FFmpeg
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
intfloat_readwrite.c
Go to the documentation of this file.
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
25  * portable IEEE float/double read/write functions
26  */
27 
28 #include <stdint.h>
29 #include "common.h"
30 #include "mathematics.h"
31 #include "intfloat_readwrite.h"
32 
33 double av_int2dbl(int64_t v){
34  if((uint64_t)v+v > 0xFFEULL<<52)
35  return NAN;
36  return ldexp(((v&((1LL<<52)-1)) + (1LL<<52)) * (v>>63|1), (v>>52&0x7FF)-1075);
37 }
38 
40  if((uint32_t)v+v > 0xFF000000U)
41  return NAN;
42  return ldexp(((v&0x7FFFFF) + (1<<23)) * (v>>31|1), (v>>23&0xFF)-150);
43 }
44 
45 double av_ext2dbl(const AVExtFloat ext){
46  uint64_t m = 0;
47  int e, i;
48 
49  for (i = 0; i < 8; i++)
50  m = (m<<8) + ext.mantissa[i];
51  e = (((int)ext.exponent[0]&0x7f)<<8) | ext.exponent[1];
52  if (e == 0x7fff && m)
53  return NAN;
54  e -= 16383 + 63; /* In IEEE 80 bits, the whole (i.e. 1.xxxx)
55  * mantissa bit is written as opposed to the
56  * single and double precision formats. */
57  if (ext.exponent[0]&0x80)
58  m= -m;
59  return ldexp(m, e);
60 }
61 
62 int64_t av_dbl2int(double d){
63  int e;
64  if ( !d) return 0;
65  else if(d-d) return 0x7FF0000000000000LL + ((int64_t)(d<0)<<63) + (d!=d);
66  d= frexp(d, &e);
67  return (int64_t)(d<0)<<63 | (e+1022LL)<<52 | (int64_t)((fabs(d)-0.5)*(1LL<<53));
68 }
69 
71  int e;
72  if ( !d) return 0;
73  else if(d-d) return 0x7F800000 + ((d<0)<<31) + (d!=d);
74  d= frexp(d, &e);
75  return (d<0)<<31 | (e+126)<<23 | (int64_t)((fabs(d)-0.5)*(1<<24));
76 }
77 
79  struct AVExtFloat ext= {{0}};
80  int e, i; double f; uint64_t m;
81 
82  f = fabs(frexp(d, &e));
83  if (f >= 0.5 && f < 1) {
84  e += 16382;
85  ext.exponent[0] = e>>8;
86  ext.exponent[1] = e;
87  m = (uint64_t)ldexp(f, 64);
88  for (i=0; i < 8; i++)
89  ext.mantissa[i] = m>>(56-(i<<3));
90  } else if (f != 0.0) {
91  ext.exponent[0] = 0x7f; ext.exponent[1] = 0xff;
92  if (!isinf(f))
93  ext.mantissa[0] = ~0;
94  }
95  if (d < 0)
96  ext.exponent[0] |= 0x80;
97  return ext;
98 }