Merge pull request 'CFDP initial packet support' (#14) from cfdp_first_support into main

Reviewed-on: #14

.idea/runConfigurations/Check.xml

@@ -0,0 +1,19 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Check" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
+    <option name="command" value="check --all-features" />
+    <option name="workingDirectory" value="file://$PROJECT_DIR$" />
+    <option name="emulateTerminal" value="false" />
+    <option name="channel" value="DEFAULT" />
+    <option name="requiredFeatures" value="true" />
+    <option name="allFeatures" value="true" />
+    <option name="withSudo" value="false" />
+    <option name="buildTarget" value="REMOTE" />
+    <option name="backtrace" value="SHORT" />
+    <envs />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
+    <method v="2">
+      <option name="CARGO.BUILD_TASK_PROVIDER" enabled="true" />
+    </method>
+  </configuration>
+</component>

.idea/runConfigurations/Test.xml

@@ -0,0 +1,19 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Test" type="CargoCommandRunConfiguration" factoryName="Cargo Command" nameIsGenerated="true">
+    <option name="command" value="test" />
+    <option name="workingDirectory" value="file://$PROJECT_DIR$" />
+    <option name="emulateTerminal" value="false" />
+    <option name="channel" value="DEFAULT" />
+    <option name="requiredFeatures" value="true" />
+    <option name="allFeatures" value="true" />
+    <option name="withSudo" value="false" />
+    <option name="buildTarget" value="REMOTE" />
+    <option name="backtrace" value="SHORT" />
+    <envs />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
+    <method v="2">
+      <option name="CARGO.BUILD_TASK_PROVIDER" enabled="true" />
+    </method>
+  </configuration>
+</component>

CHANGELOG.md

@@ -8,6 +8,23 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+## Added
+
+- Added new `util` module which contains the following (new) helper modules:
+  - `UnsignedEnum` trait as an abstraction for unsigned byte fields with variable lengths. It is
+    not tied to the ECSS PFC value like the `EcssEnumeration` trait.
+  - `GenericUnsignedByteField<TYPE>` and helper typedefs `UnsignedU8`, `UnsignedU16`, `UnsignedU32`
+    and `UnsignedU64` as helper types implementing `UnsignedEnum`
+  - `UnsignedByteField` as a type-erased helper.
+- Initial CFDP support: Added PDU packet implementation.
+
+## Changed
+ 
+- The `EcssEnumeration` now requires the `UnsignedEnum` trait and only adds the `pfc` method to it.
+- Renamed `byte_width` usages to `len` (part of new `UnsignedEnum` trait)
+- Moved `ecss::CRC_CCITT_FALSE` CRC constant to the root module. This CRC type is not just used by
+  the PUS standard, but by the CCSDS Telecommand standard and the CFDP standard as well.
+
 # [v0.5.4] 2023-02-12
 
 ## Added

Cargo.toml

@@ -18,7 +18,7 @@ crc = "3"
 delegate = ">=0.8, <0.10"
 
 [dependencies.num_enum]
-version = "0.5"
+version = "0.6"
 default-features = false
 
 [dependencies.serde]

README.md

@@ -13,6 +13,8 @@ Currently, this includes the following components:
 
 - Space Packet implementation according to
   [CCSDS Blue Book 133.0-B-2](https://public.ccsds.org/Pubs/133x0b2e1.pdf)
+- CCSDS File Delivery Protocol (CFDP) packet implementations according to
+  [CCSDS Blue Book 727.0-B-5](https://public.ccsds.org/Pubs/727x0b5.pdf)
 - PUS Telecommand and PUS Telemetry implementation according to the
   [ECSS-E-ST-70-41C standard](https://ecss.nl/standard/ecss-e-st-70-41c-space-engineering-telemetry-and-telecommand-packet-utilization-15-april-2016/).
 - CUC (CCSDS Unsegmented Time Code) implementation according to

src/cfdp/lv.rs

@@ -0,0 +1,308 @@
+//! Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
+use crate::cfdp::TlvLvError;
+use crate::{ByteConversionError, SizeMissmatch};
+use core::str::Utf8Error;
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+#[cfg(feature = "std")]
+use std::string::String;
+
+pub const MIN_LV_LEN: usize = 1;
+
+/// Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
+///
+/// # Lifetimes
+///  * `data`: If the LV is generated from a raw bytestream, this will be the lifetime of
+///    the raw bytestream. If the LV is generated from a raw slice or a similar data reference,
+///    this will be the lifetime of that data reference.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct Lv<'data> {
+    data: Option<&'data [u8]>,
+}
+
+pub(crate) fn generic_len_check_data_serialization(
+    buf: &[u8],
+    data_len: usize,
+    min_overhead: usize,
+) -> Result<(), ByteConversionError> {
+    if buf.len() < data_len + min_overhead {
+        return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+            found: buf.len(),
+            expected: data_len + min_overhead,
+        }));
+    }
+    Ok(())
+}
+
+pub(crate) fn generic_len_check_deserialization(
+    buf: &[u8],
+    min_overhead: usize,
+) -> Result<(), ByteConversionError> {
+    if buf.len() < min_overhead {
+        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            found: buf.len(),
+            expected: min_overhead,
+        }));
+    }
+    Ok(())
+}
+
+impl<'data> Lv<'data> {
+    pub fn new(data: &[u8]) -> Result<Lv, TlvLvError> {
+        if data.len() > u8::MAX as usize {
+            return Err(TlvLvError::DataTooLarge(data.len()));
+        }
+        Ok(Lv { data: Some(data) })
+    }
+
+    /// Creates a LV with an empty value field.
+    pub fn new_empty() -> Lv<'data> {
+        Lv { data: None }
+    }
+
+    /// Helper function to build a string LV. This is especially useful for the file or directory
+    /// path LVs
+    pub fn new_from_str(str_slice: &str) -> Result<Lv, TlvLvError> {
+        Self::new(str_slice.as_bytes())
+    }
+
+    /// Helper function to build a string LV. This is especially useful for the file or directory
+    /// path LVs
+    #[cfg(feature = "std")]
+    pub fn new_from_string(string: &'data String) -> Result<Lv<'data>, TlvLvError> {
+        Self::new(string.as_bytes())
+    }
+
+    /// Returns the length of the value part, not including the length byte.
+    pub fn len_value(&self) -> usize {
+        if self.data.is_none() {
+            return 0;
+        }
+        self.data.unwrap().len()
+    }
+
+    /// Returns the full raw length, including the length byte.
+    pub fn len_full(&self) -> usize {
+        self.len_value() + 1
+    }
+
+    /// Checks whether the value field is empty.
+    pub fn is_empty(&self) -> bool {
+        self.data.is_none()
+    }
+
+    pub fn value(&self) -> Option<&[u8]> {
+        self.data
+    }
+
+    /// Convenience function to extract the value as a [str]. This is useful if the LV is
+    /// known to contain a [str], for example being a file name.
+    pub fn value_as_str(&self) -> Option<Result<&'data str, Utf8Error>> {
+        self.data?;
+        Some(core::str::from_utf8(self.data.unwrap()))
+    }
+
+    /// Writes the LV to a raw buffer. Please note that the first byte will contain the length
+    /// of the value, but the values may not exceed a length of [u8::MAX].
+    pub fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        generic_len_check_data_serialization(buf, self.len_value(), MIN_LV_LEN)?;
+        Ok(self.write_to_be_bytes_no_len_check(buf))
+    }
+
+    /// Reads a LV  from a raw buffer.
+    pub fn from_bytes(buf: &'data [u8]) -> Result<Lv<'data>, ByteConversionError> {
+        generic_len_check_deserialization(buf, MIN_LV_LEN)?;
+        Self::from_be_bytes_no_len_check(buf)
+    }
+
+    pub(crate) fn write_to_be_bytes_no_len_check(&self, buf: &mut [u8]) -> usize {
+        if self.data.is_none() {
+            buf[0] = 0;
+            return MIN_LV_LEN;
+        }
+        let data = self.data.unwrap();
+        // Length check in constructor ensures the length always has a valid value.
+        buf[0] = data.len() as u8;
+        buf[MIN_LV_LEN..data.len() + MIN_LV_LEN].copy_from_slice(data);
+        MIN_LV_LEN + data.len()
+    }
+
+    pub(crate) fn from_be_bytes_no_len_check(
+        buf: &'data [u8],
+    ) -> Result<Lv<'data>, ByteConversionError> {
+        let value_len = buf[0] as usize;
+        generic_len_check_deserialization(buf, value_len + MIN_LV_LEN)?;
+        let mut data = None;
+        if value_len > 0 {
+            data = Some(&buf[MIN_LV_LEN..MIN_LV_LEN + value_len])
+        }
+        Ok(Self { data })
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use crate::cfdp::lv::Lv;
+    use crate::cfdp::TlvLvError;
+    use crate::ByteConversionError;
+    use std::string::String;
+
+    #[test]
+    fn test_basic() {
+        let lv_data: [u8; 4] = [1, 2, 3, 4];
+        let lv_res = Lv::new(&lv_data);
+        assert!(lv_res.is_ok());
+        let lv = lv_res.unwrap();
+        assert!(lv.value().is_some());
+        let val = lv.value().unwrap();
+        assert_eq!(val[0], 1);
+        assert_eq!(val[1], 2);
+        assert_eq!(val[2], 3);
+        assert_eq!(val[3], 4);
+        assert!(!lv.is_empty());
+        assert_eq!(lv.len_full(), 5);
+        assert_eq!(lv.len_value(), 4);
+    }
+
+    #[test]
+    fn test_empty() {
+        let lv_empty = Lv::new_empty();
+        assert_eq!(lv_empty.len_value(), 0);
+        assert_eq!(lv_empty.len_full(), 1);
+        assert!(lv_empty.is_empty());
+        assert_eq!(lv_empty.value(), None);
+        let mut buf: [u8; 4] = [0xff; 4];
+        let res = lv_empty.write_to_be_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(written, 1);
+        assert_eq!(buf[0], 0);
+    }
+
+    #[test]
+    fn test_serialization() {
+        let lv_data: [u8; 4] = [1, 2, 3, 4];
+        let lv_res = Lv::new(&lv_data);
+        assert!(lv_res.is_ok());
+        let lv = lv_res.unwrap();
+        let mut buf: [u8; 16] = [0; 16];
+        let res = lv.write_to_be_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(written, 5);
+        assert_eq!(buf[0], 4);
+        assert_eq!(buf[1], 1);
+        assert_eq!(buf[2], 2);
+        assert_eq!(buf[3], 3);
+        assert_eq!(buf[4], 4);
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let mut buf: [u8; 16] = [0; 16];
+        buf[0] = 4;
+        buf[1] = 1;
+        buf[2] = 2;
+        buf[3] = 3;
+        buf[4] = 4;
+        let lv = Lv::from_bytes(&buf);
+        assert!(lv.is_ok());
+        let lv = lv.unwrap();
+        assert!(!lv.is_empty());
+        assert!(lv.value().is_some());
+        assert_eq!(lv.len_value(), 4);
+        assert_eq!(lv.len_full(), 5);
+        let val = lv.value().unwrap();
+        assert_eq!(val[0], 1);
+        assert_eq!(val[1], 2);
+        assert_eq!(val[2], 3);
+        assert_eq!(val[3], 4);
+    }
+
+    #[test]
+    fn test_deserialization_empty() {
+        let buf: [u8; 2] = [0; 2];
+        let lv_empty = Lv::from_bytes(&buf);
+        assert!(lv_empty.is_ok());
+        let lv_empty = lv_empty.unwrap();
+        assert!(lv_empty.is_empty());
+        assert!(lv_empty.value().is_none());
+    }
+
+    #[test]
+    fn test_data_too_large() {
+        let data_big: [u8; u8::MAX as usize + 1] = [0; u8::MAX as usize + 1];
+        let lv = Lv::new(&data_big);
+        assert!(lv.is_err());
+        let error = lv.unwrap_err();
+        if let TlvLvError::DataTooLarge(size) = error {
+            assert_eq!(size, u8::MAX as usize + 1);
+        } else {
+            panic!("invalid exception {:?}", error)
+        }
+    }
+
+    #[test]
+    fn test_serialization_buf_too_small() {
+        let mut buf: [u8; 3] = [0; 3];
+        let lv_data: [u8; 4] = [1, 2, 3, 4];
+        let lv = Lv::new(&lv_data).unwrap();
+        let res = lv.write_to_be_bytes(&mut buf);
+        assert!(res.is_err());
+        let error = res.unwrap_err();
+        if let ByteConversionError::ToSliceTooSmall(missmatch) = error {
+            assert_eq!(missmatch.expected, 5);
+            assert_eq!(missmatch.found, 3);
+        } else {
+            panic!("invalid error {}", error);
+        }
+    }
+
+    #[test]
+    fn test_deserialization_buf_too_small() {
+        let mut buf: [u8; 3] = [0; 3];
+        buf[0] = 4;
+        let res = Lv::from_bytes(&buf);
+        assert!(res.is_err());
+        let error = res.unwrap_err();
+        if let ByteConversionError::FromSliceTooSmall(missmatch) = error {
+            assert_eq!(missmatch.found, 3);
+            assert_eq!(missmatch.expected, 5);
+        } else {
+            panic!("invalid error {}", error);
+        }
+    }
+
+    fn verify_test_str_lv(lv: Lv) {
+        let mut buf: [u8; 16] = [0; 16];
+        let res = lv.write_to_be_bytes(&mut buf);
+        assert!(res.is_ok());
+        let res = res.unwrap();
+        assert_eq!(res, 8 + 1);
+        assert_eq!(buf[0], 8);
+        assert_eq!(buf[1], 't' as u8);
+        assert_eq!(buf[2], 'e' as u8);
+        assert_eq!(buf[3], 's' as u8);
+        assert_eq!(buf[4], 't' as u8);
+        assert_eq!(buf[5], '.' as u8);
+        assert_eq!(buf[6], 'b' as u8);
+        assert_eq!(buf[7], 'i' as u8);
+        assert_eq!(buf[8], 'n' as u8);
+    }
+    #[test]
+    fn test_str_helper() {
+        let test_str = "test.bin";
+        let str_lv = Lv::new_from_str(test_str);
+        assert!(str_lv.is_ok());
+        verify_test_str_lv(str_lv.unwrap());
+    }
+
+    #[test]
+    fn test_string_helper() {
+        let string = String::from("test.bin");
+        let str_lv = Lv::new_from_string(&string);
+        assert!(str_lv.is_ok());
+        verify_test_str_lv(str_lv.unwrap());
+    }
+}

