduCreatorWithReservedDatafield<'seg_meta> {
+    #[cfg_attr(feature = "serde", serde(borrow))]
+    common: FdPduBase<'seg_meta>,
+    file_data_len: u64,
+}
+
+impl<'seg_meta> FileDataPduCreatorWithReservedDatafield<'seg_meta> {
+    pub fn new_with_seg_metadata(
+        pdu_header: PduHeader,
+        segment_metadata: SegmentMetadata<'seg_meta>,
+        offset: u64,
+        file_data_len: u64,
+    ) -> Self {
+        Self::new_generic(pdu_header, Some(segment_metadata), offset, file_data_len)
+    }
+
+    pub fn new_no_seg_metadata(pdu_header: PduHeader, offset: u64, file_data_len: u64) -> Self {
+        Self::new_generic(pdu_header, None, offset, file_data_len)
+    }
+
+    pub fn new_generic(
+        mut pdu_header: PduHeader,
+        segment_metadata: Option<SegmentMetadata<'seg_meta>>,
+        offset: u64,
+        file_data_len: u64,
+    ) -> Self {
+        pdu_header.pdu_type = PduType::FileData;
+        if segment_metadata.is_some() {
+            pdu_header.seg_metadata_flag = SegmentMetadataFlag::Present;
+        }
+        let mut pdu = Self {
+            common: FdPduBase {
+                pdu_header,
+                segment_metadata,
+                offset,
+            },
+            file_data_len,
+        };
+        pdu.common.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
+        pdu
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        self.common.calc_pdu_datafield_len(self.file_data_len)
+    }
+
+    pub fn len_written(&self) -> usize {
+        self.common.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+
+    /// This function performs a partial write by writing all data except the file data
+    /// and the CRC.
+    ///
+    /// It returns a [FileDataPduCreatorWithUnwrittenData] which provides a mutable slice to
+    /// the reserved file data field. The user can read file data into this field directly and
+    /// then finish the PDU creation using the [FileDataPduCreatorWithUnwrittenData::finish] call.
+    pub fn write_to_bytes_partially<'buf>(
+        &self,
+        buf: &'buf mut [u8],
+    ) -> Result<FileDataPduCreatorWithUnwrittenData<'buf>, PduError> {
+        if buf.len() < self.len_written() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: self.len_written(),
+            }
+            .into());
+        }
+        let mut current_idx = self.common.write_common_fields_to_bytes(buf)?;
+        let file_data_offset = current_idx as u64;
+        current_idx += self.file_data_len as usize;
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx += 2;
+        }
+        Ok(FileDataPduCreatorWithUnwrittenData {
+            write_buf: &mut buf[0..current_idx],
+            file_data_offset,
+            file_data_len: self.file_data_len,
+            needs_crc: self.crc_flag() == CrcFlag::WithCrc,
+        })
+    }
+}
+
+impl CfdpPdu for FileDataPduCreatorWithReservedDatafield<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.common.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        None
+    }
+}
+
+/// This structure is created with [FileDataPduCreatorReservedDatafield::write_to_bytes_partially]
+/// and provides an API to read file data from the virtual filesystem into the file data PDU buffer
+/// directly.
+///
+/// This structure provides a mutable slice to the reserved file data field. The user can read
+/// file data into this field directly and then finish the PDU creation using the
+/// [FileDataPduCreatorWithUnwrittenData::finish] call.
+pub struct FileDataPduCreatorWithUnwrittenData<'buf> {
+    write_buf: &'buf mut [u8],
+    file_data_offset: u64,
+    file_data_len: u64,
+    needs_crc: bool,
+}
+
+impl FileDataPduCreatorWithUnwrittenData<'_> {
+    pub fn file_data_field_mut(&mut self) -> &mut [u8] {
+        &mut self.write_buf[self.file_data_offset as usize
+            ..self.file_data_offset as usize + self.file_data_len as usize]
+    }
+
+    /// This functio needs to be called to add a CRC to the file data PDU where applicable.
+    ///
+    /// It returns the full written size of the PDU.
+    pub fn finish(self) -> usize {
+        if self.needs_crc {
+            add_pdu_crc(
+                self.write_buf,
+                self.file_data_offset as usize + self.file_data_len as usize,
+            );
+        }
+        self.write_buf.len()
+    }
+}
+
+/// This function can be used to calculate the maximum allowed file segment size for
+/// a given maximum packet length and the segment metadata if there is any.
+pub fn calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(
+    pdu_header: &PduHeader,
+    max_packet_len: usize,
+    segment_metadata: Option<&SegmentMetadata>,
+) -> usize {
+    let mut subtract = pdu_header.header_len();
+    if segment_metadata.is_some() {
+        subtract += 1 + segment_metadata.as_ref().unwrap().metadata().unwrap().len();
+    }
+    if pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
+        subtract += 8;
+    } else {
+        subtract += 4;
+    }
+    if pdu_header.common_pdu_conf().crc_flag == CrcFlag::WithCrc {
+        subtract += 2;
+    }
+    max_packet_len.saturating_sub(subtract)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -263,7 +454,7 @@ mod tests {
         assert!(fd_pdu.segment_metadata().is_none());
         assert_eq!(
             fd_pdu.len_written(),
-            fd_pdu.pdu_header.header_len() + core::mem::size_of::<u32>() + 4
+            fd_pdu.pdu_header().header_len() + core::mem::size_of::<u32>() + 4
         );
 
         assert_eq!(fd_pdu.crc_flag(), CrcFlag::NoCrc);
@@ -290,11 +481,11 @@ mod tests {
         let written = res.unwrap();
         assert_eq!(
             written,
-            fd_pdu.pdu_header.header_len() + core::mem::size_of::<u32>() + 4
+            fd_pdu.pdu_header().header_len() + core::mem::size_of::<u32>() + 4
         );
-        let mut current_idx = fd_pdu.pdu_header.header_len();
+        let mut current_idx = fd_pdu.pdu_header().header_len();
         let file_size = u32::from_be_bytes(
-            buf[fd_pdu.pdu_header.header_len()..fd_pdu.pdu_header.header_len() + 4]
+            buf[fd_pdu.pdu_header().header_len()..fd_pdu.pdu_header().header_len() + 4]
                 .try_into()
                 .unwrap(),
         );
@@ -380,7 +571,7 @@ mod tests {
         assert_eq!(*fd_pdu.segment_metadata().unwrap(), segment_meta);
         assert_eq!(
             fd_pdu.len_written(),
-            fd_pdu.pdu_header.header_len()
+            fd_pdu.pdu_header().header_len()
                 + 1
                 + seg_metadata.len()
                 + core::mem::size_of::<u32>()
@@ -390,7 +581,7 @@ mod tests {
         fd_pdu
             .write_to_bytes(&mut buf)
             .expect("writing FD PDU failed");
-        let mut current_idx = fd_pdu.pdu_header.header_len();
+        let mut current_idx = fd_pdu.pdu_header().header_len();
         assert_eq!(
             RecordContinuationState::try_from((buf[current_idx] >> 6) & 0b11).unwrap(),
             RecordContinuationState::StartAndEnd
@@ -482,4 +673,142 @@ mod tests {
         let output_converted_back: FileDataPdu = from_bytes(&output).unwrap();
         assert_eq!(output_converted_back, fd_pdu);
     }
+
+    #[test]
+    fn test_fd_pdu_creator_with_reserved_field_no_crc() {
+        let common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let test_str = "hello world!";
+        let fd_pdu = FileDataPduCreatorWithReservedDatafield::new_no_seg_metadata(
+            pdu_header,
+            10,
+            test_str.len() as u64,
+        );
+        let mut write_buf: [u8; 64] = [0; 64];
+        let mut pdu_unwritten = fd_pdu
+            .write_to_bytes_partially(&mut write_buf)
+            .expect("partial write failed");
+        pdu_unwritten
+            .file_data_field_mut()
+            .copy_from_slice(test_str.as_bytes());
+        pdu_unwritten.finish();
+
+        let pdu_reader = FileDataPdu::from_bytes(&write_buf).expect("reading file data PDU failed");
+        assert_eq!(
+            core::str::from_utf8(pdu_reader.file_data()).expect("reading utf8 string failed"),
+            "hello world!"
+        );
+    }
+
+    #[test]
+    fn test_fd_pdu_creator_with_reserved_field_with_crc() {
+        let mut common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        common_conf.crc_flag = true.into();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let test_str = "hello world!";
+        let fd_pdu = FileDataPduCreatorWithReservedDatafield::new_no_seg_metadata(
+            pdu_header,
+            10,
+            test_str.len() as u64,
+        );
+        let mut write_buf: [u8; 64] = [0; 64];
+        let mut pdu_unwritten = fd_pdu
+            .write_to_bytes_partially(&mut write_buf)
+            .expect("partial write failed");
+        pdu_unwritten
+            .file_data_field_mut()
+            .copy_from_slice(test_str.as_bytes());
+        pdu_unwritten.finish();
+
+        let pdu_reader = FileDataPdu::from_bytes(&write_buf).expect("reading file data PDU failed");
+        assert_eq!(
+            core::str::from_utf8(pdu_reader.file_data()).expect("reading utf8 string failed"),
+            "hello world!"
+        );
+    }
+
+    #[test]
+    fn test_fd_pdu_creator_with_reserved_field_with_crc_without_finish_fails() {
+        let mut common_conf =
+            CommonPduConfig::new_with_byte_fields(TEST_SRC_ID, TEST_DEST_ID, TEST_SEQ_NUM).unwrap();
+        common_conf.crc_flag = true.into();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let test_str = "hello world!";
+        let fd_pdu = FileDataPduCreatorWithReservedDatafield::new_no_seg_metadata(
+            pdu_header,
+            10,
+            test_str.len() as u64,
+        );
+        let mut write_buf: [u8; 64] = [0; 64];
+        let mut pdu_unwritten = fd_pdu
+            .write_to_bytes_partially(&mut write_buf)
+            .expect("partial write failed");
+        pdu_unwritten
+            .file_data_field_mut()
+            .copy_from_slice(test_str.as_bytes());
+
+        let pdu_reader_error = FileDataPdu::from_bytes(&write_buf);
+        assert!(pdu_reader_error.is_err());
+        let error = pdu_reader_error.unwrap_err();
+        match error {
+            PduError::ChecksumError(_) => (),
+            _ => {
+                panic!("unexpected PDU error {}", error)
+            }
+        }
+    }
+
+    #[test]
+    fn test_max_file_seg_calculator_0() {
+        let pdu_header = PduHeader::new_for_file_data_default(CommonPduConfig::default(), 0);
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 64, None),
+            53
+        );
+    }
+
+    #[test]
+    fn test_max_file_seg_calculator_1() {
+        let common_conf = CommonPduConfig {
+            crc_flag: CrcFlag::WithCrc,
+            ..Default::default()
+        };
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 64, None),
+            51
+        );
+    }
+
+    #[test]
+    fn test_max_file_seg_calculator_2() {
+        let common_conf = CommonPduConfig {
+            file_flag: LargeFileFlag::Large,
+            ..Default::default()
+        };
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 64, None),
+            49
+        );
+    }
+
+    #[test]
+    fn test_max_file_seg_calculator_saturating_sub() {
+        let common_conf = CommonPduConfig {
+            file_flag: LargeFileFlag::Large,
+            ..Default::default()
+        };
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 15, None),
+            0
+        );
+        assert_eq!(
+            calculate_max_file_seg_len_for_max_packet_len_and_pdu_header(&pdu_header, 14, None),
+            0
+        );
+    }
 }

