### comparison libtommath/bn_mp_2expt.c @ 389:5ff8218bcee9

author Matt Johnston Thu, 11 Jan 2007 03:14:55 +0000 eed26cff980b 60fc6476e044
comparison
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388:fb54020f78e1 389:5ff8218bcee9
1 #include <tommath.h>
2 #ifdef BN_MP_2EXPT_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 *
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
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.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, [email protected], http://math.libtomcrypt.com
16 */
17
18 /* computes a = 2**b
19 *
20 * Simple algorithm which zeroes the int, grows it then just sets one bit
21 * as required.
22 */
23 int
24 mp_2expt (mp_int * a, int b)
25 {
26 int res;
27
28 /* zero a as per default */
29 mp_zero (a);
30
31 /* grow a to accomodate the single bit */
32 if ((res = mp_grow (a, b / DIGIT_BIT + 1)) != MP_OKAY) {
33 return res;
34 }
35
36 /* set the used count of where the bit will go */
37 a->used = b / DIGIT_BIT + 1;
38
39 /* put the single bit in its place */
40 a->dp[b / DIGIT_BIT] = ((mp_digit)1) << (b % DIGIT_BIT);
41
42 return MP_OKAY;
43 }
44 #endif
45
46 /* \$Source: /cvs/libtom/libtommath/bn_mp_2expt.c,v \$ */
47 /* \$Revision: 1.3 \$ */
48 /* \$Date: 2006/03/31 14:18:44 \$ */