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#include "os.h"
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#include <mp.h>
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#include "dat.h"
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// diff = abs(b1) - abs(b2), i.e., subtract the magnitudes
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void
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mpmagsub(mpint *b1, mpint *b2, mpint *diff)
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{
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	int n, m, sign;
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	mpint *t;
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	// get the sizes right
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	if(mpmagcmp(b1, b2) < 0){
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		assert(((b1->flags | b2->flags | diff->flags) & MPtimesafe) == 0);
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		sign = -1;
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		t = b1;
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		b1 = b2;
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		b2 = t;
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	} else {
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		diff->flags |= (b1->flags | b2->flags) & MPtimesafe;
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		sign = 1;
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	}
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	n = b1->top;
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	m = b2->top;
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	if(m == 0){
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		mpassign(b1, diff);
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		diff->sign = sign;
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		return;
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	}
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	mpbits(diff, n*Dbits);
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	mpvecsub(b1->p, n, b2->p, m, diff->p);
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	diff->sign = sign;
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	diff->top = n;
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	mpnorm(diff);
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}
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// diff = b1 - b2
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void
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mpsub(mpint *b1, mpint *b2, mpint *diff)
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{
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	int sign;
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	if(b1->sign != b2->sign){
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		assert(((b1->flags | b2->flags | diff->flags) & MPtimesafe) == 0);
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		sign = b1->sign;
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		mpmagadd(b1, b2, diff);
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		diff->sign = sign;
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		return;
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	}
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	sign = b1->sign;
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	mpmagsub(b1, b2, diff);
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	if(diff->top != 0)
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		diff->sign *= sign;
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}