From 8e2d70d11fd852cf6e33b48a027a5fba61c08779 Mon Sep 17 00:00:00 2001 From: Fred Sundvik Date: Sun, 21 Feb 2016 00:44:25 +0200 Subject: [PATCH] Simplify the triple buffer implementation --- serial_link/protocol/triple_buffered_object.c | 46 ++++++++----------- .../tests/triple_buffered_object_tests.c | 18 ++++++++ 2 files changed, 36 insertions(+), 28 deletions(-) diff --git a/serial_link/protocol/triple_buffered_object.c b/serial_link/protocol/triple_buffered_object.c index a82cef5a..77e45ec4 100644 --- a/serial_link/protocol/triple_buffered_object.c +++ b/serial_link/protocol/triple_buffered_object.c @@ -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) { diff --git a/serial_link/tests/triple_buffered_object_tests.c b/serial_link/tests/triple_buffered_object_tests.c index bf0e3ca6..5fa1b8b6 100644 --- a/serial_link/tests/triple_buffered_object_tests.c +++ b/serial_link/tests/triple_buffered_object_tests.c @@ -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)); }