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Diffstat (limited to 'quantum/serial_link/protocol/byte_stuffer.c')
| -rw-r--r-- | quantum/serial_link/protocol/byte_stuffer.c | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/quantum/serial_link/protocol/byte_stuffer.c b/quantum/serial_link/protocol/byte_stuffer.c new file mode 100644 index 000000000..2c87d64c2 --- /dev/null +++ b/quantum/serial_link/protocol/byte_stuffer.c @@ -0,0 +1,142 @@ +/* +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 "serial_link/protocol/byte_stuffer.h" +#include "serial_link/protocol/frame_validator.h" +#include "serial_link/protocol/physical.h" +#include <stdbool.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; + bool long_frame; + uint8_t data[MAX_FRAME_SIZE]; +}byte_stuffer_state_t; + +static byte_stuffer_state_t states[NUM_LINKS]; + +void init_byte_stuffer_state(byte_stuffer_state_t* state) { + state->next_zero = 0; + state->data_pos = 0; + state->long_frame = false; +} + +void init_byte_stuffer(void) { + int i; + for (i=0;i<NUM_LINKS;i++) { + init_byte_stuffer_state(&states[i]); + } +} + +void byte_stuffer_recv_byte(uint8_t link, uint8_t data) { + byte_stuffer_state_t* state = &states[link]; + // Start of a new frame + if (state->next_zero == 0) { + state->next_zero = data; + state->long_frame = data == 0xFF; + state->data_pos = 0; + return; + } + + state->next_zero--; + if (data == 0) { + if (state->next_zero == 0) { + // The frame is completed + if (state->data_pos > 0) { + validator_recv_frame(link, state->data, state->data_pos); + } + } + else { + // The frame is invalid, so reset + init_byte_stuffer_state(state); + } + } + else { + if (state->data_pos == MAX_FRAME_SIZE) { + // We exceeded our maximum frame size + // therefore there's nothing else to do than reset to a new frame + state->next_zero = data; + state->long_frame = data == 0xFF; + state->data_pos = 0; + } + else if (state->next_zero == 0) { + if (state->long_frame) { + // This is part of a long frame, so continue + state->next_zero = data; + state->long_frame = data == 0xFF; + } + else { + // Special case for zeroes + state->next_zero = data; + state->data[state->data_pos++] = 0; + } + } + else { + state->data[state->data_pos++] = data; + } + } +} + +static void send_block(uint8_t link, uint8_t* start, uint8_t* end, uint8_t num_non_zero) { + send_data(link, &num_non_zero, 1); + if (end > start) { + send_data(link, start, end-start); + } +} + +void byte_stuffer_send_frame(uint8_t link, uint8_t* data, uint16_t size) { + const uint8_t zero = 0; + if (size > 0) { + uint16_t num_non_zero = 1; + uint8_t* end = data + size; + uint8_t* start = data; + while (data < end) { + if (num_non_zero == 0xFF) { + // There's more data after big non-zero block + // So send it, and start a new block + send_block(link, start, data, num_non_zero); + start = data; + num_non_zero = 1; + } + else { + if (*data == 0) { + // A zero encountered, so send the block + send_block(link, start, data, num_non_zero); + start = data + 1; + num_non_zero = 1; + } + else { + num_non_zero++; + } + ++data; + } + } + send_block(link, start, data, num_non_zero); + send_data(link, &zero, 1); + } +} |