lavu/fifo: deprecate av_fifo_peek2()

It returns a pointer inside the fifo's buffer, which cannot be safely
used without accessing AVFifoBuffer internals. It is easier and safer to
use av_fifo_generic_peek_at().

libavutil/fifo.h

@@ -156,6 +156,7 @@ int av_fifo_grow(AVFifoBuffer *f, unsigned int additional_space);
  */
 void av_fifo_drain(AVFifoBuffer *f, int size);
 
+#if FF_API_FIFO_PEEK2
 /**
  * Return a pointer to the data stored in a FIFO buffer at a certain offset.
  * The FIFO buffer is not modified.
@@ -165,7 +166,9 @@ void av_fifo_drain(AVFifoBuffer *f, int size);
  *             than the used buffer size or the returned pointer will
  *             point outside to the buffer data.
  *             The used buffer size can be checked with av_fifo_size().
+ * @deprecated use av_fifo_generic_peek_at()
  */
+attribute_deprecated
 static inline uint8_t *av_fifo_peek2(const AVFifoBuffer *f, int offs)
 {
     uint8_t *ptr = f->rptr + offs;
@@ -175,5 +178,6 @@ static inline uint8_t *av_fifo_peek2(const AVFifoBuffer *f, int offs)
         ptr = f->end - (f->buffer - ptr);
     return ptr;
 }
+#endif
 
 #endif /* AVUTIL_FIFO_H */

libavutil/tests/fifo.c

@@ -30,14 +30,6 @@ int main(void)
     for (i = 0; av_fifo_space(fifo) >= sizeof(int); i++)
         av_fifo_generic_write(fifo, &i, sizeof(int), NULL);
 
-    /* peek at FIFO */
-    n = av_fifo_size(fifo) / sizeof(int);
-    for (i = -n + 1; i < n; i++) {
-        int *v = (int *)av_fifo_peek2(fifo, i * sizeof(int));
-        printf("%d: %d\n", i, *v);
-    }
-    printf("\n");
-
     /* peek_at at FIFO */
     n = av_fifo_size(fifo) / sizeof(int);
     for (i = 0; i < n; i++) {

libavutil/version.h

@@ -109,6 +109,7 @@
 #define FF_API_DECLARE_ALIGNED          (LIBAVUTIL_VERSION_MAJOR < 58)
 #define FF_API_COLORSPACE_NAME          (LIBAVUTIL_VERSION_MAJOR < 58)
 #define FF_API_AV_MALLOCZ_ARRAY         (LIBAVUTIL_VERSION_MAJOR < 58)
+#define FF_API_FIFO_PEEK2               (LIBAVUTIL_VERSION_MAJOR < 58)
 
 /**
  * @}

tests/ref/fate/fifo

@@ -1,29 +1,3 @@
--12: 1
--11: 2
--10: 3
--9: 4
--8: 5
--7: 6
--6: 7
--5: 8
--4: 9
--3: 10
--2: 11
--1: 12
-0: 0
-1: 1
-2: 2
-3: 3
-4: 4
-5: 5
-6: 6
-7: 7
-8: 8
-9: 9
-10: 10
-11: 11
-12: 12
-
 0: 0
 1: 1
 2: 2