0,0 → 1,61 |
/* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */ |
/* @(#)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. |
* ==================================================== |
*/ |
|
#if defined(LIBM_SCCS) && !defined(lint) |
static char rcsid[] = "$Id: s_frexp.c,v 1.6 1994/08/18 23:06:49 jtc Exp $"; |
#endif |
|
/* |
* 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 "math.h" |
#include "math_private.h" |
|
#ifdef __STDC__ |
static const double |
#else |
static double |
#endif |
one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */ |
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; |
} |