a

libmp/mpdigdiv.c

@@ -0,0 +1,43 @@
+#include "os.h"
+#include <mp.h>
+#include "dat.h"
+
+//
+//	divide two digits by one and return quotient
+//
+void
+mpdigdiv(mpdigit *dividend, mpdigit divisor, mpdigit *quotient)
+{
+	mpdigit hi, lo, q, x, y;
+	int i;
+
+	hi = dividend[1];
+	lo = dividend[0];
+
+	// return highest digit value if the result >= 2**32
+	if(hi >= divisor || divisor == 0){
+		divisor = 0;
+		*quotient = ~divisor;
+		return;
+	}
+
+	// at this point we know that hi < divisor
+	// just shift and subtract till we're done
+	q = 0;
+	x = divisor;
+	for(i = Dbits-1; hi > 0 && i >= 0; i--){
+		x >>= 1;
+		if(x > hi)
+			continue;
+		y = divisor<<i;
+		if(x == hi && y > lo)
+			continue;
+		if(y > lo)
+			hi--;
+		lo -= y;
+		hi -= x;
+		q |= 1<<i;
+	}
+	q += lo/divisor;
+	*quotient = q;
+}