Subversion Repositories planix.SVN

#include "os.h"

#include <mp.h>

#include "dat.h"

// res = b >> shift

void

mpright(mpint *b, int shift, mpint *res)

{

	int d, l, r, i;

	mpdigit this, last;

	// a negative right shift is a left shift

	if(shift < 0){

		mpleft(b, -shift, res);

		return;

	}

	if(res != b)

		mpbits(res, b->top*Dbits - shift);

	d = shift/Dbits;

	r = shift - d*Dbits;

	l = Dbits - r;

	// special case digit shifts

	if(r == 0){

		for(i = 0; i < b->top-d; i++)

			res->p[i] = b->p[i+d];

	} else {

		last = b->p[d];

		for(i = 0; i < b->top-d-1; i++){

			this = b->p[i+d+1];

			res->p[i] = (this<<l) | (last>>r);

			last = this;

		}

		res->p[i++] = last>>r;

	}

	while(i > 0 && res->p[i-1] == 0)

		i--;

	res->top = i;

}