src/cfdp/mod.rs

@@ -0,0 +1,203 @@
+//! Low-level CCSDS File Delivery Protocol (CFDP) support according to [CCSDS 727.0-B-5](https://public.ccsds.org/Pubs/727x0b5.pdf).
+use crate::ByteConversionError;
+use core::fmt::{Display, Formatter};
+use num_enum::{IntoPrimitive, TryFromPrimitive};
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+#[cfg(feature = "std")]
+use std::error::Error;
+
+pub mod lv;
+pub mod pdu;
+pub mod tlv;
+
+/// This is the name of the standard this module is based on.
+pub const CFDP_VERSION_2_NAME: &str = "CCSDS 727.0-B-5";
+/// Currently, only this version is supported.
+pub const CFDP_VERSION_2: u8 = 0b001;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum PduType {
+    FileDirective = 0,
+    FileData = 1,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum Direction {
+    TowardsReceiver = 0,
+    TowardsSender = 1,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum TransmissionMode {
+    Acknowledged = 0,
+    Unacknowledged = 1,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum CrcFlag {
+    NoCrc = 0,
+    WithCrc = 1,
+}
+
+/// Always 0 and ignored for File Directive PDUs (CCSDS 727.0-B-5 P.75)
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum SegmentMetadataFlag {
+    NotPresent = 0,
+    Present = 1,
+}
+
+/// Always 0 and ignored for File Directive PDUs (CCSDS 727.0-B-5 P.75)
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum SegmentationControl {
+    NoRecordBoundaryPreservation = 0,
+    WithRecordBoundaryPreservation = 1,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum FaultHandlerCode {
+    NoticeOfCancellation = 0b0001,
+    NoticeOfSuspension = 0b0010,
+    IgnoreError = 0b0011,
+    AbandonTransaction = 0b0100,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum LenInBytes {
+    ZeroOrNone = 0,
+    OneByte = 1,
+    TwoBytes = 2,
+    ThreeBytes = 4,
+    FourBytes = 8,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum ConditionCode {
+    /// This is not an error condition for which a faulty handler override can be specified
+    NoError = 0b0000,
+    PositiveAckLimitReached = 0b0001,
+    KeepAliveLimitReached = 0b0010,
+    InvalidTransmissionMode = 0b0011,
+    FilestoreRejection = 0b0100,
+    FileChecksumFailure = 0b0101,
+    FileSizeError = 0b0110,
+    NakLimitReached = 0b0111,
+    InactivityDetected = 0b1000,
+    CheckLimitReached = 0b1001,
+    UnsupportedChecksumType = 0b1011,
+    /// Not an actual fault condition for which fault handler overrides can be specified
+    SuspendRequestReceived = 0b1110,
+    /// Not an actual fault condition for which fault handler overrides can be specified
+    CancelRequestReceived = 0b1111,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum LargeFileFlag {
+    /// 32 bit maximum file size and FSS size
+    Normal = 0,
+    /// 64 bit maximum file size and FSS size
+    Large = 1,
+}
+
+/// Checksum types according to the
+/// [SANA Checksum Types registry](https://sanaregistry.org/r/checksum_identifiers/)
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum ChecksumType {
+    /// Modular legacy checksum
+    Modular = 0,
+    Crc32Proximity1 = 1,
+    Crc32C = 2,
+    /// Polynomial: 0x4C11DB7. Preferred checksum for now.
+    Crc32 = 3,
+    NullChecksum = 15,
+}
+
+pub const NULL_CHECKSUM_U32: [u8; 4] = [0; 4];
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum TlvLvError {
+    DataTooLarge(usize),
+    ByteConversionError(ByteConversionError),
+    /// First value: Found value. Second value: Expected value if there is one.
+    InvalidTlvTypeField((u8, Option<u8>)),
+    /// Logically invalid value length detected. The value length may not exceed 255 bytes.
+    /// Depending on the concrete TLV type, the value length may also be logically invalid.
+    InvalidValueLength(usize),
+    /// Only applies to filestore requests and responses. Second name was missing where one is
+    /// expected.
+    SecondNameMissing,
+    /// Invalid action code for filestore requests or responses.
+    InvalidFilestoreActionCode(u8),
+}
+
+impl From<ByteConversionError> for TlvLvError {
+    fn from(value: ByteConversionError) -> Self {
+        Self::ByteConversionError(value)
+    }
+}
+
+impl Display for TlvLvError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        match self {
+            TlvLvError::DataTooLarge(data_len) => {
+                write!(
+                    f,
+                    "data with size {} larger than allowed {} bytes",
+                    data_len,
+                    u8::MAX
+                )
+            }
+            TlvLvError::ByteConversionError(e) => {
+                write!(f, "{}", e)
+            }
+            TlvLvError::InvalidTlvTypeField((found, expected)) => {
+                write!(
+                    f,
+                    "invalid TLV type field, found {found}, possibly expected {expected:?}"
+                )
+            }
+            TlvLvError::InvalidValueLength(len) => {
+                write!(f, "invalid value length {len} detected")
+            }
+            TlvLvError::SecondNameMissing => {
+                write!(f, "second name missing for filestore request or response")
+            }
+            TlvLvError::InvalidFilestoreActionCode(raw) => {
+                write!(f, "invalid filestore action code with raw value {raw}")
+            }
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for TlvLvError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match self {
+            TlvLvError::ByteConversionError(e) => Some(e),
+            _ => None,
+        }
+    }
+}

src/cfdp/pdu/eof.rs

@@ -0,0 +1,206 @@
+use crate::cfdp::pdu::{
+    add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
+    FileDirectiveType, PduError, PduHeader,
+};
+use crate::cfdp::tlv::EntityIdTlv;
+use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
+use crate::{ByteConversionError, SizeMissmatch};
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+/// Finished PDU abstraction.
+///
+/// For more information, refer to CFDP chapter 5.2.2.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct EofPdu {
+    pdu_header: PduHeader,
+    condition_code: ConditionCode,
+    file_checksum: u32,
+    file_size: u64,
+    fault_location: Option<EntityIdTlv>,
+}
+
+impl EofPdu {
+    pub fn new_no_error(pdu_header: PduHeader, file_checksum: u32, file_size: u64) -> Self {
+        let mut eof_pdu = Self {
+            pdu_header,
+            condition_code: ConditionCode::NoError,
+            file_checksum,
+            file_size,
+            fault_location: None,
+        };
+        eof_pdu.pdu_header.pdu_datafield_len = eof_pdu.calc_pdu_datafield_len() as u16;
+        eof_pdu
+    }
+
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    pub fn written_len(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+
+    pub fn condition_code(&self) -> ConditionCode {
+        self.condition_code
+    }
+
+    pub fn file_checksum(&self) -> u32 {
+        self.file_checksum
+    }
+
+    pub fn file_size(&self) -> u64 {
+        self.file_size
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        // One directive type octet, 4 bits condition code, 4 spare bits.
+        let mut len = 2 + core::mem::size_of::<u32>() + 4;
+        if self.pdu_header.pdu_conf.file_flag == LargeFileFlag::Large {
+            len += 4;
+        }
+        if let Some(fault_location) = self.fault_location {
+            len += fault_location.len_full();
+        }
+        len
+    }
+
+    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.written_len();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: expected_len,
+            })
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::EofPdu as u8;
+        current_idx += 1;
+        buf[current_idx] = (self.condition_code as u8) << 4;
+        current_idx += 1;
+        buf[current_idx..current_idx + 4].copy_from_slice(&self.file_checksum.to_be_bytes());
+        current_idx += 4;
+        current_idx += write_fss_field(
+            self.pdu_header.pdu_conf.file_flag,
+            self.file_size,
+            &mut buf[current_idx..],
+        )?;
+        if let Some(fault_location) = self.fault_location {
+            current_idx += fault_location.write_to_be_bytes(buf)?;
+        }
+        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    pub fn from_bytes(buf: &[u8]) -> Result<EofPdu, PduError> {
+        let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
+        let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
+        let is_large_file = pdu_header.pdu_conf.file_flag == LargeFileFlag::Large;
+        let mut min_expected_len = 2 + 4 + 4;
+        if is_large_file {
+            min_expected_len += 4;
+        }
+        generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
+        let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
+            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::EofPdu))
+        })?;
+        if directive_type != FileDirectiveType::EofPdu {
+            return Err(PduError::WrongDirectiveType((
+                directive_type,
+                FileDirectiveType::EofPdu,
+            )));
+        }
+        current_idx += 1;
+        let condition_code = ConditionCode::try_from((buf[current_idx] >> 4) & 0b1111)
+            .map_err(|_| PduError::InvalidConditionCode((buf[current_idx] >> 4) & 0b1111))?;
+        current_idx += 1;
+        let file_checksum =
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
+        current_idx += 4;
+        let (fss_field_len, file_size) =
+            read_fss_field(pdu_header.pdu_conf.file_flag, &buf[current_idx..]);
+        current_idx += fss_field_len;
+        let mut fault_location = None;
+        if condition_code != ConditionCode::NoError && current_idx < full_len_without_crc {
+            fault_location = Some(EntityIdTlv::from_bytes(&buf[current_idx..])?);
+        }
+        Ok(Self {
+            pdu_header,
+            condition_code,
+            file_checksum,
+            file_size,
+            fault_location,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::cfdp::pdu::eof::EofPdu;
+    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
+    use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
+
+    #[test]
+    fn test_basic() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        assert_eq!(eof_pdu.written_len(), pdu_header.header_len() + 2 + 4 + 4);
+        assert_eq!(eof_pdu.file_checksum(), 0x01020304);
+        assert_eq!(eof_pdu.file_size(), 12);
+        assert_eq!(eof_pdu.condition_code(), ConditionCode::NoError);
+    }
+
+    #[test]
+    fn test_serialization() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        let mut buf: [u8; 64] = [0; 64];
+        let res = eof_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(written, eof_pdu.written_len());
+        verify_raw_header(eof_pdu.pdu_header(), &buf);
+        let mut current_idx = eof_pdu.pdu_header().header_len();
+        buf[current_idx] = FileDirectiveType::EofPdu as u8;
+        current_idx += 1;
+        assert_eq!(
+            (buf[current_idx] >> 4) & 0b1111,
+            ConditionCode::NoError as u8
+        );
+        current_idx += 1;
+        assert_eq!(
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap()),
+            0x01020304
+        );
+        current_idx += 4;
+        assert_eq!(
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap()),
+            12
+        );
+        current_idx += 4;
+        assert_eq!(current_idx, written);
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let eof_pdu = EofPdu::new_no_error(pdu_header, 0x01020304, 12);
+        let mut buf: [u8; 64] = [0; 64];
+        eof_pdu.write_to_bytes(&mut buf).unwrap();
+        let eof_read_back = EofPdu::from_bytes(&buf);
+        if !eof_read_back.is_ok() {
+            let e = eof_read_back.unwrap_err();
+            panic!("deserialization failed with: {e}")
+        }
+        let eof_read_back = eof_read_back.unwrap();
+        assert_eq!(eof_read_back, eof_pdu);
+    }
+}

src/cfdp/pdu/file_data.rs

@@ -0,0 +1,397 @@
+use crate::cfdp::pdu::{
+    add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
+    PduError, PduHeader,
+};
+use crate::cfdp::{CrcFlag, LargeFileFlag, PduType, SegmentMetadataFlag};
+use crate::{ByteConversionError, SizeMissmatch};
+use num_enum::{IntoPrimitive, TryFromPrimitive};
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum RecordContinuationState {
+    NoStartNoEnd = 0b00,
+    StartWithoutEnd = 0b01,
+    EndWithoutStart = 0b10,
+    StartAndEnd = 0b11,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct SegmentMetadata<'seg_meta> {
+    record_continuation_state: RecordContinuationState,
+    metadata: Option<&'seg_meta [u8]>,
+}
+
+impl<'seg_meta> SegmentMetadata<'seg_meta> {
+    pub fn new(
+        record_continuation_state: RecordContinuationState,
+        metadata: Option<&'seg_meta [u8]>,
+    ) -> Option<Self> {
+        if let Some(metadata) = metadata {
+            if metadata.len() > 2_usize.pow(6) - 1 {
+                return None;
+            }
+        }
+        Some(Self {
+            record_continuation_state,
+            metadata,
+        })
+    }
+
+    pub fn written_len(&self) -> usize {
+        // Map empty metadata to 0 and slice to its length.
+        1 + self.metadata.map_or(0, |meta| meta.len())
+    }
+
+    pub(crate) fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        if buf.len() < self.written_len() {
+            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: self.written_len(),
+            }));
+        }
+        buf[0] = ((self.record_continuation_state as u8) << 6)
+            | self.metadata.map_or(0, |meta| meta.len() as u8);
+        if let Some(metadata) = self.metadata {
+            buf[1..1 + metadata.len()].copy_from_slice(metadata)
+        }
+        Ok(self.written_len())
+    }
+
+    pub(crate) fn from_bytes(buf: &'seg_meta [u8]) -> Result<Self, ByteConversionError> {
+        if buf.is_empty() {
+            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: 2,
+            }));
+        }
+        let mut metadata = None;
+        let seg_metadata_len = (buf[0] & 0b111111) as usize;
+        if seg_metadata_len > 0 {
+            metadata = Some(&buf[1..1 + seg_metadata_len]);
+        }
+        Ok(Self {
+            // Can't fail, only 2 bits
+            record_continuation_state: RecordContinuationState::try_from((buf[0] >> 6) & 0b11)
+                .unwrap(),
+            metadata,
+        })
+    }
+}
+
+/// 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,
+    file_data: &'file_data [u8],
+}
+
+impl<'seg_meta, 'file_data> FileDataPdu<'seg_meta, 'file_data> {
+    pub fn new_with_seg_metadata(
+        pdu_header: PduHeader,
+        segment_metadata: SegmentMetadata<'seg_meta>,
+        offset: u64,
+        file_data: &'file_data [u8],
+    ) -> Self {
+        Self::new_generic(pdu_header, Some(segment_metadata), offset, file_data)
+    }
+
+    pub fn new_no_seg_metadata(
+        pdu_header: PduHeader,
+        offset: u64,
+        file_data: &'file_data [u8],
+    ) -> Self {
+        Self::new_generic(pdu_header, None, offset, file_data)
+    }
+
+    pub fn new_generic(
+        mut pdu_header: PduHeader,
+        segment_metadata: Option<SegmentMetadata<'seg_meta>>,
+        offset: u64,
+        file_data: &'file_data [u8],
+    ) -> Self {
+        pdu_header.pdu_type = PduType::FileData;
+        if segment_metadata.is_some() {
+            pdu_header.seg_metadata_flag = SegmentMetadataFlag::Present;
+        }
+        let mut pdu = Self {
+            pdu_header,
+            segment_metadata,
+            offset,
+            file_data,
+        };
+        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
+        pdu
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        let mut len = core::mem::size_of::<u32>();
+        if self.pdu_header.pdu_conf.file_flag == LargeFileFlag::Large {
+            len += 4;
+        }
+        if self.segment_metadata.is_some() {
+            len += self.segment_metadata.as_ref().unwrap().written_len()
+        }
+        len += self.file_data.len();
+        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+            len += 2;
+        }
+        len
+    }
+    pub fn written_len(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+
+    pub fn offset(&self) -> u64 {
+        self.offset
+    }
+
+    pub fn file_data(&self) -> &'file_data [u8] {
+        self.file_data
+    }
+
+    pub fn segment_metadata(&self) -> Option<&SegmentMetadata> {
+        self.segment_metadata.as_ref()
+    }
+
+    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        if buf.len() < self.written_len() {
+            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: self.written_len(),
+            })
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        if self.segment_metadata.is_some() {
+            current_idx += self
+                .segment_metadata
+                .as_ref()
+                .unwrap()
+                .write_to_bytes(&mut buf[current_idx..])?;
+        }
+        current_idx += write_fss_field(
+            self.pdu_header.common_pdu_conf().file_flag,
+            self.offset,
+            &mut buf[current_idx..],
+        )?;
+        buf[current_idx..current_idx + self.file_data.len()].copy_from_slice(self.file_data);
+        current_idx += self.file_data.len();
+        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    pub fn from_bytes<'longest: 'seg_meta + 'file_data>(
+        buf: &'longest [u8],
+    ) -> Result<Self, PduError> {
+        let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
+        let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
+        let min_expected_len = current_idx + core::mem::size_of::<u32>();
+        generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
+        let mut segment_metadata = None;
+        if pdu_header.seg_metadata_flag == SegmentMetadataFlag::Present {
+            segment_metadata = Some(SegmentMetadata::from_bytes(&buf[current_idx..])?);
+            current_idx += segment_metadata.as_ref().unwrap().written_len();
+        }
+        let (fss, offset) = read_fss_field(pdu_header.pdu_conf.file_flag, &buf[current_idx..]);
+        current_idx += fss;
+        if current_idx > full_len_without_crc {
+            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+                found: current_idx,
+                expected: full_len_without_crc,
+            })
+            .into());
+        }
+        Ok(Self {
+            pdu_header,
+            segment_metadata,
+            offset,
+            file_data: &buf[current_idx..full_len_without_crc],
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::cfdp::pdu::file_data::{FileDataPdu, RecordContinuationState, SegmentMetadata};
+    use crate::cfdp::pdu::{CommonPduConfig, PduHeader};
+    use crate::cfdp::{SegmentMetadataFlag, SegmentationControl};
+    use crate::util::UbfU8;
+
+    #[test]
+    fn test_basic() {
+        let src_id = UbfU8::new(1);
+        let dest_id = UbfU8::new(2);
+        let transaction_seq_num = UbfU8::new(3);
+        let common_conf =
+            CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_seq_num).unwrap();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
+        assert_eq!(fd_pdu.file_data(), file_data);
+        assert_eq!(fd_pdu.offset(), 10);
+        assert!(fd_pdu.segment_metadata().is_none());
+        assert_eq!(
+            fd_pdu.written_len(),
+            fd_pdu.pdu_header.header_len() + core::mem::size_of::<u32>() + 4
+        );
+    }
+
+    #[test]
+    fn test_serialization() {
+        let src_id = UbfU8::new(1);
+        let dest_id = UbfU8::new(2);
+        let transaction_seq_num = UbfU8::new(3);
+        let common_conf =
+            CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_seq_num).unwrap();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
+        let mut buf: [u8; 32] = [0; 32];
+        let res = fd_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(
+            written,
+            fd_pdu.pdu_header.header_len() + core::mem::size_of::<u32>() + 4
+        );
+        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]
+                .try_into()
+                .unwrap(),
+        );
+        current_idx += 4;
+        assert_eq!(file_size, 10);
+        assert_eq!(buf[current_idx], 1);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 2);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 3);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 4);
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let src_id = UbfU8::new(1);
+        let dest_id = UbfU8::new(2);
+        let transaction_seq_num = UbfU8::new(3);
+        let common_conf =
+            CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_seq_num).unwrap();
+        let pdu_header = PduHeader::new_for_file_data_default(common_conf, 0);
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let fd_pdu = FileDataPdu::new_no_seg_metadata(pdu_header, 10, &file_data);
+        let mut buf: [u8; 32] = [0; 32];
+        fd_pdu.write_to_bytes(&mut buf).unwrap();
+        let fd_pdu_read_back = FileDataPdu::from_bytes(&buf);
+        assert!(fd_pdu_read_back.is_ok());
+        let fd_pdu_read_back = fd_pdu_read_back.unwrap();
+        assert_eq!(fd_pdu_read_back, fd_pdu);
+    }
+
+    #[test]
+    fn test_with_seg_metadata_serialization() {
+        let src_id = UbfU8::new(1);
+        let dest_id = UbfU8::new(2);
+        let transaction_seq_num = UbfU8::new(3);
+        let common_conf =
+            CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_seq_num).unwrap();
+        let pdu_header = PduHeader::new_for_file_data(
+            common_conf,
+            0,
+            SegmentMetadataFlag::Present,
+            SegmentationControl::WithRecordBoundaryPreservation,
+        );
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let seg_metadata: [u8; 4] = [4, 3, 2, 1];
+        let segment_meta =
+            SegmentMetadata::new(RecordContinuationState::StartAndEnd, Some(&seg_metadata))
+                .unwrap();
+        let fd_pdu = FileDataPdu::new_with_seg_metadata(pdu_header, segment_meta, 10, &file_data);
+        assert!(fd_pdu.segment_metadata().is_some());
+        assert_eq!(*fd_pdu.segment_metadata().unwrap(), segment_meta);
+        assert_eq!(
+            fd_pdu.written_len(),
+            fd_pdu.pdu_header.header_len()
+                + 1
+                + seg_metadata.len()
+                + core::mem::size_of::<u32>()
+                + 4
+        );
+        let mut buf: [u8; 32] = [0; 32];
+        fd_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing FD PDU failed");
+        let mut current_idx = fd_pdu.pdu_header.header_len();
+        assert_eq!(
+            RecordContinuationState::try_from((buf[current_idx] >> 6) & 0b11).unwrap(),
+            RecordContinuationState::StartAndEnd
+        );
+        assert_eq!((buf[current_idx] & 0b111111) as usize, seg_metadata.len());
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 4);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 3);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 2);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 1);
+        current_idx += 1;
+        // Still verify that the rest is written correctly.
+        assert_eq!(
+            u32::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap()),
+            10
+        );
+        current_idx += 4;
+        assert_eq!(buf[current_idx], 1);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 2);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 3);
+        current_idx += 1;
+        assert_eq!(buf[current_idx], 4);
+        current_idx += 1;
+        assert_eq!(current_idx, fd_pdu.written_len());
+    }
+
+    #[test]
+    fn test_with_seg_metadata_deserialization() {
+        let src_id = UbfU8::new(1);
+        let dest_id = UbfU8::new(2);
+        let transaction_seq_num = UbfU8::new(3);
+        let common_conf =
+            CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_seq_num).unwrap();
+        let pdu_header = PduHeader::new_for_file_data(
+            common_conf,
+            0,
+            SegmentMetadataFlag::Present,
+            SegmentationControl::WithRecordBoundaryPreservation,
+        );
+        let file_data: [u8; 4] = [1, 2, 3, 4];
+        let seg_metadata: [u8; 4] = [4, 3, 2, 1];
+        let segment_meta =
+            SegmentMetadata::new(RecordContinuationState::StartAndEnd, Some(&seg_metadata))
+                .unwrap();
+        let fd_pdu = FileDataPdu::new_with_seg_metadata(pdu_header, segment_meta, 10, &file_data);
+        let mut buf: [u8; 32] = [0; 32];
+        fd_pdu
+            .write_to_bytes(&mut buf)
+            .expect("writing FD PDU failed");
+        let fd_pdu_read_back = FileDataPdu::from_bytes(&buf);
+        assert!(fd_pdu_read_back.is_ok());
+        let fd_pdu_read_back = fd_pdu_read_back.unwrap();
+        assert_eq!(fd_pdu_read_back, fd_pdu);
+    }
+}

