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Annotation of coherent/d/usr/lib/libmp/smult.c, revision 1.1.1.1

1.1       root        1: #include "mprec.h"
                      2: #include <assert.h>
                      3: 
                      4: 
                      5: /*
                      6:  *     Smult sets the mint pointed to by "c" to the product of that pointed
                      7:  *     to by "a" and the char "n".  Note that "n" is assumed to be between
                      8:  *     0 and NEFL.  Also note that "a" == "c" is permissable.
                      9:  */
                     10: 
                     11: void
                     12: smult(a, n, c)
                     13: mint *a, *c;
                     14: char n;
                     15: {
                     16:        register char *rp, *ap;
                     17:        register int carry;
                     18:        char *limit;
                     19:        char *res;
                     20: 
                     21:        assert(0 <= n && n <= NEFL);
                     22: 
                     23:        /* handle zero specially */
                     24:        if (n == 0) {
                     25:                mcopy(mzero, c);
                     26:                return;
                     27:        }
                     28: 
                     29:        /* allocate space for result */
                     30:        rp = (char *)mpalc(a->len + 1);
                     31:        res = rp;
                     32: 
                     33:        /* perform multiplication assuming a is positive */
                     34:        ap = a->val;
                     35:        limit = ap + a->len;
                     36:        carry = 0;
                     37:        while (ap < limit) {
                     38:                carry += *ap++ * n;
                     39:                *rp++ = carry % BASE;
                     40:                carry >>= L2BASE;
                     41:        }
                     42:        --ap;
                     43: 
                     44:        /* if a was negative, correct carry */
                     45:        if (!ispos(a))
                     46:                carry += BASE - n;
                     47: 
                     48:        /* set carry in place and replace old c value */
                     49:        *rp = carry;
                     50:        assert(0 <= carry && carry <= NEFL);
                     51:        assert((carry==NEFL && *ap==NEFL) || (carry!=NEFL && *ap!=NEFL));
                     52:        mpfree(c->val);
                     53:        c->val = res;
                     54:        c->len = a->len + 1;
                     55:        norm(c);
                     56: }

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