Subversion Repositories planix.SVN

#include "os.h"
#include <mp.h>
#include "dat.h"

// res = s != 0 ? b1 : b2
void
mpsel(int s, mpint *b1, mpint *b2, mpint *res)
{
        mpdigit d;
        int n, m, i;

        res->flags |= (b1->flags | b2->flags) & MPtimesafe;
        if((res->flags & MPtimesafe) == 0){
                mpassign(s ? b1 : b2, res);
                return;
        }
        res->flags &= ~MPnorm;

        n = b1->top;
        m = b2->top;
        mpbits(res, Dbits*(n >= m ? n : m));
        res->top = n >= m ? n : m;

        s = (-s^s|s)>>(sizeof(s)*8-1);
        res->sign = (b1->sign & s) | (b2->sign & ~s);

        d = -((mpdigit)s & 1);

        i = 0;
        while(i < n && i < m){
                res->p[i] = (b1->p[i] & d) | (b2->p[i] & ~d);
                i++;
        }
        while(i < n){
                res->p[i] = b1->p[i] & d;
                i++;
        }
        while(i < m){
                res->p[i] = b2->p[i] & ~d;
                i++;
        }
}