Prex Home / Browse Source - Prex Version: 0.9.0

root/usr/lib/libc/stdlib/div.c

DEFINITIONS

1. div

   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  */
  33 #include <stdlib.h>             /* div_t */
div_t
  36 div(num, denom)
  37         int num, denom;
  38 {
div_t r;
r.quot = num / denom;
r.rem = num % denom;
  43         /*
  44          * The ANSI standard says that |r.quot| <= |n/d|, where
  45          * n/d is to be computed in infinite precision.  In other
  46          * words, we should always truncate the quotient towards
  47          * 0, never -infinity.
  48          *
  49          * Machine division and remainer may work either way when
  50          * one or both of n or d is negative.  If only one is
  51          * negative and r.quot has been truncated towards -inf,
  52          * r.rem will have the same sign as denom and the opposite
  53          * sign of num; if both are negative and r.quot has been
  54          * truncated towards -inf, r.rem will be positive (will
  55          * have the opposite sign of num).  These are considered
  56          * `wrong'.
  57          *
  58          * If both are num and denom are positive, r will always
  59          * be positive.
  60          *
  61          * This all boils down to:
  62          *      if num >= 0, but r.rem < 0, we got the wrong answer.
  63          * In that case, to get the right answer, add 1 to r.quot and
  64          * subtract denom from r.rem.
  65          */
  66         if (num >= 0 && r.rem < 0) {
r.quot++;
r.rem -= denom;
  69         }
  70         return (r);
  71 }