fixunssfdi.c revision 1.3 
1/*	$NetBSD: fixunssfdi.c,v 1.3 1995/02/27 17:30:02 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[] = "@(#)fixunssfdi.c	8.1 (Berkeley) 6/4/93";
43#else
44static char rcsid[] = "$NetBSD: fixunssfdi.c,v 1.3 1995/02/27 17:30:02 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 float to (unsigned) quad.  We do most of our work in double,
56 * out of sheer paranoia.
57 *
58 * Not sure what to do with negative numbers---for now, anything out
59 * of range becomes UQUAD_MAX.
60 *
61 * N.B.: must use new ANSI syntax (sorry).
62 */
63u_quad_t
64__fixunssfdi(float f)
65{
66	double x, toppart;
67	union uu t;
68
69	if (f < 0)
70		return (UQUAD_MAX);	/* ??? should be 0?  ERANGE??? */
71#ifdef notdef				/* this falls afoul of a GCC bug */
72	if (f >= UQUAD_MAX)
73		return (UQUAD_MAX);
74#else					/* so we wire in 2^64-1 instead */
75	if (f >= 18446744073709551615.0)	/* XXX */
76		return (UQUAD_MAX);
77#endif
78	x = f;
79	/*
80	 * Get the upper part of the result.  Note that the divide
81	 * may round up; we want to avoid this if possible, so we
82	 * subtract `1/2' first.
83	 */
84	toppart = (x - ONE_HALF) / ONE;
85	/*
86	 * Now build a u_quad_t out of the top part.  The difference
87	 * between x and this is the bottom part (this may introduce
88	 * a few fuzzy bits, but what the heck).  With any luck this
89	 * difference will be nonnegative: x should wind up in the
90	 * range [0..ULONG_MAX].  For paranoia, we assume [LONG_MIN..
91	 * 2*ULONG_MAX] instead.
92	 */
93	t.ul[H] = (unsigned long)toppart;
94	t.ul[L] = 0;
95	x -= (double)t.uq;
96	if (x < 0) {
97		t.ul[H]--;
98		x += ULONG_MAX;
99	}
100	if (x > ULONG_MAX) {
101		t.ul[H]++;
102		x -= ULONG_MAX;
103	}
104	t.ul[L] = (u_long)x;
105	return (t.uq);
106}
107