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Annotation of prex-old/usr/lib/libc/stdlib/div.c, Revision 1.1

1.1     ! nbrk        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: #include <stdlib.h>            /* div_t */
        !            34:
        !            35: div_t
        !            36: div(num, denom)
        !            37:        int num, denom;
        !            38: {
        !            39:        div_t r;
        !            40:
        !            41:        r.quot = num / denom;
        !            42:        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) {
        !            67:                r.quot++;
        !            68:                r.rem -= denom;
        !            69:        }
        !            70:        return (r);
        !            71: }