72 lines
2.8 KiB
C
72 lines
2.8 KiB
C
|
/* $OpenBSD: div.c,v 1.5 2005/08/08 08:05:36 espie Exp $ */
|
||
|
|
/*
|
||
|
|
* Copyright (c) 1990 Regents of the University of California.
|
||
|
|
* All rights reserved.
|
||
|
|
*
|
||
|
|
* This code is derived from software contributed to Berkeley by
|
||
|
|
* Chris Torek.
|
||
|
|
*
|
||
|
|
* Redistribution and use in source and binary forms, with or without
|
||
|
|
* modification, are permitted provided that the following conditions
|
||
|
|
* are met:
|
||
|
|
* 1. Redistributions of source code must retain the above copyright
|
||
|
|
* notice, this list of conditions and the following disclaimer.
|
||
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
||
|
|
* notice, this list of conditions and the following disclaimer in the
|
||
|
|
* documentation and/or other materials provided with the distribution.
|
||
|
|
* 3. Neither the name of the University nor the names of its contributors
|
||
|
|
* may be used to endorse or promote products derived from this software
|
||
|
|
* without specific prior written permission.
|
||
|
|
*
|
||
|
|
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
||
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
||
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
||
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
||
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
||
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
||
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
||
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
||
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||
|
|
* SUCH DAMAGE.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <stdlib.h> /* div_t */
|
||
|
|
|
||
|
|
div_t
|
||
|
|
div(int num, int denom)
|
||
|
|
{
|
||
|
|
div_t r;
|
||
|
|
|
||
|
|
r.quot = num / denom;
|
||
|
|
r.rem = num % denom;
|
||
|
|
/*
|
||
|
|
* The ANSI standard says that |r.quot| <= |n/d|, where
|
||
|
|
* n/d is to be computed in infinite precision. In other
|
||
|
|
* words, we should always truncate the quotient towards
|
||
|
|
* 0, never -infinity.
|
||
|
|
*
|
||
|
|
* Machine division and remainer may work either way when
|
||
|
|
* one or both of n or d is negative. If only one is
|
||
|
|
* negative and r.quot has been truncated towards -inf,
|
||
|
|
* r.rem will have the same sign as denom and the opposite
|
||
|
|
* sign of num; if both are negative and r.quot has been
|
||
|
|
* truncated towards -inf, r.rem will be positive (will
|
||
|
|
* have the opposite sign of num). These are considered
|
||
|
|
* `wrong'.
|
||
|
|
*
|
||
|
|
* If both are num and denom are positive, r will always
|
||
|
|
* be positive.
|
||
|
|
*
|
||
|
|
* This all boils down to:
|
||
|
|
* if num >= 0, but r.rem < 0, we got the wrong answer.
|
||
|
|
* In that case, to get the right answer, add 1 to r.quot and
|
||
|
|
* subtract denom from r.rem.
|
||
|
|
*/
|
||
|
|
if (num >= 0 && r.rem < 0) {
|
||
|
|
r.quot++;
|
||
|
|
r.rem -= denom;
|
||
|
|
}
|
||
|
|
return (r);
|
||
|
|
}
|