src/cfdp/pdu/finished.rs

@@ -0,0 +1,336 @@
+use crate::cfdp::pdu::{
+    add_pdu_crc, generic_length_checks_pdu_deserialization, FileDirectiveType, PduError, PduHeader,
+};
+use crate::cfdp::tlv::{EntityIdTlv, Tlv, TlvType, TlvTypeField};
+use crate::cfdp::{ConditionCode, CrcFlag, PduType, TlvLvError};
+use crate::{ByteConversionError, SizeMissmatch};
+use num_enum::{IntoPrimitive, TryFromPrimitive};
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum DeliveryCode {
+    Complete = 0,
+    Incomplete = 1,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum FileStatus {
+    DiscardDeliberately = 0b00,
+    DiscardedFsRejection = 0b01,
+    Retained = 0b10,
+    Unreported = 0b11,
+}
+
+/// Finished PDU abstraction.
+///
+/// For more information, refer to CFDP chapter 5.2.3.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct FinishedPdu<'fs_responses> {
+    pdu_header: PduHeader,
+    condition_code: ConditionCode,
+    delivery_code: DeliveryCode,
+    file_status: FileStatus,
+    fs_responses: Option<&'fs_responses [u8]>,
+    fault_location: Option<EntityIdTlv>,
+}
+
+impl<'fs_responses> FinishedPdu<'fs_responses> {
+    /// Default finished PDU: No error (no fault location field) and no filestore responses.
+    pub fn new_default(
+        pdu_header: PduHeader,
+        delivery_code: DeliveryCode,
+        file_status: FileStatus,
+    ) -> Self {
+        Self::new_generic(
+            pdu_header,
+            ConditionCode::NoError,
+            delivery_code,
+            file_status,
+            None,
+            None,
+        )
+    }
+
+    pub fn new_with_error(
+        pdu_header: PduHeader,
+        condition_code: ConditionCode,
+        delivery_code: DeliveryCode,
+        file_status: FileStatus,
+        fault_location: EntityIdTlv,
+    ) -> Self {
+        Self::new_generic(
+            pdu_header,
+            condition_code,
+            delivery_code,
+            file_status,
+            None,
+            Some(fault_location),
+        )
+    }
+
+    pub fn new_generic(
+        mut pdu_header: PduHeader,
+        condition_code: ConditionCode,
+        delivery_code: DeliveryCode,
+        file_status: FileStatus,
+        fs_responses: Option<&'fs_responses [u8]>,
+        fault_location: Option<EntityIdTlv>,
+    ) -> Self {
+        pdu_header.pdu_type = PduType::FileDirective;
+        let mut finished_pdu = Self {
+            pdu_header,
+            condition_code,
+            delivery_code,
+            file_status,
+            fs_responses,
+            fault_location,
+        };
+        finished_pdu.pdu_header.pdu_datafield_len = finished_pdu.calc_pdu_datafield_len() as u16;
+        finished_pdu
+    }
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    pub fn written_len(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+
+    pub fn condition_code(&self) -> ConditionCode {
+        self.condition_code
+    }
+
+    pub fn delivery_code(&self) -> DeliveryCode {
+        self.delivery_code
+    }
+
+    pub fn file_status(&self) -> FileStatus {
+        self.file_status
+    }
+
+    pub fn filestore_responses(&self) -> Option<&'fs_responses [u8]> {
+        self.fs_responses
+    }
+
+    pub fn fault_location(&self) -> Option<EntityIdTlv> {
+        self.fault_location
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        let mut base_len = 2;
+        if let Some(fs_responses) = self.fs_responses {
+            base_len += fs_responses.len();
+        }
+        if let Some(fault_location) = self.fault_location {
+            base_len += fault_location.len_full();
+        }
+        base_len
+    }
+
+    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.written_len();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: expected_len,
+            })
+            .into());
+        }
+
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::FinishedPdu as u8;
+        current_idx += 1;
+        buf[current_idx] = ((self.condition_code as u8) << 4)
+            | ((self.delivery_code as u8) << 2)
+            | self.file_status as u8;
+        current_idx += 1;
+        if let Some(fs_responses) = self.fs_responses {
+            buf[current_idx..current_idx + fs_responses.len()].copy_from_slice(fs_responses);
+            current_idx += fs_responses.len();
+        }
+        if let Some(fault_location) = self.fault_location {
+            current_idx += fault_location.write_to_be_bytes(&mut buf[current_idx..])?;
+        }
+        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    /// Generates [Self] from a raw bytestream.
+    pub fn from_bytes(buf: &'fs_responses [u8]) -> Result<Self, PduError> {
+        let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
+        let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
+        let min_expected_len = current_idx + 2;
+        generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
+        let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
+            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::FinishedPdu))
+        })?;
+        if directive_type != FileDirectiveType::FinishedPdu {
+            return Err(PduError::WrongDirectiveType((
+                directive_type,
+                FileDirectiveType::FinishedPdu,
+            )));
+        }
+        current_idx += 1;
+        let condition_code = ConditionCode::try_from((buf[current_idx] >> 4) & 0b1111)
+            .map_err(|_| PduError::InvalidConditionCode((buf[current_idx] >> 4) & 0b1111))?;
+        // Unwrap is okay here for both of the following operations which can not fail.
+        let delivery_code = DeliveryCode::try_from((buf[current_idx] >> 2) & 0b1).unwrap();
+        let file_status = FileStatus::try_from(buf[current_idx] & 0b11).unwrap();
+        current_idx += 1;
+        let (fs_responses, fault_location) =
+            Self::parse_tlv_fields(current_idx, full_len_without_crc, buf)?;
+        Ok(Self {
+            pdu_header,
+            condition_code,
+            delivery_code,
+            file_status,
+            fs_responses,
+            fault_location,
+        })
+    }
+
+    fn parse_tlv_fields(
+        mut current_idx: usize,
+        full_len_without_crc: usize,
+        buf: &'fs_responses [u8],
+    ) -> Result<(Option<&'fs_responses [u8]>, Option<EntityIdTlv>), PduError> {
+        let mut fs_responses = None;
+        let mut fault_location = None;
+        let start_of_fs_responses = current_idx;
+        // There are leftover filestore response(s) and/or a fault location field.
+        while current_idx < full_len_without_crc {
+            let next_tlv = Tlv::from_bytes(&buf[current_idx..])?;
+            match next_tlv.tlv_type_field() {
+                TlvTypeField::Standard(tlv_type) => {
+                    if tlv_type == TlvType::FilestoreResponse {
+                        current_idx += next_tlv.len_full();
+                        if current_idx == full_len_without_crc {
+                            fs_responses = Some(&buf[start_of_fs_responses..current_idx]);
+                        }
+                    } else if tlv_type == TlvType::EntityId {
+                        // At least one FS response is included.
+                        if current_idx > full_len_without_crc {
+                            fs_responses = Some(&buf[start_of_fs_responses..current_idx]);
+                        }
+                        fault_location = Some(EntityIdTlv::from_bytes(&buf[current_idx..])?);
+                        current_idx += fault_location.as_ref().unwrap().len_full();
+                        // This is considered a configuration error: The entity ID has to be the
+                        // last TLV, everything else would break the whole handling of the packet
+                        // TLVs.
+                        if current_idx != full_len_without_crc {
+                            return Err(PduError::FormatError);
+                        }
+                    } else {
+                        return Err(TlvLvError::InvalidTlvTypeField((tlv_type as u8, None)).into());
+                    }
+                }
+                TlvTypeField::Custom(raw) => {
+                    return Err(TlvLvError::InvalidTlvTypeField((raw, None)).into());
+                }
+            }
+        }
+        Ok((fs_responses, fault_location))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::cfdp::pdu::finished::{DeliveryCode, FileStatus, FinishedPdu};
+    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
+    use crate::cfdp::{ConditionCode, CrcFlag, LargeFileFlag};
+
+    fn generic_finished_pdu(
+        crc_flag: CrcFlag,
+        fss: LargeFileFlag,
+        delivery_code: DeliveryCode,
+        file_status: FileStatus,
+    ) -> FinishedPdu<'static> {
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_conf(crc_flag, fss), 0);
+        FinishedPdu::new_default(pdu_header, delivery_code, file_status)
+    }
+
+    #[test]
+    fn test_basic() {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::NoCrc,
+            LargeFileFlag::Normal,
+            DeliveryCode::Complete,
+            FileStatus::Retained,
+        );
+        assert_eq!(finished_pdu.condition_code(), ConditionCode::NoError);
+        assert_eq!(finished_pdu.delivery_code(), DeliveryCode::Complete);
+        assert_eq!(finished_pdu.file_status(), FileStatus::Retained);
+        assert_eq!(finished_pdu.filestore_responses(), None);
+        assert_eq!(finished_pdu.fault_location(), None);
+        assert_eq!(finished_pdu.pdu_header().pdu_datafield_len, 2);
+    }
+
+    fn generic_serialization_test_no_error(delivery_code: DeliveryCode, file_status: FileStatus) {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::NoCrc,
+            LargeFileFlag::Normal,
+            delivery_code,
+            file_status,
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        let written = finished_pdu.write_to_bytes(&mut buf);
+        assert!(written.is_ok());
+        let written = written.unwrap();
+        assert_eq!(written, finished_pdu.written_len());
+        assert_eq!(written, finished_pdu.pdu_header().header_len() + 2);
+        verify_raw_header(finished_pdu.pdu_header(), &buf);
+        let mut current_idx = finished_pdu.pdu_header().header_len();
+        assert_eq!(buf[current_idx], FileDirectiveType::FinishedPdu as u8);
+        current_idx += 1;
+        assert_eq!(
+            (buf[current_idx] >> 4) & 0b1111,
+            ConditionCode::NoError as u8
+        );
+        assert_eq!((buf[current_idx] >> 2) & 0b1, delivery_code as u8);
+        assert_eq!(buf[current_idx] & 0b11, file_status as u8);
+        assert_eq!(current_idx + 1, written);
+    }
+
+    #[test]
+    fn test_serialization_simple() {
+        generic_serialization_test_no_error(DeliveryCode::Complete, FileStatus::Retained);
+    }
+
+    #[test]
+    fn test_serialization_simple_2() {
+        generic_serialization_test_no_error(
+            DeliveryCode::Incomplete,
+            FileStatus::DiscardDeliberately,
+        );
+    }
+
+    #[test]
+    fn test_serialization_simple_3() {
+        generic_serialization_test_no_error(DeliveryCode::Incomplete, FileStatus::Unreported);
+    }
+
+    #[test]
+    fn test_deserialization_simple() {
+        let finished_pdu = generic_finished_pdu(
+            CrcFlag::NoCrc,
+            LargeFileFlag::Normal,
+            DeliveryCode::Complete,
+            FileStatus::Retained,
+        );
+        let mut buf: [u8; 64] = [0; 64];
+        finished_pdu.write_to_bytes(&mut buf).unwrap();
+        let read_back = FinishedPdu::from_bytes(&buf);
+        assert!(read_back.is_ok());
+        let read_back = read_back.unwrap();
+        assert_eq!(finished_pdu, read_back);
+    }
+}

