this is actually quite tricky..

satrs-core/Cargo.toml

@@ -68,6 +68,11 @@ version = "0.7.0-beta.1"
 # branch = ""
 default-features = false
 
+[dependencies.cobs]
+git = "https://github.com/robamu/cobs.rs.git"
+branch = "all_features"
+default-features = false
+
 [dev-dependencies]
 serde = "1"
 zerocopy = "0.7"

satrs-core/src/hal/host/mod.rs

@@ -1,3 +1,3 @@
 //! Helper modules intended to be used on hosts with a full [std] runtime
-pub mod udp_server;
 pub mod tcp_server;
+pub mod udp_server;

satrs-core/src/hal/host/tcp_server.rs

@@ -1,9 +1,296 @@
+use alloc::boxed::Box;
+use alloc::vec;
+use cobs::decode_in_place;
+use std::net::ToSocketAddrs;
+use std::vec::Vec;
+use std::{io::Read, net::TcpListener};
+
+use crate::tmtc::ReceivesTc;
+
+pub struct TcpTcServer<E> {
+    listener: TcpListener,
+    tc_receiver: Box<dyn ReceivesTc<Error = E>>,
+    reader_vec: Vec<u8>,
+}
+
+impl<E: 'static> TcpTcServer<E> {
+    pub fn new<A: ToSocketAddrs>(
+        addr: A,
+        tc_receiver: Box<dyn ReceivesTc<Error = E>>,
+        reader_vec_size: usize,
+    ) -> Result<Self, std::io::Error> {
+        Ok(TcpTcServer {
+            listener: TcpListener::bind(addr)?,
+            tc_receiver,
+            reader_vec: vec![0; reader_vec_size],
+        })
+    }
+
+    pub fn handle_connections(&mut self) -> Result<(), std::io::Error> {
+        let mut current_write_idx;
+        let mut next_write_idx = 0;
+        for stream in self.listener.incoming() {
+            current_write_idx = next_write_idx;
+            next_write_idx = 0;
+            let mut stream = stream?;
+            loop {
+                let read_len = stream.read(&mut self.reader_vec[current_write_idx..])?;
+                if read_len > 0 {
+                    current_write_idx += read_len;
+                    if current_write_idx == self.reader_vec.capacity() {
+                        // Reader vec full, need to parse for packets.
+                        let parse_result = parse_buffer_for_cobs_encoded_packets(
+                            &mut self.reader_vec,
+                            self.tc_receiver.as_mut(),
+                            &mut next_write_idx,
+                        );
+                    }
+                    continue;
+                }
+                break;
+            }
+            if current_write_idx > 0 {
+                let parse_result = parse_buffer_for_cobs_encoded_packets(
+                    &mut self.reader_vec[..current_write_idx],
+                    self.tc_receiver.as_mut(),
+                    &mut next_write_idx,
+                );
+            }
+        }
+        Ok(())
+    }
+}
+
+pub fn parse_buffer_for_cobs_encoded_packets<E>(
+    buf: &mut [u8],
+    tc_receiver: &mut dyn ReceivesTc<Error = E>,
+    next_write_idx: &mut usize,
+) -> Result<u32, E> {
+    let mut start_index_packet = 0;
+    let mut start_found = false;
+    let mut last_byte = false;
+    let mut packets_found = 0;
+    for i in 0..buf.len() {
+        if i == buf.len() - 1 {
+            last_byte = true;
+        }
+        if buf[i] == 0 {
+            if !start_found && !last_byte && buf[i + 1] == 0 {
+                // Special case: Consecutive sentinel values or all zeroes.
+                // Skip.
+                continue;
+            }
+            if start_found {
+                let decode_result = decode_in_place(&mut buf[start_index_packet..i]);
+                if let Ok(packet_len) = decode_result {
+                    packets_found += 1;
+                    tc_receiver
+                        .pass_tc(&buf[start_index_packet..start_index_packet + packet_len])?;
+                }
+                start_found = false;
+            } else {
+                start_index_packet = i + 1;
+                start_found = true;
+            }
+        }
+    }
+    // Split frame at the end for a multi-packet frame. Move it to the front of the buffer.
+    if start_index_packet > 0 && start_found && packets_found > 0 {
+        let (first_seg, last_seg) = buf.split_at_mut(start_index_packet - 1);
+        first_seg[..last_seg.len()].copy_from_slice(last_seg);
+        *next_write_idx = last_seg.len();
+    }
+    Ok(packets_found)
+}
 
