#include <tommath.h>
#ifdef BN_MP_EXPT_D_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
 *
 * LibTomMath is a library that provides multiple-precision
 * integer arithmetic as well as number theoretic functionality.
 *
 * The library was designed directly after the MPI library by
 * 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, tomstdenis@gmail.com, http://libtom.org
 */

/* calculate c = a**b  using a square-multiply algorithm */
int mp_expt_d(mp_int * a, mp_digit b, mp_int * c)
{
	int res, x;
	mp_int g;

	if ((res = mp_init_copy(&g, a)) != MP_OKAY) {
		return res;
	}

	/* set initial result */
	mp_set(c, 1);

	for (x = 0; x < (int)DIGIT_BIT; x++) {
		/* square */
		if ((res = mp_sqr(c, c)) != MP_OKAY) {
			mp_clear(&g);
			return res;
		}

		/* if the bit is set multiply */
		if ((b & (mp_digit) (((mp_digit) 1) << (DIGIT_BIT - 1))) != 0) {
			if ((res = mp_mul(c, &g, c)) != MP_OKAY) {
				mp_clear(&g);
				return res;
			}
		}

		/* shift to next bit */
		b <<= 1;
	}

	mp_clear(&g);
	return MP_OKAY;
}
#endif

/* $Source: /cvs/libtom/libtommath/bn_mp_expt_d.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/12/28 01:25:13 $ */