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)26mp_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