84 lines
3.3 KiB
C
84 lines
3.3 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/triple_buffered_object.h"
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#define GET_READ_INDEX() object->state & 3
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#define GET_WRITE1_INDEX() (object->state >> 2) & 3
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#define GET_WRITE2_INDEX() (object->state >> 4) & 3
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#define GET_FREE_INDEX() (object->state >> 6) & 3
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#define SET_READ_INDEX(i) object->state = ((object->state & ~3) | i)
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#define SET_WRITE1_INDEX(i) object->state = ((object->state & ~(3 << 2)) | (i << 2))
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#define SET_WRITE2_INDEX(i) object->state = ((object->state & ~(3 << 4)) | (i << 4))
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#define SET_FREE_INDEX(i) object->state = ((object->state & ~(3 << 6)) | (i << 6))
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void triple_buffer_init(triple_buffer_object_t* object) {
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object->state = 0;
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SET_WRITE1_INDEX(0);
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SET_WRITE2_INDEX(0);
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SET_READ_INDEX(1);
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SET_FREE_INDEX(2);
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}
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static void triple_buffer_begin_read(uint16_t object_size, triple_buffer_object_t* object) {
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uint8_t newest = GET_WRITE2_INDEX();
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uint8_t free_index = GET_READ_INDEX();
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SET_READ_INDEX(newest);
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SET_FREE_INDEX(free_index);
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}
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static void triple_buffer_actual_read(uint16_t object_size, triple_buffer_object_t* object, void* dst) {
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uint8_t read_index = GET_READ_INDEX();
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memcpy(dst, object->buffer + object_size*read_index, object_size);
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}
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static void triple_buffer_end_read(uint16_t object_size, triple_buffer_object_t* object) {
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}
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void triple_buffer_write(uint16_t object_size, triple_buffer_object_t* object, void* src) {
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uint8_t write1_index = GET_WRITE1_INDEX();
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uint8_t write2_index = GET_WRITE2_INDEX();
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uint8_t read_index = GET_READ_INDEX();
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uint8_t free_index = GET_FREE_INDEX();
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if (write2_index == read_index) {
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// We are reading from the other write index
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SET_WRITE1_INDEX(free_index);
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memcpy(object->buffer + object_size * free_index, src, object_size);
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SET_WRITE2_INDEX(free_index);
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}
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else {
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SET_WRITE1_INDEX(write2_index);
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memcpy(object->buffer + object_size * write2_index, src, object_size);
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SET_WRITE2_INDEX(write2_index);
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}
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}
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void triple_buffer_read(uint16_t object_size, triple_buffer_object_t* object, void* dst) {
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triple_buffer_begin_read(object_size, object);
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triple_buffer_actual_read(object_size, object, dst);
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triple_buffer_end_read(object_size, object);
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}
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