newlib/libc/stdlib/lldiv.c

   1 /*
   2 FUNCTION
   3 <<lldiv>>---divide two long long integers
   4
   5 INDEX
   6         lldiv
   7
   8 SYNOPSIS
   9         #include <stdlib.h>
  10         lldiv_t lldiv(long long <[n]>, long long <[d]>);
  11
  12 DESCRIPTION
  13 Divide
  14 @tex
  15 $n/d$,
  16 @end tex
  17 @ifnottex
  18 <[n]>/<[d]>,
  19 @end ifnottex
  20 returning quotient and remainder as two long long integers in a structure
  21 <<lldiv_t>>.
  22
  23 RETURNS
  24 The result is represented with the structure
  25
  26 . typedef struct
  27 . {
  28 .  long long quot;
  29 .  long long rem;
  30 . } lldiv_t;
  31
  32 where the <<quot>> field represents the quotient, and <<rem>> the
  33 remainder.  For nonzero <[d]>, if `<<<[r]> = ldiv(<[n]>,<[d]>);>>' then
  34 <[n]> equals `<<<[r]>.rem + <[d]>*<[r]>.quot>>'.
  35
  36 To divide <<long>> rather than <<long long>> values, use the similar
  37 function <<ldiv>>.
  38
  39 PORTABILITY
  40 <<lldiv>> is ISO 9899 (C99) compatable.
  41
  42 No supporting OS subroutines are required.
  43 */
  44
  45 /*-
  46  * Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
  47  * All rights reserved.
  48  *
  49  * Redistribution and use in source and binary forms, with or without
  50  * modification, are permitted provided that the following conditions
  51  * are met:
  52  * 1. Redistributions of source code must retain the above copyright
  53  *    notice, this list of conditions and the following disclaimer.
  54  * 2. Redistributions in binary form must reproduce the above copyright
  55  *    notice, this list of conditions and the following disclaimer in the
  56  *    documentation and/or other materials provided with the distribution.
  57  *
  58  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  59  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  60  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  61  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  62  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  63  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  64  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  65  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  66  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  67  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  68  * SUCH DAMAGE.
  69  */
  70
  71 #include <stdlib.h>
  72
  73 /*
  74  * The ANSI standard says that |r.quot| <= |n/d|, where
  75  * n/d is to be computed in infinite precision.  In other
  76  * words, we should always truncate the quotient towards
  77  * 0, never -infinity.
  78  *
  79  * Machine division and remainer may work either way when
  80  * one or both of n or d is negative.  If only one is
  81  * negative and r.quot has been truncated towards -inf,
  82  * r.rem will have the same sign as denom and the opposite
  83  * sign of num; if both are negative and r.quot has been
  84  * truncated towards -inf, r.rem will be positive (will
  85  * have the opposite sign of num).  These are considered
  86  * `wrong'.
  87  *
  88  * If both are num and denom are positive, r will always
  89  * be positive.
  90  *
  91  * This all boils down to:
  92  *      if num >= 0, but r.rem < 0, we got the wrong answer.
  93  * In that case, to get the right answer, add 1 to r.quot and
  94  * subtract denom from r.rem.
  95  */
  96 lldiv_t
  97 lldiv (long long numer, long long denom)
  98 {
  99         lldiv_t retval;
 100
 101         retval.quot = numer / denom;
 102         retval.rem = numer % denom;
 103         if (numer >= 0 && retval.rem < 0) {
 104                 retval.quot++;
 105                 retval.rem -= denom;
 106         }
 107         return (retval);
 108 }
 109