Subversion Repositories planix.SVN

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

// diff = abs(b1) - abs(b2), i.e., subtract the magnitudes
void
mpmagsub(mpint *b1, mpint *b2, mpint *diff)
{
        int n, m, sign;
        mpint *t;

        // get the sizes right
        if(mpmagcmp(b1, b2) < 0){
                assert(((b1->flags | b2->flags | diff->flags) & MPtimesafe) == 0);
                sign = -1;
                t = b1;
                b1 = b2;
                b2 = t;
        } else {
                diff->flags |= (b1->flags | b2->flags) & MPtimesafe;
                sign = 1;
        }
        n = b1->top;
        m = b2->top;
        if(m == 0){
                mpassign(b1, diff);
                diff->sign = sign;
                return;
        }
        mpbits(diff, n*Dbits);

        mpvecsub(b1->p, n, b2->p, m, diff->p);
        diff->sign = sign;
        diff->top = n;
        mpnorm(diff);
}

// diff = b1 - b2
void
mpsub(mpint *b1, mpint *b2, mpint *diff)
{
        int sign;

        if(b1->sign != b2->sign){
                assert(((b1->flags | b2->flags | diff->flags) & MPtimesafe) == 0);
                sign = b1->sign;
                mpmagadd(b1, b2, diff);
                diff->sign = sign;
                return;
        }

        sign = b1->sign;
        mpmagsub(b1, b2, diff);
        if(diff->top != 0)
                diff->sign *= sign;
}