mem: Add av_realloc_array and av_reallocp_array

These help avoiding overflows and simplify error handling.

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

libavutil/mem.h

@@ -111,6 +111,32 @@ av_alloc_size(1, 2) static inline void *av_malloc_array(size_t nmemb, size_t siz
  */
 void *av_realloc(void *ptr, size_t size) av_alloc_size(2);
 
+/**
+ * Allocate or reallocate an array.
+ * If ptr is NULL and nmemb > 0, allocate a new block. If
+ * nmemb is zero, free the memory block pointed to by ptr.
+ * @param ptr Pointer to a memory block already allocated with
+ * av_malloc(z)() or av_realloc() or NULL.
+ * @param nmemb Number of elements
+ * @param size Size of the single element
+ * @return Pointer to a newly reallocated block or NULL if the block
+ * cannot be reallocated or the function is used to free the memory block.
+ */
+av_alloc_size(2, 3) void *av_realloc_array(void *ptr, size_t nmemb, size_t size);
+
+/**
+ * Allocate or reallocate an array.
+ * If *ptr is NULL and nmemb > 0, allocate a new block. If
+ * nmemb is zero, free the memory block pointed to by ptr.
+ * @param ptr Pointer to a pointer to a memory block already allocated
+ * with av_malloc(z)() or av_realloc(), or pointer to a pointer to NULL.
+ * The pointer is updated on success, or freed on failure.
+ * @param nmemb Number of elements
+ * @param size Size of the single element
+ * @return Zero on success, an AVERROR error code on failure.
+ */
+av_alloc_size(2, 3) int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
+
 /**
  * Free a memory block which has been allocated with av_malloc(z)() or
  * av_realloc().