floatdidf.c revision 1.1 
1/*-
2 * Copyright (c) 1992, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This software was developed by the Computer Systems Engineering group
6 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
7 * contributed to Berkeley.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. All advertising materials mentioning features or use of this software
18 *    must display the following acknowledgement:
19 *	This product includes software developed by the University of
20 *	California, Berkeley and its contributors.
21 * 4. Neither the name of the University nor the names of its contributors
22 *    may be used to endorse or promote products derived from this software
23 *    without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * SUCH DAMAGE.
36 */
37
38#if defined(LIBC_SCCS) && !defined(lint)
39/*static char *sccsid = "from: @(#)floatdidf.c	8.1 (Berkeley) 6/4/93";*/
40static char *rcsid = "$Id: floatdidf.c,v 1.1 1993/09/16 06:05:58 mycroft Exp $";
41#endif /* LIBC_SCCS and not lint */
42
43#include "quad.h"
44
45/*
46 * Convert (signed) quad to double.
47 */
48double
49__floatdidf(x)
50	quad_t x;
51{
52	double d;
53	union uu u;
54	int neg;
55
56	/*
57	 * Get an unsigned number first, by negating if necessary.
58	 */
59	if (x < 0)
60		u.q = -x, neg = 1;
61	else
62		u.q = x, neg = 0;
63
64	/*
65	 * Now u.ul[H] has the factor of 2^32 (or whatever) and u.ul[L]
66	 * has the units.  Ideally we could just set d, add LONG_BITS to
67	 * its exponent, and then add the units, but this is portable
68	 * code and does not know how to get at an exponent.  Machine-
69	 * specific code may be able to do this more efficiently.
70	 */
71	d = (double)u.ul[H] * ((1 << (LONG_BITS - 2)) * 4.0);
72	d += u.ul[L];
73
74	return (neg ? -d : d);
75}
76