avutil/buffer: add av_buffer_pool_buffer_get_opaque

In order to access the original opaque parameter of a buffer in the buffer
pool. (The buffer pool implementation overrides the normal opaque parameter but
also saves it so it is accessible).

v2: add assertion check before dereferencing the BufferPoolEntry.

Signed-off-by: Marton Balint <cus@passwd.hu>

doc/APIchanges

@@ -15,6 +15,9 @@ libavutil:     2017-10-21
 
 API changes, most recent first:
 
+2019-12-xx - xxxxxxxxxx - lavu 56.37.100 - buffer.h
+  Add av_buffer_pool_buffer_get_opaque().
+
 2019-11-17 - 1c23abc88f - lavu 56.36.100 - eval API
   Add av_expr_count_vars().
 

libavutil/buffer.c

@@ -20,6 +20,7 @@
 #include <stdint.h>
 #include <string.h>
 
+#include "avassert.h"
 #include "buffer_internal.h"
 #include "common.h"
 #include "mem.h"
@@ -355,3 +356,10 @@ AVBufferRef *av_buffer_pool_get(AVBufferPool *pool)
 
     return ret;
 }
+
+void *av_buffer_pool_buffer_get_opaque(AVBufferRef *ref)
+{
+    BufferPoolEntry *buf = ref->buffer->opaque;
+    av_assert0(buf);
+    return buf->opaque;
+}

libavutil/buffer.h

@@ -284,6 +284,19 @@ void av_buffer_pool_uninit(AVBufferPool **pool);
  */
 AVBufferRef *av_buffer_pool_get(AVBufferPool *pool);
 
+/**
+ * Query the original opaque parameter of an allocated buffer in the pool.
+ *
+ * @param ref a buffer reference to a buffer returned by av_buffer_pool_get.
+ * @return the opaque parameter set by the buffer allocator function of the
+ *         buffer pool.
+ *
+ * @note the opaque parameter of ref is used by the buffer pool implementation,
+ * therefore you have to use this function to access the original opaque
+ * parameter of an allocated buffer.
+ */
+void *av_buffer_pool_buffer_get_opaque(AVBufferRef *ref);
+
 /**
  * @}
  */

libavutil/version.h

@@ -79,8 +79,8 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  56
-#define LIBAVUTIL_VERSION_MINOR  36
+#define LIBAVUTIL_VERSION_MINOR  37
-#define LIBAVUTIL_VERSION_MICRO 101
+#define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
                                                LIBAVUTIL_VERSION_MINOR, \