src/cfdp/pdu/metadata.rs

@@ -0,0 +1,527 @@
+use crate::cfdp::lv::Lv;
+use crate::cfdp::pdu::{
+    add_pdu_crc, generic_length_checks_pdu_deserialization, read_fss_field, write_fss_field,
+    FileDirectiveType, PduError, PduHeader,
+};
+use crate::cfdp::tlv::Tlv;
+use crate::cfdp::{ChecksumType, CrcFlag, LargeFileFlag, PduType};
+use crate::{ByteConversionError, SizeMissmatch};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct MetadataGenericParams {
+    closure_requested: bool,
+    checksum_type: ChecksumType,
+    file_size: u64,
+}
+
+impl MetadataGenericParams {
+    pub fn new(closure_requested: bool, checksum_type: ChecksumType, file_size: u64) -> Self {
+        Self {
+            closure_requested,
+            checksum_type,
+            file_size,
+        }
+    }
+}
+
+pub fn build_metadata_opts_from_slice(
+    buf: &mut [u8],
+    tlvs: &[Tlv],
+) -> Result<usize, ByteConversionError> {
+    let mut written = 0;
+    for tlv in tlvs {
+        written += tlv.write_to_bytes(&mut buf[written..])?;
+    }
+    Ok(written)
+}
+
+#[cfg(feature = "alloc")]
+pub fn build_metadata_opts_from_vec(
+    buf: &mut [u8],
+    tlvs: &Vec<Tlv>,
+) -> Result<usize, ByteConversionError> {
+    build_metadata_opts_from_slice(buf, tlvs.as_slice())
+}
+
+/// Helper structure to loop through all options of a metadata PDU. It should be noted that
+/// iterators in Rust are not fallible, but the TLV creation can fail, for example if the raw TLV
+/// data is invalid for some reason. In that case, the iterator will yield [None] because there
+/// is no way to recover from this.
+///
+/// The user can accumulate the length of all TLVs yielded by the iterator and compare it against
+/// the full length of the options to check whether the iterator was able to parse all TLVs
+/// successfully.
+pub struct OptionsIter<'opts> {
+    opt_buf: &'opts [u8],
+    current_idx: usize,
+}
+
+impl<'opts> Iterator for OptionsIter<'opts> {
+    type Item = Tlv<'opts>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current_idx == self.opt_buf.len() {
+            return None;
+        }
+        let tlv = Tlv::from_bytes(&self.opt_buf[self.current_idx..]);
+        // There are not really fallible iterators so we can't continue here..
+        if tlv.is_err() {
+            return None;
+        }
+        let tlv = tlv.unwrap();
+        self.current_idx += tlv.len_full();
+        Some(tlv)
+    }
+}
+
+/// Metadata PDU abstraction.
+///
+/// For more information, refer to CFDP chapter 5.2.5.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct MetadataPdu<'src_name, 'dest_name, 'opts> {
+    pdu_header: PduHeader,
+    metadata_params: MetadataGenericParams,
+    #[cfg_attr(feature = "serde", serde(borrow))]
+    src_file_name: Lv<'src_name>,
+    #[cfg_attr(feature = "serde", serde(borrow))]
+    dest_file_name: Lv<'dest_name>,
+    options: Option<&'opts [u8]>,
+}
+
+impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
+    pub fn new_no_opts(
+        pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+    ) -> Self {
+        Self::new(
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            None,
+        )
+    }
+
+    pub fn new_with_opts(
+        pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+        options: &'opts [u8],
+    ) -> Self {
+        Self::new(
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            Some(options),
+        )
+    }
+
+    pub fn new(
+        mut pdu_header: PduHeader,
+        metadata_params: MetadataGenericParams,
+        src_file_name: Lv<'src_name>,
+        dest_file_name: Lv<'dest_name>,
+        options: Option<&'opts [u8]>,
+    ) -> Self {
+        pdu_header.pdu_type = PduType::FileDirective;
+        let mut pdu = Self {
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            options,
+        };
+        pdu.pdu_header.pdu_datafield_len = pdu.calc_pdu_datafield_len() as u16;
+        pdu
+    }
+
+    pub fn src_file_name(&self) -> Lv<'src_name> {
+        self.src_file_name
+    }
+
+    pub fn dest_file_name(&self) -> Lv<'dest_name> {
+        self.dest_file_name
+    }
+
+    pub fn options(&self) -> Option<&'opts [u8]> {
+        self.options
+    }
+
+    /// Yield an iterator which can be used to loop through all options. Returns [None] if the
+    /// options field is empty.
+    pub fn options_iter(&self) -> Option<OptionsIter<'opts>> {
+        self.options?;
+        Some(OptionsIter {
+            opt_buf: self.options.unwrap(),
+            current_idx: 0,
+        })
+    }
+
+    pub fn written_len(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        // One directve type octet and one byte of the directive parameter field.
+        let mut len = 2;
+        if self.pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
+            len += 8;
+        } else {
+            len += 4;
+        }
+        len += self.src_file_name.len_full();
+        len += self.dest_file_name.len_full();
+        if let Some(opts) = self.options {
+            len += opts.len();
+        }
+        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+            len += 2;
+        }
+        len
+    }
+
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.written_len();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: expected_len,
+            })
+            .into());
+        }
+
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::MetadataPdu as u8;
+        current_idx += 1;
+        buf[current_idx] = ((self.metadata_params.closure_requested as u8) << 7)
+            | (self.metadata_params.checksum_type as u8);
+        current_idx += 1;
+        current_idx += write_fss_field(
+            self.pdu_header.common_pdu_conf().file_flag,
+            self.metadata_params.file_size,
+            &mut buf[current_idx..],
+        )?;
+        current_idx += self
+            .src_file_name
+            .write_to_be_bytes(&mut buf[current_idx..])?;
+        current_idx += self
+            .dest_file_name
+            .write_to_be_bytes(&mut buf[current_idx..])?;
+        if let Some(opts) = self.options {
+            buf[current_idx..current_idx + opts.len()].copy_from_slice(opts);
+            current_idx += opts.len();
+        }
+        if self.pdu_header.pdu_conf.crc_flag == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    pub fn from_bytes<'longest: 'src_name + 'dest_name + 'opts>(
+        buf: &'longest [u8],
+    ) -> Result<Self, PduError> {
+        let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
+        let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
+        let is_large_file = pdu_header.pdu_conf.file_flag == LargeFileFlag::Large;
+        // Minimal length: 1 byte + FSS (4 byte) + 2 empty LV (1 byte)
+        let mut min_expected_len = current_idx + 7;
+        if is_large_file {
+            min_expected_len += 4;
+        }
+        generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
+        let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
+            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::MetadataPdu))
+        })?;
+        if directive_type != FileDirectiveType::MetadataPdu {
+            return Err(PduError::WrongDirectiveType((
+                directive_type,
+                FileDirectiveType::MetadataPdu,
+            )));
+        }
+        current_idx += 1;
+        let (fss_len, file_size) =
+            read_fss_field(pdu_header.pdu_conf.file_flag, &buf[current_idx + 1..]);
+        let metadata_params = MetadataGenericParams {
+            closure_requested: ((buf[current_idx] >> 6) & 0b1) != 0,
+            checksum_type: ChecksumType::try_from(buf[current_idx] & 0b1111)
+                .map_err(|_| PduError::InvalidChecksumType(buf[current_idx] & 0b1111))?,
+            file_size,
+        };
+        current_idx += 1 + fss_len;
+        let src_file_name = Lv::from_bytes(&buf[current_idx..])?;
+        current_idx += src_file_name.len_full();
+        let dest_file_name = Lv::from_bytes(&buf[current_idx..])?;
+        current_idx += dest_file_name.len_full();
+        // All left-over bytes are options.
+        let mut options = None;
+        if current_idx < full_len_without_crc {
+            options = Some(&buf[current_idx..full_len_without_crc]);
+        }
+        Ok(Self {
+            pdu_header,
+            metadata_params,
+            src_file_name,
+            dest_file_name,
+            options,
+        })
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use crate::cfdp::lv::Lv;
+    use crate::cfdp::pdu::metadata::{
+        build_metadata_opts_from_slice, build_metadata_opts_from_vec, MetadataGenericParams,
+        MetadataPdu,
+    };
+    use crate::cfdp::pdu::tests::{common_pdu_conf, verify_raw_header};
+    use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
+    use crate::cfdp::tlv::{Tlv, TlvType};
+    use crate::cfdp::{
+        ChecksumType, CrcFlag, LargeFileFlag, PduType, SegmentMetadataFlag, SegmentationControl,
+    };
+    use std::vec;
+
+    const SRC_FILENAME: &'static str = "hello-world.txt";
+    const DEST_FILENAME: &'static str = "hello-world2.txt";
+
+    fn generic_metadata_pdu<'opts>(
+        crc_flag: CrcFlag,
+        fss: LargeFileFlag,
+        opts: Option<&'opts [u8]>,
+    ) -> (
+        Lv<'static>,
+        Lv<'static>,
+        MetadataPdu<'static, 'static, 'opts>,
+    ) {
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_conf(crc_flag, fss), 0);
+        let metadata_params = MetadataGenericParams::new(false, ChecksumType::Crc32, 0x1010);
+        let src_filename = Lv::new_from_str(SRC_FILENAME).expect("Generating string LV failed");
+        let dest_filename =
+            Lv::new_from_str(DEST_FILENAME).expect("Generating destination LV failed");
+        (
+            src_filename,
+            dest_filename,
+            MetadataPdu::new(
+                pdu_header,
+                metadata_params,
+                src_filename,
+                dest_filename,
+                opts,
+            ),
+        )
+    }
+
+    #[test]
+    fn test_basic() {
+        let (src_filename, dest_filename, metadata_pdu) =
+            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
+        assert_eq!(
+            metadata_pdu.written_len(),
+            metadata_pdu.pdu_header().header_len()
+                + 1
+                + 1
+                + 4
+                + src_filename.len_full()
+                + dest_filename.len_full()
+        );
+        assert_eq!(metadata_pdu.src_file_name(), src_filename);
+        assert_eq!(metadata_pdu.dest_file_name(), dest_filename);
+        assert_eq!(metadata_pdu.options(), None);
+    }
+
+    #[test]
+    fn test_serialization() {
+        let (src_filename, dest_filename, metadata_pdu) =
+            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
+        let mut buf: [u8; 64] = [0; 64];
+        let res = metadata_pdu.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(
+            written,
+            metadata_pdu.pdu_header.header_len()
+                + 1
+                + 1
+                + 4
+                + src_filename.len_full()
+                + dest_filename.len_full()
+        );
+        verify_raw_header(metadata_pdu.pdu_header(), &buf);
+        assert_eq!(buf[7], FileDirectiveType::MetadataPdu as u8);
+        assert_eq!(buf[8] >> 6, false as u8);
+        assert_eq!(buf[8] & 0b1111, ChecksumType::Crc32 as u8);
+        assert_eq!(u32::from_be_bytes(buf[9..13].try_into().unwrap()), 0x1010);
+        let mut current_idx = 13;
+        let src_name_from_raw =
+            Lv::from_bytes(&buf[current_idx..]).expect("Creating source name LV failed");
+        assert_eq!(src_name_from_raw, src_filename);
+        current_idx += src_name_from_raw.len_full();
+        let dest_name_from_raw =
+            Lv::from_bytes(&buf[current_idx..]).expect("Creating dest name LV failed");
+        assert_eq!(dest_name_from_raw, dest_filename);
+        current_idx += dest_name_from_raw.len_full();
+        // No options, so no additional data here.
+        assert_eq!(current_idx, written);
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let (_, _, metadata_pdu) =
+            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Normal, None);
+        let mut buf: [u8; 64] = [0; 64];
+        metadata_pdu.write_to_bytes(&mut buf).unwrap();
+        let pdu_read_back = MetadataPdu::from_bytes(&buf);
+        assert!(pdu_read_back.is_ok());
+        let pdu_read_back = pdu_read_back.unwrap();
+        assert_eq!(pdu_read_back, metadata_pdu);
+    }
+
+    #[test]
+    fn test_with_crc_flag() {
+        let (src_filename, dest_filename, metadata_pdu) =
+            generic_metadata_pdu(CrcFlag::WithCrc, LargeFileFlag::Normal, None);
+        let mut buf: [u8; 64] = [0; 64];
+        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
+                + core::mem::size_of::<u32>()
+                + src_filename.len_full()
+                + dest_filename.len_full()
+                + 2
+        );
+        let pdu_read_back = MetadataPdu::from_bytes(&buf).unwrap();
+        assert_eq!(pdu_read_back, metadata_pdu);
+    }
+
+    #[test]
+    fn test_with_large_file_flag() {
+        let (src_filename, dest_filename, metadata_pdu) =
+            generic_metadata_pdu(CrcFlag::NoCrc, LargeFileFlag::Large, None);
+        let mut buf: [u8; 64] = [0; 64];
+        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
+                + core::mem::size_of::<u64>()
+                + src_filename.len_full()
+                + dest_filename.len_full()
+        );
+        let pdu_read_back = MetadataPdu::from_bytes(&buf).unwrap();
+        assert_eq!(pdu_read_back, metadata_pdu);
+    }
+
+    #[test]
+    fn test_opts_builders() {
+        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_slice = [tlv1, tlv2];
+        let mut buf: [u8; 32] = [0; 32];
+        let opts = build_metadata_opts_from_slice(&mut buf, &tlv_slice);
+        assert!(opts.is_ok());
+        let opts_len = opts.unwrap();
+        assert_eq!(opts_len, tlv1.len_full() + tlv2.len_full());
+        let tlv1_conv_back = Tlv::from_bytes(&buf).unwrap();
+        assert_eq!(tlv1_conv_back, tlv1);
+        let tlv2_conv_back = Tlv::from_bytes(&buf[tlv1_conv_back.len_full()..]).unwrap();
+        assert_eq!(tlv2_conv_back, tlv2);
+    }
+
+    #[test]
+    fn test_opts_builders_from_vec() {
+        let tlv1 = Tlv::new_empty(TlvType::FlowLabel);
+        let msg_to_user: [u8; 4] = [1, 2, 3, 4];
+        let tlv2 = Tlv::new(TlvType::MsgToUser, &msg_to_user).unwrap();
+        let tlv_vec = vec![tlv1, tlv2];
+        let mut buf: [u8; 32] = [0; 32];
+        let opts = build_metadata_opts_from_vec(&mut buf, &tlv_vec);
+        assert!(opts.is_ok());
+        let opts_len = opts.unwrap();
+        assert_eq!(opts_len, tlv1.len_full() + tlv2.len_full());
+        let tlv1_conv_back = Tlv::from_bytes(&buf).unwrap();
+        assert_eq!(tlv1_conv_back, tlv1);
+        let tlv2_conv_back = Tlv::from_bytes(&buf[tlv1_conv_back.len_full()..]).unwrap();
+        assert_eq!(tlv2_conv_back, tlv2);
+    }
+
+    #[test]
+    fn test_with_opts() {
+        let tlv1 = Tlv::new_empty(TlvType::FlowLabel);
+        let msg_to_user: [u8; 4] = [1, 2, 3, 4];
+        let tlv2 = Tlv::new(TlvType::MsgToUser, &msg_to_user).unwrap();
+        let tlv_vec = vec![tlv1, tlv2];
+        let mut opts_buf: [u8; 32] = [0; 32];
+        let opts_len = build_metadata_opts_from_vec(&mut opts_buf, &tlv_vec).unwrap();
+        let (src_filename, dest_filename, metadata_pdu) = generic_metadata_pdu(
+            CrcFlag::NoCrc,
+            LargeFileFlag::Normal,
+            Some(&opts_buf[..opts_len]),
+        );
+        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()
+                + opts_len
+        );
+        let pdu_read_back = MetadataPdu::from_bytes(&buf).unwrap();
+        assert_eq!(pdu_read_back, metadata_pdu);
+        let opts_iter = pdu_read_back.options_iter();
+        assert!(opts_iter.is_some());
+        let opts_iter = opts_iter.unwrap();
+        let mut accumulated_len = 0;
+        for (idx, opt) in opts_iter.enumerate() {
+            assert_eq!(tlv_vec[idx], opt);
+            accumulated_len += opt.len_full();
+        }
+        assert_eq!(accumulated_len, pdu_read_back.options().unwrap().len());
+    }
+
+    #[test]
+    fn test_corrects_pdu_header() {
+        let pdu_header = PduHeader::new_for_file_data(
+            common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal),
+            0,
+            SegmentMetadataFlag::NotPresent,
+            SegmentationControl::NoRecordBoundaryPreservation,
+        );
+        let metadata_params = MetadataGenericParams::new(false, ChecksumType::Crc32, 10);
+        let src_filename = Lv::new_from_str(SRC_FILENAME).expect("Generating string LV failed");
+        let dest_filename =
+            Lv::new_from_str(DEST_FILENAME).expect("Generating destination LV failed");
+        let metadata_pdu =
+            MetadataPdu::new_no_opts(pdu_header, metadata_params, src_filename, dest_filename);
+        assert_eq!(metadata_pdu.pdu_header().pdu_type(), PduType::FileDirective);
+    }
+}

