1/*	$OpenBSD: frexp.c,v 1.10 2013/07/03 04:46:36 espie Exp $	*/
2
3/*-
4 * Copyright (c) 2004 David Schultz <das@FreeBSD.ORG>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * $FreeBSD: frexp.c,v 1.1 2004/07/18 21:23:39 das Exp $
29 */
30
31#include <sys/types.h>
32#include <machine/ieee.h>
33#include <float.h>
34#include <math.h>
35
36double
37frexp(double v, int *ex)
38{
39	union  {
40		double v;
41		struct ieee_double s;
42	} u;
43
44	u.v = v;
45	switch (u.s.dbl_exp) {
46	case 0:		/* 0 or subnormal */
47		if ((u.s.dbl_fracl | u.s.dbl_frach) == 0) {
48			*ex = 0;
49		} else {
50			/*
51			 * The power of 2 is arbitrary, any value from 54 to
52			 * 1024 will do.
53			 */
54			u.v *= 0x1.0p514;
55			*ex = u.s.dbl_exp - (DBL_EXP_BIAS - 1 + 514);
56			u.s.dbl_exp = DBL_EXP_BIAS - 1;
57		}
58		break;
59	case DBL_EXP_INFNAN:	/* Inf or NaN; value of *ex is unspecified */
60		break;
61	default:	/* normal */
62		*ex = u.s.dbl_exp - (DBL_EXP_BIAS - 1);
63		u.s.dbl_exp = DBL_EXP_BIAS - 1;
64		break;
65	}
66	return (u.v);
67}
68
69#if	LDBL_MANT_DIG == DBL_MANT_DIG
70__strong_alias(frexpl, frexp);
71#endif	/* LDBL_MANT_DIG == DBL_MANT_DIG */
72