In some circumstances it is useful to be able to push the entire content of a memory buffer to the fifo or to pop multiple bytes with a single operation.
The functions fifo8_has_space() and fifo8_push_all() added by this patch allow to perform the first kind of operation efficiently. The function fifo8_pop_buf() can be used instead to pop multiple bytes from the fifo, returning a pointer to the backing buffer. Signed-off-by: Beniamino Galvani <b.galv...@gmail.com> --- include/qemu/fifo8.h | 43 +++++++++++++++++++++++++++++++++++++++++++ util/fifo8.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 87 insertions(+) diff --git a/include/qemu/fifo8.h b/include/qemu/fifo8.h index d318f71..ea6e9f6 100644 --- a/include/qemu/fifo8.h +++ b/include/qemu/fifo8.h @@ -44,6 +44,19 @@ void fifo8_destroy(Fifo8 *fifo); void fifo8_push(Fifo8 *fifo, uint8_t data); /** + * fifo8_push_all: + * @fifo: FIFO to push to + * @data: data to push + * @size: number of bytes to push + * + * Push a byte array to the FIFO. Behaviour is undefined is the FIFO is + * full. Clients are responsible for checking the space left in the FIFO using + * fifo8_has_space(). + */ + +void fifo8_push_all(Fifo8 *fifo, const uint8_t *data, uint32_t num); + +/** * fifo8_pop: * @fifo: fifo to pop from * @@ -56,6 +69,24 @@ void fifo8_push(Fifo8 *fifo, uint8_t data); uint8_t fifo8_pop(Fifo8 *fifo); /** + * fifo8_pop_buf: + * @fifo: FIFO to pop from + * @max: maximum number of bytes to pop + * @num: actual number of returned bytes + * + * Pop a number of elements from the FIFO up to a maximum of max. The buffer + * containing the popped data is returned. This buffer points directly into + * the FIFO backing store and data is invalidated once any of the fifo8_* APIs + * are called on the FIFO. + * + * May short return, the number of valid bytes returned is populated in + * *num. Will always return at least 1 byte. + * + * Behavior is undefined if max == 0. + */ +const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *num); + +/** * fifo8_reset: * @fifo: FIFO to reset * @@ -86,6 +117,18 @@ bool fifo8_is_empty(Fifo8 *fifo); bool fifo8_is_full(Fifo8 *fifo); +/** + * fifo8_has_space: + * @fifo: FIFO to check + * @num: number of bytes + * + * Check if a given number of bytes can be pushed to a FIFO. + * + * Returns: True if the fifo can hold the given elements, false otherwise. + */ + +bool fifo8_has_space(Fifo8 *fifo, uint32_t num); + extern const VMStateDescription vmstate_fifo8; #define VMSTATE_FIFO8(_field, _state) { \ diff --git a/util/fifo8.c b/util/fifo8.c index 013e903..2808169 100644 --- a/util/fifo8.c +++ b/util/fifo8.c @@ -15,6 +15,8 @@ #include "qemu-common.h" #include "qemu/fifo8.h" +#define min(a, b) ((a) < (b) ? (a) : (b)) + void fifo8_create(Fifo8 *fifo, uint32_t capacity) { fifo->data = g_new(uint8_t, capacity); @@ -37,6 +39,27 @@ void fifo8_push(Fifo8 *fifo, uint8_t data) fifo->num++; } +void fifo8_push_all(Fifo8 *fifo, const uint8_t *data, uint32_t num) +{ + uint32_t start, avail; + + if (fifo->num + num > fifo->capacity) { + abort(); + } + + start = (fifo->head + fifo->num) % fifo->capacity; + + if (start + num <= fifo->capacity) { + memcpy(&fifo->data[start], data, num); + } else { + avail = fifo->capacity - start; + memcpy(&fifo->data[start], data, avail); + memcpy(&fifo->data[0], &data[avail], num - avail); + } + + fifo->num += num; +} + uint8_t fifo8_pop(Fifo8 *fifo) { uint8_t ret; @@ -50,9 +73,25 @@ uint8_t fifo8_pop(Fifo8 *fifo) return ret; } +const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *num) +{ + uint8_t *ret; + + *num = min(fifo->capacity - fifo->head, max); + *num = min(*num, fifo->num); + + ret = &fifo->data[fifo->head]; + + fifo->head += *num; + fifo->head %= fifo->capacity; + + return ret; +} + void fifo8_reset(Fifo8 *fifo) { fifo->num = 0; + fifo->head = 0; } bool fifo8_is_empty(Fifo8 *fifo) @@ -65,6 +104,11 @@ bool fifo8_is_full(Fifo8 *fifo) return (fifo->num == fifo->capacity); } +bool fifo8_has_space(Fifo8 *fifo, uint32_t num) +{ + return (fifo->num + num <= fifo->capacity); +} + const VMStateDescription vmstate_fifo8 = { .name = "Fifo8", .version_id = 1, -- 1.7.10.4