FFmpeg/libavutil/intmath.h

/*
 * Copyright (c) 2010 Mans Rullgard <mans@mansr.com>
 *
 * 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
 */

#ifndef AVUTIL_INTMATH_H
#define AVUTIL_INTMATH_H

#include <stdint.h>
#include "config.h"
#include "attributes.h"

/**
 * @addtogroup lavu_internal
 * @{
 */

extern const uint32_t ff_inverse[257];

#if   ARCH_ARM
#   include "arm/intmath.h"
#endif

#if HAVE_FAST_CLZ && AV_GCC_VERSION_AT_LEAST(3,4)

#ifndef av_log2
#   define av_log2(x) (31 - __builtin_clz((x)|1))
#   ifndef av_log2_16bit
#      define av_log2_16bit av_log2
#   endif
#endif /* av_log2 */

#endif /* AV_GCC_VERSION_AT_LEAST(3,4) */

#ifndef FASTDIV
#   define FASTDIV(a,b) ((uint32_t)((((uint64_t)a) * ff_inverse[b]) >> 32))
#endif /* FASTDIV */

#include "common.h"

extern const uint8_t ff_sqrt_tab[256];

static inline av_const unsigned int ff_sqrt(unsigned int a)
{
    unsigned int b;

    if (a < 255) return (ff_sqrt_tab[a + 1] - 1) >> 4;
    else if (a < (1 << 12)) b = ff_sqrt_tab[a >> 4] >> 2;
#if !CONFIG_SMALL
    else if (a < (1 << 14)) b = ff_sqrt_tab[a >> 6] >> 1;
    else if (a < (1 << 16)) b = ff_sqrt_tab[a >> 8]   ;
#endif
    else {
        int s = av_log2_16bit(a >> 16) >> 1;
        unsigned int c = a >> (s + 2);
        b = ff_sqrt_tab[c >> (s + 8)];
        b = FASTDIV(c,b) + (b << s);
    }

    return b - (a < b * b);
}

/**
 * @}
 */
#endif /* AVUTIL_INTMATH_H */