115 lines
2.6 KiB
C
115 lines
2.6 KiB
C
|
|
/* @(#)s_frexp.c 5.1 93/09/24 */
|
|
/*
|
|
* ====================================================
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
*
|
|
* Developed at SunPro, a Sun Microsystems, Inc. business.
|
|
* Permission to use, copy, modify, and distribute this
|
|
* software is freely granted, provided that this notice
|
|
* is preserved.
|
|
* ====================================================
|
|
*/
|
|
|
|
/*
|
|
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 non zero, 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]>.
|
|
|
|
@ifinfo
|
|
<[m]> and <[p]> are calculated so that
|
|
<[val]> is <[m]> times <<2>> to the power <[p]>.
|
|
@end ifinfo
|
|
@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.
|
|
|
|
|
|
*/
|
|
|
|
/*
|
|
* for non-zero x
|
|
* x = frexp(arg,&exp);
|
|
* return a double fp quantity x such that 0.5 <= |x| <1.0
|
|
* and the corresponding binary exponent "exp". That is
|
|
* arg = x*2^exp.
|
|
* If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
|
|
* with *exp=0.
|
|
*/
|
|
|
|
#include "fdlibm.h"
|
|
|
|
#ifndef _DOUBLE_IS_32BITS
|
|
|
|
#ifdef __STDC__
|
|
static const double
|
|
#else
|
|
static double
|
|
#endif
|
|
two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
|
|
|
|
#ifdef __STDC__
|
|
double frexp(double x, int *eptr)
|
|
#else
|
|
double frexp(x, eptr)
|
|
double x; int *eptr;
|
|
#endif
|
|
{
|
|
__int32_t hx, ix, lx;
|
|
EXTRACT_WORDS(hx,lx,x);
|
|
ix = 0x7fffffff&hx;
|
|
*eptr = 0;
|
|
if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */
|
|
if (ix<0x00100000) { /* subnormal */
|
|
x *= two54;
|
|
GET_HIGH_WORD(hx,x);
|
|
ix = hx&0x7fffffff;
|
|
*eptr = -54;
|
|
}
|
|
*eptr += (ix>>20)-1022;
|
|
hx = (hx&0x800fffff)|0x3fe00000;
|
|
SET_HIGH_WORD(x,hx);
|
|
return x;
|
|
}
|
|
|
|
#endif /* _DOUBLE_IS_32BITS */
|