On 08/10/2024 02:18, Octavian Purdila wrote:
Add fifo32_peek() that returns the first element from the queue
without popping it.
Signed-off-by: Octavian Purdila <ta...@google.com>
---
include/qemu/fifo32.h | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/include/qemu/fifo32.h b/include/qemu/fifo32.h
index 4e9fd1b5ef..9de1807375 100644
--- a/include/qemu/fifo32.h
+++ b/include/qemu/fifo32.h
@@ -140,6 +140,34 @@ static inline uint32_t fifo32_pop(Fifo32 *fifo)
return ret;
}
+/**
+ * fifo32_peek:
+ * @fifo: fifo to peek at
+ *
+ * Returns the value from the FIFO's head without poping it. Behaviour
+ * is undefined if the FIFO is empty. Clients are responsible for
+ * checking for emptiness using fifo32_is_empty().
+ *
+ * Returns: the value from the FIFO's head
+ */
+
+static inline uint32_t fifo32_peek(Fifo32 *fifo)
+{
+ uint32_t ret = 0, num;
+ const uint8_t *buf;
+
+ buf = fifo8_peek_bufptr(&fifo->fifo, 4, &num);
Are you sure that you want to use fifo8_peek_bufptr() as opposed to fifo8_peek_buf()
here? The reason for using the latter function (and why fifo8_*_bufptr() functions
are not generally recommended) is that they will correctly handle the FIFO wraparound
caused by the drifting head pointer which can occur if you don't empty the entire
FIFO contents in a single *_pop() or *_pop_buf() operation.
+ if (num != 4) {
+ return ret;
+ }
+
+ for (int i = 0; i < sizeof(uint32_t); i++) {
+ ret |= buf[i] << (i * 8);
+ }
+
+ return ret;
+}
+
/**
* There is no fifo32_pop_buf() because the data is not stored in the buffer
* as a set of native-order words.
ATB,
Mark.
