[RFC PATCH v2 01/23] fifo32: add peek function

[Octavian Purdila]

Add fifo32_peek() that returns the first element from the queue
without popping it.

Signed-off-by: Octavian Purdila <tavip@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..77aab488ae 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_buf(&fifo->fifo, 4, &num);
+    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.
-- 
2.46.0.184.g6999bdac58-goog