68 lines
1.5 KiB
C
68 lines
1.5 KiB
C
/* TomsFastMath, a fast ISO C bignum library.
|
|
*
|
|
* This project is meant to fill in where LibTomMath
|
|
* falls short. That is speed ;-)
|
|
*
|
|
* This project is public domain and free for all purposes.
|
|
*
|
|
* Tom St Denis, tomstdenis@gmail.com
|
|
*/
|
|
#include "bignum_fast.h"
|
|
|
|
void fp_mul_2(fp_int * a, fp_int * b)
|
|
{
|
|
int x, oldused;
|
|
|
|
oldused = b->used;
|
|
b->used = a->used;
|
|
|
|
{
|
|
register fp_digit r, rr, *tmpa, *tmpb;
|
|
|
|
/* alias for source */
|
|
tmpa = a->dp;
|
|
|
|
/* alias for dest */
|
|
tmpb = b->dp;
|
|
|
|
/* carry */
|
|
r = 0;
|
|
for (x = 0; x < a->used; x++) {
|
|
|
|
/* get what will be the *next* carry bit from the
|
|
* MSB of the current digit
|
|
*/
|
|
rr = *tmpa >> ((fp_digit)(DIGIT_BIT - 1));
|
|
|
|
/* now shift up this digit, add in the carry [from the previous] */
|
|
*tmpb++ = ((*tmpa++ << ((fp_digit)1)) | r);
|
|
|
|
/* copy the carry that would be from the source
|
|
* digit into the next iteration
|
|
*/
|
|
r = rr;
|
|
}
|
|
|
|
/* new leading digit? */
|
|
if (r != 0 && b->used != (FP_SIZE-1)) {
|
|
/* add a MSB which is always 1 at this point */
|
|
*tmpb = 1;
|
|
++(b->used);
|
|
}
|
|
|
|
/* now zero any excess digits on the destination
|
|
* that we didn't write to
|
|
*/
|
|
tmpb = b->dp + b->used;
|
|
for (x = b->used; x < oldused; x++) {
|
|
*tmpb++ = 0;
|
|
}
|
|
}
|
|
b->sign = a->sign;
|
|
}
|
|
|
|
|
|
/* $Source: /cvs/libtom/tomsfastmath/src/mul/fp_mul_2.c,v $ */
|
|
/* $Revision: 1.1 $ */
|
|
/* $Date: 2006/12/31 21:25:53 $ */
|