-static void modmult(Bignum r1, Bignum r2, Bignum modulus, Bignum result) {
- Bignum temp = newbn(modulus[0]+1);
- Bignum tmp2 = newbn(modulus[0]+1);
- int i;
- int bit, bits, digit, smallbit;
-
- enter((">modmult\n"));
- debug(r1);
- debug(r2);
- debug(modulus);
-
- for (i=1; i<=result[0]; i++)
- result[i] = 0; /* result := 0 */
- for (i=1; i<=temp[0]; i++)
- temp[i] = (i > r2[0] ? 0 : r2[i]); /* temp := r2 */
-
- bits = 1+msb(r1);
-
- for (bit = 0; bit < bits; bit++) {
- digit = 1 + bit / 16;
- smallbit = bit % 16;
-
- debug(temp);
- if (digit <= r1[0] && (r1[digit] & (1<<smallbit))) {
- dmsg(("bit %d\n", bit));
- add(temp, result, tmp2);
- if (ge(tmp2, modulus))
- sub(tmp2, modulus, result);
- else
- add(tmp2, Zero, result);
- debug(result);
+ /* Substract q * m from a[i...] */
+ c = 0;
+ for (k = len - 1; k >= 0; k--) {
+ t = (long) q * (long) m[k];
+ t += c;
+ c = t >> 16;
+ if ((unsigned short) t > a[i+k]) c++;
+ a[i+k] -= (unsigned short) t;