sl@0: /*
sl@0: * FUNCTION
sl@0: * <<div>>---divide two integers
sl@0: * INDEX
sl@0: * div
sl@0: * ANSI_SYNOPSIS
sl@0: * #include <stdlib.h>
sl@0: * div_t div(int <[n]>, int <[d]>);
sl@0: * TRAD_SYNOPSIS
sl@0: * #include <stdlib.h>
sl@0: * div_t div(<[n]>, <[d]>)
sl@0: * int <[n]>, <[d]>;
sl@0: * Divide
sl@0: * @tex
sl@0: * $n/d$,
sl@0: * @end tex
sl@0: * @ifinfo
sl@0: * <[n]>/<[d]>,
sl@0: * @end ifinfo
sl@0: * returning quotient and remainder as two integers in a structure <<div_t>>.
sl@0: * RETURNS
sl@0: * The result is represented with the structure
sl@0: * . typedef struct
sl@0: * .  int quot;
sl@0: * .  int rem;
sl@0: * . } div_t;
sl@0: * where the <<quot>> field represents the quotient, and <<rem>> the
sl@0: * remainder.  For nonzero <[d]>, if `<<<[r]> = div(<[n]>,<[d]>);>>' then
sl@0: * <[n]> equals `<<<[r]>.rem + <[d]>*<[r]>.quot>>'.
sl@0: * To divide <<long>> rather than <<int>> values, use the similar
sl@0: * function <<ldiv>>.
sl@0: * PORTABILITY
sl@0: * <<div>> is ANSI.
sl@0: * No supporting OS subroutines are required.
sl@0: * 
sl@0: *
sl@0: */
sl@0: 
sl@0: 
sl@0: 
sl@0: /*
sl@0:  * Copyright (c) 1990 Regents of the University of California.
sl@0:  * All rights reserved.
sl@0:  *
sl@0:  * This code is derived from software contributed to Berkeley by
sl@0:  * Chris Torek.
sl@0:  *
sl@0:  * Redistribution and use in source and binary forms, with or without
sl@0:  * modification, are permitted provided that the following conditions
sl@0:  * are met:
sl@0:  * 1. Redistributions of source code must retain the above copyright
sl@0:  *    notice, this list of conditions and the following disclaimer.
sl@0:  * 2. Redistributions in binary form must reproduce the above copyright
sl@0:  *    notice, this list of conditions and the following disclaimer in the
sl@0:  *    documentation and/or other materials provided with the distribution.
sl@0:  * 3. All advertising materials mentioning features or use of this software
sl@0:  *    must display the following acknowledgement:
sl@0:  *	This product includes software developed by the University of
sl@0:  *	California, Berkeley and its contributors.
sl@0:  * 4. Neither the name of the University nor the names of its contributors
sl@0:  *    may be used to endorse or promote products derived from this software
sl@0:  *    without specific prior written permission.
sl@0:  *
sl@0:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
sl@0:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
sl@0:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
sl@0:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
sl@0:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
sl@0:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
sl@0:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
sl@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
sl@0:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
sl@0:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
sl@0:  * SUCH DAMAGE.
sl@0:  */
sl@0: 
sl@0: #include <_ansi.h>
sl@0: #include <stdlib.h>		/* div_t */
sl@0: 
sl@0: /**
sl@0: Divide two integer values.
sl@0: numer is divided by denom. 
sl@0: Quotient and remainder are returned in a div_t structure.
sl@0: @return   A div_t structure is returned
sl@0: @param num Numerator. 
sl@0: @param denom Denominator.
sl@0: */
sl@0: EXPORT_C div_t div (int num, int denom)
sl@0: {
sl@0: 	div_t r;
sl@0: 
sl@0: 	r.quot = num / denom;
sl@0: 	r.rem = num % denom;
sl@0: 	/*
sl@0: 	 * The ANSI standard says that |r.quot| <= |n/d|, where
sl@0: 	 * n/d is to be computed in infinite precision.  In other
sl@0: 	 * words, we should always truncate the quotient towards
sl@0: 	 * 0, never -infinity.
sl@0: 	 *
sl@0: 	 * Machine division and remainer may work either way when
sl@0: 	 * one or both of n or d is negative.  If only one is
sl@0: 	 * negative and r.quot has been truncated towards -inf,
sl@0: 	 * r.rem will have the same sign as denom and the opposite
sl@0: 	 * sign of num; if both are negative and r.quot has been
sl@0: 	 * truncated towards -inf, r.rem will be positive (will
sl@0: 	 * have the opposite sign of num).  These are considered
sl@0: 	 * `wrong'.
sl@0: 	 *
sl@0: 	 * If both are num and denom are positive, r will always
sl@0: 	 * be positive.
sl@0: 	 *
sl@0: 	 * This all boils down to:
sl@0: 	 *	if num >= 0, but r.rem < 0, we got the wrong answer.
sl@0: 	 * In that case, to get the right answer, add 1 to r.quot and
sl@0: 	 * subtract denom from r.rem.
sl@0: 	 */
sl@0: 	if (num >= 0 && r.rem < 0) {
sl@0: 		r.quot++;
sl@0: 		r.rem -= denom;
sl@0: 	}
sl@0: 	return (r);
sl@0: }