src/cfdp/pdu/mod.rs

@@ -0,0 +1,907 @@
+//! CFDP Packet Data Unit (PDU) support.
+use crate::cfdp::*;
+use crate::util::{UnsignedByteField, UnsignedEnum};
+use crate::CRC_CCITT_FALSE;
+use crate::{ByteConversionError, SizeMissmatch};
+use core::fmt::{Display, Formatter};
+#[cfg(feature = "std")]
+use std::error::Error;
+
+pub mod eof;
+pub mod file_data;
+pub mod finished;
+pub mod metadata;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum FileDirectiveType {
+    EofPdu = 0x04,
+    FinishedPdu = 0x05,
+    AckPdu = 0x06,
+    MetadataPdu = 0x07,
+    NakPdu = 0x08,
+    PromptPdu = 0x09,
+    KeepAlivePdu = 0x0c,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum PduError {
+    ByteConversionError(ByteConversionError),
+    /// Found version ID invalid, not equal to [CFDP_VERSION_2].
+    CfdpVersionMissmatch(u8),
+    /// Invalid length for the entity ID detected. Only the values 1, 2, 4 and 8 are supported.
+    InvalidEntityLen(u8),
+    /// Invalid length for the entity ID detected. Only the values 1, 2, 4 and 8 are supported.
+    InvalidTransactionSeqNumLen(u8),
+    /// The first entry will be the source entity ID length, the second one the destination entity
+    /// ID length.
+    SourceDestIdLenMissmatch((usize, usize)),
+    /// The first tuple entry will be the found directive type, the second entry the expected entry
+    /// type.
+    WrongDirectiveType((FileDirectiveType, FileDirectiveType)),
+    /// The directive type field contained a value not in the range of permitted values.
+    /// The first tuple entry will be the found raw number, the second entry the expected entry
+    /// type.
+    InvalidDirectiveType((u8, FileDirectiveType)),
+    /// Invalid condition code. Contains the raw detected value.
+    InvalidConditionCode(u8),
+    /// Invalid checksum type which is not part of the checksums listed in the
+    /// [SANA Checksum Types registry](https://sanaregistry.org/r/checksum_identifiers/).
+    InvalidChecksumType(u8),
+    FileSizeTooLarge(u64),
+    /// If the CRC flag for a PDU is enabled and the checksum check fails. Contains raw 16-bit CRC.
+    ChecksumError(u16),
+    /// Generic error for invalid PDU formats.
+    FormatError,
+    /// Error handling a TLV field.
+    TlvLvError(TlvLvError),
+}
+
+impl Display for PduError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        match self {
+            PduError::InvalidEntityLen(raw_id) => {
+                write!(
+                    f,
+                    "Invalid PDU entity ID length {raw_id}, only [1, 2, 4, 8] are allowed"
+                )
+            }
+            PduError::InvalidTransactionSeqNumLen(raw_id) => {
+                write!(
+                    f,
+                    "invalid PDUtransaction seq num length {raw_id}, only [1, 2, 4, 8] are allowed"
+                )
+            }
+            PduError::CfdpVersionMissmatch(raw) => {
+                write!(
+                    f,
+                    "cfdp version missmatch, found {raw}, expected {CFDP_VERSION_2}"
+                )
+            }
+            PduError::SourceDestIdLenMissmatch((src_len, dest_len)) => {
+                write!(
+                    f,
+                    "missmatch of PDU source length {src_len} and destination length {dest_len}"
+                )
+            }
+            PduError::ByteConversionError(e) => {
+                write!(f, "{}", e)
+            }
+            PduError::FileSizeTooLarge(value) => {
+                write!(f, "file size value {value} exceeds allowed 32 bit width")
+            }
+            PduError::WrongDirectiveType((found, expected)) => {
+                write!(f, "found directive type {found:?}, expected {expected:?}")
+            }
+            PduError::InvalidConditionCode(raw_code) => {
+                write!(f, "found invalid condition code with raw value {raw_code}")
+            }
+            PduError::InvalidDirectiveType((found, expected)) => {
+                write!(
+                    f,
+                    "invalid directive type value {found}, expected {expected:?} ({})",
+                    *expected as u8
+                )
+            }
+            PduError::InvalidChecksumType(checksum_type) => {
+                write!(f, "invalid checksum type {checksum_type}")
+            }
+            PduError::ChecksumError(checksum) => {
+                write!(f, "checksum error for CRC {checksum:#04x}")
+            }
+            PduError::TlvLvError(error) => {
+                write!(f, "pdu tlv error: {error}")
+            }
+            PduError::FormatError => {
+                write!(f, "generic PDU format error")
+            }
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for PduError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match self {
+            PduError::ByteConversionError(e) => Some(e),
+            PduError::TlvLvError(e) => Some(e),
+            _ => None,
+        }
+    }
+}
+
+impl From<ByteConversionError> for PduError {
+    fn from(value: ByteConversionError) -> Self {
+        Self::ByteConversionError(value)
+    }
+}
+
+impl From<TlvLvError> for PduError {
+    fn from(e: TlvLvError) -> Self {
+        Self::TlvLvError(e)
+    }
+}
+
+/// Common configuration fields for a PDU.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct CommonPduConfig {
+    source_entity_id: UnsignedByteField,
+    dest_entity_id: UnsignedByteField,
+    pub transaction_seq_num: UnsignedByteField,
+    pub trans_mode: TransmissionMode,
+    pub file_flag: LargeFileFlag,
+    pub crc_flag: CrcFlag,
+    pub direction: Direction,
+}
+
+// TODO: Builder pattern might be applicable here..
+impl CommonPduConfig {
+    pub fn new(
+        source_id: impl Into<UnsignedByteField>,
+        dest_id: impl Into<UnsignedByteField>,
+        transaction_seq_num: impl Into<UnsignedByteField>,
+        trans_mode: TransmissionMode,
+        file_flag: LargeFileFlag,
+        crc_flag: CrcFlag,
+        direction: Direction,
+    ) -> Result<Self, PduError> {
+        let source_id = source_id.into();
+        let dest_id = dest_id.into();
+        let transaction_seq_num = transaction_seq_num.into();
+        if source_id.len() != dest_id.len() {
+            return Err(PduError::SourceDestIdLenMissmatch((
+                source_id.len(),
+                dest_id.len(),
+            )));
+        }
+        if source_id.len() != 1
+            && source_id.len() != 2
+            && source_id.len() != 4
+            && source_id.len() != 8
+        {
+            return Err(PduError::InvalidEntityLen(source_id.len() as u8));
+        }
+        if transaction_seq_num.len() != 1
+            && transaction_seq_num.len() != 2
+            && transaction_seq_num.len() != 4
+            && transaction_seq_num.len() != 8
+        {
+            return Err(PduError::InvalidTransactionSeqNumLen(
+                transaction_seq_num.len() as u8,
+            ));
+        }
+        Ok(Self {
+            source_entity_id: source_id,
+            dest_entity_id: dest_id,
+            transaction_seq_num,
+            trans_mode,
+            file_flag,
+            crc_flag,
+            direction,
+        })
+    }
+
+    pub fn new_with_defaults(
+        source_id: impl Into<UnsignedByteField>,
+        dest_id: impl Into<UnsignedByteField>,
+        transaction_seq_num: impl Into<UnsignedByteField>,
+    ) -> Result<Self, PduError> {
+        Self::new(
+            source_id,
+            dest_id,
+            transaction_seq_num,
+            TransmissionMode::Acknowledged,
+            LargeFileFlag::Normal,
+            CrcFlag::NoCrc,
+            Direction::TowardsReceiver,
+        )
+    }
+
+    pub fn source_id(&self) -> UnsignedByteField {
+        self.source_entity_id
+    }
+
+    pub fn dest_id(&self) -> UnsignedByteField {
+        self.dest_entity_id
+    }
+}
+
+pub const FIXED_HEADER_LEN: usize = 4;
+
+/// Abstraction for the PDU header common to all CFDP PDUs.
+///
+/// For detailed information, refer to chapter 5.1 of the CFDP standard.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct PduHeader {
+    pdu_type: PduType,
+    pdu_conf: CommonPduConfig,
+    seg_metadata_flag: SegmentMetadataFlag,
+    seg_ctrl: SegmentationControl,
+    pdu_datafield_len: u16,
+}
+
+impl PduHeader {
+    pub fn new_for_file_data(
+        pdu_conf: CommonPduConfig,
+        pdu_datafield_len: u16,
+        seg_metadata_flag: SegmentMetadataFlag,
+        seg_ctrl: SegmentationControl,
+    ) -> Self {
+        Self::new_generic(
+            PduType::FileData,
+            pdu_conf,
+            pdu_datafield_len,
+            seg_metadata_flag,
+            seg_ctrl,
+        )
+    }
+
+    pub fn new_for_file_data_default(pdu_conf: CommonPduConfig, pdu_datafield_len: u16) -> Self {
+        Self::new_generic(
+            PduType::FileData,
+            pdu_conf,
+            pdu_datafield_len,
+            SegmentMetadataFlag::NotPresent,
+            SegmentationControl::NoRecordBoundaryPreservation,
+        )
+    }
+    pub fn new_no_file_data(pdu_conf: CommonPduConfig, pdu_datafield_len: u16) -> Self {
+        Self::new_generic(
+            PduType::FileDirective,
+            pdu_conf,
+            pdu_datafield_len,
+            SegmentMetadataFlag::NotPresent,
+            SegmentationControl::NoRecordBoundaryPreservation,
+        )
+    }
+
+    pub fn new_generic(
+        pdu_type: PduType,
+        pdu_conf: CommonPduConfig,
+        pdu_datafield_len: u16,
+        seg_metadata_flag: SegmentMetadataFlag,
+        seg_ctrl: SegmentationControl,
+    ) -> Self {
+        Self {
+            pdu_type,
+            pdu_conf,
+            seg_metadata_flag,
+            seg_ctrl,
+            pdu_datafield_len,
+        }
+    }
+
+    /// Returns only the length of the PDU header when written to a raw buffer.
+    pub fn header_len(&self) -> usize {
+        FIXED_HEADER_LEN
+            + self.pdu_conf.source_entity_id.len()
+            + self.pdu_conf.transaction_seq_num.len()
+            + self.pdu_conf.dest_entity_id.len()
+    }
+
+    /// Returns the full length of the PDU when written to a raw buffer, which is the header length
+    /// plus the PDU datafield length.
+    pub fn pdu_len(&self) -> usize {
+        self.header_len() + self.pdu_datafield_len as usize
+    }
+
+    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        // Internal note: There is currently no way to pass a PDU configuration like this, but
+        // this check is still kept for defensive programming.
+        if self.pdu_conf.source_entity_id.len() != self.pdu_conf.dest_entity_id.len() {
+            return Err(PduError::SourceDestIdLenMissmatch((
+                self.pdu_conf.source_entity_id.len(),
+                self.pdu_conf.dest_entity_id.len(),
+            )));
+        }
+        if buf.len()
+            < FIXED_HEADER_LEN
+                + self.pdu_conf.source_entity_id.len()
+                + self.pdu_conf.transaction_seq_num.len()
+        {
+            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: FIXED_HEADER_LEN,
+            })
+            .into());
+        }
+        let mut current_idx = 0;
+        buf[current_idx] = (CFDP_VERSION_2 << 5)
+            | ((self.pdu_type as u8) << 4)
+            | ((self.pdu_conf.direction as u8) << 3)
+            | ((self.pdu_conf.trans_mode as u8) << 2)
+            | ((self.pdu_conf.crc_flag as u8) << 1)
+            | (self.pdu_conf.file_flag as u8);
+        current_idx += 1;
+        buf[current_idx..current_idx + 2].copy_from_slice(&self.pdu_datafield_len.to_be_bytes());
+        current_idx += 2;
+        buf[current_idx] = ((self.seg_ctrl as u8) << 7)
+            | (((self.pdu_conf.source_entity_id.len() - 1) as u8) << 4)
+            | ((self.seg_metadata_flag as u8) << 3)
+            | ((self.pdu_conf.transaction_seq_num.len() - 1) as u8);
+        current_idx += 1;
+        self.pdu_conf.source_entity_id.write_to_be_bytes(
+            &mut buf[current_idx..current_idx + self.pdu_conf.source_entity_id.len()],
+        )?;
+        current_idx += self.pdu_conf.source_entity_id.len();
+        self.pdu_conf.transaction_seq_num.write_to_be_bytes(
+            &mut buf[current_idx..current_idx + self.pdu_conf.transaction_seq_num.len()],
+        )?;
+        current_idx += self.pdu_conf.transaction_seq_num.len();
+        self.pdu_conf.dest_entity_id.write_to_be_bytes(
+            &mut buf[current_idx..current_idx + self.pdu_conf.dest_entity_id.len()],
+        )?;
+        current_idx += self.pdu_conf.dest_entity_id.len();
+        Ok(current_idx)
+    }
+
+    /// This function first verifies that the buffer can hold the full length of the PDU parsed from
+    /// the header. Then, it verifies the checksum as specified in the standard if the CRC flag
+    /// of the PDU header is set.
+    ///
+    /// This function will return the PDU length excluding the 2 CRC bytes on success. If the CRC
+    /// flag is not set, it will simply return the PDU length.
+    pub fn verify_length_and_checksum(&self, buf: &[u8]) -> Result<usize, PduError> {
+        if buf.len() < self.pdu_len() {
+            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: self.pdu_len(),
+            })
+            .into());
+        }
+        if self.pdu_conf.crc_flag == CrcFlag::WithCrc {
+            let mut digest = CRC_CCITT_FALSE.digest();
+            digest.update(&buf[..self.pdu_len()]);
+            if digest.finalize() != 0 {
+                return Err(PduError::ChecksumError(u16::from_be_bytes(
+                    buf[self.pdu_len() - 2..self.pdu_len()].try_into().unwrap(),
+                )));
+            }
+            return Ok(self.pdu_len() - 2);
+        }
+        Ok(self.pdu_len())
+    }
+
+    /// Please note that this function will not verify that the passed buffer can hold the full
+    /// PDU length. This allows recovering the header portion even if the data field length is
+    /// invalid. This function will also not do the CRC procedure specified in chapter 4.1.1
+    /// and 4.1.2 because performing the CRC procedure requires the buffer to be large enough
+    /// to hold the full PDU.
+    ///
+    /// Both functions can however be performed with the [Self::verify_length_and_checksum]
+    /// function.
+    pub fn from_bytes(buf: &[u8]) -> Result<(Self, usize), PduError> {
+        if buf.len() < FIXED_HEADER_LEN {
+            return Err(PduError::ByteConversionError(
+                ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+                    found: buf.len(),
+                    expected: FIXED_HEADER_LEN,
+                }),
+            ));
+        }
+        let cfdp_version_raw = (buf[0] >> 5) & 0b111;
+        if cfdp_version_raw != CFDP_VERSION_2 {
+            return Err(PduError::CfdpVersionMissmatch(cfdp_version_raw));
+        }
+        // unwrap for single bit fields: This operation will always succeed.
+        let pdu_type = PduType::try_from((buf[0] >> 4) & 0b1).unwrap();
+        let direction = Direction::try_from((buf[0] >> 3) & 0b1).unwrap();
+        let trans_mode = TransmissionMode::try_from((buf[0] >> 2) & 0b1).unwrap();
+        let crc_flag = CrcFlag::try_from((buf[0] >> 1) & 0b1).unwrap();
+        let file_flag = LargeFileFlag::try_from(buf[0] & 0b1).unwrap();
+        let pdu_datafield_len = u16::from_be_bytes(buf[1..3].try_into().unwrap());
+        let seg_ctrl = SegmentationControl::try_from((buf[3] >> 7) & 0b1).unwrap();
+        let expected_len_entity_ids = (((buf[3] >> 4) & 0b111) + 1) as usize;
+        if (expected_len_entity_ids != 1)
+            && (expected_len_entity_ids != 2)
+            && (expected_len_entity_ids != 4)
+            && (expected_len_entity_ids != 8)
+        {
+            return Err(PduError::InvalidEntityLen(expected_len_entity_ids as u8));
+        }
+        let seg_metadata_flag = SegmentMetadataFlag::try_from((buf[3] >> 3) & 0b1).unwrap();
+        let expected_len_seq_num = ((buf[3] & 0b111) + 1) as usize;
+        if (expected_len_seq_num != 1)
+            && (expected_len_seq_num != 2)
+            && (expected_len_seq_num != 4)
+            && (expected_len_seq_num != 8)
+        {
+            return Err(PduError::InvalidTransactionSeqNumLen(
+                expected_len_seq_num as u8,
+            ));
+        }
+        if buf.len() < (4 + 2 * expected_len_entity_ids + expected_len_seq_num) {
+            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: 4 + 2 * expected_len_entity_ids + expected_len_seq_num,
+            })
+            .into());
+        }
+        let mut current_idx = 4;
+        // It is okay to unwrap here because we checked the validity of the expected length and of
+        // the remaining buffer length.
+        let source_id =
+            UnsignedByteField::new_from_be_bytes(expected_len_entity_ids, &buf[current_idx..])
+                .unwrap();
+        current_idx += expected_len_entity_ids;
+        let transaction_seq_num =
+            UnsignedByteField::new_from_be_bytes(expected_len_seq_num, &buf[current_idx..])
+                .unwrap();
+        current_idx += expected_len_seq_num;
+        let dest_id =
+            UnsignedByteField::new_from_be_bytes(expected_len_entity_ids, &buf[current_idx..])
+                .unwrap();
+        current_idx += expected_len_entity_ids;
+        let common_pdu_conf = CommonPduConfig::new(
+            source_id,
+            dest_id,
+            transaction_seq_num,
+            trans_mode,
+            file_flag,
+            crc_flag,
+            direction,
+        )