src/cfdp/pdu/finished.rs

@@ -10,6 +10,7 @@ use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::tlv::ReadableTlv;
 use super::{CfdpPdu, WritablePduPacket};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]

src/cfdp/pdu/metadata.rs

@@ -1,3 +1,5 @@
+#[cfg(feature = "alloc")]
+use super::tlv::TlvOwned;
 use crate::cfdp::lv::Lv;
 use crate::cfdp::pdu::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
@@ -11,6 +13,7 @@ use alloc::vec::Vec;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::tlv::ReadableTlv;
 use super::{CfdpPdu, WritablePduPacket};
 
 #[derive(Default, Debug, Copy, Clone, PartialEq, Eq)]
@@ -51,18 +54,26 @@ pub fn build_metadata_opts_from_vec(
     build_metadata_opts_from_slice(buf, tlvs.as_slice())
 }
 
+#[cfg(feature = "alloc")]
+pub fn build_metadata_opts_from_owned_slice(tlvs: &[TlvOwned]) -> Vec<u8> {
+    let mut sum_vec = Vec::new();
+    for tlv in tlvs {
+        sum_vec.extend(tlv.to_vec());
+    }
+    sum_vec
+}
+
 /// Metadata PDU creator abstraction.
 ///
 /// This abstraction exposes a specialized API for creating metadata PDUs as specified in
 /// CFDP chapter 5.2.5.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
-#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 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>],
+    options: &'opts [u8],
 }
 
 impl<'src_name, 'dest_name, 'opts> MetadataPduCreator<'src_name, 'dest_name, 'opts> {
@@ -86,7 +97,7 @@ impl<'src_name, 'dest_name, 'opts> MetadataPduCreator<'src_name, 'dest_name, 'op
         metadata_params: MetadataGenericParams,
         src_file_name: Lv<'src_name>,
         dest_file_name: Lv<'dest_name>,
-        options: &'opts [Tlv<'opts>],
+        options: &'opts [u8],
     ) -> Self {
         Self::new(
             pdu_header,
@@ -102,7 +113,7 @@ impl<'src_name, 'dest_name, 'opts> MetadataPduCreator<'src_name, 'dest_name, 'op
         metadata_params: MetadataGenericParams,
         src_file_name: Lv<'src_name>,
         dest_file_name: Lv<'dest_name>,
-        options: &'opts [Tlv<'opts>],
+        options: &'opts [u8],
     ) -> Self {
         pdu_header.pdu_type = PduType::FileDirective;
         pdu_header.pdu_conf.direction = Direction::TowardsReceiver;
@@ -129,10 +140,19 @@ impl<'src_name, 'dest_name, 'opts> MetadataPduCreator<'src_name, 'dest_name, 'op
         self.dest_file_name
     }
 
-    pub fn options(&self) -> &'opts [Tlv<'opts>] {
+    pub fn options(&self) -> &'opts [u8] {
         self.options
     }
 
+    /// Yield an iterator which can be used to loop through all options. Returns [None] if the
+    /// options field is empty.
+    pub fn options_iter(&self) -> OptionsIter<'_> {
+        OptionsIter {
+            opt_buf: self.options,
+            current_idx: 0,
+        }
+    }
+
     fn calc_pdu_datafield_len(&self) -> usize {
         // One directve type octet and one byte of the directive parameter field.
         let mut len = 2;
@@ -143,9 +163,7 @@ impl<'src_name, 'dest_name, 'opts> MetadataPduCreator<'src_name, 'dest_name, 'op
         }
         len += self.src_file_name.len_full();
         len += self.dest_file_name.len_full();
-        for tlv in self.options() {
-            len += tlv.len_full()
-        }
+        len += self.options().len();
         if self.crc_flag() == CrcFlag::WithCrc {
             len += 2;
         }
@@ -191,10 +209,8 @@ impl WritablePduPacket for MetadataPduCreator<'_, '_, '_> {
         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();
-        }
+        buf[current_idx..current_idx + self.options.len()].copy_from_slice(self.options);
+        current_idx += self.options.len();
         if self.crc_flag() == CrcFlag::WithCrc {
             current_idx = add_pdu_crc(buf, current_idx);
         }
@@ -355,7 +371,7 @@ pub mod tests {
     };
     use crate::cfdp::pdu::{CfdpPdu, PduError, WritablePduPacket};
     use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
-    use crate::cfdp::tlv::{Tlv, TlvType};
+    use crate::cfdp::tlv::{ReadableTlv, Tlv, TlvOwned, TlvType, WritableTlv};
     use crate::cfdp::{
         ChecksumType, CrcFlag, Direction, LargeFileFlag, PduType, SegmentMetadataFlag,
         SegmentationControl, TransmissionMode,
@@ -365,16 +381,16 @@ pub mod tests {
     const SRC_FILENAME: &str = "hello-world.txt";
     const DEST_FILENAME: &str = "hello-world2.txt";
 
-    fn generic_metadata_pdu<'opts>(
+    fn generic_metadata_pdu(
         crc_flag: CrcFlag,
         checksum_type: ChecksumType,
         closure_requested: bool,
         fss: LargeFileFlag,
-        opts: &'opts [Tlv],
+        opts: &[u8],
     ) -> (
         Lv<'static>,
         Lv<'static>,
-        MetadataPduCreator<'static, 'static, 'opts>,
+        MetadataPduCreator<'static, 'static, '_>,
     ) {
         let pdu_header = PduHeader::new_no_file_data(common_pdu_conf(crc_flag, fss), 0);
         let metadata_params = MetadataGenericParams::new(closure_requested, checksum_type, 0x1010);
@@ -544,9 +560,9 @@ pub mod tests {
         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);
+        let opts = written.options_iter();
+        for (tlv_written, tlv_read) in opts.zip(read.options_iter().unwrap()) {
+            assert_eq!(&tlv_written, &tlv_read);
         }
     }
 
