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#include <sys/cdefs.h>
14__FBSDID("$FreeBSD$");
15
16/*
17 * for non-zero x
18 *	x = frexp(arg,&exp);
19 * return a double fp quantity x such that 0.5 <= |x| <1.0
20 * and the corresponding binary exponent "exp". That is
21 *	arg = x*2^exp.
22 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
23 * with *exp=0.
24 */
25
26#include <float.h>
27
28#include "math.h"
29#include "math_private.h"
30
31static const double
32two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
33
34double
35frexp(double x, int *eptr)
36{
37	int32_t hx, ix, lx;
38	EXTRACT_WORDS(hx,lx,x);
39	ix = 0x7fffffff&hx;
40	*eptr = 0;
41	if(ix>=0x7ff00000||((ix|lx)==0)) return x;	/* 0,inf,nan */
42	if (ix<0x00100000) {		/* subnormal */
43	    x *= two54;
44	    GET_HIGH_WORD(hx,x);
45	    ix = hx&0x7fffffff;
46	    *eptr = -54;
47	}
48	*eptr += (ix>>20)-1022;
49	hx = (hx&0x800fffff)|0x3fe00000;
50	SET_HIGH_WORD(x,hx);
51	return x;
52}
53
54#if (LDBL_MANT_DIG == 53)
55__weak_reference(frexp, frexpl);
56#endif
57