86 lines
1.9 KiB
C
86 lines
1.9 KiB
C
|
#include <tommath.h>
|
||
|
|
#ifdef BN_MP_MUL_2D_C
|
||
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis
|
||
|
|
*
|
||
|
|
* LibTomMath is a library that provides multiple-precision
|
||
|
|
* integer arithmetic as well as number theoretic functionality.
|
||
|
|
*
|
||
|
|
* The library was 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@gmail.com, http://libtom.org
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* shift left by a certain bit count */
|
||
|
|
int mp_mul_2d (mp_int * a, int b, mp_int * c)
|
||
|
|
{
|
||
|
|
mp_digit d;
|
||
|
|
int res;
|
||
|
|
|
||
|
|
/* copy */
|
||
|
|
if (a != c) {
|
||
|
|
if ((res = mp_copy (a, c)) != MP_OKAY) {
|
||
|
|
return res;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
if (c->alloc < (int)(c->used + b/DIGIT_BIT + 1)) {
|
||
|
|
if ((res = mp_grow (c, c->used + b / DIGIT_BIT + 1)) != MP_OKAY) {
|
||
|
|
return res;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* shift by as many digits in the bit count */
|
||
|
|
if (b >= (int)DIGIT_BIT) {
|
||
|
|
if ((res = mp_lshd (c, b / DIGIT_BIT)) != MP_OKAY) {
|
||
|
|
return res;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* shift any bit count < DIGIT_BIT */
|
||
|
|
d = (mp_digit) (b % DIGIT_BIT);
|
||
|
|
if (d != 0) {
|
||
|
|
register mp_digit *tmpc, shift, mask, r, rr;
|
||
|
|
register int x;
|
||
|
|
|
||
|
|
/* bitmask for carries */
|
||
|
|
mask = (((mp_digit)1) << d) - 1;
|
||
|
|
|
||
|
|
/* shift for msbs */
|
||
|
|
shift = DIGIT_BIT - d;
|
||
|
|
|
||
|
|
/* alias */
|
||
|
|
tmpc = c->dp;
|
||
|
|
|
||
|
|
/* carry */
|
||
|
|
r = 0;
|
||
|
|
for (x = 0; x < c->used; x++) {
|
||
|
|
/* get the higher bits of the current word */
|
||
|
|
rr = (*tmpc >> shift) & mask;
|
||
|
|
|
||
|
|
/* shift the current word and OR in the carry */
|
||
|
|
*tmpc = ((*tmpc << d) | r) & MP_MASK;
|
||
|
|
++tmpc;
|
||
|
|
|
||
|
|
/* set the carry to the carry bits of the current word */
|
||
|
|
r = rr;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* set final carry */
|
||
|
|
if (r != 0) {
|
||
|
|
c->dp[(c->used)++] = r;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
mp_clamp (c);
|
||
|
|
return MP_OKAY;
|
||
|
|
}
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/* $Source$ */
|
||
|
|
/* $Revision: 0.41 $ */
|
||
|
|
/* $Date: 2007-04-18 09:58:18 +0000 $ */
|