intfloat_readwrite.c 2.87 KB
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/*
 * portable IEEE float/double read/write functions
 *
 * Copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
 * 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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 * Libav is distributed in the hope that it will be useful,
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 * 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
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 * License along with Libav; 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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 * portable IEEE float/double read/write functions
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 */
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#include <stdint.h>
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#include "mathematics.h"
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#include "intfloat_readwrite.h"
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double av_int2dbl(int64_t v){
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    if((uint64_t)v+v > 0xFFEULL<<52)
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        return NAN;
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    return ldexp(((v&((1LL<<52)-1)) + (1LL<<52)) * (v>>63|1), (v>>52&0x7FF)-1075);
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}

float av_int2flt(int32_t v){
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    if((uint32_t)v+v > 0xFF000000U)
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        return NAN;
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    return ldexp(((v&0x7FFFFF) + (1<<23)) * (v>>31|1), (v>>23&0xFF)-150);
}

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double av_ext2dbl(const AVExtFloat ext){
    uint64_t m = 0;
    int e, i;

    for (i = 0; i < 8; i++)
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        m = (m<<8) + ext.mantissa[i];
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    e = (((int)ext.exponent[0]&0x7f)<<8) | ext.exponent[1];
    if (e == 0x7fff && m)
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        return NAN;
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    e -= 16383 + 63;        /* In IEEE 80 bits, the whole (i.e. 1.xxxx)
                             * mantissa bit is written as opposed to the
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                             * single and double precision formats. */
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    if (ext.exponent[0]&0x80)
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        m= -m;
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    return ldexp(m, e);
}

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int64_t av_dbl2int(double d){
    int e;
    if     ( !d) return 0;
    else if(d-d) return 0x7FF0000000000000LL + ((int64_t)(d<0)<<63) + (d!=d);
    d= frexp(d, &e);
    return (int64_t)(d<0)<<63 | (e+1022LL)<<52 | (int64_t)((fabs(d)-0.5)*(1LL<<53));
}

int32_t av_flt2int(float d){
    int e;
    if     ( !d) return 0;
    else if(d-d) return 0x7F800000 + ((d<0)<<31) + (d!=d);
    d= frexp(d, &e);
    return (d<0)<<31 | (e+126)<<23 | (int64_t)((fabs(d)-0.5)*(1<<24));
}
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AVExtFloat av_dbl2ext(double d){
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    struct AVExtFloat ext= {{0}};
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    int e, i; double f; uint64_t m;

    f = fabs(frexp(d, &e));
    if (f >= 0.5 && f < 1) {
        e += 16382;
        ext.exponent[0] = e>>8;
        ext.exponent[1] = e;
        m = (uint64_t)ldexp(f, 64);
        for (i=0; i < 8; i++)
            ext.mantissa[i] = m>>(56-(i<<3));
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    } else if (f != 0.0) {
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        ext.exponent[0] = 0x7f; ext.exponent[1] = 0xff;
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        if (f != INFINITY)
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            ext.mantissa[0] = ~0;
    }
    if (d < 0)
        ext.exponent[0] |= 0x80;
    return ext;
}