From 1b4d327b1c7ab01495ea896cf9034d5eed8c4893 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Reimar=20D=C3=B6ffinger?= <Reimar.Doeffinger@gmx.de>
Date: Mon, 6 Sep 2010 17:51:44 +0000
Subject: [PATCH] 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
---
libavformat/matroskadec.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 888f099ff22..0d0285e6c0b 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -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;
}
--
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