///
/// For efficiency, `data` and `len` are exposed directly and received KISS data may
/// be streamed directly into a pre-allocated `KissFrame`.
+#[derive(Debug, PartialEq, Eq, Clone)]
pub struct KissFrame {
pub data: [u8; MAX_FRAME_LEN],
pub len: usize,
}
impl KissFrame {
+ /// Construct empty frame
+ pub fn new_empty() -> Self {
+ Self {
+ data: [0u8; MAX_FRAME_LEN],
+ len: 0,
+ }
+ }
+
/// Request to transmit a data packet (basic mode).
///
/// A raw payload up to 822 bytes can be provided. The TNC will mark it as Raw format
*idx += 1;
}
+#[derive(Debug, PartialEq, Eq, Clone)]
pub enum KissCommand {
DataFrame,
TxDelay,
}
}
-#[derive(Debug)]
+/// Accepts raw KISS data and emits one frame at a time.
+///
+/// A frame will be emitted if there is at least one byte between FEND markers. It is up to the consumer
+/// to determine whether it's actually a valid frame.
+pub struct KissBuffer {
+ /// Provisional frame, whose buffer might contain more than one sequential frame at a time
+ frame: KissFrame,
+ /// Number of bytes that have been written into `frame.data`, which may be more than the the length
+ /// of the first valid frame, `frame.len`.
+ written: usize,
+ /// Whether we have emitted the first frame in `frame`'s buffer and now need to flush it out.
+ first_frame_returned: bool,
+}
+
+impl KissBuffer {
+ /// Create new buffer
+ pub fn new() -> Self {
+ Self {
+ frame: KissFrame::new_empty(),
+ written: 0,
+ first_frame_returned: false,
+ }
+ }
+
+ /// Return the space remaining for more data
+ pub fn buf_remaining(&mut self) -> &mut [u8] {
+ self.flush_first_frame();
+ if self.written == self.frame.data.len() {
+ // full buffer with no data means oversized frame
+ // sender is doing something weird or a FEND got dropped
+ // either way: flush it all and try to sync up again
+ self.written = 0;
+ }
+ &mut self.frame.data[self.written..]
+ }
+
+ /// Indicate how much data was written into the buffer provided by `buf_remaining()`.
+ pub fn did_write(&mut self, len: usize) {
+ self.written += len;
+ }
+
+ /// Try to construct and retrieve the next frame in the buffer
+ pub fn next_frame(&mut self) -> Option<&KissFrame> {
+ self.flush_first_frame();
+
+ // If we have any data without a leading FEND, scan past it
+ let mut i = 0;
+ while i < self.written && self.frame.data[i] != FEND {
+ i += 1;
+ }
+ self.move_to_start(i);
+
+ // If we do have a leading FEND, scan up up to the last one in the series
+ i = 0;
+ while (i + 1) < self.written && self.frame.data[i + 1] == FEND {
+ i += 1;
+ }
+ if i != 0 {
+ self.move_to_start(i);
+ }
+
+ // Now, if we have FEND-something-FEND, return it
+ if self.written >= 2 && self.frame.data[0] == FEND && self.frame.data[1] != FEND {
+ i = 2;
+ while i < self.written && self.frame.data[i] != FEND {
+ i += 1;
+ }
+ if i < self.written && self.frame.data[i] == FEND {
+ self.frame.len = i + 1;
+ self.first_frame_returned = true;
+ return Some(&self.frame);
+ }
+ }
+
+ None
+ }
+
+ /// Check if we just returned a frame; if so, clear it out and position the buffer for the next frame.
+ fn flush_first_frame(&mut self) {
+ if !self.first_frame_returned {
+ return;
+ }
+ self.first_frame_returned = false;
+ // If we have previously returned a valid frame, in the simplest case `frame.data` contains FEND-something-FEND
+ // So to find the trailing FEND we can start at index 2
+ // Loop forward until we find that FEND, which must exist, and leave its index in `i`
+ let mut i = 2;
+ while self.frame.data[i] != FEND {
+ i += 1;
+ }
+ // However if we have consecutive trailing FENDs we want to ignore them
+ // Having found the trailing FEND, increment past any additional FENDs until we reach the end or something else
+ while (i + 1) < self.written && self.frame.data[i + 1] == FEND {
+ i += 1;
+ }
+ // Now take that final FEND and make it the start of our frame
+ self.move_to_start(i);
+ }
+
+ /// Shift all data in the buffer back to the beginning starting from the given index.