@@ -661,14 +677,14 @@ pub mod tests {
         let tlv1 = Tlv::new_empty(TlvType::FlowLabel);
         let msg_to_user: [u8; 4] = [1, 2, 3, 4];
         let tlv2 = Tlv::new(TlvType::MsgToUser, &msg_to_user).unwrap();
-        let tlv_vec = vec![tlv1, tlv2];
-        let opts_len = tlv1.len_full() + tlv2.len_full();
+        let mut tlv_buf: [u8; 64] = [0; 64];
+        let opts_len = build_metadata_opts_from_slice(&mut tlv_buf, &[tlv1, tlv2]).unwrap();
         let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
             CrcFlag::NoCrc,
             ChecksumType::Crc32,
             false,
             LargeFileFlag::Normal,
-            &tlv_vec,
+            &tlv_buf[0..opts_len],
         );
         let mut buf: [u8; 128] = [0; 128];
         let write_res = metadata_pdu.write_to_bytes(&mut buf);
@@ -691,7 +707,55 @@ pub mod tests {
         let opts_iter = opts_iter.unwrap();
         let mut accumulated_len = 0;
         for (idx, opt) in opts_iter.enumerate() {
-            assert_eq!(tlv_vec[idx], opt);
+            if idx == 0 {
+                assert_eq!(tlv1, opt);
+            } else if idx == 1 {
+                assert_eq!(tlv2, opt);
+            }
+            accumulated_len += opt.len_full();
+        }
+        assert_eq!(accumulated_len, pdu_read_back.options().len());
+    }
+    #[test]
+    fn test_with_owned_opts() {
+        let tlv1 = TlvOwned::new_empty(TlvType::FlowLabel);
+        let msg_to_user: [u8; 4] = [1, 2, 3, 4];
+        let tlv2 = TlvOwned::new(TlvType::MsgToUser, &msg_to_user).unwrap();
+        let mut all_tlvs = tlv1.to_vec();
+        all_tlvs.extend(tlv2.to_vec());
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            ChecksumType::Crc32,
+            false,
+            LargeFileFlag::Normal,
+            &all_tlvs,
+        );
+        let mut buf: [u8; 128] = [0; 128];
+        let write_res = metadata_pdu.write_to_bytes(&mut buf);
+        assert!(write_res.is_ok());
+        let written = write_res.unwrap();
+        assert_eq!(
+            written,
+            metadata_pdu.pdu_header.header_len()
+                + 1
+                + 1
+                + 4
+                + src_filename.len_full()
+                + dest_filename.len_full()
+                + all_tlvs.len()
+        );
+        let pdu_read_back = MetadataPduReader::from_bytes(&buf).unwrap();
+        compare_read_pdu_to_written_pdu(&metadata_pdu, &pdu_read_back);
+        let opts_iter = pdu_read_back.options_iter();
+        assert!(opts_iter.is_some());
+        let opts_iter = opts_iter.unwrap();
+        let mut accumulated_len = 0;
+        for (idx, opt) in opts_iter.enumerate() {
+            if idx == 0 {
+                assert_eq!(tlv1, opt);
+            } else if idx == 1 {
+                assert_eq!(tlv2, opt);
+            }
             accumulated_len += opt.len_full();
         }
         assert_eq!(accumulated_len, pdu_read_back.options().len());

src/cfdp/tlv/mod.rs

@@ -9,10 +9,14 @@ use crate::ByteConversionError;
 use alloc::vec;
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
+#[cfg(feature = "alloc")]
+pub use alloc_mod::*;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::TlvLvDataTooLarge;
+
 pub mod msg_to_user;
 
 pub const MIN_TLV_LEN: usize = 2;
@@ -39,6 +43,26 @@ pub trait GenericTlv {
     }
 }
 
+pub trait ReadableTlv {
+    fn value(&self) -> &[u8];
+
+    /// Checks whether the value field is empty.
+    fn is_empty(&self) -> bool {
+        self.value().is_empty()
+    }
+
+    /// Helper method to retrieve the length of the value. Simply calls the [slice::len] method of
+    /// [Self::value]
+    fn len_value(&self) -> usize {
+        self.value().len()
+    }
+
+    /// Returns the full raw length, including the length byte.
+    fn len_full(&self) -> usize {
+        self.len_value() + 2
+    }
+}
+
 pub trait WritableTlv {
     fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
     fn len_written(&self) -> usize;
@@ -129,14 +153,14 @@ pub struct Tlv<'data> {
 }
 
 impl<'data> Tlv<'data> {
-    pub fn new(tlv_type: TlvType, data: &[u8]) -> Result<Tlv, TlvLvError> {
+    pub fn new(tlv_type: TlvType, data: &[u8]) -> Result<Tlv, TlvLvDataTooLarge> {
         Ok(Tlv {
             tlv_type_field: TlvTypeField::Standard(tlv_type),
             lv: Lv::new(data)?,
         })
     }
 
-    pub fn new_with_custom_type(tlv_type: u8, data: &[u8]) -> Result<Tlv, TlvLvError> {
+    pub fn new_with_custom_type(tlv_type: u8, data: &[u8]) -> Result<Tlv, TlvLvDataTooLarge> {
         Ok(Tlv {
             tlv_type_field: TlvTypeField::Custom(tlv_type),
             lv: Lv::new(data)?,
@@ -151,26 +175,6 @@ impl<'data> Tlv<'data> {
         }
     }
 
-    pub fn value(&self) -> &[u8] {
-        self.lv.value()
-    }
-
-    /// Checks whether the value field is empty.
-    pub fn is_empty(&self) -> bool {
-        self.value().is_empty()
-    }
-
-    /// Helper method to retrieve the length of the value. Simply calls the [slice::len] method of
-    /// [Self::value]
-    pub fn len_value(&self) -> usize {
-        self.value().len()
-    }
-
-    /// Returns the full raw length, including the length byte.
-    pub fn len_full(&self) -> usize {
-        self.len_value() + 2
-    }
-
     /// Creates a TLV give a raw bytestream. Please note that is is not necessary to pass the
     /// bytestream with the exact size of the expected TLV. This function will take care
     /// of parsing the length byte, and the length of the parsed TLV can be retrieved using
@@ -192,6 +196,27 @@ impl<'data> Tlv<'data> {
     pub fn raw_data(&self) -> Option<&[u8]> {
         self.lv.raw_data()
     }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        TlvOwned {
+            tlv_type_field: self.tlv_type_field,
+            data: self.value().to_vec(),
+        }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl PartialEq<TlvOwned> for Tlv<'_> {
+    fn eq(&self, other: &TlvOwned) -> bool {
+        self.tlv_type_field == other.tlv_type_field && self.value() == other.value()
+    }
+}
+
+impl ReadableTlv for Tlv<'_> {
+    fn value(&self) -> &[u8] {
+        self.lv.value()
+    }
 }
 
 impl WritableTlv for Tlv<'_> {
@@ -212,18 +237,98 @@ impl GenericTlv for Tlv<'_> {
     }
 }
 
-pub(crate) fn verify_tlv_type(raw_type: u8, expected_tlv_type: TlvType) -> Result<(), TlvLvError> {
-    let tlv_type = TlvType::try_from(raw_type).map_err(|_| TlvLvError::InvalidTlvTypeField {
-        found: raw_type,
-        expected: Some(expected_tlv_type.into()),
-    })?;
-    if tlv_type != expected_tlv_type {
-        return Err(TlvLvError::InvalidTlvTypeField {
-            found: tlv_type as u8,
-            expected: Some(expected_tlv_type as u8),
-        });
+#[cfg(feature = "alloc")]
+pub mod alloc_mod {
+    use crate::cfdp::TlvLvDataTooLarge;
+
+    use super::*;
+
+    /// Owned variant of [Tlv] which is consequently [Clone]able and does not have a lifetime
+    /// associated to a data slice.
+    #[derive(Debug, Clone, PartialEq, Eq)]
+    #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+    #[cfg_attr(feature = "defmt", derive(defmt::Format))]
+    pub struct TlvOwned {
+        pub(crate) tlv_type_field: TlvTypeField,
+        pub(crate) data: Vec<u8>,
+    }
+
+    impl TlvOwned {
+        pub fn new(tlv_type: TlvType, data: &[u8]) -> Result<Self, TlvLvDataTooLarge> {
+            if data.len() > u8::MAX as usize {
+                return Err(TlvLvDataTooLarge(data.len()));
+            }
+            Ok(Self {
+                tlv_type_field: TlvTypeField::Standard(tlv_type),
+                data: data.to_vec(),
+            })
+        }
+
+        pub fn new_with_custom_type(tlv_type: u8, data: &[u8]) -> Result<Self, TlvLvDataTooLarge> {
+            if data.len() > u8::MAX as usize {
+                return Err(TlvLvDataTooLarge(data.len()));
+            }
+            Ok(Self {
+                tlv_type_field: TlvTypeField::Custom(tlv_type),
+                data: data.to_vec(),
+            })
+        }
+
+        /// Creates a TLV with an empty value field.
+        pub fn new_empty(tlv_type: TlvType) -> Self {
+            Self {
+                tlv_type_field: TlvTypeField::Standard(tlv_type),
+                data: Vec::new(),
+            }
+        }
+
+        pub fn as_tlv(&self) -> Tlv<'_> {
+            Tlv {
+                tlv_type_field: self.tlv_type_field,
+                // The API should ensure that the data length is never to large, so the unwrap for the
+                // LV creation should never be an issue.
+                lv: Lv::new(&self.data).expect("lv creation failed unexpectedly"),
+            }
+        }
+    }
+
+    impl ReadableTlv for TlvOwned {
+        fn value(&self) -> &[u8] {
+            &self.data
+        }
+    }
+
+    impl WritableTlv for TlvOwned {
+        fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+            generic_len_check_data_serialization(buf, self.data.len(), MIN_TLV_LEN)?;
+            buf[0] = self.tlv_type_field.into();
+            buf[1] = self.data.len() as u8;
+            buf[2..2 + self.data.len()].copy_from_slice(&self.data);
+            Ok(self.len_written())
+        }
+
+        fn len_written(&self) -> usize {
+            self.data.len() + 2
+        }
+    }
+
+    impl GenericTlv for TlvOwned {
+        fn tlv_type_field(&self) -> TlvTypeField {
+            self.tlv_type_field
+        }
+    }
+
+    impl From<Tlv<'_>> for TlvOwned {
+        fn from(value: Tlv<'_>) -> Self {
+            value.to_owned()
+        }
+    }
+
+    impl PartialEq<Tlv<'_>> for TlvOwned {
+        fn eq(&self, other: &Tlv) -> bool {
+            self.tlv_type_field == other.tlv_type_field && self.data == other.value()
+        }
     }
-    Ok(())
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -238,7 +343,7 @@ impl EntityIdTlv {
         Self { entity_id }
     }
 
