avutil: Add functions for allocating opaque contexts for algorithms

The current API where the plain size is exposed is not of much
use - in most cases it is allocated dynamically anyway.

If allocated e.g. on the stack via an uint8_t array, there's no
guarantee that the struct's members are aligned properly (unless
the array is overallocated and the opaque pointer within it
manually aligned to some unspecified alignment).

Signed-off-by: Martin Storsjö <martin@martin.st>

1 files changed, 7 insertions, 0 deletions

diff --git a/libavutil/tree.c b/libavutil/tree.c
index 0e68bb75f1..55dcbc59a7 100644
--- a/libavutil/tree.c
+++ b/libavutil/tree.c
@@ -28,7 +28,14 @@ typedef struct AVTreeNode {
     int state;
 } AVTreeNode;
 
+#if FF_API_CONTEXT_SIZE
 const int av_tree_node_size = sizeof(AVTreeNode);
+#endif
+
+struct AVTreeNode *av_tree_node_alloc(void)
+{
+    return av_mallocz(sizeof(struct AVTreeNode));
+}
 
 void *av_tree_find(const AVTreeNode *t, void *key,
                    int (*cmp)(void *key, const void *b), void *next[2])