From ff6a5fc1f0a3db6ea949e1c8738def0cfebbf57e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Reimar=20D=C3=B6ffinger?= <Reimar.Doeffinger@gmx.de>
Date: Thu, 2 Sep 2010 19:17:46 +0000
Subject: [PATCH] Optimize/simplify ebml_read_num.
Originally committed as revision 25026 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
libavformat/matroskadec.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 27dd9b2e03c..5de60fa18c5 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -538,8 +538,8 @@ static int ebml_level_end(MatroskaDemuxContext *matroska)
static int ebml_read_num(MatroskaDemuxContext *matroska, ByteIOContext *pb,
int max_size, uint64_t *number)
{
- int len_mask = 0x80, read = 1, n = 1;
- int64_t total = 0;
+ int read = 1, n = 1;
+ uint64_t total = 0;
/* The first byte tells us the length in bytes - get_byte() can normally
* return 0, but since that's not a valid first ebmlID byte, we can
@@ -556,10 +556,7 @@ static int ebml_read_num(MatroskaDemuxContext *matroska, ByteIOContext *pb,
}
/* get the length of the EBML number */
- while (read <= max_size && !(total & len_mask)) {
- read++;
- len_mask >>= 1;
- }
+ read = 8 - ff_log2_tab[total];
if (read > max_size) {
int64_t pos = url_ftell(pb) - 1;
av_log(matroska->ctx, AV_LOG_ERROR,
@@ -569,7 +566,7 @@ static int ebml_read_num(MatroskaDemuxContext *matroska, ByteIOContext *pb,
}
/* read out length */
- total &= ~len_mask;
+ total ^= 1 << ff_log2_tab[total];
while (n++ < read)
total = (total << 8) | get_byte(pb);
--
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