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|
use std::{collections::VecDeque, mem};
use tokio::time::Instant;
use tracing::trace;
use crate::{
encoding::crc16,
transport::{
MESSAGE_DEST, MESSAGE_HEADER_SIZE, MESSAGE_LENGTH_MAX, MESSAGE_LENGTH_MIN,
MESSAGE_POSITION_SEQ, MESSAGE_SEQ_MASK, MESSAGE_TRAILER_CRC, MESSAGE_TRAILER_SIZE,
MESSAGE_VALUE_SYNC,
},
};
/// A link-level frame. See [klipper docs](https://www.klipper3d.org/Protocol.html#message-blocks)
#[derive(Debug)]
pub(crate) struct ReceivedFrame {
pub receive_time: Instant,
pub sequence: u8,
pub payload: Vec<u8>,
}
/// Buffers and reads link-level frames. See [`ReceivedFrame`].
#[derive(Debug, Default)]
pub struct FrameReader {
buf: VecDeque<ReceivedFrame>,
partial: PartialFrameState,
}
impl FrameReader {
/// Process new data from `b`
pub fn receive_data(&mut self, mut b: &[u8]) {
while !b.is_empty() {
if let Some((frame, remaining)) = self.partial.receive_data(b) {
self.buf.push_back(frame);
b = remaining;
};
}
}
/// Attempt to read a parsed frame from the data already processed.
pub fn read_frame(&mut self) -> Option<ReceivedFrame> {
self.buf.pop_front()
}
}
/// State machine for receiving a frame.
#[derive(Debug, Default)]
pub enum PartialFrameState {
/// Waiting to sync with the other side
#[default]
Unsynced,
/// Synchronised and ready to receive data
Synced,
/// Received length byte, waiting to receive more data.
Receiving {
/// The total length of this frame, including header and footer.
len: usize,
/// Accumulated data so far.
so_far: Vec<u8>,
/// When the packet started being received.
receive_time: Instant,
},
}
impl PartialFrameState {
pub fn receive_data<'a>(&mut self, mut b: &'a [u8]) -> Option<(ReceivedFrame, &'a [u8])> {
while !b.is_empty() {
match self {
Self::Unsynced => {
// Wait for sync byte before doing anything else
if let Some(idx) = b.iter().position(|x| *x == MESSAGE_VALUE_SYNC) {
*self = Self::Synced;
b = &b[idx + 1..];
}
}
PartialFrameState::Synced => {
// Attempt to start a new frame
let len = b[0] as usize;
if !(MESSAGE_LENGTH_MIN..=MESSAGE_LENGTH_MAX).contains(&len) {
*self = Self::Unsynced;
continue;
}
let receive_time = Instant::now();
let mut so_far = Vec::with_capacity(len);
so_far.push(b[0]);
*self = Self::Receiving {
len,
so_far,
receive_time,
};
b = &b[1..];
}
PartialFrameState::Receiving { len, so_far, .. } => {
// Continue to receive data for frame
let len = *len;
let take = len - so_far.len();
so_far.extend_from_slice(&b[..take]);
if so_far.len() < len {
// Frame not yet done, most likely b is empty now.
b = &b[take + 1..];
continue;
}
let seq = so_far[MESSAGE_POSITION_SEQ];
trace!(frame = ?so_far, seq = seq, "Received frame");
// Check validity of frame
if seq & !MESSAGE_SEQ_MASK != MESSAGE_DEST {
*self = Self::Unsynced;
continue;
}
let actual_crc = crc16(&so_far);
let frame_crc = (so_far[len - MESSAGE_TRAILER_CRC] as u16) << 8
| (so_far[len - MESSAGE_TRAILER_CRC + 1] as u16);
if frame_crc != actual_crc {
*self = Self::Unsynced;
continue;
}
// Set current state back to synced
let Self::Receiving {
so_far,
receive_time,
..
} = mem::replace(self, Self::Synced)
else {
unreachable!()
};
// Return received frame and unused buffer.
return Some((
ReceivedFrame {
receive_time,
sequence: seq & MESSAGE_SEQ_MASK,
payload: so_far[MESSAGE_HEADER_SIZE..len - MESSAGE_TRAILER_SIZE].into(),
},
&b[take..],
));
}
}
}
None
}
}
|
