1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
/* @(#)z_frexp.c 1.0 98/08/13 */
/*
FUNCTION
<<frexp>>, <<frexpf>>---split floating-point number
INDEX
frexp
INDEX
frexpf
ANSI_SYNOPSIS
#include <math.h>
double frexp(double <[val]>, int *<[exp]>);
float frexpf(float <[val]>, int *<[exp]>);
TRAD_SYNOPSIS
#include <math.h>
double frexp(<[val]>, <[exp]>)
double <[val]>;
int *<[exp]>;
float frexpf(<[val]>, <[exp]>)
float <[val]>;
int *<[exp]>;
DESCRIPTION
All nonzero, normal numbers can be described as <[m]> * 2**<[p]>.
<<frexp>> represents the double <[val]> as a mantissa <[m]>
and a power of two <[p]>. The resulting mantissa will always
be greater than or equal to <<0.5>>, and less than <<1.0>> (as
long as <[val]> is nonzero). The power of two will be stored
in <<*>><[exp]>.
@ifnottex
<[m]> and <[p]> are calculated so that
<[val]> is <[m]> times <<2>> to the power <[p]>.
@end ifnottex
@tex
<[m]> and <[p]> are calculated so that
$ val = m \times 2^p $.
@end tex
<<frexpf>> is identical, other than taking and returning
floats rather than doubles.
RETURNS
<<frexp>> returns the mantissa <[m]>. If <[val]> is <<0>>, infinity,
or Nan, <<frexp>> will set <<*>><[exp]> to <<0>> and return <[val]>.
PORTABILITY
<<frexp>> is ANSI.
<<frexpf>> is an extension.
*/
/*****************************************************************
* frexp
*
* Input:
* d - floating point value
* exp - exponent value
*
* Output:
* A floating point value in the range [0.5, 1).
*
* Description:
* This routine breaks a floating point value into a number f and
* an exponent exp such that d = f * 2 ^ exp.
*
*****************************************************************/
#include "fdlibm.h"
#include "zmath.h"
#ifndef _DOUBLE_IS_32BITS
double frexp (double d, int *exp)
{
double f;
__uint32_t hd, ld, hf, lf;
/* Check for special values. */
switch (numtest (d))
{
case NAN:
case INF:
errno = EDOM;
case 0:
*exp = 0;
return (d);
}
EXTRACT_WORDS (hd, ld, d);
/* Get the exponent. */
*exp = ((hd & 0x7ff00000) >> 20) - 1022;
/* Get the mantissa. */
lf = ld;
hf = hd & 0x800fffff;
hf |= 0x3fe00000;
INSERT_WORDS (f, hf, lf);
return (f);
}
#endif /* _DOUBLE_IS_32BITS */
|
