Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

72 lines (59 sloc) 1.731 kb
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
* LibTomMath is library that provides for multiple-precision
* integer arithmetic as well as number theoretic functionality.
*
* The library is designed directly after the MPI library by
* Michael Fromberger but has been written from scratch with
* additional optimizations in place.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
*/
#include <tommath.h>
/* multiply by a digit */
int
mp_mul_d (mp_int * a, mp_digit b, mp_int * c)
{
int res, pa, olduse;
/* make sure c is big enough to hold a*b */
pa = a->used;
if (c->alloc < pa + 1) {
if ((res = mp_grow (c, pa + 1)) != MP_OKAY) {
return res;
}
}
/* get the original destinations used count */
olduse = c->used;
/* set the new temporary used count */
c->used = pa + 1;
{
register mp_digit u, *tmpa, *tmpc;
register mp_word r;
register int ix;
/* alias for a->dp [source] */
tmpa = a->dp;
/* alias for c->dp [dest] */
tmpc = c->dp;
/* zero carry */
u = 0;
for (ix = 0; ix < pa; ix++) {
/* compute product and carry sum for this term */
r = ((mp_word) u) + ((mp_word) * tmpa++) * ((mp_word) b);
/* mask off higher bits to get a single digit */
*tmpc++ = (mp_digit) (r & ((mp_word) MP_MASK));
/* send carry into next iteration */
u = (mp_digit) (r >> ((mp_word) DIGIT_BIT));
}
/* store final carry [if any] */
*tmpc++ = u;
/* now zero digits above the top */
for (; pa < olduse; pa++) {
*tmpc++ = 0;
}
}
mp_clamp (c);
return MP_OKAY;
}
Jump to Line
Something went wrong with that request. Please try again.