forked from mirrors/qmk_firmware
73 lines
2.3 KiB
C
73 lines
2.3 KiB
C
/*
|
|
The MIT License (MIT)
|
|
|
|
Copyright (c) 2016 Fred Sundvik
|
|
|
|
Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
of this software and associated documentation files (the "Software"), to deal
|
|
in the Software without restriction, including without limitation the rights
|
|
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
copies of the Software, and to permit persons to whom the Software is
|
|
furnished to do so, subject to the following conditions:
|
|
|
|
The above copyright notice and this permission notice shall be included in all
|
|
copies or substantial portions of the Software.
|
|
|
|
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
|
SOFTWARE.
|
|
*/
|
|
|
|
#include "protocol/byte_stuffer.h"
|
|
#include "protocol/frame_validator.h"
|
|
|
|
// This implements the "Consistent overhead byte stuffing protocol"
|
|
// https://en.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuffing
|
|
// http://www.stuartcheshire.org/papers/COBSforToN.pdf
|
|
|
|
typedef struct byte_stuffer_state {
|
|
uint16_t next_zero;
|
|
uint16_t data_pos;
|
|
uint8_t data[256];
|
|
}byte_stuffer_state_t;
|
|
|
|
void init_byte_stuffer_state(byte_stuffer_state_t* state) {
|
|
state->next_zero = 0;
|
|
state->data_pos = 0;
|
|
}
|
|
|
|
void recv_byte(byte_stuffer_state_t* state, uint8_t data) {
|
|
// Start of a new frame
|
|
if (state->next_zero == 0) {
|
|
state->next_zero = data;
|
|
state->data_pos = 0;
|
|
return;
|
|
}
|
|
|
|
state->next_zero--;
|
|
if (data == 0) {
|
|
if (state->next_zero == 0) {
|
|
// The frame is completed
|
|
recv_frame(state->data, state->data_pos);
|
|
}
|
|
else {
|
|
// The frame is invalid, so reset
|
|
state->next_zero = 0;
|
|
state->data_pos = 0;
|
|
}
|
|
}
|
|
else {
|
|
if (state->next_zero == 0) {
|
|
// Special case for zeroes
|
|
state->next_zero = data;
|
|
state->data[state->data_pos++] = 0;
|
|
}
|
|
else {
|
|
state->data[state->data_pos++] = data;
|
|
}
|
|
}
|
|
}
|