221 lines
8.6 KiB
Rust
221 lines
8.6 KiB
Rust
use crate::{tmtc::ReceivesTcCore, ValidatorU16Id};
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/// This function parses a given buffer for tightly packed CCSDS space packets. It uses the
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/// [PacketId] field of the CCSDS packets to detect the start of a CCSDS space packet and then
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/// uses the length field of the packet to extract CCSDS packets.
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///
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/// This function is also able to deal with broken tail packets at the end as long a the parser
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/// can read the full 7 bytes which constitue a space packet header plus one byte minimal size.
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/// If broken tail packets are detected, they are moved to the front of the buffer, and the write
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/// index for future write operations will be written to the `next_write_idx` argument.
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///
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/// The parser will write all packets which were decoded successfully to the given `tc_receiver`
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/// and return the number of packets found. If the [ReceivesTcCore::pass_tc] calls fails, the
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/// error will be returned.
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pub fn parse_buffer_for_ccsds_space_packets<E>(
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buf: &mut [u8],
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packet_id_validator: &(impl ValidatorU16Id + ?Sized),
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tc_receiver: &mut (impl ReceivesTcCore<Error = E> + ?Sized),
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next_write_idx: &mut usize,
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) -> Result<u32, E> {
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*next_write_idx = 0;
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let mut packets_found = 0;
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let mut current_idx = 0;
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let buf_len = buf.len();
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loop {
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if current_idx + 7 >= buf.len() {
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break;
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}
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let packet_id = u16::from_be_bytes(buf[current_idx..current_idx + 2].try_into().unwrap());
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if packet_id_validator.validate(packet_id) {
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let length_field =
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u16::from_be_bytes(buf[current_idx + 4..current_idx + 6].try_into().unwrap());
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let packet_size = length_field + 7;
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if (current_idx + packet_size as usize) <= buf_len {
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tc_receiver.pass_tc(&buf[current_idx..current_idx + packet_size as usize])?;
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packets_found += 1;
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} else {
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// Move packet to start of buffer if applicable.
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if current_idx > 0 {
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buf.copy_within(current_idx.., 0);
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*next_write_idx = buf.len() - current_idx;
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}
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}
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current_idx += packet_size as usize;
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continue;
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}
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current_idx += 1;
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}
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Ok(packets_found)
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}
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#[cfg(test)]
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mod tests {
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use spacepackets::{
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ecss::{tc::PusTcCreator, WritablePusPacket},
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PacketId, SpHeader,
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};
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use crate::encoding::tests::TcCacher;
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use super::parse_buffer_for_ccsds_space_packets;
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const TEST_APID_0: u16 = 0x02;
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const TEST_APID_1: u16 = 0x10;
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const TEST_PACKET_ID_0: PacketId = PacketId::new_for_tc(true, TEST_APID_0);
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const TEST_PACKET_ID_1: PacketId = PacketId::new_for_tc(true, TEST_APID_1);
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#[test]
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fn test_basic() {
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let sph = SpHeader::new_from_apid(TEST_APID_0);
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let ping_tc = PusTcCreator::new_simple(sph, 17, 1, &[], true);
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let mut buffer: [u8; 32] = [0; 32];
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let packet_len = ping_tc
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.write_to_bytes(&mut buffer)
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.expect("writing packet failed");
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let valid_packet_ids = [TEST_PACKET_ID_0];
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let mut tc_cacher = TcCacher::default();
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let mut next_write_idx = 0;
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let parse_result = parse_buffer_for_ccsds_space_packets(
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&mut buffer,
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valid_packet_ids.as_slice(),
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&mut tc_cacher,
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&mut next_write_idx,
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);
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assert!(parse_result.is_ok());
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let parsed_packets = parse_result.unwrap();
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assert_eq!(parsed_packets, 1);
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assert_eq!(tc_cacher.tc_queue.len(), 1);
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assert_eq!(
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tc_cacher.tc_queue.pop_front().unwrap(),
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buffer[..packet_len]
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);
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}
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#[test]
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fn test_multi_packet() {
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let sph = SpHeader::new_from_apid(TEST_APID_0);
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let ping_tc = PusTcCreator::new_simple(sph, 17, 1, &[], true);
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let action_tc = PusTcCreator::new_simple(sph, 8, 0, &[], true);
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let mut buffer: [u8; 32] = [0; 32];
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let packet_len_ping = ping_tc
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.write_to_bytes(&mut buffer)
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.expect("writing packet failed");
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let packet_len_action = action_tc
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.write_to_bytes(&mut buffer[packet_len_ping..])
