libavutil/intfloat_readwrite.c

   1 /*
   2  * portable IEEE float/double read/write functions
   3  *
   4  * Copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 /**
  24  * @file intfloat_readwrite.c
  25  * Portable IEEE float/double read/write functions.
  26  */
  27
  28 #include "common.h"
  29 #include "intfloat_readwrite.h"
  30
  31 double av_int2dbl(int64_t v){
  32     if(v+v > 0xFFEULL<<52)
  33         return 0.0/0.0;
  34     return ldexp(((v&((1LL<<52)-1)) + (1LL<<52)) * (v>>63|1), (v>>52&0x7FF)-1075);
  35 }
  36
  37 float av_int2flt(int32_t v){
  38     if(v+v > 0xFF000000U)
  39         return 0.0/0.0;
  40     return ldexp(((v&0x7FFFFF) + (1<<23)) * (v>>31|1), (v>>23&0xFF)-150);
  41 }
  42
  43 double av_ext2dbl(const AVExtFloat ext){
  44     uint64_t m = 0;
  45     int e, i;
  46
  47     for (i = 0; i < 8; i++)
  48         m = (m<<8) + ext.mantissa[i];
  49     e = (((int)ext.exponent[0]&0x7f)<<8) | ext.exponent[1];
  50     if (e == 0x7fff && m)
  51         return 0.0/0.0;
  52     e -= 16383 + 63;        /* In IEEE 80 bits, the whole (i.e. 1.xxxx)
  53                              * mantissa bit is written as opposed to the
  54                              * single and double precision formats */
  55     if (ext.exponent[0]&0x80)
  56         m= -m;
  57     return ldexp(m, e);
  58 }
  59
  60 int64_t av_dbl2int(double d){
  61     int e;
  62     if     ( !d) return 0;
  63     else if(d-d) return 0x7FF0000000000000LL + ((int64_t)(d<0)<<63) + (d!=d);
  64     d= frexp(d, &e);
  65     return (int64_t)(d<0)<<63 | (e+1022LL)<<52 | (int64_t)((fabs(d)-0.5)*(1LL<<53));
  66 }
  67
  68 int32_t av_flt2int(float d){
  69     int e;
  70     if     ( !d) return 0;
  71     else if(d-d) return 0x7F800000 + ((d<0)<<31) + (d!=d);
  72     d= frexp(d, &e);
  73     return (d<0)<<31 | (e+126)<<23 | (int64_t)((fabs(d)-0.5)*(1<<24));
  74 }
  75
  76 AVExtFloat av_dbl2ext(double d){
  77     struct AVExtFloat ext= {{0}};
  78     int e, i; double f; uint64_t m;
  79
  80     f = fabs(frexp(d, &e));
  81     if (f >= 0.5 && f < 1) {
  82         e += 16382;
  83         ext.exponent[0] = e>>8;
  84         ext.exponent[1] = e;
  85         m = (uint64_t)ldexp(f, 64);
  86         for (i=0; i < 8; i++)
  87             ext.mantissa[i] = m>>(56-(i<<3));
  88     } else if (f != 0.0) {
  89         ext.exponent[0] = 0x7f; ext.exponent[1] = 0xff;
  90         if (f != 1/0.0)
  91             ext.mantissa[0] = ~0;
  92     }
  93     if (d < 0)
  94         ext.exponent[0] |= 0x80;
  95     return ext;
  96 }
  97