fixunssfdi.c revision 1.6 
1/*	$NetBSD: fixunssfdi.c,v 1.6 2003/08/07 16:43:16 agc 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. Neither the name of the University nor the names of its contributors
20 *    may be used to endorse or promote products derived from this software
21 *    without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36#include <sys/cdefs.h>
37#if defined(LIBC_SCCS) && !defined(lint)
38#if 0
39static char sccsid[] = "@(#)fixunssfdi.c	8.1 (Berkeley) 6/4/93";
40#else
41__RCSID("$NetBSD: fixunssfdi.c,v 1.6 2003/08/07 16:43:16 agc Exp $");
42#endif
43#endif /* LIBC_SCCS and not lint */
44
45#include "quad.h"
46
47#define	ONE_FOURTH	((int)1 << (INT_BITS - 2))
48#define	ONE_HALF	(ONE_FOURTH * 2.0)
49#define	ONE		(ONE_FOURTH * 4.0)
50
51/*
52 * Convert float to (unsigned) quad.  We do most of our work in double,
53 * out of sheer paranoia.
54 *
55 * Not sure what to do with negative numbers---for now, anything out
56 * of range becomes UQUAD_MAX.
57 *
58 * N.B.: must use new ANSI syntax (sorry).
59 */
60u_quad_t
61__fixunssfdi(float f)
62{
63	double x, toppart;
64	union uu t;
65
66	if (f < 0)
67		return (UQUAD_MAX);	/* ??? should be 0?  ERANGE??? */
68#ifdef notdef				/* this falls afoul of a GCC bug */
69	if (f >= UQUAD_MAX)
70		return (UQUAD_MAX);
71#else					/* so we wire in 2^64-1 instead */
72	if (f >= 18446744073709551615.0)	/* XXX */
73		return (UQUAD_MAX);
74#endif
75	x = f;
76	/*
77	 * Get the upper part of the result.  Note that the divide
78	 * may round up; we want to avoid this if possible, so we
79	 * subtract `1/2' first.
80	 */
81	toppart = (x - ONE_HALF) / ONE;
82	/*
83	 * Now build a u_quad_t out of the top part.  The difference
84	 * between x and this is the bottom part (this may introduce
85	 * a few fuzzy bits, but what the heck).  With any luck this
86	 * difference will be nonnegative: x should wind up in the
87	 * range [0..UINT_MAX].  For paranoia, we assume [INT_MIN..
88	 * 2*UINT_MAX] instead.
89	 */
90	t.ul[H] = (unsigned int)toppart;
91	t.ul[L] = 0;
92	x -= (double)t.uq;
93	if (x < 0) {
94		t.ul[H]--;
95		x += UINT_MAX;
96	}
97	if (x > UINT_MAX) {
98		t.ul[H]++;
99		x -= UINT_MAX;
100	}
101	t.ul[L] = (u_int)x;
102	return (t.uq);
103}
104