a

libmp/mptov.c

@@ -0,0 +1,69 @@
+#include "os.h"
+#include <mp.h>
+#include "dat.h"
+
+#define VLDIGITS (sizeof(vlong)/sizeof(mpdigit))
+
+/*
+ *  this code assumes that a vlong is an integral number of
+ *  mpdigits long.
+ */
+mpint*
+vtomp(vlong v, mpint *b)
+{
+	int s;
+	uvlong uv;
+
+	if(b == nil)
+		b = mpnew(VLDIGITS*sizeof(mpdigit));
+	else
+		mpbits(b, VLDIGITS*sizeof(mpdigit));
+	mpassign(mpzero, b);
+	if(v == 0)
+		return b;
+	if(v < 0){
+		b->sign = -1;
+		uv = -v;
+	} else
+		uv = v;
+	for(s = 0; s < VLDIGITS && uv != 0; s++){
+		b->p[s] = uv;
+		uv >>= sizeof(mpdigit)*8;
+	}
+	b->top = s;
+	return b;
+}
+
+vlong
+mptov(mpint *b)
+{
+	uvlong v;
+	int s;
+
+	if(b->top == 0)
+		return (vlong) 0;
+
+	mpnorm(b);
+	if(b->top > VLDIGITS){
+		if(b->sign > 0)
+			return (vlong)MAXVLONG;
+		else
+			return (vlong)MINVLONG;
+	}
+
+	v = (uvlong) 0;
+	for(s = 0; s < b->top; s++)
+		v |= b->p[s]<<(s*sizeof(mpdigit)*8);
+
+	if(b->sign > 0){
+		if(v > MAXVLONG)
+			v = MAXVLONG;
+	} else {
+		if(v > MINVLONG)
+			v = MINVLONG;
+		else
+			v = -(vlong)v;
+	}
+
+	return (vlong)v;
+}