+        .unwrap();
+        Ok((
+            PduHeader {
+                pdu_type,
+                pdu_conf: common_pdu_conf,
+                seg_metadata_flag,
+                seg_ctrl,
+                pdu_datafield_len,
+            },
+            current_idx,
+        ))
+    }
+    pub fn pdu_type(&self) -> PduType {
+        self.pdu_type
+    }
+
+    pub fn common_pdu_conf(&self) -> &CommonPduConfig {
+        &self.pdu_conf
+    }
+
+    pub fn seg_metadata_flag(&self) -> SegmentMetadataFlag {
+        self.seg_metadata_flag
+    }
+    pub fn seg_ctrl(&self) -> SegmentationControl {
+        self.seg_ctrl
+    }
+}
+
+pub(crate) fn write_fss_field(
+    file_flag: LargeFileFlag,
+    file_size: u64,
+    buf: &mut [u8],
+) -> Result<usize, PduError> {
+    Ok(if file_flag == LargeFileFlag::Large {
+        buf[..core::mem::size_of::<u64>()].copy_from_slice(&file_size.to_be_bytes());
+        core::mem::size_of::<u64>()
+    } else {
+        if file_size > u32::MAX as u64 {
+            return Err(PduError::FileSizeTooLarge(file_size));
+        }
+        buf[..core::mem::size_of::<u32>()].copy_from_slice(&(file_size as u32).to_be_bytes());
+        core::mem::size_of::<u32>()
+    })
+}
+
+pub(crate) fn read_fss_field(file_flag: LargeFileFlag, buf: &[u8]) -> (usize, u64) {
+    if file_flag == LargeFileFlag::Large {
+        (
+            core::mem::size_of::<u64>(),
+            u64::from_be_bytes(buf[..core::mem::size_of::<u64>()].try_into().unwrap()),
+        )
+    } else {
+        (
+            core::mem::size_of::<u32>(),
+            u32::from_be_bytes(buf[..core::mem::size_of::<u32>()].try_into().unwrap()).into(),
+        )
+    }
+}
+
+// This is a generic length check applicable to most PDU deserializations. It first checks whether
+// a given buffer can hold an expected minimum size, and then it checks whether the PDU datafield
+// length is larger than that expected minimum size.
+pub(crate) fn generic_length_checks_pdu_deserialization(
+    buf: &[u8],
+    min_expected_len: usize,
+    full_len_without_crc: usize,
+) -> Result<(), ByteConversionError> {
+    // Buffer too short to hold additional expected minimum datasize.
+    if buf.len() < min_expected_len {
+        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            found: buf.len(),
+            expected: min_expected_len,
+        }));
+    }
+    // This can happen if the PDU datafield length value is invalid.
+    if full_len_without_crc < min_expected_len {
+        return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+            found: full_len_without_crc,
+            expected: min_expected_len,
+        }));
+    }
+    Ok(())
+}
+
+pub(crate) fn add_pdu_crc(buf: &mut [u8], mut current_idx: usize) -> usize {
+    let mut digest = CRC_CCITT_FALSE.digest();
+    digest.update(&buf[..current_idx]);
+    buf[current_idx..current_idx + 2].copy_from_slice(&digest.finalize().to_be_bytes());
+    current_idx += 2;
+    current_idx
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::cfdp::pdu::{CommonPduConfig, PduError, PduHeader, FIXED_HEADER_LEN};
+    use crate::cfdp::{
+        CrcFlag, Direction, LargeFileFlag, PduType, SegmentMetadataFlag, SegmentationControl,
+        TransmissionMode, CFDP_VERSION_2,
+    };
+    use crate::util::{
+        UbfU8, UnsignedByteField, UnsignedByteFieldU16, UnsignedByteFieldU8, UnsignedEnum,
+    };
+    use crate::ByteConversionError;
+    use std::format;
+
+    pub(crate) fn common_pdu_conf(crc_flag: CrcFlag, fss: LargeFileFlag) -> CommonPduConfig {
+        let src_id = UbfU8::new(5);
+        let dest_id = UbfU8::new(10);
+        let transaction_seq_num = UbfU8::new(20);
+        let mut pdu_conf = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_seq_num)
+            .expect("Generating common PDU config");
+        pdu_conf.crc_flag = crc_flag;
+        pdu_conf.file_flag = fss;
+        pdu_conf
+    }
+
+    pub(crate) fn verify_raw_header(pdu_conf: &PduHeader, buf: &[u8]) {
+        assert_eq!((buf[0] >> 5) & 0b111, CFDP_VERSION_2);
+        // File directive
+        assert_eq!((buf[0] >> 4) & 1, pdu_conf.pdu_type as u8);
+        // Towards receiver
+        assert_eq!((buf[0] >> 3) & 1, pdu_conf.pdu_conf.direction as u8);
+        // Acknowledged
+        assert_eq!((buf[0] >> 2) & 1, pdu_conf.pdu_conf.trans_mode as u8);
+        // No CRC
+        assert_eq!((buf[0] >> 1) & 1, pdu_conf.pdu_conf.crc_flag as u8);
+        // Regular file size
+        assert_eq!(buf[0] & 1, pdu_conf.pdu_conf.file_flag as u8);
+        let pdu_datafield_len = u16::from_be_bytes(buf[1..3].try_into().unwrap());
+        assert_eq!(pdu_datafield_len, pdu_conf.pdu_datafield_len);
+        // No record boundary preservation
+        assert_eq!((buf[3] >> 7) & 1, pdu_conf.seg_ctrl as u8);
+        // Entity ID length raw value is actual number of octets - 1 => 0
+        let entity_id_len = pdu_conf.pdu_conf.source_entity_id.len();
+        assert_eq!((buf[3] >> 4) & 0b111, entity_id_len as u8 - 1);
+        // No segment metadata
+        assert_eq!((buf[3] >> 3) & 0b1, pdu_conf.seg_metadata_flag as u8);
+        // Transaction Sequence ID length raw value is actual number of octets - 1 => 0
+        let seq_num_len = pdu_conf.pdu_conf.transaction_seq_num.len();
+        assert_eq!(buf[3] & 0b111, seq_num_len as u8 - 1);
+        let mut current_idx = 4;
+        let mut byte_field_check = |field_len: usize, ubf: &UnsignedByteField| {
+            match field_len {
+                1 => assert_eq!(buf[current_idx], ubf.value() as u8),
+                2 => assert_eq!(
+                    u16::from_be_bytes(
+                        buf[current_idx..current_idx + field_len]
+                            .try_into()
+                            .unwrap()
+                    ),
+                    ubf.value() as u16
+                ),
+                4 => assert_eq!(
+                    u32::from_be_bytes(
+                        buf[current_idx..current_idx + field_len]
+                            .try_into()
+                            .unwrap()
+                    ),
+                    ubf.value() as u32
+                ),
+                8 => assert_eq!(
+                    u64::from_be_bytes(
+                        buf[current_idx..current_idx + field_len]
+                            .try_into()
+                            .unwrap()
+                    ),
+                    ubf.value() as u64
+                ),
+                _ => panic!("invalid entity ID length"),
+            }
+            current_idx += field_len
+        };
+        byte_field_check(entity_id_len, &pdu_conf.pdu_conf.source_entity_id);
+        byte_field_check(seq_num_len, &pdu_conf.pdu_conf.transaction_seq_num);
+        byte_field_check(entity_id_len, &pdu_conf.pdu_conf.dest_entity_id);
+    }
+
+    #[test]
+    fn test_basic_state() {
+        let src_id = UnsignedByteFieldU8::new(1);
+        let dest_id = UnsignedByteFieldU8::new(2);
+        let transaction_id = UnsignedByteFieldU8::new(3);
+        let common_pdu_cfg = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+            .expect("common config creation failed");
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        assert_eq!(pdu_header.pdu_type(), PduType::FileDirective);
+        let common_conf_ref = pdu_header.common_pdu_conf();
+        assert_eq!(*common_conf_ref, common_pdu_cfg);
+        // These should be 0 and ignored for non-filedata PDUs
+        assert_eq!(
+            pdu_header.seg_metadata_flag(),
+            SegmentMetadataFlag::NotPresent
+        );
+        assert_eq!(
+            pdu_header.seg_ctrl(),
+            SegmentationControl::NoRecordBoundaryPreservation
+        );
+        assert_eq!(pdu_header.pdu_datafield_len, 5);
+        assert_eq!(pdu_header.header_len(), 7);
+    }
+
+    #[test]
+    fn test_serialization_1() {
+        let src_id = UnsignedByteFieldU8::new(1);
+        let dest_id = UnsignedByteFieldU8::new(2);
+        let transaction_id = UnsignedByteFieldU8::new(3);
+        let common_pdu_cfg = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+            .expect("common config creation failed");
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let mut buf: [u8; 7] = [0; 7];
+        let res = pdu_header.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        // 4 byte fixed header plus three bytes src, dest ID and transaction ID
+        assert_eq!(res.unwrap(), 7);
+        verify_raw_header(&pdu_header, &buf);
+    }
+
+    #[test]
+    fn test_deserialization_1() {
+        let src_id = UnsignedByteFieldU8::new(1);
+        let dest_id = UnsignedByteFieldU8::new(2);
+        let transaction_id = UnsignedByteFieldU8::new(3);
+        let common_pdu_cfg = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+            .expect("common config creation failed");
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let mut buf: [u8; 7] = [0; 7];
+        let res = pdu_header.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let deser_res = PduHeader::from_bytes(&buf);
+        assert!(deser_res.is_ok());
+        let (header_read_back, read_size) = deser_res.unwrap();
+        assert_eq!(read_size, 7);
+        assert_eq!(header_read_back, pdu_header);
+    }
+
+    #[test]
+    fn test_serialization_2() {
+        let src_id = UnsignedByteFieldU16::new(0x0001);
+        let dest_id = UnsignedByteFieldU16::new(0x0203);
+        let transaction_id = UnsignedByteFieldU16::new(0x0405);
+        let mut common_pdu_cfg =
+            CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+                .expect("common config creation failed");
+        common_pdu_cfg.crc_flag = CrcFlag::WithCrc;
+        common_pdu_cfg.direction = Direction::TowardsSender;
+        common_pdu_cfg.trans_mode = TransmissionMode::Unacknowledged;
+        common_pdu_cfg.file_flag = LargeFileFlag::Large;
+        let pdu_header = PduHeader::new_for_file_data(
+            common_pdu_cfg,
+            5,
+            SegmentMetadataFlag::Present,
+            SegmentationControl::WithRecordBoundaryPreservation,
+        );
+        assert_eq!(pdu_header.header_len(), 10);
+        let mut buf: [u8; 16] = [0; 16];
+        let res = pdu_header.write_to_bytes(&mut buf);
+        assert!(res.is_ok(), "{}", format!("Result {res:?} not okay"));
+        // 4 byte fixed header, 6 bytes additional fields
+        assert_eq!(res.unwrap(), 10);
+        verify_raw_header(&pdu_header, &buf);
+    }
+
+    #[test]
+    fn test_deserialization_2() {
+        let src_id = UnsignedByteFieldU16::new(0x0001);
+        let dest_id = UnsignedByteFieldU16::new(0x0203);
+        let transaction_id = UnsignedByteFieldU16::new(0x0405);
+        let mut common_pdu_cfg =
+            CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+                .expect("common config creation failed");
+        common_pdu_cfg.crc_flag = CrcFlag::WithCrc;
+        common_pdu_cfg.direction = Direction::TowardsSender;
+        common_pdu_cfg.trans_mode = TransmissionMode::Unacknowledged;
+        common_pdu_cfg.file_flag = LargeFileFlag::Large;
+        let pdu_header = PduHeader::new_for_file_data(
+            common_pdu_cfg,
+            5,
+            SegmentMetadataFlag::Present,
+            SegmentationControl::WithRecordBoundaryPreservation,
+        );
+        let mut buf: [u8; 16] = [0; 16];
+        let res = pdu_header.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let deser_res = PduHeader::from_bytes(&buf);
+        assert!(deser_res.is_ok());
+        let (header_read_back, read_size) = deser_res.unwrap();
+        assert_eq!(read_size, 10);
+        assert_eq!(header_read_back, pdu_header);
+    }
+
+    #[test]
+    fn test_invalid_raw_version() {
+        let src_id = UnsignedByteFieldU8::new(1);
+        let dest_id = UnsignedByteFieldU8::new(2);
+        let transaction_id = UnsignedByteFieldU8::new(3);
+        let common_pdu_cfg = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+            .expect("common config creation failed");
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let mut buf: [u8; 7] = [0; 7];
+        let res = pdu_header.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        buf[0] &= !0b1110_0000;
+        buf[0] |= (CFDP_VERSION_2 + 1) << 5;
+        let res = PduHeader::from_bytes(&buf);
+        assert!(res.is_err());
+        let error = res.unwrap_err();
+        if let PduError::CfdpVersionMissmatch(raw_version) = error {
+            assert_eq!(raw_version, CFDP_VERSION_2 + 1);
+        } else {
+            panic!("invalid exception: {}", error);
+        }
+    }
+
+    #[test]
+    fn test_buf_too_small_1() {
+        let buf: [u8; 3] = [0; 3];
+        let res = PduHeader::from_bytes(&buf);
+        assert!(res.is_err());
+        let error = res.unwrap_err();
+        if let PduError::ByteConversionError(ByteConversionError::FromSliceTooSmall(missmatch)) =
+            error
+        {
+            assert_eq!(missmatch.found, 3);
+            assert_eq!(missmatch.expected, FIXED_HEADER_LEN);
+        } else {
+            panic!("invalid exception: {}", error);
+        }
+    }
+
+    #[test]
+    fn test_buf_too_small_2() {
+        let src_id = UnsignedByteFieldU8::new(1);
+        let dest_id = UnsignedByteFieldU8::new(2);
+        let transaction_id = UnsignedByteFieldU8::new(3);
+        let common_pdu_cfg = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+            .expect("common config creation failed");
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let mut buf: [u8; 7] = [0; 7];
+        let res = pdu_header.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        let header = PduHeader::from_bytes(&buf[0..6]);
+        assert!(header.is_err());
+        let error = header.unwrap_err();
+        if let PduError::ByteConversionError(ByteConversionError::FromSliceTooSmall(missmatch)) =
+            error
+        {
+            assert_eq!(missmatch.found, 6);
+            assert_eq!(missmatch.expected, 7);
+        }
+    }
+
+    #[test]
+    fn test_invalid_seq_len() {
+        let src_id = UbfU8::new(1);
+        let dest_id = UbfU8::new(2);
+        let transaction_seq_id = UbfU8::new(3);
+        let invalid_byte_field = UnsignedByteField::new(3, 5);
+        let pdu_conf_res = CommonPduConfig::new_with_defaults(src_id, dest_id, invalid_byte_field);
+        assert!(pdu_conf_res.is_err());
+        let error = pdu_conf_res.unwrap_err();
+        if let PduError::InvalidTransactionSeqNumLen(len) = error {
+            assert_eq!(len, 3);
+        } else {
+            panic!("Invalid exception: {}", error)
+        }
+        let pdu_conf_res = CommonPduConfig::new_with_defaults(
+            invalid_byte_field,
+            invalid_byte_field,
+            transaction_seq_id,
+        );
+        assert!(pdu_conf_res.is_err());
+        let error = pdu_conf_res.unwrap_err();
+        if let PduError::InvalidEntityLen(len) = error {
+            assert_eq!(len, 3);
+        } else {
+            panic!("Invalid exception: {}", error)
+        }
+    }
+    #[test]
+    fn test_missmatch_src_dest_id() {
+        let src_id = UnsignedByteField::new(1, 5);
+        let dest_id = UnsignedByteField::new(2, 5);
+        let transaction_seq_id = UbfU8::new(3);
+        let pdu_conf_res = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_seq_id);
+        assert!(pdu_conf_res.is_err());
+        let error = pdu_conf_res.unwrap_err();
+        if let PduError::SourceDestIdLenMissmatch((src_len, dest_len)) = error {
+            assert_eq!(src_len, 1);
+            assert_eq!(dest_len, 2);
+        }
+    }
+
+    #[test]
+    fn test_invalid_raw_src_id_len() {
+        let src_id = UnsignedByteFieldU8::new(1);
+        let dest_id = UnsignedByteFieldU8::new(2);
+        let transaction_id = UnsignedByteFieldU8::new(3);
+        let common_pdu_cfg = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+            .expect("common config creation failed");
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let mut buf: [u8; 7] = [0; 7];
+        let res = pdu_header.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        buf[3] &= !0b0111_0000;
+        // Equivalent to the length of three
+        buf[3] |= 0b10 << 4;
+        let header_res = PduHeader::from_bytes(&buf);
+        assert!(header_res.is_err());
+        let error = header_res.unwrap_err();
+        if let PduError::InvalidEntityLen(len) = error {
+            assert_eq!(len, 3);
+        } else {
+            panic!("invalid exception {:?}", error)
+        }
+    }
+
+    #[test]
+    fn test_invalid_transaction_seq_id_len() {
+        let src_id = UnsignedByteFieldU8::new(1);
+        let dest_id = UnsignedByteFieldU8::new(2);
+        let transaction_id = UnsignedByteFieldU8::new(3);
+        let common_pdu_cfg = CommonPduConfig::new_with_defaults(src_id, dest_id, transaction_id)
+            .expect("common config creation failed");
+        let pdu_header = PduHeader::new_no_file_data(common_pdu_cfg, 5);
+        let mut buf: [u8; 7] = [0; 7];
+        let res = pdu_header.write_to_bytes(&mut buf);
+        assert!(res.is_ok());
+        buf[3] &= !0b0000_0111;
+        // Equivalent to the length of three
+        buf[3] |= 0b10;
+        let header_res = PduHeader::from_bytes(&buf);
+        assert!(header_res.is_err());
+        let error = header_res.unwrap_err();
+        if let PduError::InvalidTransactionSeqNumLen(len) = error {
+            assert_eq!(len, 3);
+        } else {
+            panic!("invalid exception {:?}", error)
+        }
+    }
+}

