3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
12 * The library is free for all purposes without any express
15 * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
18 /* shift left by a certain bit count */
19 int mp_mul_2d (mp_int * a, int b, mp_int * c)
26 if ((res = mp_copy (a, c)) != MP_OKAY) {
31 if (c->alloc < (int)(c->used + b/DIGIT_BIT + 1)) {
32 if ((res = mp_grow (c, c->used + b / DIGIT_BIT + 1)) != MP_OKAY) {
37 /* shift by as many digits in the bit count */
38 if (b >= (int)DIGIT_BIT) {
39 if ((res = mp_lshd (c, b / DIGIT_BIT)) != MP_OKAY) {
44 /* shift any bit count < DIGIT_BIT */
45 d = (mp_digit) (b % DIGIT_BIT);
47 register mp_digit *tmpc, shift, mask, r, rr;
50 /* bitmask for carries */
51 mask = (((mp_digit)1) << d) - 1;
54 shift = DIGIT_BIT - d;
61 for (x = 0; x < c->used; x++) {
62 /* get the higher bits of the current word */
63 rr = (*tmpc >> shift) & mask;
65 /* shift the current word and OR in the carry */
66 *tmpc = ((*tmpc << d) | r) & MP_MASK;
69 /* set the carry to the carry bits of the current word */
75 c->dp[(c->used)++] = r;
83 /* $Source: /cvs/libtom/libtommath/bn_mp_mul_2d.c,v $ */
84 /* $Revision: 1.3 $ */
85 /* $Date: 2006/03/31 14:18:44 $ */