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#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){
sign = -1;
t = b1;
b1 = b2;
b2 = t;
} else
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){
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;
}
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