util/fifo8: Allow fifo8_pop_buf() to not populate popped length

There might be cases where we know the number of bytes we can
pop from the FIFO, or we simply don't care how many bytes is
returned. Allow fifo8_pop_buf() to take a NULL numptr.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
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: <20231109192814.95977-2-philmd@linaro.org>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

diff --git a/include/qemu/fifo8.h b/include/qemu/fifo8.h
index 16be02f361fc37f2483030ba034e1fd381441ddd..d0d02bc73db234a805723b4b6c020bf9fb8c3572 100644 (file)
--- a/include/qemu/fifo8.h
+++ b/include/qemu/fifo8.h
@@ -71,7 +71,7 @@ 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
+ * @numptr: pointer filled with number of bytes returned (can be NULL)
  *
  * 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
@@ -82,16 +82,16 @@ uint8_t fifo8_pop(Fifo8 *fifo);
  * 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 *num; will always return
- * at least 1 byte. max must not be 0 or greater than the number of bytes in
- * the FIFO.
+ * 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 popped data.
  */
-const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *num);
+const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr);
 
 /**
  * fifo8_reset:

diff --git a/util/fifo8.c b/util/fifo8.c
index de8fd0f1c5c5ec0bd7c3d8e220e64eaa1530c742..2eeed56e809a6e3b96a01785e0183d0c718f9bc9 100644 (file)
--- a/util/fifo8.c
+++ b/util/fifo8.c
@@ -66,16 +66,20 @@ uint8_t fifo8_pop(Fifo8 *fifo)
     return ret;
 }
 
-const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *num)
+const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *numptr)
 {
     uint8_t *ret;
+    uint32_t num;
 
     assert(max > 0 && max <= fifo->num);
-    *num = MIN(fifo->capacity - fifo->head, max);
+    num = MIN(fifo->capacity - fifo->head, max);
     ret = &fifo->data[fifo->head];
-    fifo->head += *num;
+    fifo->head += num;
     fifo->head %= fifo->capacity;
-    fifo->num -= *num;
+    fifo->num -= num;
+    if (numptr) {
+        *numptr = num;
+    }
     return ret;
 }