[FFmpeg-cvslog] r24478 - trunk/libavformat/aviobuf.c

[mstorsjo]

Author: mstorsjo
Date: Sat Jul 24 11:04:44 2010
New Revision: 24478

Log:
Never shrink the ByteIOContext buffer in ff_rewind_with_probe_data

If there is little unread data in the ByteIOContext buffer, this may lead
to reducing the size of the ByteIOContext buffer to little more the probe
data size. This can lead to suboptimal aviobuf behaviour, e.g. making some
demuxers fail to do short seeks backwards (if the input isn't seekable).

Modified:
   trunk/libavformat/aviobuf.c

Modified: trunk/libavformat/aviobuf.c
==============================================================================
--- trunk/libavformat/aviobuf.c	Sat Jul 24 10:43:52 2010	(r24477)
+++ trunk/libavformat/aviobuf.c	Sat Jul 24 11:04:44 2010	(r24478)
@@ -667,7 +667,7 @@ int ff_rewind_with_probe_data(ByteIOCont
 {
     int64_t buffer_start;
     int buffer_size;
-    int overlap, new_size;
+    int overlap, new_size, alloc_size;
 
     if (s->write_flag)
         return AVERROR(EINVAL);
@@ -681,17 +681,20 @@ int ff_rewind_with_probe_data(ByteIOCont
     overlap = buf_size - buffer_start;
     new_size = buf_size + buffer_size - overlap;
 
-    if (new_size > buf_size) {
-        if (!(buf = av_realloc(buf, new_size)))
+    alloc_size = FFMAX(s->buffer_size, new_size);
+    if (alloc_size > buf_size)
+        if (!(buf = av_realloc(buf, alloc_size)))
             return AVERROR(ENOMEM);
 
+    if (new_size > buf_size) {
         memcpy(buf + buf_size, s->buffer + overlap, buffer_size - overlap);
         buf_size = new_size;
     }
 
     av_free(s->buffer);
     s->buf_ptr = s->buffer = buf;
-    s->pos = s->buffer_size = buf_size;
+    s->buffer_size = alloc_size;
+    s->pos = buf_size;
     s->buf_end = s->buf_ptr + buf_size;
     s->eof_reached = 0;
     s->must_flush = 0;