FFmpeg/libavcodec/startcode.c

/*
 * Copyright (c) 2003-2010 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; 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 "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 &&
            !((~*(const uint64_t *)(buf + i) &
                    (*(const uint64_t *)(buf + i) - 0x0101010101010101ULL)) &
                    0x8080808080808080ULL))
        i += 8;
#else
    while (i < size &&
            !((~*(const uint32_t *)(buf + i) &
                    (*(const uint32_t *)(buf + i) - 0x01010101U)) &
                    0x80808080U))
        i += 4;
#endif
#endif
    for (; i < size; i++)
        if (!buf[i])
            break;
    return i;
}