-    fn len_check(buf: &[u8]) -> Result<(), ByteConversionError> {
+    fn check_min_len(buf: &[u8]) -> Result<(), ByteConversionError> {
         if buf.len() < 2 {
             return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
@@ -261,7 +366,7 @@ impl EntityIdTlv {
     }
 
     pub fn from_bytes(buf: &[u8]) -> Result<Self, TlvLvError> {
-        Self::len_check(buf)?;
+        Self::check_min_len(buf)?;
         verify_tlv_type(buf[0], TlvType::EntityId)?;
         let len = buf[1];
         if len != 1 && len != 2 && len != 4 && len != 8 {
@@ -272,22 +377,31 @@ impl EntityIdTlv {
         Ok(Self { entity_id })
     }
 
-    /// Convert to a generic [Tlv], which also erases the programmatic type information.
+    /// Convert to a generic [Tlv], which also erases the type information.
     pub fn to_tlv(self, buf: &mut [u8]) -> Result<Tlv, ByteConversionError> {
-        Self::len_check(buf)?;
+        Self::check_min_len(buf)?;
         self.entity_id
             .write_to_be_bytes(&mut buf[2..2 + self.entity_id.size()])?;
-        Tlv::new(TlvType::EntityId, &buf[2..2 + self.entity_id.size()]).map_err(|e| match e {
-            TlvLvError::ByteConversion(e) => e,
-            // All other errors are impossible.
-            _ => panic!("unexpected TLV error"),
-        })
+        if buf.len() < self.len_value() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: self.len_value(),
+            });
+        }
+        // We performed all checks necessary to ensure this call never panics.
+        Ok(Tlv::new(TlvType::EntityId, &buf[2..2 + self.entity_id.size()]).unwrap())
+    }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        // Unwrap is okay here, entity ID should never be larger than maximum allowed size.
+        TlvOwned::new(TlvType::EntityId, &self.entity_id.to_vec()).unwrap()
     }
 }
 
 impl WritableTlv for EntityIdTlv {
     fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        Self::len_check(buf)?;
+        Self::check_min_len(buf)?;
         buf[0] = TlvType::EntityId as u8;
         buf[1] = self.entity_id.size() as u8;
         Ok(2 + self.entity_id.write_to_be_bytes(&mut buf[2..])?)
@@ -526,6 +640,12 @@ impl<'first_name, 'second_name> FilestoreRequestTlv<'first_name, 'second_name> {
             },
         })
     }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        // The API should ensure the data field is never too large, so unwrapping here is okay.
+        TlvOwned::new(TlvType::FilestoreRequest, &self.to_vec()[2..]).unwrap()
+    }
 }
 
 impl WritableTlv for FilestoreRequestTlv<'_, '_> {
@@ -711,6 +831,12 @@ impl<'first_name, 'second_name, 'fs_msg> FilestoreResponseTlv<'first_name, 'seco
             filestore_message,
         })
     }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        // The API should ensure the data field is never too large, so unwrap is okay here.
+        TlvOwned::new(TlvType::FilestoreResponse, &self.to_vec()[2..]).unwrap()
+    }
 }
 
 impl WritableTlv for FilestoreResponseTlv<'_, '_, '_> {
@@ -752,6 +878,20 @@ impl GenericTlv for FilestoreResponseTlv<'_, '_, '_> {
     }
 }
 
+pub(crate) fn verify_tlv_type(raw_type: u8, expected_tlv_type: TlvType) -> Result<(), TlvLvError> {
+    let tlv_type = TlvType::try_from(raw_type).map_err(|_| TlvLvError::InvalidTlvTypeField {
+        found: raw_type,
+        expected: Some(expected_tlv_type.into()),
+    })?;
+    if tlv_type != expected_tlv_type {
+        return Err(TlvLvError::InvalidTlvTypeField {
+            found: tlv_type as u8,
+            expected: Some(expected_tlv_type as u8),
+        });
+    }
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -939,15 +1079,11 @@ mod tests {
         let tlv_res = Tlv::new(TlvType::MsgToUser, &buf_too_large);
         assert!(tlv_res.is_err());
         let error = tlv_res.unwrap_err();
-        if let TlvLvError::DataTooLarge(size) = error {
-            assert_eq!(size, u8::MAX as usize + 1);
-            assert_eq!(
-                error.to_string(),
-                "data with size 256 larger than allowed 255 bytes"
-            );
-        } else {
-            panic!("unexpected error {:?}", error);
-        }
+        assert_eq!(error.0, u8::MAX as usize + 1);
+        assert_eq!(
+            error.to_string(),
+            "data with size 256 larger than allowed 255 bytes"
+        );
     }
 
     #[test]
@@ -1300,4 +1436,71 @@ mod tests {
         assert_eq!(tlv_as_vec[0], 20);
         assert_eq!(tlv_as_vec[1], 0);
     }
+
+    #[test]
+    fn test_tlv_to_owned() {
+        let entity_id = UbfU8::new(5);
+        let mut buf: [u8; 4] = [0; 4];
+        assert!(entity_id.write_to_be_bytes(&mut buf).is_ok());
+        let tlv_res = Tlv::new(TlvType::EntityId, &buf[0..1]);
+        assert!(tlv_res.is_ok());
+        let tlv_res = tlv_res.unwrap();
+        let tlv_owned = tlv_res.to_owned();
+        assert_eq!(tlv_res, tlv_owned);
+        let tlv_owned_from_conversion: TlvOwned = tlv_res.into();
+        assert_eq!(tlv_owned_from_conversion, tlv_owned);
+        assert_eq!(tlv_owned_from_conversion, tlv_res);
+    }
+
+    #[test]
+    fn test_owned_tlv() {
+        let entity_id = UbfU8::new(5);
+        let mut buf: [u8; 4] = [0; 4];
+        assert!(entity_id.write_to_be_bytes(&mut buf).is_ok());
+        let tlv_res = TlvOwned::new(TlvType::EntityId, &buf[0..1]).expect("creating TLV failed");
+        assert_eq!(
+            tlv_res.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::EntityId)
+        );
+        assert_eq!(tlv_res.len_full(), 3);
+        assert_eq!(tlv_res.value().len(), 1);
+        assert_eq!(tlv_res.len_value(), 1);
+        assert!(!tlv_res.is_empty());
+        assert_eq!(tlv_res.value()[0], 5);
+    }
+
+    #[test]
+    fn test_owned_tlv_empty() {
+        let tlv_res = TlvOwned::new_empty(TlvType::FlowLabel);
+        assert_eq!(
+            tlv_res.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::FlowLabel)
+        );
+        assert_eq!(tlv_res.len_full(), 2);
+        assert_eq!(tlv_res.value().len(), 0);
+        assert_eq!(tlv_res.len_value(), 0);
+        assert!(tlv_res.is_empty());
+    }
+
+    #[test]
+    fn test_owned_tlv_custom_type() {
+        let tlv_res = TlvOwned::new_with_custom_type(32, &[]).unwrap();
+        assert_eq!(tlv_res.tlv_type_field(), TlvTypeField::Custom(32));
+        assert_eq!(tlv_res.len_full(), 2);
+        assert_eq!(tlv_res.value().len(), 0);
+        assert_eq!(tlv_res.len_value(), 0);
+        assert!(tlv_res.is_empty());
+    }
+
+    #[test]
+    fn test_owned_tlv_conversion_to_bytes() {
+        let entity_id = UbfU8::new(5);
+        let mut buf: [u8; 4] = [0; 4];
+        assert!(entity_id.write_to_be_bytes(&mut buf).is_ok());
+        let tlv_res = Tlv::new(TlvType::EntityId, &buf[0..1]);
+        assert!(tlv_res.is_ok());
+        let tlv_res = tlv_res.unwrap();
+        let tlv_owned_from_conversion: TlvOwned = tlv_res.into();
+        assert_eq!(tlv_res.to_vec(), tlv_owned_from_conversion.to_vec());
+    }
 }

src/cfdp/tlv/msg_to_user.rs

@@ -1,6 +1,8 @@
 //! Abstractions for the Message to User CFDP TLV subtype.
-use super::{GenericTlv, Tlv, TlvLvError, TlvType, TlvTypeField, WritableTlv};
-use crate::ByteConversionError;
+#[cfg(feature = "alloc")]
+use super::TlvOwned;
+use super::{GenericTlv, ReadableTlv, Tlv, TlvLvError, TlvType, TlvTypeField, WritableTlv};
+use crate::{cfdp::TlvLvDataTooLarge, ByteConversionError};
 use delegate::delegate;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -10,7 +12,7 @@ pub struct MsgToUserTlv<'data> {
 
 impl<'data> MsgToUserTlv<'data> {
     /// Create a new message to user TLV where the type field is set correctly.
-    pub fn new(value: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvError> {
+    pub fn new(value: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvDataTooLarge> {
         Ok(Self {
             tlv: Tlv::new(TlvType::MsgToUser, value)?,
         })
@@ -75,6 +77,21 @@ impl<'data> MsgToUserTlv<'data> {
         }
         Ok(msg_to_user)
     }
+
+    pub fn to_tlv(&self) -> Tlv<'data> {
+        self.tlv
+    }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        self.tlv.to_owned()
+    }
+}
+
+impl<'a> From<MsgToUserTlv<'a>> for Tlv<'a> {
+    fn from(value: MsgToUserTlv<'a>) -> Tlv<'a> {
+        value.to_tlv()
+    }
 }
 
