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

1.1     ! root        1: #include "mprec.h"
        !             2: 
        !             3: 
        !             4: /*
        !             5:  *     Mult multiplies the mint pointed to by "a" by that pointed to
        !             6:  *     by "b" and places the result in "c".  Note that no assumption
        !             7:  *     is made as to "a", "b" and "c" all being different.
        !             8:  */
        !             9: 
        !            10: void
        !            11: mult(a, b, c)
        !            12: register mint *a, *b;
        !            13: mint *c;
        !            14: {
        !            15:        mint res, al;
        !            16:        int apos;       /* a-is-positive flag */
        !            17:        char *ap;
        !            18:        register unsigned count;
        !            19: 
        !            20:        /* make sure that b is at least as long as a */
        !            21:        if (a->len > b->len) {
        !            22:                register mint *temp;
        !            23: 
        !            24:                temp = a;
        !            25:                a = b;
        !            26:                b = temp;
        !            27:        }
        !            28: 
        !            29:        /* replace a by abs. value */
        !            30:        apos = ispos(a);
        !            31:        if (!apos) {
        !            32:                minit(&al);
        !            33:                mneg(a, &al);
        !            34:                a = &al;
        !            35:        }
        !            36: 
        !            37:        /* if a is one byte, use smult */
        !            38:        if (a->len == 1) {
        !            39:                smult(b, *a->val, c);
        !            40:                if (!apos) {
        !            41:                        mneg(c, c);
        !            42:                        mpfree(al.val);
        !            43:                }
        !            44:                return;
        !            45:        }
        !            46: 
        !            47:        /* allocate result and zero it out */
        !            48:        res.len = a->len + b->len;
        !            49:        res.val = (char *)mpalc(res.len);
        !            50:        count = res.len;
        !            51:        {
        !            52:                register char *ap;
        !            53: 
        !            54:                ap = res.val;
        !            55:                while (count-- != 0)
        !            56:                        *ap++ = 0;
        !            57:        }
        !            58: 
        !            59:        /* form partial products and total in res */
        !            60:        count = a->len;
        !            61:        ap = a->val + a->len;
        !            62:        while (count-- != 0) {
        !            63:                msma(b, *--ap, count, &res);
        !            64:        }
        !            65:        norm(&res);
        !            66: 
        !            67:        /* if needed, negate result and throw away negated a */
        !            68:        if (!apos) {
        !            69:                mpfree(al.val);
        !            70:                mneg(&res, &res);
        !            71:        }
        !            72: 
        !            73:        /* replace old c value by new one */
        !            74:        mpfree(c->val);
        !            75:        *c = res;
        !            76: }

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