src/cfdp/tlv.rs

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

src/ecss/mod.rs

@@ -3,10 +3,9 @@
 //!
 //! You can find the PUS telecommand definitions in the [crate::tc] module and ithe PUS telemetry definitions
 //! inside the [crate::tm] module.
-use crate::{ByteConversionError, CcsdsPacket, SizeMissmatch};
+use crate::{ByteConversionError, CcsdsPacket, CRC_CCITT_FALSE};
 use core::fmt::{Debug, Display, Formatter};
 use core::mem::size_of;
-use crc::{Crc, CRC_16_IBM_3740};
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -19,9 +18,6 @@ pub mod scheduling;
 pub mod verification;
 
 pub type CrcType = u16;
-
-/// CRC algorithm used by the PUS standard.
-pub const CRC_CCITT_FALSE: Crc<u16> = Crc::<u16>::new(&CRC_16_IBM_3740);
 pub const CCSDS_HEADER_LEN: usize = size_of::<crate::zc::SpHeader>();
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq, IntoPrimitive, TryFromPrimitive)]
@@ -261,7 +257,10 @@ pub(crate) fn user_data_from_raw(
     }
 }
 
-pub(crate) fn verify_crc16_from_raw(raw_data: &[u8], crc16: u16) -> Result<(), PusError> {
+pub(crate) fn verify_crc16_ccitt_false_from_raw(
+    raw_data: &[u8],
+    crc16: u16,
+) -> Result<(), PusError> {
     let mut digest = CRC_CCITT_FALSE.digest();
     digest.update(raw_data);
     if digest.finalize() == 0 {
@@ -291,6 +290,7 @@ macro_rules! sp_header_impls {
     }
 }
 
+use crate::util::{GenericUnsignedByteField, ToBeBytes, UnsignedEnum};
 pub(crate) use ccsds_impl;
 pub(crate) use sp_header_impls;
 
@@ -298,66 +298,17 @@ pub(crate) use sp_header_impls;
 /// and an unsigned value. The trait makes no assumptions about the actual type of the unsigned
 /// value and only requires implementors to implement a function which writes the enumeration into
 /// a raw byte format.
-pub trait EcssEnumeration {
+pub trait EcssEnumeration: UnsignedEnum {
     /// Packet Format Code, which denotes the number of bits of the enumeration
     fn pfc(&self) -> u8;
-    fn byte_width(&self) -> usize {
-        (self.pfc() / 8) as usize
-    }
-    fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<(), ByteConversionError>;
 }
 
 pub trait EcssEnumerationExt: EcssEnumeration + Debug + Copy + Clone + PartialEq + Eq {}
 
-pub trait ToBeBytes {
-    type ByteArray: AsRef<[u8]>;
-    fn to_be_bytes(&self) -> Self::ByteArray;
-}
-
-impl ToBeBytes for () {
-    type ByteArray = [u8; 0];
-
-    fn to_be_bytes(&self) -> Self::ByteArray {
-        []
-    }
-}
-
-impl ToBeBytes for u8 {
-    type ByteArray = [u8; 1];
-
-    fn to_be_bytes(&self) -> Self::ByteArray {
-        u8::to_be_bytes(*self)
-    }
-}
-
-impl ToBeBytes for u16 {
-    type ByteArray = [u8; 2];
-
-    fn to_be_bytes(&self) -> Self::ByteArray {
-        u16::to_be_bytes(*self)
-    }
-}
-
-impl ToBeBytes for u32 {
-    type ByteArray = [u8; 4];
-
-    fn to_be_bytes(&self) -> Self::ByteArray {
-        u32::to_be_bytes(*self)
-    }
-}
-
-impl ToBeBytes for u64 {
-    type ByteArray = [u8; 8];
-
-    fn to_be_bytes(&self) -> Self::ByteArray {
-        u64::to_be_bytes(*self)
-    }
-}
-
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct GenericEcssEnumWrapper<TYPE> {
-    val: TYPE,
+    field: GenericUnsignedByteField<TYPE>,
 }
 
 impl<TYPE> GenericEcssEnumWrapper<TYPE> {
@@ -366,7 +317,19 @@ impl<TYPE> GenericEcssEnumWrapper<TYPE> {
     }
 
     pub fn new(val: TYPE) -> Self {
-        Self { val }
+        Self {
+            field: GenericUnsignedByteField::new(val),
+        }
+    }
+}
+
+impl<TYPE: ToBeBytes> UnsignedEnum for GenericEcssEnumWrapper<TYPE> {
+    fn len(&self) -> usize {
+        (self.pfc() / 8) as usize
+    }
+
+    fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        self.field.write_to_be_bytes(buf)
     }
 }
 
@@ -374,17 +337,6 @@ impl<TYPE: ToBeBytes> EcssEnumeration for GenericEcssEnumWrapper<TYPE> {
     fn pfc(&self) -> u8 {
         size_of::<TYPE>() as u8 * 8_u8
     }
-
-    fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<(), ByteConversionError> {
-        if buf.len() < self.byte_width() {
-            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: self.byte_width(),
-            }));
-        }
-        buf[0..self.byte_width()].copy_from_slice(self.val.to_be_bytes().as_ref());
-        Ok(())
-    }
 }
 
 impl<TYPE: Debug + Copy + Clone + PartialEq + Eq + ToBeBytes> EcssEnumerationExt
@@ -399,7 +351,7 @@ pub type EcssEnumU64 = GenericEcssEnumWrapper<u64>;
 
 #[cfg(test)]
 mod tests {
-    use crate::ecss::{EcssEnumU16, EcssEnumU32, EcssEnumU8, EcssEnumeration};
+    use crate::ecss::{EcssEnumU16, EcssEnumU32, EcssEnumU8, UnsignedEnum};
     use crate::ByteConversionError;
 
     #[test]

src/lib.rs

@@ -7,6 +7,8 @@
 //!
 //!  - Space Packet implementation according to
 //!    [CCSDS Blue Book 133.0-B-2](https://public.ccsds.org/Pubs/133x0b2e1.pdf)
+//!  - CCSDS File Delivery Protocol (CFDP) packet implementations according to
+//!    [CCSDS Blue Book 727.0-B-5](https://public.ccsds.org/Pubs/727x0b5.pdf)
 //!  - PUS Telecommand and PUS Telemetry implementation according to the
 //!    [ECSS-E-ST-70-41C standard](https://ecss.nl/standard/ecss-e-st-70-41c-space-engineering-telemetry-and-telecommand-packet-utilization-15-april-2016/).
 //!  - CUC (CCSDS Unsegmented Time Code) implementation according to
@@ -60,23 +62,31 @@ extern crate alloc;
 extern crate std;
 
 use crate::ecss::CCSDS_HEADER_LEN;
-use core::fmt::{Display, Formatter};
+use core::fmt::{Debug, Display, Formatter};
+use crc::{Crc, CRC_16_IBM_3740};
 use delegate::delegate;
+#[cfg(not(feature = "std"))]
+use num_traits::Unsigned;
 #[cfg(feature = "std")]
 use std::error::Error;
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+pub mod cfdp;
 pub mod ecss;
 pub mod tc;
 pub mod time;
 pub mod tm;
+pub mod util;
 
 mod private {
     pub trait Sealed {}
 }
 
+/// CRC algorithm used by the PUS standard, the CCSDS TC standard and the CFDP standard.
+pub const CRC_CCITT_FALSE: Crc<u16> = Crc::<u16>::new(&CRC_16_IBM_3740);
+
 pub const MAX_APID: u16 = 2u16.pow(11) - 1;
 pub const MAX_SEQ_COUNT: u16 = 2u16.pow(14) - 1;
 

src/tc.rs

@@ -33,12 +33,12 @@
 //! ```
 use crate::ecss::{
     ccsds_impl, crc_from_raw_data, crc_procedure, sp_header_impls, user_data_from_raw,
-    verify_crc16_from_raw, CrcType, PusError, PusPacket, PusVersion, CRC_CCITT_FALSE,
+    verify_crc16_ccitt_false_from_raw, CrcType, PusError, PusPacket, PusVersion,
 };
-use crate::SpHeader;
 use crate::{
     ByteConversionError, CcsdsPacket, PacketType, SequenceFlags, SizeMissmatch, CCSDS_HEADER_LEN,
 };
+use crate::{SpHeader, CRC_CCITT_FALSE};
 use core::mem::size_of;
 use delegate::delegate;
 #[cfg(feature = "serde")]
@@ -437,7 +437,7 @@ impl<'raw_data> PusTc<'raw_data> {
             calc_crc_on_serialization: false,
             crc16: Some(crc_from_raw_data(raw_data)?),
         };
-        verify_crc16_from_raw(raw_data, pus_tc.crc16.expect("CRC16 invalid"))?;
+        verify_crc16_ccitt_false_from_raw(raw_data, pus_tc.crc16.expect("CRC16 invalid"))?;
         Ok((pus_tc, total_len))
     }
 

src/tm.rs

@@ -2,11 +2,11 @@
 //! to [ECSS-E-ST-70-41C](https://ecss.nl/standard/ecss-e-st-70-41c-space-engineering-telemetry-and-telecommand-packet-utilization-15-april-2016/).
 use crate::ecss::{
     ccsds_impl, crc_from_raw_data, crc_procedure, sp_header_impls, user_data_from_raw,
-    verify_crc16_from_raw, CrcType, PusError, PusPacket, PusVersion, CRC_CCITT_FALSE,
+    verify_crc16_ccitt_false_from_raw, CrcType, PusError, PusPacket, PusVersion,
 };
 use crate::{
     ByteConversionError, CcsdsPacket, PacketType, SequenceFlags, SizeMissmatch, SpHeader,
-    CCSDS_HEADER_LEN,
+    CCSDS_HEADER_LEN, CRC_CCITT_FALSE,
 };
 use core::mem::size_of;
 #[cfg(feature = "serde")]
@@ -439,7 +439,7 @@ impl<'raw_data> PusTm<'raw_data> {
             calc_crc_on_serialization: false,
             crc16: Some(crc_from_raw_data(raw_data)?),
         };
-        verify_crc16_from_raw(raw_data, pus_tm.crc16.expect("CRC16 invalid"))?;
+        verify_crc16_ccitt_false_from_raw(raw_data, pus_tm.crc16.expect("CRC16 invalid"))?;
         Ok((pus_tm, total_len))
     }
 