 impl WritableTlv for MsgToUserTlv<'_> {
@@ -139,6 +156,40 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_msg_to_user_type_reduction() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let tlv = msg_to_user.to_tlv();
+        assert_eq!(
+            tlv.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::MsgToUser)
+        );
+
+        assert_eq!(tlv.value(), custom_value);
+    }
+
+    #[test]
+    fn test_msg_to_user_to_tlv() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let tlv: Tlv = msg_to_user.into();
+        assert_eq!(msg_to_user.to_tlv(), tlv);
+    }
+
+    #[test]
+    fn test_msg_to_user_owner_converter() {
+        let custom_value: [u8; 4] = [1, 2, 3, 4];
+        let msg_to_user = MsgToUserTlv::new(&custom_value).unwrap();
+        let tlv = msg_to_user.to_owned();
+        assert_eq!(
+            tlv.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::MsgToUser)
+        );
+
+        assert_eq!(tlv.value(), custom_value);
+    }
+
     #[test]
     fn test_reserved_msg_deserialization() {
         let custom_value: [u8; 3] = [1, 2, 3];

src/lib.rs

@@ -55,7 +55,7 @@
 //! println!("{:x?}", &ccsds_buf[0..6]);
 //! ```
 #![no_std]
-#![cfg_attr(docs_rs, feature(doc_auto_cfg))]
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
 #[cfg(feature = "alloc")]
 extern crate alloc;
 #[cfg(any(feature = "std", test))]
@@ -76,7 +76,9 @@ use serde::{Deserialize, Serialize};
 
 pub mod cfdp;
 pub mod ecss;
+pub mod seq_count;
 pub mod time;
+pub mod uslp;
 pub mod util;
 
 mod private {
@@ -505,8 +507,8 @@ pub struct SpHeader {
 pub type SpacePacketHeader = SpHeader;
 
 impl Default for SpHeader {
-    /// The default function sets the sequence flag field to [SequenceFlags::Unsegmented]. The data
-    /// length field is set to 1, which denotes an empty space packets.
+    /// The default function sets the sequence flag field to [SequenceFlags::Unsegmented] and the
+    /// data length to 0.
     #[inline]
     fn default() -> Self {
         SpHeader {
@@ -516,7 +518,7 @@ impl Default for SpHeader {
                 seq_flags: SequenceFlags::Unsegmented,
                 seq_count: 0,
             },
-            data_len: 1,
+            data_len: 0,
         }
     }
 }
@@ -532,8 +534,8 @@ impl SpHeader {
         }
     }
 
-    /// This constructor sets the sequence flag field to [SequenceFlags::Unsegmented]. The data
-    /// length field is set to 1, which denotes an empty space packets.
+    /// This constructor sets the sequence flag field to [SequenceFlags::Unsegmented] and the data
+    /// length to 0.
     ///
     /// This constructor will panic if the APID exceeds [MAX_APID].
     #[inline]
@@ -545,7 +547,7 @@ impl SpHeader {
                 seq_flags: SequenceFlags::Unsegmented,
                 seq_count: 0,
             },
-            data_len: 1,
+            data_len: 0,
         }
     }
 
@@ -559,7 +561,7 @@ impl SpHeader {
                 seq_flags: SequenceFlags::Unsegmented,
                 seq_count: 0,
             },
-            data_len: 1,
+            data_len: 0,
         })
     }
 
@@ -568,7 +570,7 @@ impl SpHeader {
     ///
     /// The checked constructor variants can be used to avoid panics.
     #[inline]
-    const fn new_from_fields(
+    pub const fn new_from_fields(
         ptype: PacketType,
         sec_header: bool,
         apid: u16,
@@ -755,6 +757,15 @@ impl SpHeader {
             .ok_or(ByteConversionError::ZeroCopyToError)?;
         Ok(&mut buf[CCSDS_HEADER_LEN..])
     }
+
+    /// Create a vector containing the CCSDS header.
+    #[cfg(feature = "alloc")]
+    pub fn to_vec(&self) -> alloc::vec::Vec<u8> {
+        let mut vec = alloc::vec![0; CCSDS_HEADER_LEN];
+        // This can not fail.
+        self.write_to_be_bytes(&mut vec[..]).unwrap();
+        vec
+    }
 }
 
 impl CcsdsPacket for SpHeader {
@@ -1260,12 +1271,14 @@ pub(crate) mod tests {
     fn sp_header_from_apid() {
         let sp_header = SpHeader::new_from_apid(0x03);
         assert_eq!(sp_header.apid(), 0x03);
+        assert_eq!(sp_header.data_len(), 0);
     }
 
     #[test]
     fn sp_header_from_apid_checked() {
         let sp_header = SpHeader::new_from_apid_checked(0x03).unwrap();
         assert_eq!(sp_header.apid(), 0x03);
+        assert_eq!(sp_header.data_len(), 0);
     }
 
     #[cfg(feature = "defmt")]
@@ -1279,4 +1292,14 @@ pub(crate) mod tests {
             expected: 2,
         });
     }
+
+    #[test]
+    fn test_sp_header_as_vec() {
+        let sp_header = SpHeader::new_for_unseg_tc(0x42, 25, 1);
+        let sp_header_as_vec = sp_header.to_vec();
+        let sp_header_read_back = SpHeader::from_be_bytes(&sp_header_as_vec)
+            .expect("Error reading back SP header")
+            .0;
+        assert_eq!(sp_header, sp_header_read_back);
+    }
 }

src/seq_count.rs

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

src/time/ascii.rs

@@ -71,7 +71,19 @@ mod tests {
     use std::format;
 
     #[test]
-    fn test_ascii_timestamp_a_unterminated() {
+    fn test_ascii_timestamp_a_unterminated_epoch() {
+        let date = chrono::DateTime::UNIX_EPOCH;
+        let stamp_formatter = generate_time_code_a(&date);
+        let stamp = format!("{}", stamp_formatter);
+        let t_sep = stamp.find('T');
+        assert!(t_sep.is_some());
+        assert_eq!(t_sep.unwrap(), 10);
+        assert_eq!(stamp.len(), FMT_STR_CODE_A_WITH_SIZE.1);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_ascii_timestamp_a_unterminated_now() {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_a(&date);
         let stamp = format!("{}", stamp_formatter);
@@ -82,7 +94,24 @@ mod tests {
     }
 
     #[test]
-    fn test_ascii_timestamp_a_terminated() {
+    fn test_ascii_timestamp_a_terminated_epoch() {
+        let date = chrono::DateTime::UNIX_EPOCH;
+        let stamp_formatter = generate_time_code_a_terminated(&date);
+        let stamp = format!("{}", stamp_formatter);
+        let t_sep = stamp.find('T');
+        assert!(t_sep.is_some());
+        assert_eq!(t_sep.unwrap(), 10);
+        let z_terminator = stamp.find('Z');
+        assert!(z_terminator.is_some());
+        assert_eq!(
+            z_terminator.unwrap(),
+            FMT_STR_CODE_A_TERMINATED_WITH_SIZE.1 - 1
+        );
+        assert_eq!(stamp.len(), FMT_STR_CODE_A_TERMINATED_WITH_SIZE.1);
+    }
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_ascii_timestamp_a_terminated_now() {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_a_terminated(&date);
         let stamp = format!("{}", stamp_formatter);
@@ -99,7 +128,19 @@ mod tests {
     }
 
     #[test]
-    fn test_ascii_timestamp_b_unterminated() {
+    fn test_ascii_timestamp_b_unterminated_epoch() {
+        let date = chrono::DateTime::UNIX_EPOCH;
+        let stamp_formatter = generate_time_code_b(&date);
+        let stamp = format!("{}", stamp_formatter);
+        let t_sep = stamp.find('T');
+        assert!(t_sep.is_some());
+        assert_eq!(t_sep.unwrap(), 8);
+        assert_eq!(stamp.len(), FMT_STR_CODE_B_WITH_SIZE.1);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_ascii_timestamp_b_unterminated_now() {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_b(&date);
         let stamp = format!("{}", stamp_formatter);
@@ -110,7 +151,25 @@ mod tests {
     }
 
