fixunssfdi.c revision 1.4 
1/*	$NetBSD: fixunssfdi.c,v 1.4 1997/07/13 20:01:45 christos 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#include <sys/cdefs.h>
41#if defined(LIBC_SCCS) && !defined(lint)
42#if 0
43static char sccsid[] = "@(#)fixunssfdi.c	8.1 (Berkeley) 6/4/93";
44#else
45__RCSID("$NetBSD: fixunssfdi.c,v 1.4 1997/07/13 20:01:45 christos Exp $");
46#endif
47#endif /* LIBC_SCCS and not lint */
48
49#include "quad.h"
50
51#define	ONE_FOURTH	((long)1 << (LONG_BITS - 2))
52#define	ONE_HALF	(ONE_FOURTH * 2.0)
53#define	ONE		(ONE_FOURTH * 4.0)
54
55/*
56 * Convert float to (unsigned) quad.  We do most of our work in double,
57 * out of sheer paranoia.
58 *
59 * Not sure what to do with negative numbers---for now, anything out
60 * of range becomes UQUAD_MAX.
61 *
62 * N.B.: must use new ANSI syntax (sorry).
63 */
64u_quad_t
65__fixunssfdi(float f)
66{
67	double x, toppart;
68	union uu t;
69
70	if (f < 0)
71		return (UQUAD_MAX);	/* ??? should be 0?  ERANGE??? */
72#ifdef notdef				/* this falls afoul of a GCC bug */
73	if (f >= UQUAD_MAX)
74		return (UQUAD_MAX);
75#else					/* so we wire in 2^64-1 instead */
76	if (f >= 18446744073709551615.0)	/* XXX */
77		return (UQUAD_MAX);
78#endif
79	x = f;
80	/*
81	 * Get the upper part of the result.  Note that the divide
82	 * may round up; we want to avoid this if possible, so we
83	 * subtract `1/2' first.
84	 */
85	toppart = (x - ONE_HALF) / ONE;
86	/*
87	 * Now build a u_quad_t out of the top part.  The difference
88	 * between x and this is the bottom part (this may introduce
89	 * a few fuzzy bits, but what the heck).  With any luck this
90	 * difference will be nonnegative: x should wind up in the
91	 * range [0..ULONG_MAX].  For paranoia, we assume [LONG_MIN..
92	 * 2*ULONG_MAX] instead.
93	 */
94	t.ul[H] = (unsigned long)toppart;
95	t.ul[L] = 0;
96	x -= (double)t.uq;
97	if (x < 0) {
98		t.ul[H]--;
99		x += ULONG_MAX;
100	}
101	if (x > ULONG_MAX) {
102		t.ul[H]++;
103		x -= ULONG_MAX;
104	}
105	t.ul[L] = (u_long)x;
106	return (t.uq);
107}
108