| 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 | * 4. 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: src/lib/libc/stdlib/div.c,v 1.3 2007/01/09 00:28:09 imp Exp $");␊ |
| 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 | |
