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
19 int mp_div_2(mp_int * a, mp_int * b)
24 if (b->alloc < a->used) {
25 if ((res = mp_grow (b, a->used)) != MP_OKAY) {
33 register mp_digit r, rr, *tmpa, *tmpb;
36 tmpa = a->dp + b->used - 1;
39 tmpb = b->dp + b->used - 1;
43 for (x = b->used - 1; x >= 0; x--) {
44 /* get the carry for the next iteration */
47 /* shift the current digit, add in carry and store */
48 *tmpb-- = (*tmpa-- >> 1) | (r << (DIGIT_BIT - 1));
50 /* forward carry to next iteration */
54 /* zero excess digits */
55 tmpb = b->dp + b->used;
56 for (x = b->used; x < oldused; x++) {
66 /* $Source: /cvs/libtom/libtommath/bn_mp_div_2.c,v $ */
67 /* $Revision: 1.3 $ */
68 /* $Date: 2006/03/31 14:18:44 $ */