mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-11-26 19:01:44 +02:00
30e1f5ec77
Up until now, ff_startcode_find_candidate_c() simply casts an uint8_t* to uint64_t*/uint32_t* to read 64/32 bits at a time in case HAVE_FAST_UNALIGNED is true. Yet this ignores the alignment requirement of these types as well as effective type rules of the C standard. This commit therefore replaces these direct accesses with AV_RN64/32; this also improves readability. UBSan reported these unaligned accesses which happened in 233 FATE-tests involving H.264 and VC-1 (this has also been reported in tickets #8138 and #8485); these tests are fixed by this commit. The output of GCC with -O3 is unchanged for aarch64, loongarch, ppc and x64 (as well as for arches like alpha for which HAVE_FAST_UNALIGNED is never true in the first place). There was only a slight difference for mips and arm. I don't know about the speed impact of them. Reviewed-by: Anton Khirnov <anton@khirnov.net> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
59 lines
1.8 KiB
C
59 lines
1.8 KiB
C
/*
|
|
* Copyright (c) 2003-2010 Michael Niedermayer <michaelni@gmx.at>
|
|
*
|
|
* This file is part of FFmpeg.
|
|
*
|
|
* FFmpeg is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* FFmpeg is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with FFmpeg; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
* Accelerated start code search function for start codes common to
|
|
* MPEG-1/2/4 video, VC-1, H.264/5
|
|
* @author Michael Niedermayer <michaelni@gmx.at>
|
|
*/
|
|
|
|
#include "libavutil/intreadwrite.h"
|
|
#include "startcode.h"
|
|
#include "config.h"
|
|
|
|
int ff_startcode_find_candidate_c(const uint8_t *buf, int size)
|
|
{
|
|
int i = 0;
|
|
#if HAVE_FAST_UNALIGNED
|
|
/* we check i < size instead of i + 3 / 7 because it is
|
|
* simpler and there must be AV_INPUT_BUFFER_PADDING_SIZE
|
|
* bytes at the end.
|
|
*/
|
|
#if HAVE_FAST_64BIT
|
|
while (i < size &&
|
|
!((~AV_RN64(buf + i) &
|
|
(AV_RN64(buf + i) - 0x0101010101010101ULL)) &
|
|
0x8080808080808080ULL))
|
|
i += 8;
|
|
#else
|
|
while (i < size &&
|
|
!((~AV_RN32(buf + i) &
|
|
(AV_RN32(buf + i) - 0x01010101U)) &
|
|
0x80808080U))
|
|
i += 4;
|
|
#endif
|
|
#endif
|
|
for (; i < size; i++)
|
|
if (!buf[i])
|
|
break;
|
|
return i;
|
|
}
|