1 /*	$NetBSD: bn_mp_2expt.c,v 1.1.1.2 2014/04/24 12:45:31 pettai Exp $	*/
2 
3 #include <tommath.h>
4 #ifdef BN_MP_2EXPT_C
5 /* LibTomMath, multiple-precision integer library -- Tom St Denis
6  *
7  * LibTomMath is a library that provides multiple-precision
8  * integer arithmetic as well as number theoretic functionality.
9  *
10  * The library was designed directly after the MPI library by
11  * Michael Fromberger but has been written from scratch with
12  * additional optimizations in place.
13  *
14  * The library is free for all purposes without any express
15  * guarantee it works.
16  *
17  * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
18  */
19 
20 /* computes a = 2**b
21  *
22  * Simple algorithm which zeroes the int, grows it then just sets one bit
23  * as required.
24  */
25 int
mp_2expt(mp_int * a,int b)26 mp_2expt (mp_int * a, int b)
27 {
28   int     res;
29 
30   /* zero a as per default */
31   mp_zero (a);
32 
33   /* grow a to accomodate the single bit */
34   if ((res = mp_grow (a, b / DIGIT_BIT + 1)) != MP_OKAY) {
35     return res;
36   }
37 
38   /* set the used count of where the bit will go */
39   a->used = b / DIGIT_BIT + 1;
40 
41   /* put the single bit in its place */
42   a->dp[b / DIGIT_BIT] = ((mp_digit)1) << (b % DIGIT_BIT);
43 
44   return MP_OKAY;
45 }
46 #endif
47 
48 /* Source: /cvs/libtom/libtommath/bn_mp_2expt.c,v  */
49 /* Revision: 1.4  */
50 /* Date: 2006/12/28 01:25:13  */
51