     #[test]
-    fn test_ascii_timestamp_b_terminated() {
+    fn test_ascii_timestamp_b_terminated_epoch() {
+        let date = chrono::DateTime::UNIX_EPOCH;
+        let stamp_formatter = generate_time_code_b_terminated(&date);
+        let stamp = format!("{}", stamp_formatter);
+        let t_sep = stamp.find('T');
+        assert!(t_sep.is_some());
+        assert_eq!(t_sep.unwrap(), 8);
+        let z_terminator = stamp.find('Z');
+        assert!(z_terminator.is_some());
+        assert_eq!(
+            z_terminator.unwrap(),
+            FMT_STR_CODE_B_TERMINATED_WITH_SIZE.1 - 1
+        );
+        assert_eq!(stamp.len(), FMT_STR_CODE_B_TERMINATED_WITH_SIZE.1);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_ascii_timestamp_b_terminated_now() {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_b_terminated(&date);
         let stamp = format!("{}", stamp_formatter);

src/time/cds.rs

@@ -1622,6 +1622,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_time_now() {
         let timestamp_now = CdsTime::now_with_u16_days().unwrap();
         let compare_stamp = chrono::Utc::now();
@@ -1629,6 +1630,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_time_now_us_prec() {
         let timestamp_now = CdsTime::now_with_u16_days_us_precision().unwrap();
         let compare_stamp = chrono::Utc::now();
@@ -1636,6 +1638,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_time_now_ps_prec() {
         let timestamp_now = CdsTime::from_now_with_u16_days_ps_precision().unwrap();
         let compare_stamp = chrono::Utc::now();
@@ -1643,6 +1646,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_time_now_ps_prec_u16_days() {
         let timestamp_now = CdsTime::from_now_with_u16_days_ps_precision().unwrap();
         let compare_stamp = chrono::Utc::now();
@@ -1650,6 +1654,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_time_now_ps_prec_u24_days() {
         let timestamp_now = CdsTime::now_with_u24_days_ps_precision().unwrap();
         let compare_stamp = chrono::Utc::now();
@@ -2306,6 +2311,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_update_from_now() {
         let mut stamp = CdsTime::new_with_u16_days(0, 0);
         let _ = stamp.update_from_now();
@@ -2321,6 +2327,7 @@ mod tests {
 
     #[test]
     #[cfg(feature = "serde")]
+    #[cfg_attr(miri, ignore)]
     fn test_serialization() {
         let stamp_now = CdsTime::now_with_u16_days().expect("Error retrieving time");
         let val = to_allocvec(&stamp_now).expect("Serializing timestamp failed");

src/time/cuc.rs

@@ -9,7 +9,6 @@ use serde::{Deserialize, Serialize};
 use core::fmt::{Debug, Display, Formatter};
 use core::ops::{Add, AddAssign};
 use core::time::Duration;
-use core::u64;
 
 use crate::ByteConversionError;
 
@@ -947,6 +946,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_datetime_now() {
         let now = chrono::Utc::now();
         let cuc_now = CucTime::now(FractionalResolution::SixtyNs, LEAP_SECONDS);
@@ -1278,6 +1278,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn set_fract_resolution() {
         let mut stamp = CucTime::new(2000);
         stamp.set_fractional_resolution(FractionalResolution::SixtyNs);

src/time/mod.rs

@@ -6,7 +6,6 @@ use core::cmp::Ordering;
 use core::fmt::{Display, Formatter};
 use core::ops::{Add, AddAssign, Sub};
 use core::time::Duration;
-use core::u8;
 
 #[allow(unused_imports)]
 #[cfg(not(feature = "std"))]
@@ -551,6 +550,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_get_current_time() {
         let sec_floats = seconds_since_epoch();
         assert!(sec_floats > 0.0);
@@ -565,6 +565,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_ccsds_epoch() {
         let now = SystemTime::now()
             .duration_since(SystemTime::UNIX_EPOCH)
@@ -685,6 +686,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_from_now() {
         let stamp_now = UnixTime::now().unwrap();
         let dt_now = stamp_now.chrono_date_time().unwrap();