 #[cfg(test)]
 mod tests {
+    use crate::tmtc::ReceivesTcCore;
+    use alloc::vec::Vec;
+    use cobs::encode;
+
+    use super::parse_buffer_for_cobs_encoded_packets;
+
+    const SIMPLE_PACKET: [u8; 5] = [1, 2, 3, 4, 5];
+
+    #[derive(Default)]
+    struct TestSender {
+        received_tcs: Vec<Vec<u8>>,
+    }
+
+    impl ReceivesTcCore for TestSender {
+        type Error = ();
+
+        fn pass_tc(&mut self, tc_raw: &[u8]) -> Result<(), Self::Error> {
+            self.received_tcs.push(tc_raw.to_vec());
+            Ok(())
+        }
+    }
+
+    fn encode_simple_packet(encoded_buf: &mut [u8], current_idx: &mut usize) {
+        encoded_buf[*current_idx] = 0;
+        *current_idx += 1;
+        *current_idx += encode(&SIMPLE_PACKET, &mut encoded_buf[*current_idx..]);
+        encoded_buf[*current_idx] = 0;
+        *current_idx += 1;
+    }
 
     #[test]
-    fn basic_test() {
+    fn test_parsing_simple_packet() {
+        let mut test_sender = TestSender::default();
+        let mut encoded_buf: [u8; 16] = [0; 16];
+        let mut current_idx = 0;
+        encode_simple_packet(&mut encoded_buf, &mut current_idx);
+        let mut next_read_idx = 0;
+        let packets = parse_buffer_for_cobs_encoded_packets(
+            &mut encoded_buf[0..current_idx],
+            &mut test_sender,
+            &mut next_read_idx,
+        )
+        .unwrap();
+        assert_eq!(packets, 1);
+        assert_eq!(test_sender.received_tcs.len(), 1);
+        let packet = &test_sender.received_tcs[0];
+        assert_eq!(packet, &SIMPLE_PACKET);
+    }
 
