1  /*
 2   * Copyright (c) 1990, 1993
 3   *	The Regents of the University of California.  All rights reserved.
 4   *
 5   * This code is derived from software contributed to Berkeley by
 6   * Chris Torek.
 7   *
 8   * Redistribution and use in source and binary forms, with or without
 9   * modification, are permitted provided that the following conditions
10   * are met:
11   * 1. Redistributions of source code must retain the above copyright
12   *    notice, this list of conditions and the following disclaimer.
13   * 2. Redistributions in binary form must reproduce the above copyright
14   *    notice, this list of conditions and the following disclaimer in the
15   *    documentation and/or other materials provided with the distribution.
16   * 4. Neither the name of the University nor the names of its contributors
17   *    may be used to endorse or promote products derived from this software
18   *    without specific prior written permission.
19   *
20   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30   * SUCH DAMAGE.
31   */
32  
33  #if defined(LIBC_SCCS) && !defined(lint)
34  static char sccsid[] = "@(#)div.c	8.1 (Berkeley) 6/4/93";
35  #endif /* LIBC_SCCS and not lint */
36  #include <sys/cdefs.h>
37  __FBSDID("$FreeBSD: src/lib/libc/stdlib/div.c,v 1.3 2007/01/09 00:28:09 imp Exp $");
38  
39  #include <stdlib.h>		/* div_t */
40  
41  div_t
42  div(num, denom)
43  	int num, denom;
44  {
45  	div_t r;
46  
47  	r.quot = num / denom;
48  	r.rem = num % denom;
49  	/*
50  	 * The ANSI standard says that |r.quot| <= |n/d|, where
51  	 * n/d is to be computed in infinite precision.  In other
52  	 * words, we should always truncate the quotient towards
53  	 * 0, never -infinity.
54  	 *
55  	 * Machine division and remainer may work either way when
56  	 * one or both of n or d is negative.  If only one is
57  	 * negative and r.quot has been truncated towards -inf,
58  	 * r.rem will have the same sign as denom and the opposite
59  	 * sign of num; if both are negative and r.quot has been
60  	 * truncated towards -inf, r.rem will be positive (will
61  	 * have the opposite sign of num).  These are considered
62  	 * `wrong'.
63  	 *
64  	 * If both are num and denom are positive, r will always
65  	 * be positive.
66  	 *
67  	 * This all boils down to:
68  	 *	if num >= 0, but r.rem < 0, we got the wrong answer.
69  	 * In that case, to get the right answer, add 1 to r.quot and
70  	 * subtract denom from r.rem.
71  	 */
72  	if (num >= 0 && r.rem < 0) {
73  		r.quot++;
74  		r.rem -= denom;
75  	}
76  	return (r);
77  }