src/uslp/mod.rs

@@ -0,0 +1,685 @@
+/// # Support of the CCSDS Unified Space Data Link Protocol (USLP)
+use crate::{ByteConversionError, CRC_CCITT_FALSE};
+
+/// Only this version is supported by the library
+pub const USLP_VERSION_NUMBER: u8 = 0b1100;
+
+/// Identifies the association of the data contained in the transfer frame.
+#[derive(
+    Debug, Copy, Clone, PartialEq, Eq, num_enum::TryFromPrimitive, num_enum::IntoPrimitive,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
+pub enum SourceOrDestField {
+    /// SCID refers to the source of the transfer frame.
+    Source = 0,
+    /// SCID refers to the destination of the transfer frame.
+    Dest = 1,
+}
+
+#[derive(
+    Debug, Copy, Clone, PartialEq, Eq, num_enum::TryFromPrimitive, num_enum::IntoPrimitive,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
+pub enum BypassSequenceControlFlag {
+    /// Acceptance of this frame on the receiving end is subject to normal frame acceptance
+    /// checks of FARM.
+    SequenceControlledQoS = 0,
+    /// Frame Acceptance Checks of FARM by the receiving end shall be bypassed.
+    ExpeditedQoS = 1,
+}
+
+#[derive(
+    Debug, Copy, Clone, PartialEq, Eq, num_enum::TryFromPrimitive, num_enum::IntoPrimitive,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
+pub enum ProtocolControlCommandFlag {
+    TfdfContainsUserData = 0,
+    TfdfContainsProtocolInfo = 1,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum UslpError {
+    ByteConversion(ByteConversionError),
+    HeaderIsTruncated,
+    InvalidProtocolId(u8),
+    InvalidConstructionRule(u8),
+    InvalidVersionNumber(u8),
+    InvalidVcid(u8),
+    InvalidMapId(u8),
+    ChecksumFailure(u16),
+}
+
+impl From<ByteConversionError> for UslpError {
+    fn from(value: ByteConversionError) -> Self {
+        Self::ByteConversion(value)
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct InvalidValueForLen {
+    value: u64,
+    len: u8,
+}
+
+#[derive(Debug, Copy, Clone, Eq)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct PrimaryHeader {
+    pub spacecraft_id: u16,
+    pub source_or_dest_field: SourceOrDestField,
+    pub vc_id: u8,
+    pub map_id: u8,
+    frame_len_field: u16,
+    pub sequence_control_flag: BypassSequenceControlFlag,
+    pub protocol_control_command_flag: ProtocolControlCommandFlag,
+    pub ocf_flag: bool,
+    vc_frame_count_len: u8,
+    vc_frame_count: u64,
+}
+
+impl PrimaryHeader {
+    pub fn new(
+        spacecraft_id: u16,
+        source_or_dest_field: SourceOrDestField,
+        vc_id: u8,
+        map_id: u8,
+        frame_len: u16,
+    ) -> Result<Self, UslpError> {
+        if vc_id > 0b111111 {
+            return Err(UslpError::InvalidVcid(vc_id));
+        }
+        if map_id > 0b1111 {
+            return Err(UslpError::InvalidMapId(map_id));
+        }
+        Ok(Self {
+            spacecraft_id,
+            source_or_dest_field,
+            vc_id,
+            map_id,
+            frame_len_field: frame_len.saturating_sub(1),
+            sequence_control_flag: BypassSequenceControlFlag::SequenceControlledQoS,
+            protocol_control_command_flag: ProtocolControlCommandFlag::TfdfContainsUserData,
+            ocf_flag: false,
+            vc_frame_count_len: 0,
+            vc_frame_count: 0,
+        })
+    }
+
+    pub fn set_vc_frame_count(
+        &mut self,
+        count_len: u8,
+        count: u64,
+    ) -> Result<(), InvalidValueForLen> {
+        if count > 2_u64.pow(count_len as u32 * 8) - 1 {
+            return Err(InvalidValueForLen {
+                value: count,
+                len: count_len,
+            });
+        }
+        self.vc_frame_count_len = count_len;
+        self.vc_frame_count = count;
+        Ok(())
+    }
+
+    #[inline(always)]
+    pub fn vc_frame_count(&self) -> u64 {
+        self.vc_frame_count
+    }
+
+    #[inline(always)]
+    pub fn vc_frame_count_len(&self) -> u8 {
+        self.vc_frame_count_len
+    }
+
+    pub fn from_bytes(buf: &[u8]) -> Result<Self, UslpError> {
+        if buf.len() < 4 {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: buf.len(),
+                expected: 4,
+            }
+            .into());
+        }
+        // Can only deal with regular frames for now.
+        if (buf[3] & 0b1) == 1 {
+            return Err(UslpError::HeaderIsTruncated);
+        }
+        // We could check this above, but this is a better error for the case where the user
+        // tries to read a truncated frame.
+        if buf.len() < 7 {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: buf.len(),
+                expected: 7,
+            }
+            .into());
+        }
+        let version_number = (buf[0] >> 4) & 0b1111;
+        if version_number != USLP_VERSION_NUMBER {
+            return Err(UslpError::InvalidVersionNumber(version_number));
+        }
+        let source_or_dest_field = match (buf[2] >> 3) & 1 {
+            0 => SourceOrDestField::Source,
+            1 => SourceOrDestField::Dest,
+            _ => unreachable!(),
+        };
+        let vc_frame_count_len = buf[6] & 0b111;
+        if buf.len() < 7 + vc_frame_count_len as usize {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: buf.len(),
+                expected: 7 + vc_frame_count_len as usize,
+            }
+            .into());
+        }
+        let vc_frame_count = match vc_frame_count_len {
+            1 => buf[7] as u64,
+            2 => u16::from_be_bytes(buf[7..9].try_into().unwrap()) as u64,
+            4 => u32::from_be_bytes(buf[7..11].try_into().unwrap()) as u64,
+            len => {
+                let mut vcf_count = 0u64;
+                let mut end = len;
+                for byte in buf[7..7 + len as usize].iter() {
+                    vcf_count |= (*byte as u64) << ((end - 1) * 8);
+                    end -= 1;
+                }
+                vcf_count
+            }
+        };
+        Ok(Self {
+            spacecraft_id: (((buf[0] as u16) & 0b1111) << 12)
+                | ((buf[1] as u16) << 4)
+                | ((buf[2] as u16) >> 4) & 0b1111,
+            source_or_dest_field,
+            vc_id: ((buf[2] & 0b111) << 3) | (buf[3] >> 5) & 0b111,
+            map_id: (buf[3] >> 1) & 0b1111,
+            frame_len_field: ((buf[4] as u16) << 8) | buf[5] as u16,
+            sequence_control_flag: ((buf[6] >> 7) & 0b1).try_into().unwrap(),
+            protocol_control_command_flag: ((buf[6] >> 6) & 0b1).try_into().unwrap(),
+            ocf_flag: ((buf[6] >> 3) & 0b1) != 0,
+            vc_frame_count_len,
+            vc_frame_count,
+        })
+    }
+
+    pub fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        if buf.len() < self.len_header() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: self.len_header(),
+            });
+        }
+        buf[0] = (USLP_VERSION_NUMBER << 4) | ((self.spacecraft_id >> 12) as u8) & 0b1111;
+        buf[1] = (self.spacecraft_id >> 4) as u8;
+        buf[2] = (((self.spacecraft_id & 0b1111) as u8) << 4)
+            | ((self.source_or_dest_field as u8) << 3)
+            | (self.vc_id >> 3) & 0b111;
+        buf[3] = ((self.vc_id & 0b111) << 5) | (self.map_id << 1);
+        buf[4..6].copy_from_slice(&self.frame_len_field.to_be_bytes());
+        buf[6] = ((self.sequence_control_flag as u8) << 7)
+            | ((self.protocol_control_command_flag as u8) << 6)
+            | ((self.ocf_flag as u8) << 3)
+            | self.vc_frame_count_len;
+        let mut packet_idx = 7;
+        for idx in (0..self.vc_frame_count_len).rev() {
+            buf[packet_idx] = ((self.vc_frame_count >> (idx * 8)) & 0xff) as u8;
+            packet_idx += 1;
+        }
+        Ok(self.len_header())
+    }
+
+    #[inline(always)]
+    pub fn set_frame_len(&mut self, frame_len: usize) {
+        // 4.1.2.7.2
+        // The field contains a length count C that equals one fewer than the total octets
+        // in the transfer frame.
+        self.frame_len_field = frame_len.saturating_sub(1) as u16;
+    }
+
+    #[inline(always)]
+    pub fn len_header(&self) -> usize {
+        7 + self.vc_frame_count_len as usize
+    }
+
+    #[inline(always)]
+    pub fn len_frame(&self) -> usize {
+        // 4.1.2.7.2
+        // The field contains a length count C that equals one fewer than the total octets
+        // in the transfer frame.
+        self.frame_len_field as usize + 1
+    }
+}
+
+/// Custom implementation which skips the check whether the VC frame count length field is equal.
+/// Only the actual VC count value is compared.
+impl PartialEq for PrimaryHeader {
+    fn eq(&self, other: &Self) -> bool {
+        self.spacecraft_id == other.spacecraft_id
+            && self.source_or_dest_field == other.source_or_dest_field
+            && self.vc_id == other.vc_id
+            && self.map_id == other.map_id
+            && self.frame_len_field == other.frame_len_field
+            && self.sequence_control_flag == other.sequence_control_flag
+            && self.protocol_control_command_flag == other.protocol_control_command_flag
+            && self.ocf_flag == other.ocf_flag
+            && self.vc_frame_count == other.vc_frame_count
+    }
+}
+
+#[derive(
+    Debug, Copy, Clone, PartialEq, Eq, num_enum::TryFromPrimitive, num_enum::IntoPrimitive,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
+#[non_exhaustive]
+pub enum UslpProtocolId {
+    SpacePacketsOrEncapsulation = 0b00000,
+    /// COP-1 control commands within the TFDZ.
+    Cop1ControlCommands = 0b00001,
+    /// COP-P control commands within the TFDZ.
+    CopPControlCommands = 0b00010,
+    /// SDLS control commands within the TFDZ.
+    Sdls = 0b00011,
+    UserDefinedOctetStream = 0b00100,
+    /// Proximity-1 Supervisory Protocol Data Units (SPDUs) within the TFDZ.
+    Spdu = 0b00111,
+    /// Entire fixed-length TFDZ contains idle data.
+    Idle = 0b11111,
+}
+
+#[derive(
+    Debug, Copy, Clone, PartialEq, Eq, num_enum::TryFromPrimitive, num_enum::IntoPrimitive,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[repr(u8)]
+pub enum ConstructionRule {
+    /// Indicated fixed-length TFDZ whose contents are CCSDS packets concatenated together, which
+    /// span transfer frame boundaries. The First Header Pointer (FHP) is required for packet
+    /// extraction.
+    PacketSpanningMultipleFrames = 0b000,
+    StartOfMapaSduOrVcaSdu = 0b001,
+    ContinuingPortionOfMapaSdu = 0b010,
+    OctetStream = 0b011,
+    StartingSegment = 0b100,
+    ContinuingSegment = 0b101,
+    LastSegment = 0b110,
+    NoSegmentation = 0b111,
+}
+
+impl ConstructionRule {
+    pub const fn applicable_to_fixed_len_tfdz(&self) -> bool {
+        match self {
+            ConstructionRule::PacketSpanningMultipleFrames => true,
+            ConstructionRule::StartOfMapaSduOrVcaSdu => true,
+            ConstructionRule::ContinuingPortionOfMapaSdu => true,
+            ConstructionRule::OctetStream => false,
+            ConstructionRule::StartingSegment => false,
+            ConstructionRule::ContinuingSegment => false,
+            ConstructionRule::LastSegment => false,
+            ConstructionRule::NoSegmentation => false,
+        }
+    }
+}
+
+pub struct TransferFrameDataFieldHeader {
+    /// Construction rule for the TFDZ.
+    construction_rule: ConstructionRule,
+    uslp_protocol_id: UslpProtocolId,
+    /// First header or last valid octet pointer. Only present if the constuction rule indicated
+    /// a fixed-length TFDZ.
+    fhp_or_lvo: Option<u16>,
+}
+
+impl TransferFrameDataFieldHeader {
+    pub fn len_header(&self) -> usize {
