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Simplify the triple buffer implementation

master
Fred Sundvik 2016-02-21 00:44:25 +02:00
parent 4bb5733cdc
commit 8e2d70d11f
2 changed files with 36 additions and 28 deletions
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46
serial_link/protocol/triple_buffered_object.c
View File

@ -25,28 +25,28 @@ SOFTWARE.
#include "protocol/triple_buffered_object.h"
#define GET_READ_INDEX() object->state & 3
#define GET_WRITE1_INDEX() (object->state >> 2) & 3
#define GET_WRITE2_INDEX() (object->state >> 4) & 3
#define GET_FREE_INDEX() (object->state >> 6) & 3
#define GET_WRITE_INDEX() (object->state >> 2) & 3
#define GET_SHARED_INDEX() (object->state >> 4) & 3
#define GET_DATA_AVAILABLE() (object->state >> 6) & 1
#define SET_READ_INDEX(i) object->state = ((object->state & ~3) | i)
#define SET_WRITE1_INDEX(i) object->state = ((object->state & ~(3 << 2)) | (i << 2))
#define SET_WRITE2_INDEX(i) object->state = ((object->state & ~(3 << 4)) | (i << 4))
#define SET_FREE_INDEX(i) object->state = ((object->state & ~(3 << 6)) | (i << 6))
#define SET_WRITE_INDEX(i) object->state = ((object->state & ~(3 << 2)) | (i << 2))
#define SET_SHARED_INDEX(i) object->state = ((object->state & ~(3 << 4)) | (i << 4))
#define SET_DATA_AVAILABLE(i) object->state = ((object->state & ~(1 << 6)) | (i << 6))
void triple_buffer_init(triple_buffer_object_t* object) {
object->state = 0;
SET_WRITE1_INDEX(0);
SET_WRITE2_INDEX(0);
SET_WRITE_INDEX(0);
SET_READ_INDEX(1);
SET_FREE_INDEX(2);
SET_SHARED_INDEX(2);
SET_DATA_AVAILABLE(0);
}
static void triple_buffer_begin_read(uint16_t object_size, triple_buffer_object_t* object) {
uint8_t newest = GET_WRITE2_INDEX();
uint8_t free_index = GET_READ_INDEX();
SET_READ_INDEX(newest);
SET_FREE_INDEX(free_index);
uint8_t shared_index = GET_SHARED_INDEX();
uint8_t read_index = GET_READ_INDEX();
SET_READ_INDEX(shared_index);
SET_SHARED_INDEX(read_index);
}
static void triple_buffer_actual_read(uint16_t object_size, triple_buffer_object_t* object, void* dst) {
@ -58,22 +58,12 @@ static void triple_buffer_end_read(uint16_t object_size, triple_buffer_object_t*
}
void triple_buffer_write(uint16_t object_size, triple_buffer_object_t* object, void* src) {
uint8_t write1_index = GET_WRITE1_INDEX();
uint8_t write2_index = GET_WRITE2_INDEX();
uint8_t read_index = GET_READ_INDEX();
uint8_t free_index = GET_FREE_INDEX();
if (write2_index == read_index) {
// We are reading from the other write index
SET_WRITE1_INDEX(free_index);
memcpy(object->buffer + object_size * free_index, src, object_size);
SET_WRITE2_INDEX(free_index);
}
else {
SET_WRITE1_INDEX(write2_index);
memcpy(object->buffer + object_size * write2_index, src, object_size);
SET_WRITE2_INDEX(write2_index);
}
uint8_t write_index = GET_WRITE_INDEX();
memcpy(object->buffer + object_size * write_index, src, object_size);
uint8_t shared_index = GET_SHARED_INDEX();
SET_SHARED_INDEX(write_index);
SET_WRITE_INDEX(shared_index);
}
void triple_buffer_read(uint16_t object_size, triple_buffer_object_t* object, void* dst) {

18
serial_link/tests/triple_buffered_object_tests.c
View File

@ -77,4 +77,22 @@ Ensure(TripleBufferedObject, performs_another_write_in_the_middle_of_read) {
triple_buffer_actual_read(4, (triple_buffer_object_t*)&test_object, &dst);
triple_buffer_end_read(4, (triple_buffer_object_t*)&test_object);
assert_that(dst, is_equal_to(1));
triple_buffer_read(4, (triple_buffer_object_t*)&test_object, &dst);
assert_that(dst, is_equal_to(2));
}
Ensure(TripleBufferedObject, performs_two_writes_in_the_middle_of_read) {
uint32_t src = 1;
uint32_t dst;
triple_buffer_write(4, (triple_buffer_object_t*)&test_object, &src);
triple_buffer_begin_read(4, (triple_buffer_object_t*)&test_object);
src = 2;
triple_buffer_write(4, (triple_buffer_object_t*)&test_object, &src);
src = 3;
triple_buffer_write(4, (triple_buffer_object_t*)&test_object, &src);
triple_buffer_actual_read(4, (triple_buffer_object_t*)&test_object, &dst);
triple_buffer_end_read(4, (triple_buffer_object_t*)&test_object);
assert_that(dst, is_equal_to(1));
triple_buffer_read(4, (triple_buffer_object_t*)&test_object, &dst);
assert_that(dst, is_equal_to(3));
}