tommath/bn_mp_2expt.c

49 lines
1.1 KiB
C
Raw Normal View History

#include <tommath_private.h>
2004-10-29 18:07:18 -04:00
#ifdef BN_MP_2EXPT_C
2003-02-28 11:08:34 -05:00
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
2003-08-04 21:24:44 -04:00
* LibTomMath is a library that provides multiple-precision
2003-02-28 11:08:34 -05:00
* integer arithmetic as well as number theoretic functionality.
*
2003-08-04 21:24:44 -04:00
* The library was designed directly after the MPI library by
2003-02-28 11:08:34 -05:00
* Michael Fromberger but has been written from scratch with
* additional optimizations in place.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tstdenis82@gmail.com, http://libtom.org
2003-02-28 11:08:34 -05:00
*/
2003-05-29 09:35:26 -04:00
/* computes a = 2**b
2003-02-28 11:09:08 -05:00
*
* Simple algorithm which zeroes the int, grows it then just sets one bit
* as required.
*/
2003-02-28 11:08:34 -05:00
int
mp_2expt (mp_int * a, int b)
{
2003-02-28 11:09:08 -05:00
int res;
2003-02-28 11:08:34 -05:00
2003-08-04 21:24:44 -04:00
/* zero a as per default */
2003-02-28 11:08:34 -05:00
mp_zero (a);
2003-08-04 21:24:44 -04:00
/* grow a to accomodate the single bit */
if ((res = mp_grow (a, (b / DIGIT_BIT) + 1)) != MP_OKAY) {
2003-02-28 11:08:34 -05:00
return res;
}
2003-08-04 21:24:44 -04:00
/* set the used count of where the bit will go */
a->used = (b / DIGIT_BIT) + 1;
2003-08-04 21:24:44 -04:00
/* put the single bit in its place */
2004-08-09 18:15:59 -04:00
a->dp[b / DIGIT_BIT] = ((mp_digit)1) << (b % DIGIT_BIT);
2003-02-28 11:08:34 -05:00
return MP_OKAY;
}
2004-10-29 18:07:18 -04:00
#endif
2005-08-01 12:37:28 -04:00
/* $Source$ */
/* $Revision$ */
/* $Date$ */