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ffmpeg / libavutil / intmath.h @ 08675bb3

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/*
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 * Copyright (c) 2010 Mans Rullgard <mans@mansr.com>
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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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#ifndef AVUTIL_INTMATH_H
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#define AVUTIL_INTMATH_H
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#include <stdint.h>
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#include "config.h"
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#include "attributes.h"
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extern const uint32_t ff_inverse[257];
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#if   ARCH_ARM
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#   include "arm/intmath.h"
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#elif ARCH_X86
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#   include "x86/intmath.h"
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#endif
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#if HAVE_FAST_CLZ && AV_GCC_VERSION_AT_LEAST(3,4)
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#ifndef av_log2
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#   define av_log2(x) (31 - __builtin_clz((x)|1))
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#   ifndef av_log2_16bit
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#      define av_log2_16bit av_log2
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#   endif
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#endif /* av_log2 */
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#endif /* AV_GCC_VERSION_AT_LEAST(3,4) */
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#ifndef FASTDIV
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#   if CONFIG_FASTDIV
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#       define FASTDIV(a,b) ((uint32_t)((((uint64_t)a) * ff_inverse[b]) >> 32))
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#   else
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#       define FASTDIV(a,b) ((a) / (b))
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#   endif
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#endif /* FASTDIV */
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#include "common.h"
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extern const uint8_t ff_sqrt_tab[256];
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static inline av_const unsigned int ff_sqrt(unsigned int a)
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{
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    unsigned int b;
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    if (a < 255) return (ff_sqrt_tab[a + 1] - 1) >> 4;
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    else if (a < (1 << 12)) b = ff_sqrt_tab[a >> 4] >> 2;
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#if !CONFIG_SMALL
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    else if (a < (1 << 14)) b = ff_sqrt_tab[a >> 6] >> 1;
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    else if (a < (1 << 16)) b = ff_sqrt_tab[a >> 8]   ;
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#endif
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    else {
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        int s = av_log2_16bit(a >> 16) >> 1;
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        unsigned int c = a >> (s + 2);
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        b = ff_sqrt_tab[c >> (s + 8)];
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        b = FASTDIV(c,b) + (b << s);
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    }
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    return b - (a < b * b);
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}
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#endif /* AVUTIL_INTMATH_H */