a

libmp/mpadd.c

@@ -0,0 +1,54 @@
+#include "os.h"
+#include <mp.h>
+#include "dat.h"
+
+// sum = abs(b1) + abs(b2), i.e., add the magnitudes
+void
+mpmagadd(mpint *b1, mpint *b2, mpint *sum)
+{
+	int m, n;
+	mpint *t;
+
+	// get the sizes right
+	if(b2->top > b1->top){
+		t = b1;
+		b1 = b2;
+		b2 = t;
+	}
+	n = b1->top;
+	m = b2->top;
+	if(n == 0){
+		mpassign(mpzero, sum);
+		return;
+	}
+	if(m == 0){
+		mpassign(b1, sum);
+		return;
+	}
+	mpbits(sum, (n+1)*Dbits);
+	sum->top = n+1;
+
+	mpvecadd(b1->p, n, b2->p, m, sum->p);
+	sum->sign = 1;
+
+	mpnorm(sum);
+}
+
+// sum = b1 + b2
+void
+mpadd(mpint *b1, mpint *b2, mpint *sum)
+{
+	int sign;
+
+	if(b1->sign != b2->sign){
+		if(b1->sign < 0)
+			mpmagsub(b2, b1, sum);
+		else
+			mpmagsub(b1, b2, sum);
+	} else {
+		sign = b1->sign;
+		mpmagadd(b1, b2, sum);
+		if(sum->top != 0)
+			sum->sign = sign;
+	}
+}