| /* $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); |
| } |