| |
| /* @(#)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 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. |
| |
| |
| */ |
| |
| /* |
| * 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 */ |