floatdidf.c revision 1.3 
1/*	$NetBSD: floatdidf.c,v 1.3 1995/02/27 17:30:07 cgd 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. All advertising materials mentioning features or use of this software
20 *    must display the following acknowledgement:
21 *	This product includes software developed by the University of
22 *	California, Berkeley and its contributors.
23 * 4. Neither the name of the University nor the names of its contributors
24 *    may be used to endorse or promote products derived from this software
25 *    without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 * SUCH DAMAGE.
38 */
39
40#if defined(LIBC_SCCS) && !defined(lint)
41#if 0
42static char sccsid[] = "@(#)floatdidf.c	8.1 (Berkeley) 6/4/93";
43#else
44static char rcsid[] = "$NetBSD: floatdidf.c,v 1.3 1995/02/27 17:30:07 cgd Exp $";
45#endif
46#endif /* LIBC_SCCS and not lint */
47
48#include "quad.h"
49
50/*
51 * Convert (signed) quad to double.
52 */
53double
54__floatdidf(x)
55	quad_t x;
56{
57	double d;
58	union uu u;
59	int neg;
60
61	/*
62	 * Get an unsigned number first, by negating if necessary.
63	 */
64	if (x < 0)
65		u.q = -x, neg = 1;
66	else
67		u.q = x, neg = 0;
68
69	/*
70	 * Now u.ul[H] has the factor of 2^32 (or whatever) and u.ul[L]
71	 * has the units.  Ideally we could just set d, add LONG_BITS to
72	 * its exponent, and then add the units, but this is portable
73	 * code and does not know how to get at an exponent.  Machine-
74	 * specific code may be able to do this more efficiently.
75	 */
76	d = (double)u.ul[H] * (((long)1 << (LONG_BITS - 2)) * 4.0);
77	d += u.ul[L];
78
79	return (neg ? -d : d);
80}
81