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.expect("writing packet failed");
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let valid_packet_ids = [TEST_PACKET_ID_0];
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let mut tc_cacher = TcCacher::default();
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let mut next_write_idx = 0;
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let parse_result = parse_buffer_for_ccsds_space_packets(
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&mut buffer,
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valid_packet_ids.as_slice(),
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&mut tc_cacher,
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&mut next_write_idx,
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);
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assert!(parse_result.is_ok());
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let parsed_packets = parse_result.unwrap();
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assert_eq!(parsed_packets, 2);
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assert_eq!(tc_cacher.tc_queue.len(), 2);
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assert_eq!(
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tc_cacher.tc_queue.pop_front().unwrap(),
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buffer[..packet_len_ping]
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);
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assert_eq!(
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tc_cacher.tc_queue.pop_front().unwrap(),
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buffer[packet_len_ping..packet_len_ping + packet_len_action]
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);
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}
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#[test]
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fn test_multi_apid() {
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let sph = SpHeader::new_from_apid(TEST_APID_0);
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let ping_tc = PusTcCreator::new_simple(sph, 17, 1, &[], true);
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let sph = SpHeader::new_from_apid(TEST_APID_1);
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let action_tc = PusTcCreator::new_simple(sph, 8, 0, &[], true);
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let mut buffer: [u8; 32] = [0; 32];
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let packet_len_ping = ping_tc
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.write_to_bytes(&mut buffer)
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.expect("writing packet failed");
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let packet_len_action = action_tc
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.write_to_bytes(&mut buffer[packet_len_ping..])
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.expect("writing packet failed");
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let valid_packet_ids = [TEST_PACKET_ID_0, TEST_PACKET_ID_1];
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let mut tc_cacher = TcCacher::default();
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let mut next_write_idx = 0;
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let parse_result = parse_buffer_for_ccsds_space_packets(
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&mut buffer,
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valid_packet_ids.as_slice(),
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&mut tc_cacher,
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&mut next_write_idx,
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);
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assert!(parse_result.is_ok());
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let parsed_packets = parse_result.unwrap();
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assert_eq!(parsed_packets, 2);
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assert_eq!(tc_cacher.tc_queue.len(), 2);
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assert_eq!(
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tc_cacher.tc_queue.pop_front().unwrap(),
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buffer[..packet_len_ping]
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);
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assert_eq!(
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tc_cacher.tc_queue.pop_front().unwrap(),
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buffer[packet_len_ping..packet_len_ping + packet_len_action]
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);
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}
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#[test]
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fn test_split_packet_multi() {
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let ping_tc =
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PusTcCreator::new_simple(SpHeader::new_from_apid(TEST_APID_0), 17, 1, &[], true);
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let action_tc =
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PusTcCreator::new_simple(SpHeader::new_from_apid(TEST_APID_1), 8, 0, &[], true);
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let mut buffer: [u8; 32] = [0; 32];
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let packet_len_ping = ping_tc
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.write_to_bytes(&mut buffer)
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.expect("writing packet failed");
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let packet_len_action = action_tc
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.write_to_bytes(&mut buffer[packet_len_ping..])
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.expect("writing packet failed");
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let valid_packet_ids = [TEST_PACKET_ID_0, TEST_PACKET_ID_1];
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let mut tc_cacher = TcCacher::default();
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let mut next_write_idx = 0;
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let parse_result = parse_buffer_for_ccsds_space_packets(
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&mut buffer[..packet_len_ping + packet_len_action - 4],
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valid_packet_ids.as_slice(),
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&mut tc_cacher,
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&mut next_write_idx,
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);
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assert!(parse_result.is_ok());
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let parsed_packets = parse_result.unwrap();
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assert_eq!(parsed_packets, 1);
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assert_eq!(tc_cacher.tc_queue.len(), 1);
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// The broken packet was moved to the start, so the next write index should be after the
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// last segment missing 4 bytes.
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assert_eq!(next_write_idx, packet_len_action - 4);
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}
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#[test]
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fn test_one_split_packet() {
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let ping_tc =
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PusTcCreator::new_simple(SpHeader::new_from_apid(TEST_APID_0), 17, 1, &[], true);
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let mut buffer: [u8; 32] = [0; 32];
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let packet_len_ping = ping_tc
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.write_to_bytes(&mut buffer)
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.expect("writing packet failed");
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let valid_packet_ids = [TEST_PACKET_ID_0, TEST_PACKET_ID_1];
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let mut tc_cacher = TcCacher::default();
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let mut next_write_idx = 0;
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let parse_result = parse_buffer_for_ccsds_space_packets(
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&mut buffer[..packet_len_ping - 4],
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valid_packet_ids.as_slice(),
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&mut tc_cacher,
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&mut next_write_idx,
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);
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assert_eq!(next_write_idx, 0);
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assert!(parse_result.is_ok());
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let parsed_packets = parse_result.unwrap();
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assert_eq!(parsed_packets, 0);
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assert_eq!(tc_cacher.tc_queue.len(), 0);
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}
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}
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