intfloat_readwrite.c
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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 Libav.
7  *
8  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
28 #include <stdint.h>
29 #include "mathematics.h"
30 #include "intfloat_readwrite.h"
31 
32 double av_int2dbl(int64_t v){
33  if((uint64_t)v+v > 0xFFEULL<<52)
34  return NAN;
35  return ldexp(((v&((1LL<<52)-1)) + (1LL<<52)) * (v>>63|1), (v>>52&0x7FF)-1075);
36 }
37 
38 float av_int2flt(int32_t v){
39  if((uint32_t)v+v > 0xFF000000U)
40  return NAN;
41  return ldexp(((v&0x7FFFFF) + (1<<23)) * (v>>31|1), (v>>23&0xFF)-150);
42 }
43 
44 double av_ext2dbl(const AVExtFloat ext){
45  uint64_t m = 0;
46  int e, i;
47 
48  for (i = 0; i < 8; i++)
49  m = (m<<8) + ext.mantissa[i];
50  e = (((int)ext.exponent[0]&0x7f)<<8) | ext.exponent[1];
51  if (e == 0x7fff && m)
52  return NAN;
53  e -= 16383 + 63; /* In IEEE 80 bits, the whole (i.e. 1.xxxx)
54  * mantissa bit is written as opposed to the
55  * single and double precision formats. */
56  if (ext.exponent[0]&0x80)
57  m= -m;
58  return ldexp(m, e);
59 }
60 
61 int64_t av_dbl2int(double d){
62  int e;
63  if ( !d) return 0;
64  else if(d-d) return 0x7FF0000000000000LL + ((int64_t)(d<0)<<63) + (d!=d);
65  d= frexp(d, &e);
66  return (int64_t)(d<0)<<63 | (e+1022LL)<<52 | (int64_t)((fabs(d)-0.5)*(1LL<<53));
67 }
68 
69 int32_t av_flt2int(float d){
70  int e;
71  if ( !d) return 0;
72  else if(d-d) return 0x7F800000 + ((d<0)<<31) + (d!=d);
73  d= frexp(d, &e);
74  return (d<0)<<31 | (e+126)<<23 | (int64_t)((fabs(d)-0.5)*(1<<24));
75 }
76 
78  struct AVExtFloat ext= {{0}};
79  int e, i; double f; uint64_t m;
80 
81  f = fabs(frexp(d, &e));
82  if (f >= 0.5 && f < 1) {
83  e += 16382;
84  ext.exponent[0] = e>>8;
85  ext.exponent[1] = e;
86  m = (uint64_t)ldexp(f, 64);
87  for (i=0; i < 8; i++)
88  ext.mantissa[i] = m>>(56-(i<<3));
89  } else if (f != 0.0) {
90  ext.exponent[0] = 0x7f; ext.exponent[1] = 0xff;
91  if (f != INFINITY)
92  ext.mantissa[0] = ~0;
93  }
94  if (d < 0)
95  ext.exponent[0] |= 0x80;
96  return ext;
97 }
98