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 | }␊ |
78 | |