1 /* $NetBSD: compat_frexp_ieee754.c,v 1.6 2024/01/20 14:52:45 christos Exp $ */
2
3 /*
4 * Copyright (c) 1992, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 *
35 * from: Header: frexp.c,v 1.1 91/07/07 04:45:01 torek Exp
36 */
37
38 #include <sys/cdefs.h>
39 #if defined(LIBC_SCCS) && !defined(lint)
40 #if 0
41 static char sccsid[] = "@(#)frexp.c 8.1 (Berkeley) 6/4/93";
42 #else
43 __RCSID("$NetBSD: compat_frexp_ieee754.c,v 1.6 2024/01/20 14:52:45 christos Exp $");
44 #endif
45 #endif /* LIBC_SCCS and not lint */
46
47 #include <sys/types.h>
48 #include <machine/ieee.h>
49 #include <math.h>
50
51 /*
52 * Split the given value into a fraction in the range [0.5, 1.0) and
53 * an exponent, such that frac * (2^exp) == value. If value is 0,
54 * return 0.
55 */
56 double
frexp(double value,int * eptr)57 frexp(double value, int *eptr)
58 {
59 union ieee_double_u u;
60
61 if (value) {
62 /*
63 * Fractions in [0.5..1.0) have an exponent of 2^-1.
64 * Leave Inf and NaN alone, however.
65 */
66 u.dblu_d = value;
67 if (u.dblu_dbl.dbl_exp != DBL_EXP_INFNAN) {
68 *eptr = 0;
69 if (u.dblu_dbl.dbl_exp == 0) {
70 /* denormal, scale out of mantissa */
71 *eptr = -DBL_FRACBITS;
72 u.dblu_d *= 4.50359962737049600000e+15;
73 }
74 *eptr += u.dblu_dbl.dbl_exp - (DBL_EXP_BIAS - 1);
75 u.dblu_dbl.dbl_exp = DBL_EXP_BIAS - 1;
76 }
77 return (u.dblu_d);
78 } else {
79 *eptr = 0;
80 return (value);
81 }
82 }
83