+    #[test]
+    fn test_parsing_consecutive_packets() {
+        let mut test_sender = TestSender::default();
+        let mut encoded_buf: [u8; 16] = [0; 16];
+        let mut current_idx = 0;
+        encode_simple_packet(&mut encoded_buf, &mut current_idx);
+
+        let inverted_packet: [u8; 5] = [5, 4, 3, 2, 1];
+        // Second packet
+        encoded_buf[current_idx] = 0;
+        current_idx += 1;
+        current_idx += encode(&inverted_packet, &mut encoded_buf[current_idx..]);
+        encoded_buf[current_idx] = 0;
+        current_idx += 1;
+        let mut next_read_idx = 0;
+        let packets = parse_buffer_for_cobs_encoded_packets(
+            &mut encoded_buf[0..current_idx],
+            &mut test_sender,
+            &mut next_read_idx,
+        )
+        .unwrap();
+        assert_eq!(packets, 2);
+        assert_eq!(test_sender.received_tcs.len(), 2);
+        let packet0 = &test_sender.received_tcs[0];
+        assert_eq!(packet0, &SIMPLE_PACKET);
+        let packet1 = &test_sender.received_tcs[1];
+        assert_eq!(packet1, &inverted_packet);
+    }
+
+    #[test]
+    fn test_split_tail_packet_only() {
+        let mut test_sender = TestSender::default();
+        let mut encoded_buf: [u8; 16] = [0; 16];
+        let mut current_idx = 0;
+        encode_simple_packet(&mut encoded_buf, &mut current_idx);
+        let mut next_read_idx = 0;
+        let packets = parse_buffer_for_cobs_encoded_packets(
+            // Cut off the sentinel byte at the end.
+            &mut encoded_buf[0..current_idx - 1],
+            &mut test_sender,
+            &mut next_read_idx,
+        )
+        .unwrap();
+        assert_eq!(packets, 0);
+        assert_eq!(test_sender.received_tcs.len(), 0);
+        assert_eq!(next_read_idx, 0);
+    }
+
+    fn generic_test_split_packet(cut_off: usize) {
+        let mut test_sender = TestSender::default();
+        let mut encoded_buf: [u8; 16] = [0; 16];
+        let inverted_packet: [u8; 5] = [5, 4, 3, 2, 1];
+        assert!(cut_off < inverted_packet.len() + 1);
+        let mut current_idx = 0;
+        encode_simple_packet(&mut encoded_buf, &mut current_idx);
+        // Second packet
+        encoded_buf[current_idx] = 0;
+        let packet_start = current_idx;
+        current_idx += 1;
+        let encoded_len = encode(&inverted_packet, &mut encoded_buf[current_idx..]);
+        assert_eq!(encoded_len, 6);
+        current_idx += encoded_len;
+        // We cut off the sentinel byte, so we expecte the write index to be the length of the
+        // packet minus the sentinel byte plus the first sentinel byte.
+        let next_expected_write_idx = 1 + encoded_len - cut_off + 1;
+        encoded_buf[current_idx] = 0;
+        current_idx += 1;
+        let mut next_write_idx = 0;
+        let expected_at_start = encoded_buf[packet_start..current_idx - cut_off].to_vec();
+        let packets = parse_buffer_for_cobs_encoded_packets(
+            // Cut off the sentinel byte at the end.
+            &mut encoded_buf[0..current_idx - cut_off],
+            &mut test_sender,
+            &mut next_write_idx,
+        )
+        .unwrap();
+        assert_eq!(packets, 1);
+        assert_eq!(test_sender.received_tcs.len(), 1);
+        assert_eq!(&test_sender.received_tcs[0], &SIMPLE_PACKET);
+        assert_eq!(next_write_idx, next_expected_write_idx);
+        assert_eq!(encoded_buf[..next_expected_write_idx], expected_at_start);
+    }
+
+    #[test]
+    fn test_one_packet_and_split_tail_packet_0() {
+        generic_test_split_packet(1);
+    }
+
+    #[test]
+    fn test_one_packet_and_split_tail_packet_1() {
+        generic_test_split_packet(2);
+    }
+
+    #[test]
+    fn test_one_packet_and_split_tail_packet_2() {
+        generic_test_split_packet(3);
+    }
+
+    #[test]
+    fn test_zero_at_end() {
+        let mut test_sender = TestSender::default();
+        let mut encoded_buf: [u8; 16] = [0; 16];
+        let mut next_write_idx = 0;
+        let mut current_idx = 0;
+        encoded_buf[current_idx] = 5;
+        current_idx += 1;
+        encode_simple_packet(&mut encoded_buf, &mut current_idx);
+        encoded_buf[current_idx] = 0;
+        current_idx += 1;
+        let packets = parse_buffer_for_cobs_encoded_packets(
+            // Cut off the sentinel byte at the end.
+            &mut encoded_buf[0..current_idx],
+            &mut test_sender,
+            &mut next_write_idx,
+        )
+        .unwrap();
+        assert_eq!(packets, 1);
+        assert_eq!(test_sender.received_tcs.len(), 1);
+        assert_eq!(&test_sender.received_tcs[0], &SIMPLE_PACKET);
+        assert_eq!(next_write_idx, 1);
+        assert_eq!(encoded_buf[0], 0);
+    }
+
+    #[test]
+    fn test_all_zeroes() {
+        let mut test_sender = TestSender::default();
+        let mut all_zeroes: [u8; 5] = [0; 5];
+        let mut next_write_idx = 0;
+        let packets = parse_buffer_for_cobs_encoded_packets(
+            // Cut off the sentinel byte at the end.
+            &mut all_zeroes,
+            &mut test_sender,
+            &mut next_write_idx,
+        )
+        .unwrap();
+        assert_eq!(packets, 0);
+        assert!(test_sender.received_tcs.is_empty());
+        assert_eq!(next_write_idx, 0);
     }
 }