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Annotation of coherent/d/usr/lib/libmp/sdiv.c, revision 1.1

1.1     ! root        1: #include "mprec.h"
        !             2: #include <assert.h>
        !             3: 
        !             4: 
        !             5: /*
        !             6:  *     Sdiv divides the mint pointed to by "a" by the int "n".  It sets
        !             7:  *     the mint pointed to by "q" to the quotient and the int pointed to
        !             8:  *     by "r" to the remainder.
        !             9:  *     Note that it is assumed that 1 <= "n" <= BASE.
        !            10:  *     The division is performed such that the following two properties
        !            11:  *     hold :
        !            12:  *             1. r + q * n = a.
        !            13:  *             2. the sign of r = the sign of q.
        !            14:  *             3. the abs. value of r < the abs. value of b.
        !            15:  *     Note that "a" == "q" is permissable.
        !            16:  */
        !            17: 
        !            18: void
        !            19: sdiv(a, n, q, r)
        !            20: mint *a, *q;
        !            21: register int n;
        !            22: int *r;
        !            23: {
        !            24:        register char   *qp, *ap;
        !            25:        char    *res;
        !            26:        int     npfl;   /* numerator positive flag */
        !            27:        char    dmfl;   /* denominator minus flag */
        !            28:        mint    al;
        !            29:        register int    rem;
        !            30: 
        !            31:        if (n == 0)
        !            32:                mperr("division by zero attempted");
        !            33:        if (dmfl = n < 0)
        !            34:                n = -n;
        !            35:        assert(1 <= n && n <= BASE);
        !            36: 
        !            37:        /* set npfl and negate a if necessary */
        !            38:        npfl = ispos(a);
        !            39:        if (!npfl) {
        !            40:                minit(&al);
        !            41:                mneg(a, &al);
        !            42:                a = &al;
        !            43:        }
        !            44: 
        !            45:        /* allocate space for result */
        !            46:        res = (char *)mpalc(a->len);
        !            47: 
        !            48:        /* compute quotient, most sig. digit first */
        !            49:        qp = res + a->len;
        !            50:        ap = a->val + a->len;
        !            51:        rem = 0;
        !            52:        while (qp > res) {
        !            53:                rem = BASE * rem + *--ap;
        !            54:                *--qp = rem / n;
        !            55:                rem %= n;
        !            56:        }
        !            57:        mpfree(q->val);
        !            58:        q->val = res;
        !            59:        q->len = a->len;
        !            60:        norm(q);
        !            61: 
        !            62:        /* fix up sign if a was negative */
        !            63:        if (npfl ? dmfl : !dmfl) {
        !            64:                rem = -rem;
        !            65:                mneg(q, q);
        !            66:        }
        !            67:        if (!npfl)
        !            68:                mpfree(al.val);
        !            69:        *r = rem;
        !            70: }

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