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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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