+        if self.construction_rule.applicable_to_fixed_len_tfdz() {
+            3
+        } else {
+            1
+        }
+    }
+
+    pub fn construction_rule(&self) -> ConstructionRule {
+        self.construction_rule
+    }
+
+    pub fn uslp_protocol_id(&self) -> UslpProtocolId {
+        self.uslp_protocol_id
+    }
+
+    pub fn fhp_or_lvo(&self) -> Option<u16> {
+        self.fhp_or_lvo
+    }
+
+    pub fn from_bytes(buf: &[u8]) -> Result<Self, UslpError> {
+        if buf.is_empty() {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: 0,
+                expected: 1,
+            }
+            .into());
+        }
+        let construction_rule = ConstructionRule::try_from((buf[0] >> 5) & 0b111)
+            .map_err(|e| UslpError::InvalidConstructionRule(e.number))?;
+        let mut fhp_or_lvo = None;
+        if construction_rule.applicable_to_fixed_len_tfdz() {
+            if buf.len() < 3 {
+                return Err(ByteConversionError::FromSliceTooSmall {
+                    found: buf.len(),
+                    expected: 3,
+                }
+                .into());
+            }
+            fhp_or_lvo = Some(u16::from_be_bytes(buf[1..3].try_into().unwrap()));
+        }
+        Ok(Self {
+            construction_rule,
+            uslp_protocol_id: UslpProtocolId::try_from(buf[0] & 0b11111)
+                .map_err(|e| UslpError::InvalidProtocolId(e.number))?,
+            fhp_or_lvo,
+        })
+    }
+}
+
+/// Simple USLP transfer frame reader.
+///
+/// Currently, only insert zone lengths of 0 are supported.
+pub struct TransferFrameReader<'buf> {
+    primary_header: PrimaryHeader,
+    data_field_header: TransferFrameDataFieldHeader,
+    data: &'buf [u8],
+    operational_control_field: Option<u32>,
+}
+
+impl<'buf> TransferFrameReader<'buf> {
+    /// This function assumes an insert zone length of 0.
+    pub fn from_bytes(
+        buf: &'buf [u8],
+        has_fecf: bool,
+    ) -> Result<TransferFrameReader<'buf>, UslpError> {
+        let primary_header = PrimaryHeader::from_bytes(buf)?;
+        if primary_header.len_frame() > buf.len() {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                expected: primary_header.len_frame(),
+                found: buf.len(),
+            }
+            .into());
+        }
+        let data_field_header =
+            TransferFrameDataFieldHeader::from_bytes(&buf[primary_header.len_header()..])?;
+        let data_idx = primary_header.len_header() + data_field_header.len_header();
+        let frame_len = primary_header.len_frame();
+        let mut operational_control_field = None;
+        let mut data_len = frame_len - data_idx;
+        if has_fecf {
+            data_len -= 2;
+        }
+        if primary_header.ocf_flag {
+            data_len -= 4;
+            operational_control_field = Some(u32::from_be_bytes(
+                buf[data_idx + data_len..data_idx + data_len + 4]
+                    .try_into()
+                    .unwrap(),
+            ));
+        }
+        let data_end = data_idx + data_len;
+        let mut digest = CRC_CCITT_FALSE.digest();
+        digest.update(&buf[0..frame_len]);
+        if digest.finalize() != 0 {
+            return Err(UslpError::ChecksumFailure(u16::from_be_bytes(
+                buf[frame_len - 2..frame_len].try_into().unwrap(),
+            )));
+        }
+        Ok(Self {
+            primary_header,
+            data_field_header,
+            data: buf[data_idx..data_end].try_into().unwrap(),
+            operational_control_field,
+        })
+    }
+
+    pub fn len_frame(&self) -> usize {
+        self.primary_header.len_frame()
+    }
+
+    pub fn primary_header(&self) -> &PrimaryHeader {
+        &self.primary_header
+    }
+
+    pub fn data_field_header(&self) -> &TransferFrameDataFieldHeader {
+        &self.data_field_header
+    }
+
+    pub fn data(&self) -> &'buf [u8] {
+        self.data
+    }
+
+    pub fn operational_control_field(&self) -> &Option<u32> {
+        &self.operational_control_field
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::println;
+
+    use super::*;
+
+    fn common_basic_check(buf: &[u8]) {
+        assert_eq!(buf[0] >> 4, USLP_VERSION_NUMBER);
+        // First four bits SCID.
+        assert_eq!(buf[0] & 0b1111, 0b1010);
+        // Next eight bits SCID.
+        assert_eq!(buf[1], 0b01011100);
+        // Last four bits SCID.
+        assert_eq!(buf[2] >> 4, 0b0011);
+        assert_eq!((buf[2] >> 3) & 0b1, SourceOrDestField::Dest as u8);
+        // First three bits VCID.
+        assert_eq!(buf[2] & 0b111, 0b110);
+        // Last three bits VCID.
+        assert_eq!(buf[3] >> 5, 0b101);
+        // MAP ID
+        assert_eq!((buf[3] >> 1) & 0b1111, 0b1010);
+        // End of primary header flag
+        assert_eq!(buf[3] & 0b1, 0);
+        assert_eq!(u16::from_be_bytes(buf[4..6].try_into().unwrap()), 0x2345);
+    }
+    #[test]
+    fn test_basic_0() {
+        let mut buf: [u8; 8] = [0; 8];
+        // Should be all zeros after writing.
+        buf[6] = 0xff;
+        let primary_header = PrimaryHeader::new(
+            0b10100101_11000011,
+            SourceOrDestField::Dest,
+            0b110101,
+            0b1010,
+            0x2345,
+        )
+        .unwrap();
+        // Virtual channel count 0.
+        assert_eq!(primary_header.write_to_be_bytes(&mut buf).unwrap(), 7);
+        common_basic_check(&buf);
+        // Bypass / Sequence Control Flag.
+        assert_eq!(
+            (buf[6] >> 7) & 0b1,
+            BypassSequenceControlFlag::SequenceControlledQoS as u8
+        );
+        // Protocol Control Command Flag.
+        assert_eq!(
+            (buf[6] >> 6) & 0b1,
+            ProtocolControlCommandFlag::TfdfContainsUserData as u8
+        );
+        // OCF flag.
+        assert_eq!((buf[6] >> 3) & 0b1, false as u8);
+        // VCF count length.
+        assert_eq!(buf[6] & 0b111, 0);
+    }
+
+    #[test]
+    fn test_basic_1() {
+        let mut buf: [u8; 16] = [0; 16];
+        // Should be all zeros after writing.
+        buf[6] = 0xff;
+        let mut primary_header = PrimaryHeader::new(
+            0b10100101_11000011,
+            SourceOrDestField::Dest,
+            0b110101,
+            0b1010,
+            0x2345,
+        )
+        .unwrap();
+        primary_header.sequence_control_flag = BypassSequenceControlFlag::ExpeditedQoS;
+        primary_header.protocol_control_command_flag =
+            ProtocolControlCommandFlag::TfdfContainsProtocolInfo;
+        primary_header.ocf_flag = true;
+        primary_header.set_vc_frame_count(4, 0x12345678).unwrap();
+        // Virtual channel count 4.
+        assert_eq!(primary_header.write_to_be_bytes(&mut buf).unwrap(), 11);
+        common_basic_check(&buf);
+        // Bypass / Sequence Control Flag.
+        assert_eq!(
+            (buf[6] >> 7) & 0b1,
+            BypassSequenceControlFlag::ExpeditedQoS as u8
+        );
+        // Protocol Control Command Flag.
+        assert_eq!(
+            (buf[6] >> 6) & 0b1,
+            ProtocolControlCommandFlag::TfdfContainsProtocolInfo as u8
+        );
+        // OCF flag.
+        assert_eq!((buf[6] >> 3) & 0b1, true as u8);
+        // VCF count length.
+        assert_eq!(buf[6] & 0b111, 4);
+        assert_eq!(
+            u32::from_be_bytes(buf[7..11].try_into().unwrap()),
+            0x12345678
+        );
+    }
+
+    #[test]
+    fn test_reading_0() {
+        let mut buf: [u8; 8] = [0; 8];
+        let primary_header = PrimaryHeader::new(
+            0b10100101_11000011,
+            SourceOrDestField::Dest,
+            0b110101,
+            0b1010,
+            0x2345,
+        )
+        .unwrap();
+        assert_eq!(primary_header.write_to_be_bytes(&mut buf).unwrap(), 7);
+        let parsed_header = PrimaryHeader::from_bytes(&buf).unwrap();
+        assert_eq!(parsed_header, primary_header);
+    }
+
+    #[test]
+    fn test_reading_1() {
+        let mut buf: [u8; 16] = [0; 16];
+        let mut primary_header = PrimaryHeader::new(
+            0b10100101_11000011,
+            SourceOrDestField::Dest,
+            0b110101,
+            0b1010,
+            0x2345,
+        )
+        .unwrap();
+        primary_header.sequence_control_flag = BypassSequenceControlFlag::ExpeditedQoS;
+        primary_header.protocol_control_command_flag =
+            ProtocolControlCommandFlag::TfdfContainsProtocolInfo;
+        primary_header.ocf_flag = true;
+        primary_header.set_vc_frame_count(4, 0x12345678).unwrap();
+        assert_eq!(primary_header.write_to_be_bytes(&mut buf).unwrap(), 11);
+        let parsed_header = PrimaryHeader::from_bytes(&buf).unwrap();
+        assert_eq!(parsed_header, primary_header);
+    }
+
+    #[test]
+    fn test_invalid_vcid() {
+        let error = PrimaryHeader::new(
+            0b10100101_11000011,
+            SourceOrDestField::Dest,
+            0b1101011,
+            0b1010,
+            0x2345,
+        );
+        assert!(error.is_err());
+        let error = error.unwrap_err();
+        matches!(error, UslpError::InvalidVcid(0b1101011));
+    }
+
+    #[test]
+    fn test_invalid_mapid() {
+        let error = PrimaryHeader::new(
+            0b10100101_11000011,
+            SourceOrDestField::Dest,
+            0b110101,
+            0b10101,
+            0x2345,
+        );
+        assert!(error.is_err());
+        let error = error.unwrap_err();
+        matches!(error, UslpError::InvalidMapId(0b10101));
+    }
+
+    #[test]
+    fn test_invalid_vc_count() {
+        let mut primary_header = PrimaryHeader::new(
+            0b10100101_11000011,
+            SourceOrDestField::Dest,
+            0b110101,
+            0b1010,
+            0x2345,
+        )
+        .unwrap();
+        matches!(
+            primary_header.set_vc_frame_count(0, 1).unwrap_err(),
+            InvalidValueForLen { value: 1, len: 0 }
+        );
+        matches!(
+            primary_header.set_vc_frame_count(1, 256).unwrap_err(),
+            InvalidValueForLen { value: 256, len: 1 }
+        );
+    }
+
+    #[test]
+    fn test_frame_parser() {
+        let mut buf: [u8; 32] = [0; 32];
+        // Build a variable frame manually.
+        let mut primary_header =
+            PrimaryHeader::new(0x01, SourceOrDestField::Dest, 0b110101, 0b1010, 0).unwrap();
+        let header_len = primary_header.len_header();
+        buf[header_len] = ((ConstructionRule::NoSegmentation as u8) << 5)
+            | (UslpProtocolId::UserDefinedOctetStream as u8) & 0b11111;
+        buf[header_len + 1] = 0x42;
+        // 1 byte TFDH, 1 byte data, 2 bytes CRC.
+        primary_header.set_frame_len(header_len + 4);
+        primary_header.write_to_be_bytes(&mut buf).unwrap();
+        // Calculate and write CRC16.
+        let mut digest = CRC_CCITT_FALSE.digest();
+        digest.update(&buf[0..header_len + 2]);
+        buf[header_len + 2..header_len + 4].copy_from_slice(&digest.finalize().to_be_bytes());
+        println!("Buffer: {:x?}", buf);
+        // Now parse the frame.
+        let frame = TransferFrameReader::from_bytes(&buf, true).unwrap();
+        assert_eq!(frame.data().len(), 1);
+        assert_eq!(frame.data()[0], 0x42);
+        assert_eq!(
+            frame.data_field_header().uslp_protocol_id,
+            UslpProtocolId::UserDefinedOctetStream
+        );
+        assert_eq!(
+            frame.data_field_header().construction_rule,
+            ConstructionRule::NoSegmentation
+        );
+        assert!(frame.data_field_header().fhp_or_lvo().is_none());
+        assert_eq!(frame.len_frame(), 11);
+    }
+}