1 /* 2 * Copyright (c) 1990 Regents of the University of California. 3 * 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. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 /*static char *sccsid = "from: @(#)div.c 5.2 (Berkeley) 4/16/91";*/ 39 static char *rcsid = "$Id: div.c,v 1.3 1993/08/26 00:47:55 jtc Exp $"; 40 #endif /* LIBC_SCCS and not lint */ 41 42 #include <stdlib.h> /* div_t */ 43 44 div_t 45 div(num, denom) 46 int num, denom; 47 { 48 div_t r; 49 50 r.quot = num / denom; 51 r.rem = num % denom; 52 /* 53 * The ANSI standard says that |r.quot| <= |n/d|, where 54 * n/d is to be computed in infinite precision. In other 55 * words, we should always truncate the quotient towards 56 * 0, never -infinity. 57 * 58 * Machine division and remainer may work either way when 59 * one or both of n or d is negative. If only one is 60 * negative and r.quot has been truncated towards -inf, 61 * r.rem will have the same sign as denom and the opposite 62 * sign of num; if both are negative and r.quot has been 63 * truncated towards -inf, r.rem will be positive (will 64 * have the opposite sign of num). These are considered 65 * `wrong'. 66 * 67 * If both are num and denom are positive, r will always 68 * be positive. 69 * 70 * This all boils down to: 71 * if num >= 0, but r.rem < 0, we got the wrong answer. 72 * In that case, to get the right answer, add 1 to r.quot and 73 * subtract denom from r.rem. 74 */ 75 if (num >= 0 && r.rem < 0) { 76 r.quot++; 77 r.rem -= denom; 78 } 79 return (r); 80 } 81