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 #if defined(LIBC_SCCS) && !defined(lint) 34 static char sccsid[] = "@(#)div.c 8.1 (Berkeley) 6/4/93"; 35 #endif /* LIBC_SCCS and not lint */ 36 #include <sys/cdefs.h> 37 __FBSDID("$FreeBSD$"); 38 39 #include <stdlib.h> /* div_t */ 40 41 div_t 42 div(num, denom) 43 int num, denom; 44 { 45 div_t r; 46 47 r.quot = num / denom; 48 r.rem = num % denom; 49 /* 50 * The ANSI standard says that |r.quot| <= |n/d|, where 51 * n/d is to be computed in infinite precision. In other 52 * words, we should always truncate the quotient towards 53 * 0, never -infinity. 54 * 55 * Machine division and remainer may work either way when 56 * one or both of n or d is negative. If only one is 57 * negative and r.quot has been truncated towards -inf, 58 * r.rem will have the same sign as denom and the opposite 59 * sign of num; if both are negative and r.quot has been 60 * truncated towards -inf, r.rem will be positive (will 61 * have the opposite sign of num). These are considered 62 * `wrong'. 63 * 64 * If both are num and denom are positive, r will always 65 * be positive. 66 * 67 * This all boils down to: 68 * if num >= 0, but r.rem < 0, we got the wrong answer. 69 * In that case, to get the right answer, add 1 to r.quot and 70 * subtract denom from r.rem. 71 */ 72 if (num >= 0 && r.rem < 0) { 73 r.quot++; 74 r.rem -= denom; 75 } 76 return (r); 77 } 78