fixunsdfdi.c revision 1.3 
1/*	$NetBSD: fixunsdfdi.c,v 1.3 1995/02/27 17:29:58 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[] = "@(#)fixunsdfdi.c	8.1 (Berkeley) 6/4/93";
43#else
44static char rcsid[] = "$NetBSD: fixunsdfdi.c,v 1.3 1995/02/27 17:29:58 cgd Exp $";
45#endif
46#endif /* LIBC_SCCS and not lint */
47
48#include "quad.h"
49
50#define	ONE_FOURTH	((long)1 << (LONG_BITS - 2))
51#define	ONE_HALF	(ONE_FOURTH * 2.0)
52#define	ONE		(ONE_FOURTH * 4.0)
53
54/*
55 * Convert double to (unsigned) quad.
56 * Not sure what to do with negative numbers---for now, anything out
57 * of range becomes UQUAD_MAX.
58 */
59u_quad_t
60__fixunsdfdi(x)
61	double x;
62{
63	double toppart;
64	union uu t;
65
66	if (x < 0)
67		return (UQUAD_MAX);	/* ??? should be 0?  ERANGE??? */
68#ifdef notdef				/* this falls afoul of a GCC bug */
69	if (x >= UQUAD_MAX)
70		return (UQUAD_MAX);
71#else					/* so we wire in 2^64-1 instead */
72	if (x >= 18446744073709551615.0)	/* XXX */
73		return (UQUAD_MAX);
74#endif
75	/*
76	 * Get the upper part of the result.  Note that the divide
77	 * may round up; we want to avoid this if possible, so we
78	 * subtract `1/2' first.
79	 */
80	toppart = (x - ONE_HALF) / ONE;
81	/*
82	 * Now build a u_quad_t out of the top part.  The difference
83	 * between x and this is the bottom part (this may introduce
84	 * a few fuzzy bits, but what the heck).  With any luck this
85	 * difference will be nonnegative: x should wind up in the
86	 * range [0..ULONG_MAX].  For paranoia, we assume [LONG_MIN..
87	 * 2*ULONG_MAX] instead.
88	 */
89	t.ul[H] = (unsigned long)toppart;
90	t.ul[L] = 0;
91	x -= (double)t.uq;
92	if (x < 0) {
93		t.ul[H]--;
94		x += ULONG_MAX;
95	}
96	if (x > ULONG_MAX) {
97		t.ul[H]++;
98		x -= ULONG_MAX;
99	}
100	t.ul[L] = (u_long)x;
101	return (t.uq);
102}
103