[FFmpeg-devel] [PATCH 2/2] lavf/id3v2: seek back to previous offset if header size is not matched

[Matthieu Bouron]

On Sat, Jan 19, 2013 at 03:22:49PM +0100, Matthieu Bouron wrote:
> On Sat, Jan 19, 2013 at 02:41:00PM +0100, Michael Niedermayer wrote:
> > On Sat, Jan 19, 2013 at 01:38:27PM +0100, Matthieu Bouron wrote:
> > > ---
> > >  libavformat/id3v2.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
> > > index 98f8f9e..2cab5ac 100644
> > > --- a/libavformat/id3v2.c
> > > +++ b/libavformat/id3v2.c
> > > @@ -788,8 +788,10 @@ void ff_id3v2_read(AVFormatContext *s, const char *magic, ID3v2ExtraMeta **extra
> > >          /* save the current offset in case there's nothing to read/skip */
> > >          off = avio_tell(s->pb);
> > >          ret = avio_read(s->pb, buf, ID3v2_HEADER_SIZE);
> > > -        if (ret != ID3v2_HEADER_SIZE)
> > > +        if (ret != ID3v2_HEADER_SIZE) {
> > > +            avio_seek(s->pb, off, SEEK_SET);
> > >              break;
> > > +        }
> > 
> > the change looks fine but please explain (also in the commit message)
> > why this change is done
> > 
> 
> New patch attached including commit description.
> 
> [...]
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>From 14f743ce5c4847e78e99d8e60f81b015c999a94c Mon Sep 17 00:00:00 2001
From: Matthieu Bouron <matthieu.bouron at gmail.com>
Date: Sat, 19 Jan 2013 13:32:58 +0100
Subject: [PATCH 2/2] lavf/id3v2: seek back to previous offset if header size
 is not matched

Makes ff_id3v2_read reset stream position at the end of ID3 data if the
header size is not matched (caused by an EOF for example).

Current behaviour (without the patch):
    filesize = 400
    id3 data size = 399
    file offset after ff_id3v2_read is 400 instead of 399
---
 libavformat/id3v2.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
index 98f8f9e..2cab5ac 100644
--- a/libavformat/id3v2.c
+++ b/libavformat/id3v2.c
@@ -788,8 +788,10 @@ void ff_id3v2_read(AVFormatContext *s, const char *magic, ID3v2ExtraMeta **extra
         /* save the current offset in case there's nothing to read/skip */
         off = avio_tell(s->pb);
         ret = avio_read(s->pb, buf, ID3v2_HEADER_SIZE);
-        if (ret != ID3v2_HEADER_SIZE)
+        if (ret != ID3v2_HEADER_SIZE) {
+            avio_seek(s->pb, off, SEEK_SET);
             break;
+        }
         found_header = ff_id3v2_match(buf, magic);
         if (found_header) {
             /* parse ID3v2 header */
-- 
1.8.1.1