lavu/fifo: add av_fifo_alloc_array function

Allows to alloc fifo buffer by passing
number of elements and size of element.
Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>

doc/APIchanges

@@ -15,6 +15,9 @@ libavutil:     2012-10-22
 
 API changes, most recent first:
 
+2014-05-xx - xxxxxxx - lavu 52.86.100 - fifo.h
+  Add av_fifo_alloc_array() function.
+
 2014-05-xx - xxxxxxx - lavu 53.15.0 - frame.h, display.h
   Add AV_FRAME_DATA_DISPLAYMATRIX for exporting frame-level
   spatial rendering on video frames for proper display.

libavutil/fifo.c

@@ -24,19 +24,34 @@
 #include "common.h"
 #include "fifo.h"
 
-AVFifoBuffer *av_fifo_alloc(unsigned int size)
+static AVFifoBuffer *fifo_alloc_common(void *buffer, size_t size)
 {
-    AVFifoBuffer *f = av_mallocz(sizeof(AVFifoBuffer));
-    if (!f)
+    AVFifoBuffer *f;
+    if (!buffer)
+        return NULL;
+    f = av_mallocz(sizeof(AVFifoBuffer));
+    if (!f) {
+        av_free(buffer);
         return NULL;
-    f->buffer = av_malloc(size);
+    }
+    f->buffer = buffer;
     f->end    = f->buffer + size;
     av_fifo_reset(f);
-    if (!f->buffer)
-        av_freep(&f);
     return f;
 }
 
+AVFifoBuffer *av_fifo_alloc(unsigned int size)
+{
+    void *buffer = av_malloc(size);
+    return fifo_alloc_common(buffer, size);
+}
+
+AVFifoBuffer *av_fifo_alloc_array(size_t nmemb, size_t size)
+{
+    void *buffer = av_malloc_array(nmemb, size);
+    return fifo_alloc_common(buffer, nmemb * size);
+}
+
 void av_fifo_free(AVFifoBuffer *f)
 {
     if (f) {

libavutil/fifo.h

@@ -41,6 +41,14 @@ typedef struct AVFifoBuffer {
  */
 AVFifoBuffer *av_fifo_alloc(unsigned int size);
 
+/**
+ * Initialize an AVFifoBuffer.
+ * @param nmemb number of elements
+ * @param size  size of the single element
+ * @return AVFifoBuffer or NULL in case of memory allocation failure
+ */
+AVFifoBuffer *av_fifo_alloc_array(size_t nmemb, size_t size);
+
 /**
  * Free an AVFifoBuffer.
  * @param f AVFifoBuffer to free

libavutil/version.h

@@ -56,7 +56,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  52
-#define LIBAVUTIL_VERSION_MINOR  85
+#define LIBAVUTIL_VERSION_MINOR  86
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \