Simplify the triple buffer implementation
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4bb5733cdc
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8e2d70d11f
2 changed files with 36 additions and 28 deletions
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@ -25,28 +25,28 @@ SOFTWARE.
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#include "protocol/triple_buffered_object.h"
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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_READ_INDEX() object->state & 3
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#define GET_WRITE1_INDEX() (object->state >> 2) & 3
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#define GET_WRITE_INDEX() (object->state >> 2) & 3
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#define GET_WRITE2_INDEX() (object->state >> 4) & 3
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#define GET_SHARED_INDEX() (object->state >> 4) & 3
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#define GET_FREE_INDEX() (object->state >> 6) & 3
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#define GET_DATA_AVAILABLE() (object->state >> 6) & 1
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#define SET_READ_INDEX(i) object->state = ((object->state & ~3) | i)
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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_WRITE_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_SHARED_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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#define SET_DATA_AVAILABLE(i) object->state = ((object->state & ~(1 << 6)) | (i << 6))
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void triple_buffer_init(triple_buffer_object_t* object) {
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void triple_buffer_init(triple_buffer_object_t* object) {
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object->state = 0;
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object->state = 0;
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SET_WRITE1_INDEX(0);
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SET_WRITE_INDEX(0);
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SET_WRITE2_INDEX(0);
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SET_READ_INDEX(1);
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SET_READ_INDEX(1);
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SET_FREE_INDEX(2);
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SET_SHARED_INDEX(2);
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SET_DATA_AVAILABLE(0);
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}
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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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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 shared_index = GET_SHARED_INDEX();
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uint8_t free_index = GET_READ_INDEX();
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uint8_t read_index = GET_READ_INDEX();
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SET_READ_INDEX(newest);
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SET_READ_INDEX(shared_index);
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SET_FREE_INDEX(free_index);
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SET_SHARED_INDEX(read_index);
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}
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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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static void triple_buffer_actual_read(uint16_t object_size, triple_buffer_object_t* object, void* dst) {
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@ -58,22 +58,12 @@ static void triple_buffer_end_read(uint16_t object_size, triple_buffer_object_t*
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}
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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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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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uint8_t write_index = GET_WRITE_INDEX();
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// We are reading from the other write index
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memcpy(object->buffer + object_size * write_index, src, object_size);
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SET_WRITE1_INDEX(free_index);
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uint8_t shared_index = GET_SHARED_INDEX();
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memcpy(object->buffer + object_size * free_index, src, object_size);
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SET_SHARED_INDEX(write_index);
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SET_WRITE2_INDEX(free_index);
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SET_WRITE_INDEX(shared_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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}
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void triple_buffer_read(uint16_t object_size, triple_buffer_object_t* object, void* dst) {
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void triple_buffer_read(uint16_t object_size, triple_buffer_object_t* object, void* dst) {
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@ -77,4 +77,22 @@ Ensure(TripleBufferedObject, performs_another_write_in_the_middle_of_read) {
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triple_buffer_actual_read(4, (triple_buffer_object_t*)&test_object, &dst);
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triple_buffer_actual_read(4, (triple_buffer_object_t*)&test_object, &dst);
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triple_buffer_end_read(4, (triple_buffer_object_t*)&test_object);
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triple_buffer_end_read(4, (triple_buffer_object_t*)&test_object);
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assert_that(dst, is_equal_to(1));
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assert_that(dst, is_equal_to(1));
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triple_buffer_read(4, (triple_buffer_object_t*)&test_object, &dst);
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assert_that(dst, is_equal_to(2));
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}
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Ensure(TripleBufferedObject, performs_two_writes_in_the_middle_of_read) {
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uint32_t src = 1;
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uint32_t dst;
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triple_buffer_write(4, (triple_buffer_object_t*)&test_object, &src);
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triple_buffer_begin_read(4, (triple_buffer_object_t*)&test_object);
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src = 2;
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triple_buffer_write(4, (triple_buffer_object_t*)&test_object, &src);
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src = 3;
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triple_buffer_write(4, (triple_buffer_object_t*)&test_object, &src);
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triple_buffer_actual_read(4, (triple_buffer_object_t*)&test_object, &dst);
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triple_buffer_end_read(4, (triple_buffer_object_t*)&test_object);
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assert_that(dst, is_equal_to(1));
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triple_buffer_read(4, (triple_buffer_object_t*)&test_object, &dst);
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assert_that(dst, is_equal_to(3));
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}
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}
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