src/util.rs

@@ -0,0 +1,642 @@
+use crate::{ByteConversionError, SizeMissmatch};
+use core::fmt::{Debug, Display, Formatter};
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+#[cfg(feature = "std")]
+use std::error::Error;
+
+pub trait ToBeBytes {
+    type ByteArray: AsRef<[u8]>;
+    /// Length when written to big endian bytes.
+    fn written_len(&self) -> usize;
+    fn to_be_bytes(&self) -> Self::ByteArray;
+}
+
+impl ToBeBytes for () {
+    type ByteArray = [u8; 0];
+
+    fn written_len(&self) -> usize {
+        0
+    }
+
+    fn to_be_bytes(&self) -> Self::ByteArray {
+        []
+    }
+}
+
+impl ToBeBytes for u8 {
+    type ByteArray = [u8; 1];
+
+    fn written_len(&self) -> usize {
+        1
+    }
+    fn to_be_bytes(&self) -> Self::ByteArray {
+        u8::to_be_bytes(*self)
+    }
+}
+
+impl ToBeBytes for u16 {
+    type ByteArray = [u8; 2];
+
+    fn written_len(&self) -> usize {
+        2
+    }
+    fn to_be_bytes(&self) -> Self::ByteArray {
+        u16::to_be_bytes(*self)
+    }
+}
+
+impl ToBeBytes for u32 {
+    type ByteArray = [u8; 4];
+
+    fn written_len(&self) -> usize {
+        4
+    }
+    fn to_be_bytes(&self) -> Self::ByteArray {
+        u32::to_be_bytes(*self)
+    }
+}
+
+impl ToBeBytes for u64 {
+    type ByteArray = [u8; 8];
+
+    fn written_len(&self) -> usize {
+        8
+    }
+    fn to_be_bytes(&self) -> Self::ByteArray {
+        u64::to_be_bytes(*self)
+    }
+}
+
+#[allow(clippy::len_without_is_empty)]
+pub trait UnsignedEnum {
+    fn len(&self) -> usize;
+    /// Write the unsigned enumeration to a raw buffer. Returns the written size on success.
+    fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
+}
+
+pub trait UnsignedEnumExt: UnsignedEnum + Debug + Copy + Clone + PartialEq + Eq {}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum UnsignedByteFieldError {
+    /// Value is too large for specified width of byte field. The first value contains the width,
+    /// the second value contains the detected value.
+    ValueTooLargeForWidth((usize, u64)),
+    /// Only 1, 2, 4 and 8 are allow width values. Optionally contains the expected width if
+    /// applicable, for example for conversions.
+    InvalidWidth(usize, Option<usize>),
+    ByteConversionError(ByteConversionError),
+}
+
+impl From<ByteConversionError> for UnsignedByteFieldError {
+    fn from(value: ByteConversionError) -> Self {
+        Self::ByteConversionError(value)
+    }
+}
+
+impl Display for UnsignedByteFieldError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::ByteConversionError(e) => {
+                write!(f, "low level byte conversion error: {e}")
+            }
+            Self::InvalidWidth(val, _) => {
+                write!(f, "invalid width {val}, only 1, 2, 4 and 8 are allowed.")
+            }
+            Self::ValueTooLargeForWidth((width, value)) => {
+                write!(f, "value {value} too large for width {width}")
+            }
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for UnsignedByteFieldError {}
+
+/// Type erased variant.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct UnsignedByteField {
+    width: usize,
+    value: u64,
+}
+
+impl UnsignedByteField {
+    pub fn new(width: usize, value: u64) -> Self {
+        Self { width, value }
+    }
+
+    pub fn value(&self) -> u64 {
+        self.value
+    }
+
+    pub fn new_from_be_bytes(width: usize, buf: &[u8]) -> Result<Self, UnsignedByteFieldError> {
+        if width > buf.len() {
+            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
+                expected: width,
+                found: buf.len(),
+            })
+            .into());
+        }
+        match width {
+            0 => Ok(Self::new(width, 0)),
+            1 => Ok(Self::new(width, buf[0] as u64)),
+            2 => Ok(Self::new(
+                width,
+                u16::from_be_bytes(buf[0..2].try_into().unwrap()) as u64,
+            )),
+            4 => Ok(Self::new(
+                width,
+                u32::from_be_bytes(buf[0..4].try_into().unwrap()) as u64,
+            )),
+            8 => Ok(Self::new(
+                width,
+                u64::from_be_bytes(buf[0..8].try_into().unwrap()),
+            )),
+            _ => Err(UnsignedByteFieldError::InvalidWidth(width, None)),
+        }
+    }
+}
+
+impl UnsignedEnum for UnsignedByteField {
+    fn len(&self) -> usize {
+        self.width
+    }
+
+    fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        if buf.len() < self.len() {
+            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                expected: self.len(),
+                found: buf.len(),
+            }));
+        }
+        match self.len() {
+            0 => Ok(0),
+            1 => {
+                let u8 = UnsignedByteFieldU8::try_from(*self).unwrap();
+                u8.write_to_be_bytes(buf)
+            }
+            2 => {
+                let u16 = UnsignedByteFieldU16::try_from(*self).unwrap();
+                u16.write_to_be_bytes(buf)
+            }
+            4 => {
+                let u32 = UnsignedByteFieldU32::try_from(*self).unwrap();
+                u32.write_to_be_bytes(buf)
+            }
+            8 => {
+                let u64 = UnsignedByteFieldU64::try_from(*self).unwrap();
+                u64.write_to_be_bytes(buf)
+            }
+            _ => {
+                // The API does not allow this.
+                panic!("unexpected written length");
+            }
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct GenericUnsignedByteField<TYPE> {
+    value: TYPE,
+}
+
+impl<TYPE> GenericUnsignedByteField<TYPE> {
+    pub fn new(val: TYPE) -> Self {
+        Self { value: val }
+    }
+}
+
+impl<TYPE: ToBeBytes> UnsignedEnum for GenericUnsignedByteField<TYPE> {
+    fn len(&self) -> usize {
+        self.value.written_len()
+    }
+
+    fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        if buf.len() < self.len() {
+            return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
+                found: buf.len(),
+                expected: self.len(),
+            }));
+        }
+        buf[0..self.len()].copy_from_slice(self.value.to_be_bytes().as_ref());
+        Ok(self.value.written_len())
+    }
+}
+
+pub type UnsignedByteFieldEmpty = GenericUnsignedByteField<()>;
+pub type UnsignedByteFieldU8 = GenericUnsignedByteField<u8>;
+pub type UnsignedByteFieldU16 = GenericUnsignedByteField<u16>;
+pub type UnsignedByteFieldU32 = GenericUnsignedByteField<u32>;
+pub type UnsignedByteFieldU64 = GenericUnsignedByteField<u64>;
+
+pub type UbfU8 = UnsignedByteFieldU8;
+pub type UbfU16 = UnsignedByteFieldU16;
+pub type UbfU32 = UnsignedByteFieldU32;
+pub type UbfU64 = UnsignedByteFieldU64;
+
+impl From<UnsignedByteFieldU8> for UnsignedByteField {
+    fn from(value: UnsignedByteFieldU8) -> Self {
+        Self::new(1, value.value as u64)
+    }
+}
+
+impl TryFrom<UnsignedByteField> for UnsignedByteFieldU8 {
+    type Error = UnsignedByteFieldError;
+
+    fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
+        if value.width != 1 {
+            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(1)));
+        }
+        Ok(Self::new(value.value as u8))
+    }
+}
+
+impl From<UnsignedByteFieldU16> for UnsignedByteField {
+    fn from(value: UnsignedByteFieldU16) -> Self {
+        Self::new(2, value.value as u64)
+    }
+}
+
+impl TryFrom<UnsignedByteField> for UnsignedByteFieldU16 {
+    type Error = UnsignedByteFieldError;
+
+    fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
+        if value.width != 2 {
+            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(2)));
+        }
+        Ok(Self::new(value.value as u16))
+    }
+}
+
+impl From<UnsignedByteFieldU32> for UnsignedByteField {
+    fn from(value: UnsignedByteFieldU32) -> Self {
+        Self::new(4, value.value as u64)
+    }
+}
+
+impl TryFrom<UnsignedByteField> for UnsignedByteFieldU32 {
+    type Error = UnsignedByteFieldError;
+
+    fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
+        if value.width != 4 {
+            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(4)));
+        }
+        Ok(Self::new(value.value as u32))
+    }
+}
+
+impl From<UnsignedByteFieldU64> for UnsignedByteField {
+    fn from(value: UnsignedByteFieldU64) -> Self {
+        Self::new(8, value.value)
+    }
+}
+
+impl TryFrom<UnsignedByteField> for UnsignedByteFieldU64 {
+    type Error = UnsignedByteFieldError;
+
+    fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
+        if value.width != 8 {
+            return Err(UnsignedByteFieldError::InvalidWidth(value.width, Some(8)));
+        }
+        Ok(Self::new(value.value))
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use crate::util::{
+        UnsignedByteField, UnsignedByteFieldError, UnsignedByteFieldU16, UnsignedByteFieldU32,
+        UnsignedByteFieldU64, UnsignedByteFieldU8, UnsignedEnum,
+    };
+    use crate::ByteConversionError;
+    use std::format;
+
+    #[test]
+    fn test_simple_u8() {
+        let u8 = UnsignedByteFieldU8::new(5);
+        assert_eq!(u8.len(), 1);
+        let mut buf: [u8; 8] = [0; 8];
+        let len = u8
+            .write_to_be_bytes(&mut buf)
+            .expect("writing to raw buffer failed");
+        assert_eq!(len, 1);
+        assert_eq!(buf[0], 5);
+        for i in 1..8 {
+            assert_eq!(buf[i], 0);
+        }
+    }
+
+    #[test]
+    fn test_simple_u16() {
+        let u16 = UnsignedByteFieldU16::new(3823);
+        assert_eq!(u16.len(), 2);
+        let mut buf: [u8; 8] = [0; 8];
+        let len = u16
+            .write_to_be_bytes(&mut buf)
+            .expect("writing to raw buffer failed");
+        assert_eq!(len, 2);
+        let raw_val = u16::from_be_bytes(buf[0..2].try_into().unwrap());
+        assert_eq!(raw_val, 3823);
+        for i in 2..8 {
+            assert_eq!(buf[i], 0);
+        }
+    }
+
+    #[test]
+    fn test_simple_u32() {
+        let u32 = UnsignedByteFieldU32::new(80932);
+        assert_eq!(u32.len(), 4);
+        let mut buf: [u8; 8] = [0; 8];
+        let len = u32
+            .write_to_be_bytes(&mut buf)
+            .expect("writing to raw buffer failed");
+        assert_eq!(len, 4);
+        let raw_val = u32::from_be_bytes(buf[0..4].try_into().unwrap());
+        assert_eq!(raw_val, 80932);
+        for i in 4..8 {
+            assert_eq!(buf[i], 0);
+        }
+    }
+
+    #[test]
+    fn test_simple_u64() {
+        let u64 = UnsignedByteFieldU64::new(5999999);
+        assert_eq!(u64.len(), 8);
+        let mut buf: [u8; 8] = [0; 8];
+        let len = u64
+            .write_to_be_bytes(&mut buf)
+            .expect("writing to raw buffer failed");
+        assert_eq!(len, 8);
+        let raw_val = u64::from_be_bytes(buf[0..8].try_into().unwrap());
+        assert_eq!(raw_val, 5999999);
+    }
+
+    #[test]
+    fn conversions_u8() {
+        let u8 = UnsignedByteFieldU8::new(5);
+        let u8_type_erased = UnsignedByteField::from(u8);
+        assert_eq!(u8_type_erased.width, 1);
+        assert_eq!(u8_type_erased.value, 5);
+        let u8_conv_back =
+            UnsignedByteFieldU8::try_from(u8_type_erased).expect("conversion failed for u8");
+        assert_eq!(u8, u8_conv_back);
+        assert_eq!(u8_conv_back.value, 5);
+    }
+
+    #[test]
+    fn conversion_u8_fails() {
+        let field = UnsignedByteField::new(2, 60000);
+        let conv_fails = UnsignedByteFieldU8::try_from(field);
+        assert!(conv_fails.is_err());
+        let err = conv_fails.unwrap_err();
+        match err {
+            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
+                assert_eq!(width, 2);
+                assert_eq!(expected, 1);
+            }
+            _ => {
+                panic!("{}", format!("invalid error {err}"))
+            }
+        }
+    }
+
+    #[test]
+    fn conversions_u16() {
+        let u16 = UnsignedByteFieldU16::new(64444);
+        let u16_type_erased = UnsignedByteField::from(u16);
+        assert_eq!(u16_type_erased.width, 2);
+        assert_eq!(u16_type_erased.value, 64444);
+        let u16_conv_back =
+            UnsignedByteFieldU16::try_from(u16_type_erased).expect("conversion failed for u16");
+        assert_eq!(u16, u16_conv_back);
+        assert_eq!(u16_conv_back.value, 64444);
+    }
+
+    #[test]
+    fn conversion_u16_fails() {
+        let field = UnsignedByteField::new(4, 75000);
+        let conv_fails = UnsignedByteFieldU16::try_from(field);
+        assert!(conv_fails.is_err());
+        let err = conv_fails.unwrap_err();
+        match err {
+            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
+                assert_eq!(width, 4);
+                assert_eq!(expected, 2);
+            }
+            _ => {
+                panic!("{}", format!("invalid error {err}"))
+            }
+        }
+    }
+
+    #[test]
+    fn conversions_u32() {
+        let u32 = UnsignedByteFieldU32::new(75000);
+        let u32_type_erased = UnsignedByteField::from(u32);
+        assert_eq!(u32_type_erased.width, 4);
+        assert_eq!(u32_type_erased.value, 75000);
+        let u32_conv_back =
+            UnsignedByteFieldU32::try_from(u32_type_erased).expect("conversion failed for u32");
+        assert_eq!(u32, u32_conv_back);
+        assert_eq!(u32_conv_back.value, 75000);
+    }
+
+    #[test]
+    fn conversion_u32_fails() {
+        let field = UnsignedByteField::new(8, 75000);
+        let conv_fails = UnsignedByteFieldU32::try_from(field);
+        assert!(conv_fails.is_err());
+        let err = conv_fails.unwrap_err();
+        match err {
+            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
+                assert_eq!(width, 8);
+                assert_eq!(expected, 4);
+            }
+            _ => {
+                panic!("{}", format!("invalid error {err}"))
+            }
+        }
+    }
+
+    #[test]
+    fn conversions_u64() {
+        let u64 = UnsignedByteFieldU64::new(5999999);
+        let u64_type_erased = UnsignedByteField::from(u64);
+        assert_eq!(u64_type_erased.width, 8);
+        assert_eq!(u64_type_erased.value, 5999999);
+        let u64_conv_back =
+            UnsignedByteFieldU64::try_from(u64_type_erased).expect("conversion failed for u64");
+        assert_eq!(u64, u64_conv_back);
+        assert_eq!(u64_conv_back.value, 5999999);
+    }
+
+    #[test]
+    fn conversion_u64_fails() {
+        let field = UnsignedByteField::new(4, 60000);
+        let conv_fails = UnsignedByteFieldU64::try_from(field);
+        assert!(conv_fails.is_err());
+        let err = conv_fails.unwrap_err();
+        match err {
+            UnsignedByteFieldError::InvalidWidth(width, Some(expected)) => {
+                assert_eq!(width, 4);
+                assert_eq!(expected, 8);
+            }
+            _ => {
+                panic!("{}", format!("invalid error {err}"))
+            }
+        }
+    }
+
+    #[test]
+    fn type_erased_u8_write() {
+        let u8 = UnsignedByteField::new(1, 5);
+        assert_eq!(u8.len(), 1);
+        let mut buf: [u8; 8] = [0; 8];
+        u8.write_to_be_bytes(&mut buf)
+            .expect("writing to raw buffer failed");
+        assert_eq!(buf[0], 5);
+        for i in 1..8 {
+            assert_eq!(buf[i], 0);
+        }
+    }
+
+    #[test]
+    fn type_erased_u16_write() {
+        let u16 = UnsignedByteField::new(2, 3823);
+        assert_eq!(u16.len(), 2);
+        let mut buf: [u8; 8] = [0; 8];
+        u16.write_to_be_bytes(&mut buf)
+            .expect("writing to raw buffer failed");
+        let raw_val = u16::from_be_bytes(buf[0..2].try_into().unwrap());
+        assert_eq!(raw_val, 3823);
+        for i in 2..8 {
+            assert_eq!(buf[i], 0);
+        }
+    }
+
+    #[test]
+    fn type_erased_u32_write() {
+        let u32 = UnsignedByteField::new(4, 80932);
+        assert_eq!(u32.len(), 4);
+        let mut buf: [u8; 8] = [0; 8];
+        u32.write_to_be_bytes(&mut buf)
+            .expect("writing to raw buffer failed");
+        let raw_val = u32::from_be_bytes(buf[0..4].try_into().unwrap());
+        assert_eq!(raw_val, 80932);
+        for i in 4..8 {
+            assert_eq!(buf[i], 0);
+        }
+    }
+
+    #[test]
+    fn type_erased_u64_write() {
+        let u64 = UnsignedByteField::new(8, 5999999);
+        assert_eq!(u64.len(), 8);
+        let mut buf: [u8; 8] = [0; 8];
+        u64.write_to_be_bytes(&mut buf)
+            .expect("writing to raw buffer failed");
+        let raw_val = u64::from_be_bytes(buf[0..8].try_into().unwrap());
+        assert_eq!(raw_val, 5999999);
+    }
+
+    #[test]
+    fn type_erased_u8_construction() {
+        let buf: [u8; 2] = [5, 10];
+        let u8 = UnsignedByteField::new_from_be_bytes(1, &buf).expect("construction failed");
+        assert_eq!(u8.width, 1);
+        assert_eq!(u8.value, 5);
+    }
+
+    #[test]
+    fn type_erased_u16_construction() {
+        let buf: [u8; 2] = [0x10, 0x15];
+        let u16 = UnsignedByteField::new_from_be_bytes(2, &buf).expect("construction failed");
+        assert_eq!(u16.width, 2);
+        assert_eq!(u16.value, 0x1015);
+    }
+
+    #[test]
+    fn type_erased_u32_construction() {
+        let buf: [u8; 4] = [0x01, 0x02, 0x03, 0x04];
+        let u32 = UnsignedByteField::new_from_be_bytes(4, &buf).expect("construction failed");
+        assert_eq!(u32.width, 4);
+        assert_eq!(u32.value, 0x01020304);
+    }
+
+    #[test]
+    fn type_erased_u64_construction() {
+        let buf: [u8; 8] = [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08];
+        let u64 = UnsignedByteField::new_from_be_bytes(8, &buf).expect("construction failed");
+        assert_eq!(u64.width, 8);
+        assert_eq!(u64.value, 0x0102030405060708);
+    }
+
+    #[test]
+    fn type_u16_target_buf_too_small() {
+        let u16 = UnsignedByteFieldU16::new(500);
+        let mut buf: [u8; 1] = [0; 1];
+        let res = u16.write_to_be_bytes(&mut buf);
+        assert!(res.is_err());
+        let err = res.unwrap_err();
+        match err {
+            ByteConversionError::ToSliceTooSmall(missmatch) => {
+                assert_eq!(missmatch.found, 1);
+                assert_eq!(missmatch.expected, 2);
+            }
+            _ => {
+                panic!("invalid exception")
+            }
+        }
+    }
+
+    #[test]
+    fn type_erased_u16_target_buf_too_small() {
+        let u16 = UnsignedByteField::new(2, 500);
+        let mut buf: [u8; 1] = [0; 1];
+        let res = u16.write_to_be_bytes(&mut buf);
+        assert!(res.is_err());
+        let err = res.unwrap_err();
+        match err {
+            ByteConversionError::ToSliceTooSmall(missmatch) => {
+                assert_eq!(missmatch.found, 1);
+                assert_eq!(missmatch.expected, 2);
+            }
+            _ => {
+                panic!("invalid exception {}", err)
+            }
+        }
+        let u16 = UnsignedByteField::new_from_be_bytes(2, &buf);
+        assert!(u16.is_err());
+        let err = u16.unwrap_err();
+        if let UnsignedByteFieldError::ByteConversionError(
+            ByteConversionError::FromSliceTooSmall(missmatch),
+        ) = err
+        {
+            assert_eq!(missmatch.expected, 2);
+            assert_eq!(missmatch.found, 1);
+        } else {
+            panic!("unexpected exception {}", err);
+        }
+    }
+
+    #[test]
+    fn type_u32_target_buf_too_small() {
+        let u16 = UnsignedByteFieldU32::new(500);
+        let mut buf: [u8; 3] = [0; 3];
+        let res = u16.write_to_be_bytes(&mut buf);
+        assert!(res.is_err());
+        let err = res.unwrap_err();
+        match err {
+            ByteConversionError::ToSliceTooSmall(missmatch) => {
+                assert_eq!(missmatch.found, 3);
+                assert_eq!(missmatch.expected, 4);
+            }
+            _ => {
+                panic!("invalid exception")
+            }
+        }
+    }
+}