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
36 double
frexp(double v,int * ex)37 frexp(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