+ fn move_to_start(&mut self, idx: usize) {
+ for i in idx..self.written {
+ self.frame.data[i - idx] = self.frame.data[i];
+ }
+ self.written -= idx;
+ }
+}
+
+#[derive(Debug, PartialEq, Eq, Clone)]
pub enum KissError {
MalformedKissFrame,
UnsupportedKissCommand,
let n = f.decode_payload(&mut buf).unwrap();
assert_eq!(&buf[..n], &[0, 1, 2, 3]);
}
+
+ #[test]
+ fn test_buffer_basic() {
+ let mut buffer = KissBuffer::new();
+
+ // initial write is not a complete frame
+ let buf = buffer.buf_remaining();
+ buf[0] = FEND;
+ buffer.did_write(1);
+ assert!(buffer.next_frame().is_none());
+
+ // complete the frame
+ let buf = buffer.buf_remaining();
+ buf[0] = 0x10;
+ buf[1] = 0x01;
+ buf[2] = FEND;
+ buffer.did_write(3);
+
+ // everything should parse
+ let next = buffer.next_frame().unwrap();
+ assert_eq!(next.len, 4);
+ assert_eq!(&next.data[0..4], &[FEND, 0x10, 0x01, FEND]);
+ assert_eq!(next.port().unwrap(), 1);
+ assert_eq!(next.command().unwrap(), KissCommand::DataFrame);
+ let mut payload_buf = [0u8; 1024];
+ let n = next.decode_payload(&mut payload_buf).unwrap();
+ assert_eq!(n, 1);
+ assert_eq!(&payload_buf[0..n], &[0x01]);
+ }
+
+ #[test]
+ fn test_buffer_double() {
+ let mut buffer = KissBuffer::new();
+ let buf = buffer.buf_remaining();
+ buf[0..8].copy_from_slice(&[FEND, 0x10, 0x01, FEND, FEND, 0x20, 02, FEND]);
+ buffer.did_write(8);
+
+ let next = buffer.next_frame().unwrap();
+ assert_eq!(next.port().unwrap(), 1);
+ let next = buffer.next_frame().unwrap();
+ assert_eq!(next.port().unwrap(), 2);
+ assert!(buffer.next_frame().is_none());
+ }
+
+ #[test]
+ fn test_buffer_double_shared_fend() {
+ let mut buffer = KissBuffer::new();
+ let buf = buffer.buf_remaining();
+ buf[0..7].copy_from_slice(&[FEND, 0x10, 0x01, FEND, 0x20, 02, FEND]);
+ buffer.did_write(7);
+
+ let next = buffer.next_frame().unwrap();
+ assert_eq!(next.port().unwrap(), 1);
+ let next = buffer.next_frame().unwrap();
+ assert_eq!(next.port().unwrap(), 2);
+ assert!(buffer.next_frame().is_none());
+ }
+
+ #[test]
+ fn test_buffer_extra_fend() {
+ let mut buffer = KissBuffer::new();
+ let buf = buffer.buf_remaining();
+ buf[0..10].copy_from_slice(&[FEND, FEND, FEND, 0x10, 0x01, FEND, FEND, 0x20, 02, FEND]);
+ buffer.did_write(10);
+
+ let next = buffer.next_frame().unwrap();
+ assert_eq!(next.port().unwrap(), 1);
+ let next = buffer.next_frame().unwrap();
+ assert_eq!(next.port().unwrap(), 2);
+ assert!(buffer.next_frame().is_none());
+ }
+
+ #[test]
+ fn test_buffer_oversize_frame() {
+ let mut buffer = KissBuffer::new();
+ let buf = buffer.buf_remaining();
+ buf[0] = FEND;
+ let len = buf.len();
+ assert_eq!(len, MAX_FRAME_LEN);
+ buffer.did_write(len);
+ assert!(buffer.next_frame().is_none());
+
+ let buf = buffer.buf_remaining();
+ let len = buf.len();
+ assert_eq!(len, MAX_FRAME_LEN); // should have flushed
+ for i in 0..len / 2 {
+ buf[i] = 0x00;
+ }
+ buffer.did_write(len / 2);
+ assert!(buffer.next_frame().is_none());
+
+ // confirm we resync if input goes back to normal
+ let buf = buffer.buf_remaining();
+ buf[0..4].copy_from_slice(&[FEND, 0x10, 0x01, FEND]);
+ buffer.did_write(4);
+ let next = buffer.next_frame().unwrap();
+ assert_eq!(next.port().unwrap(), 1);
+ assert!(buffer.next_frame().is_none());
+ }
}
projects / m17rt / blobdiff