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Add a special function to mkv demxuer to parse length values that includes 

special-case code to handle all possible encodings of "unknown length".

Originally committed as revision 25049 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Reimar Döffinger 2010-09-06 17:51:44 +00:00
parent 2b0bcfc917
commit 1b4d327b1c
1 changed files with 15 additions and 1 deletions
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16
libavformat/matroskadec.c
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@ -575,6 +575,20 @@ static int ebml_read_num(MatroskaDemuxContext *matroska, ByteIOContext *pb,
return read;
}
/**
* Read a EBML length value.
* This needs special handling for the "unknown length" case which has multiple
* encodings.
*/
static int ebml_read_length(MatroskaDemuxContext *matroska, ByteIOContext *pb,
uint64_t *number)
{
int res = ebml_read_num(matroska, pb, 8, number);
if (res > 0 && *number + 1 == 1ULL << (7 * res))
*number = 0xffffffffffffffULL;
return res;
}
/*
* Read the next element as an unsigned int.
* 0 is success, < 0 is failure.
@ -782,7 +796,7 @@ static int ebml_parse_elem(MatroskaDemuxContext *matroska,
if (syntax->type != EBML_PASS && syntax->type != EBML_STOP) {
matroska->current_id = 0;
if ((res = ebml_read_num(matroska, pb, 8, &length)) < 0)
if ((res = ebml_read_length(matroska, pb, &length)) < 0)
return res;
}