1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
|
use std::{collections::VecDeque, mem, sync::Arc};
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)]
#[allow(clippy::module_name_repetitions)]
pub 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 Reader {
buf: VecDeque<ReceivedFrame>,
partial: PartialFrameState,
}
impl Reader {
/// 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..];
}
}
Self::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..];
}
Self::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 = (u16::from(so_far[len - MESSAGE_TRAILER_CRC])) << 8
| (u16::from(so_far[len - MESSAGE_TRAILER_CRC + 1]));
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
}
}
/// A frame to be sent to the MCU
#[derive(Debug, Clone)]
#[allow(clippy::module_name_repetitions)]
pub struct SentFrame {
/// When the frame was first sent
pub sent_at: Instant,
/// The payload of the message, including frame header
pub payload: Arc<Vec<u8>>,
/// True iff the frame has been retransmitted at least once
pub is_retransmit: bool,
}
impl SentFrame {
pub fn new(sequence: u64, data: &[u8]) -> Result<Self, MessageEncodeError> {
let len = MESSAGE_LENGTH_MIN + data.len();
if len > MESSAGE_LENGTH_MAX {
return Err(MessageEncodeError::MessageTooLong);
}
let mut payload = Vec::with_capacity(len);
let Ok(len) = u8::try_from(len) else {
unreachable!()
};
payload.push(len);
payload.push(
MESSAGE_DEST
| ((u8::try_from(sequence).expect("sequence number overflow")) & MESSAGE_SEQ_MASK),
);
payload.extend_from_slice(data);
let crc = crc16(&payload[0..len as usize - MESSAGE_TRAILER_SIZE]);
payload.push(((crc >> 8) & 0xFF) as u8);
payload.push((crc & 0xFF) as u8);
payload.push(MESSAGE_VALUE_SYNC);
Ok(Self {
sent_at: Instant::now(),
payload: Arc::new(payload),
is_retransmit: false,
})
}
}
#[derive(thiserror::Error, Debug)]
pub enum MessageEncodeError {
#[error("message would exceed the maximum packet length of {MESSAGE_LENGTH_MAX} bytes")]
MessageTooLong,
}
|
