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/* 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 <tfm_private.h>
/* c = a * 2**d */
void fp_mul_2d(fp_int *a, int b, fp_int *c)
{
fp_digit carry, carrytmp, shift;
int x;
/* copy it */
fp_copy(a, c);
/* handle whole digits */
if (b >= DIGIT_BIT) {
fp_lshd(c, b/DIGIT_BIT);
}
b %= DIGIT_BIT;
/* shift the digits */
if (b != 0) {
carry = 0;
shift = DIGIT_BIT - b;
for (x = 0; x < c->used; x++) {
carrytmp = c->dp[x] >> shift;
c->dp[x] = (c->dp[x] << b) + carry;
carry = carrytmp;
}
/* store last carry if room */
if (carry && x < FP_SIZE) {
c->dp[c->used++] = carry;
}
}
fp_clamp(c);
}
/* $Source$ */
/* $Revision$ */
/* $Date$ */