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>

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:     2012-10-22
 
 API changes, most recent first:
 
+2013-06-xx - xxxxxxx - lavu 52.13.0 - mem.h
+  Add av_realloc_array and av_reallocp_array
+
 2013-05-xx - xxxxxxx - lavfi 3.10.0 - avfilter.h
   Add support for slice multithreading to lavfi. Filters supporting threading
   are marked with AVFILTER_FLAG_SLICE_THREADS.

libavutil/mem.c

@@ -136,6 +136,32 @@ void *av_realloc(void *ptr, size_t size)
 #endif
 }
 
+void *av_realloc_array(void *ptr, size_t nmemb, size_t size)
+{
+    if (size <= 0 || nmemb >= INT_MAX / size)
+        return NULL;
+    return av_realloc(ptr, nmemb * size);
+}
+
+int av_reallocp_array(void *ptr, size_t nmemb, size_t size)
+{
+    void **ptrptr = ptr;
+    void *ret;
+    if (size <= 0 || nmemb >= INT_MAX / size)
+        return AVERROR(ENOMEM);
+    if (nmemb <= 0) {
+        av_freep(ptr);
+        return 0;
+    }
+    ret = av_realloc(*ptrptr, nmemb * size);
+    if (!ret) {
+        av_freep(ptr);
+        return AVERROR(ENOMEM);
+    }
+    *ptrptr = ret;
+    return 0;
+}
+
 void av_free(void *ptr)
 {
 #if CONFIG_MEMALIGN_HACK

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().

libavutil/version.h

@@ -37,7 +37,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR 52
-#define LIBAVUTIL_VERSION_MINOR 12
+#define LIBAVUTIL_VERSION_MINOR 13
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \