floatdidf.c revision 1.6 
1/*	$NetBSD: floatdidf.c,v 1.6 2003/08/07 16:43:16 agc 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
36#include <sys/cdefs.h>
37#if defined(LIBC_SCCS) && !defined(lint)
38#if 0
39static char sccsid[] = "@(#)floatdidf.c	8.1 (Berkeley) 6/4/93";
40#else
41__RCSID("$NetBSD: floatdidf.c,v 1.6 2003/08/07 16:43:16 agc Exp $");
42#endif
43#endif /* LIBC_SCCS and not lint */
44
45#include "quad.h"
46
47/*
48 * Convert (signed) quad to double.
49 */
50double
51__floatdidf(x)
52	quad_t x;
53{
54	double d;
55	union uu u;
56	int neg;
57
58	/*
59	 * Get an unsigned number first, by negating if necessary.
60	 */
61	if (x < 0)
62		u.q = -x, neg = 1;
63	else
64		u.q = x, neg = 0;
65
66	/*
67	 * Now u.ul[H] has the factor of 2^32 (or whatever) and u.ul[L]
68	 * has the units.  Ideally we could just set d, add INT_BITS to
69	 * its exponent, and then add the units, but this is portable
70	 * code and does not know how to get at an exponent.  Machine-
71	 * specific code may be able to do this more efficiently.
72	 */
73	d = (double)u.ul[H] * (((int)1 << (INT_BITS - 2)) * 4.0);
74	d += u.ul[L];
75
76	return (neg ? -d : d);
77}
78