Add av_fifo_reset function to completely reset fifo state, which makes

it easier to reuse the fifo.

Originally committed as revision 17901 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/fifo.c

@@ -27,9 +27,9 @@ AVFifoBuffer *av_fifo_alloc(unsigned int size)
     AVFifoBuffer *f= av_mallocz(sizeof(AVFifoBuffer));
     if(!f)
         return NULL;
-    f->wptr = f->rptr =
     f->buffer = av_malloc(size);
     f->end = f->buffer + size;
+    av_fifo_reset(f);
     if (!f->buffer)
         av_freep(&f);
     return f;
@@ -43,6 +43,12 @@ void av_fifo_free(AVFifoBuffer *f)
     }
 }
 
+void av_fifo_reset(AVFifoBuffer *f)
+{
+    f->wptr = f->rptr = f->buffer;
+    f->wndx = f->rndx = 0;
+}
+
 int av_fifo_size(AVFifoBuffer *f)
 {
     return (uint32_t)(f->wndx - f->rndx);

libavutil/fifo.h

@@ -47,6 +47,12 @@ AVFifoBuffer *av_fifo_alloc(unsigned int size);
  */
 void av_fifo_free(AVFifoBuffer *f);
 
+/**
+ * Resets the AVFifoBuffer to the state right after av_fifo_alloc, in particular it is emptied.
+ * @param *f AVFifoBuffer to reset
+ */
+void av_fifo_reset(AVFifoBuffer *f);
+
 /**
  * Returns the amount of data in bytes in the AVFifoBuffer, that is the
  * amount of data you can read from it.