fixunssfdi.c revision 1574 
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)
39static char sccsid[] = "@(#)fixunssfdi.c	8.1 (Berkeley) 6/4/93";
40#endif /* LIBC_SCCS and not lint */
41
42#include "quad.h"
43
44#define	ONE_FOURTH	(1 << (LONG_BITS - 2))
45#define	ONE_HALF	(ONE_FOURTH * 2.0)
46#define	ONE		(ONE_FOURTH * 4.0)
47
48/*
49 * Convert float to (unsigned) quad.  We do most of our work in double,
50 * out of sheer paranoia.
51 *
52 * Not sure what to do with negative numbers---for now, anything out
53 * of range becomes UQUAD_MAX.
54 *
55 * N.B.: must use new ANSI syntax (sorry).
56 */
57u_quad_t
58__fixunssfdi(float f)
59{
60	double x, toppart;
61	union uu t;
62
63	if (f < 0)
64		return (UQUAD_MAX);	/* ??? should be 0?  ERANGE??? */
65#ifdef notdef				/* this falls afoul of a GCC bug */
66	if (f >= UQUAD_MAX)
67		return (UQUAD_MAX);
68#else					/* so we wire in 2^64-1 instead */
69	if (f >= 18446744073709551615.0)
70		return (UQUAD_MAX);
71#endif
72	x = f;
73	/*
74	 * Get the upper part of the result.  Note that the divide
75	 * may round up; we want to avoid this if possible, so we
76	 * subtract `1/2' first.
77	 */
78	toppart = (x - ONE_HALF) / ONE;
79	/*
80	 * Now build a u_quad_t out of the top part.  The difference
81	 * between x and this is the bottom part (this may introduce
82	 * a few fuzzy bits, but what the heck).  With any luck this
83	 * difference will be nonnegative: x should wind up in the
84	 * range [0..ULONG_MAX].  For paranoia, we assume [LONG_MIN..
85	 * 2*ULONG_MAX] instead.
86	 */
87	t.ul[H] = (unsigned long)toppart;
88	t.ul[L] = 0;
89	x -= (double)t.uq;
90	if (x < 0) {
91		t.ul[H]--;
92		x += ULONG_MAX;
93	}
94	if (x > ULONG_MAX) {
95		t.ul[H]++;
96		x -= ULONG_MAX;
97	}
98	t.ul[L] = (u_long)x;
99	return (t.uq);
100}
101