#include <tommath.h>
#ifdef BN_MP_DIV_2_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
 */

/* b = a/2 */
int mp_div_2(mp_int * a, mp_int * b)
{
	int x, res, oldused;

	/* copy */
	if (b->alloc < a->used) {
		if ((res = mp_grow(b, a->used)) != MP_OKAY) {
			return res;
		}
	}

	oldused = b->used;
	b->used = a->used;
	{
		register mp_digit r, rr, *tmpa, *tmpb;

		/* source alias */
		tmpa = a->dp + b->used - 1;

		/* dest alias */
		tmpb = b->dp + b->used - 1;

		/* carry */
		r = 0;
		for (x = b->used - 1; x >= 0; x--) {
			/* get the carry for the next iteration */
			rr = *tmpa & 1;

			/* shift the current digit, add in carry and store */
			*tmpb-- = (*tmpa-- >> 1) | (r << (DIGIT_BIT - 1));

			/* forward carry to next iteration */
			r = rr;
		}

		/* zero excess digits */
		tmpb = b->dp + b->used;
		for (x = b->used; x < oldused; x++) {
			*tmpb++ = 0;
		}
	}
	b->sign = a->sign;
	mp_clamp(b);
	return MP_OKAY;
}
#endif

/* $Source: /cvs/libtom/libtommath/bn_mp_div_2.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/12/28 01:25:13 $ */