s_frexp.c revision 1dc9e472e19acfe6dc7f41e429236e7eef7ceda1 
1/* @(#)s_frexp.c 5.1 93/09/24 */
2/*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13#ifndef lint
14static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_frexp.c,v 1.10 2005/03/07 21:27:37 das Exp $";
15#endif
16
17/*
18 * for non-zero x
19 *	x = frexp(arg,&exp);
20 * return a double fp quantity x such that 0.5 <= |x| <1.0
21 * and the corresponding binary exponent "exp". That is
22 *	arg = x*2^exp.
23 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
24 * with *exp=0.
25 */
26
27#include <sys/cdefs.h>
28#include <float.h>
29
30#include "math.h"
31#include "math_private.h"
32
33static const double
34two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
35
36double
37frexp(double x, int *eptr)
38{
39	int32_t hx, ix, lx;
40	EXTRACT_WORDS(hx,lx,x);
41	ix = 0x7fffffff&hx;
42	*eptr = 0;
43	if(ix>=0x7ff00000||((ix|lx)==0)) return x;	/* 0,inf,nan */
44	if (ix<0x00100000) {		/* subnormal */
45	    x *= two54;
46	    GET_HIGH_WORD(hx,x);
47	    ix = hx&0x7fffffff;
48	    *eptr = -54;
49	}
50	*eptr += (ix>>20)-1022;
51	hx = (hx&0x800fffff)|0x3fe00000;
52	SET_HIGH_WORD(x,hx);
53	return x;
54}
55
56#if (LDBL_MANT_DIG == 53)
57__weak_reference(frexp, frexpl);
58#endif
59