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