Separate the packet fetching from the data reading, so that the data reading

function is assured to parse at most one packet. This makes this function
useful for ASF data packet parsing in a "push-mode" in addition to the
current "pull-mode", and therefore allows for use of these functions in,
for example, the RTSP demuxer (for MS-RTSP support). Tested to give identical
output before and after for regular ASF playback, also see discussion in the
ML thread "[PATCH] asf.c: move packet_time_start=0 statement". Testsuite also
works after the patch, tested by Benoit Fouet.

Originally committed as revision 16108 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/asf.c

@@ -705,7 +705,13 @@ static int asf_read_frame_header(AVFormatContext *s){
     return 0;
 }
 
-static int asf_read_packet(AVFormatContext *s, AVPacket *pkt)
+/**
+ * Parse data from individual ASF packets (which were previously loaded
+ * with asf_get_packet()).
+ * @returns 0 if data was stored in pkt, <0 on error or 1 if more ASF
+ *          packets need to be loaded (through asf_get_packet())
+ */
+static int asf_parse_packet(AVFormatContext *s, AVPacket *pkt)
 {
     ASFContext *asf = s->priv_data;
     ASFStream *asf_st = 0;
@@ -726,11 +732,7 @@ static int asf_read_packet(AVFormatContext *s, AVPacket *pkt)
             if (asf->data_object_size != (uint64_t)-1 &&
                 (asf->packet_pos - asf->data_object_offset >= asf->data_object_size))
                 return AVERROR(EIO); /* Do not exceed the size of the data object */
-            ret = asf_get_packet(s);
-            if (ret < 0)
-                assert(asf->packet_size_left < FRAME_HEADER_SIZE || asf->packet_segments < 1);
-            asf->packet_time_start = 0;
-            continue;
+            return 1;
         }
         if (asf->packet_time_start == 0) {
             if(asf_read_frame_header(s) < 0){
@@ -877,6 +879,24 @@ static int asf_read_packet(AVFormatContext *s, AVPacket *pkt)
     return 0;
 }
 
+static int asf_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    ASFContext *asf = s->priv_data;
+
+    for (;;) {
+        int ret;
+
+        /* parse cached packets, if any */
+        if ((ret = asf_parse_packet(s, pkt)) <= 0)
+            return ret;
+        if ((ret = asf_get_packet(s)) < 0)
+            assert(asf->packet_size_left < FRAME_HEADER_SIZE || asf->packet_segments < 1);
+        asf->packet_time_start = 0;
+    }
+
+    return 0;
+}
+
 // Added to support seeking after packets have been read
 // If information is not reset, read_packet fails due to
 // leftover information from previous reads