util/fifo8: Introduce fifo8_peek_buf()

To be able to peek at FIFO content without popping it,
introduce the fifo8_peek_buf() method by factoring
common content from fifo8_pop_buf().

Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231109192814.95977-3-philmd@linaro.org>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
This commit is contained in:
Philippe Mathieu-Daudé 2023-11-09 20:28:06 +01:00 committed by Mark Cave-Ayland
parent cd04033dbe
commit 995d8348eb
2 changed files with 45 additions and 4 deletions

View File

@ -93,6 +93,33 @@ uint8_t fifo8_pop(Fifo8 *fifo);
*/
const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr);
/**
* fifo8_peek_buf: read upto max bytes from the fifo
* @fifo: FIFO to read from
* @max: maximum number of bytes to peek
* @numptr: pointer filled with number of bytes returned (can be NULL)
*
* Peek into a number of elements from the FIFO up to a maximum of max.
* The buffer containing the data peeked into is returned. This buffer points
* directly into the FIFO backing store. Since data is invalidated once any
* of the fifo8_* APIs are called on the FIFO, it is the caller responsibility
* to access it before doing further API calls.
*
* The function may return fewer bytes than requested when the data wraps
* around in the ring buffer; in this case only a contiguous part of the data
* is returned.
*
* The number of valid bytes returned is populated in *numptr; will always
* return at least 1 byte. max must not be 0 or greater than the number of
* bytes in the FIFO.
*
* Clients are responsible for checking the availability of requested data
* using fifo8_num_used().
*
* Returns: A pointer to peekable data.
*/
const uint8_t *fifo8_peek_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr);
/**
* fifo8_reset:
* @fifo: FIFO to reset

View File

@ -66,7 +66,8 @@ uint8_t fifo8_pop(Fifo8 *fifo)
return ret;
}
const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr)
static const uint8_t *fifo8_peekpop_buf(Fifo8 *fifo, uint32_t max,
uint32_t *numptr, bool do_pop)
{
uint8_t *ret;
uint32_t num;
@ -74,15 +75,28 @@ const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr)
assert(max > 0 && max <= fifo->num);
num = MIN(fifo->capacity - fifo->head, max);
ret = &fifo->data[fifo->head];
fifo->head += num;
fifo->head %= fifo->capacity;
fifo->num -= num;
if (do_pop) {
fifo->head += num;
fifo->head %= fifo->capacity;
fifo->num -= num;
}
if (numptr) {
*numptr = num;
}
return ret;
}
const uint8_t *fifo8_peek_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr)
{
return fifo8_peekpop_buf(fifo, max, numptr, false);
}
const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr)
{
return fifo8_peekpop_buf(fifo, max, numptr, true);
}
void fifo8_reset(Fifo8 *fifo)
{
fifo->num = 0;