1/*	$NetBSD: div.c,v 1.8 2012/06/25 22:32:45 abs Exp $	*/
2
3/*
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include <sys/cdefs.h>
36#if defined(LIBC_SCCS) && !defined(lint)
37#if 0
38static char sccsid[] = "@(#)div.c	8.1 (Berkeley) 6/4/93";
39#else
40__RCSID("$NetBSD: div.c,v 1.8 2012/06/25 22:32:45 abs Exp $");
41#endif
42#endif /* LIBC_SCCS and not lint */
43
44#include <stdlib.h>		/* div_t */
45
46div_t
47div(int num, int denom)
48{
49	div_t r;
50
51	r.quot = num / denom;
52	r.rem = num % denom;
53	/*
54	 * The ANSI standard says that |r.quot| <= |n/d|, where
55	 * n/d is to be computed in infinite precision.  In other
56	 * words, we should always truncate the quotient towards
57	 * 0, never -infinity.
58	 *
59	 * Machine division and remainer may work either way when
60	 * one or both of n or d is negative.  If only one is
61	 * negative and r.quot has been truncated towards -inf,
62	 * r.rem will have the same sign as denom and the opposite
63	 * sign of num; if both are negative and r.quot has been
64	 * truncated towards -inf, r.rem will be positive (will
65	 * have the opposite sign of num).  These are considered
66	 * `wrong'.
67	 *
68	 * If both are num and denom are positive, r will always
69	 * be positive.
70	 *
71	 * This all boils down to:
72	 *	if num >= 0, but r.rem < 0, we got the wrong answer.
73	 * In that case, to get the right answer, add 1 to r.quot and
74	 * subtract denom from r.rem.
75	 */
76	if (num >= 0 && r.rem < 0) {
77		r.quot++;
78		r.rem -= denom;
79	}
80	return (r);
81}
82