root / prex-0.9.0 / usr / lib / libc / stdlib / div.c @ 03e9c04a
History | View | Annotate | Download (2.71 KB)
| 1 | 03e9c04a | Brad Neuman | /*
|
|---|---|---|---|
| 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 | } |