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
38 static 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
46 div_t
div(int num,int denom)47 div(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