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