Make av_fifo*_read() ignore the available amount of data.

This is more efficient as in practice the check is redundant most of the
time. Callers which do not know if enough data is available have to check
it with av_fifo_size(). Doing the check in *read() means the caller has
no choice to skip the check when its known to be redundant.
Also the return value was never documented in a public header so
changing it should not break the API. Besides this fixes the case where
read() failed on a 100% full fifo.

Originally committed as revision 13404 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -592,10 +592,12 @@ static void do_audio_out(AVFormatContext *s,
 
         frame_bytes = enc->frame_size * 2 * enc->channels;
 
-        while (av_fifo_read(&ost->fifo, audio_buf, frame_bytes) == 0) {
+        while (av_fifo_size(&ost->fifo) >= frame_bytes) {
             AVPacket pkt;
             av_init_packet(&pkt);
 
+            av_fifo_read(&ost->fifo, audio_buf, frame_bytes);
+
             //FIXME pass ost->sync_opts as AVFrame.pts in avcodec_encode_audio()
 
             ret = avcodec_encode_audio(enc, audio_out, audio_out_size,
@@ -1385,9 +1387,8 @@ static int output_packet(AVInputStream *ist, int ist_index,
                             if(fifo_bytes > 0 && enc->codec->capabilities & CODEC_CAP_SMALL_LAST_FRAME) {
                                 int fs_tmp = enc->frame_size;
                                 enc->frame_size = fifo_bytes / (2 * enc->channels);
-                                if(av_fifo_read(&ost->fifo, (uint8_t *)samples, fifo_bytes) == 0) {
+                                av_fifo_read(&ost->fifo, (uint8_t *)samples, fifo_bytes);
                                     ret = avcodec_encode_audio(enc, bit_buffer, bit_buffer_size, samples);
-                                }
                                 enc->frame_size = fs_tmp;
                             }
                             if(ret <= 0) {

libavformat/mpegenc.c

@@ -913,8 +913,8 @@ static int flush_packet(AVFormatContext *ctx, int stream_index,
         }
 
         /* output data */
-        if(av_fifo_generic_read(&stream->fifo, payload_size - stuffing_size, &put_buffer, ctx->pb) < 0)
-            return -1;
+        assert(payload_size - stuffing_size <= av_fifo_size(&stream->fifo));
+        av_fifo_generic_read(&stream->fifo, payload_size - stuffing_size, &put_buffer, ctx->pb);
         stream->bytes_to_iframe -= payload_size - stuffing_size;
     }else{
         payload_size=

libavutil/fifo.c

@@ -45,9 +45,6 @@ int av_fifo_size(AVFifoBuffer *f)
     return size;
 }
 
-/**
- * Get data from the fifo (returns -1 if not enough data).
- */
 int av_fifo_read(AVFifoBuffer *f, uint8_t *buf, int buf_size)
 {
     return av_fifo_generic_read(f, buf_size, NULL, buf);
@@ -97,13 +94,8 @@ int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size, int (*func)(void
 }
 
 
-/** get data from the fifo (return -1 if not enough data) */
 int av_fifo_generic_read(AVFifoBuffer *f, int buf_size, void (*func)(void*, void*, int), void* dest)
 {
-    int size = av_fifo_size(f);
-
-    if (size < buf_size)
-        return -1;
     do {
         int len = FFMIN(f->end - f->rptr, buf_size);
         if(func) func(dest, f->rptr, len);