Annotation of prex/usr/lib/libc/stdlib/div.c, Revision 1.1.1.1
1.1 nbrk 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: * 3. 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: #include <stdlib.h> /* div_t */
34:
35: div_t
36: div(num, denom)
37: int num, denom;
38: {
39: div_t r;
40:
41: r.quot = num / denom;
42: r.rem = num % denom;
43: /*
44: * The ANSI standard says that |r.quot| <= |n/d|, where
45: * n/d is to be computed in infinite precision. In other
46: * words, we should always truncate the quotient towards
47: * 0, never -infinity.
48: *
49: * Machine division and remainer may work either way when
50: * one or both of n or d is negative. If only one is
51: * negative and r.quot has been truncated towards -inf,
52: * r.rem will have the same sign as denom and the opposite
53: * sign of num; if both are negative and r.quot has been
54: * truncated towards -inf, r.rem will be positive (will
55: * have the opposite sign of num). These are considered
56: * `wrong'.
57: *
58: * If both are num and denom are positive, r will always
59: * be positive.
60: *
61: * This all boils down to:
62: * if num >= 0, but r.rem < 0, we got the wrong answer.
63: * In that case, to get the right answer, add 1 to r.quot and
64: * subtract denom from r.rem.
65: */
66: if (num >= 0 && r.rem < 0) {
67: r.quot++;
68: r.rem -= denom;
69: }
70: return (r);
71: }
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