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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
/*
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* Copyright (c) 2003-2010 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* Accelerated start code search function for start codes common to
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* MPEG-1/2/4 video, VC-1, H.264/5
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* @author Michael Niedermayer <michaelni@gmx.at>
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*/
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#include "libavutil/intreadwrite.h"
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#include "startcode.h"
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#include "config.h"
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int ff_startcode_find_candidate_c(const uint8_t *buf, int size)
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{
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int i = 0;
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#if HAVE_FAST_UNALIGNED
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/* we check i < size instead of i + 3 / 7 because it is
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* simpler and there must be AV_INPUT_BUFFER_PADDING_SIZE
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* bytes at the end.
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*/
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#if HAVE_FAST_64BIT
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while (i < size &&
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!((~AV_RN64(buf + i) &
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(AV_RN64(buf + i) - 0x0101010101010101ULL)) &
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0x8080808080808080ULL))
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i += 8;
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#else
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while (i < size &&
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!((~AV_RN32(buf + i) &
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(AV_RN32(buf + i) - 0x01010101U)) &
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0x80808080U))
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i += 4;
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#endif
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#endif
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for (; i < size; i++)
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if (!buf[i])
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break;
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return i;
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}
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