+/* Templates for conversions of BigUnsigned to and from primitive integers.
+ * BigInteger.cc needs to instantiate convertToPrimitive, and the uses in
+ * BigUnsigned.cc didn't do the trick; I think gcc inlined convertToPrimitive
+ * instead of generating linkable instantiations. So for consistency, I put
+ * all the templates here. */
+
+// CONSTRUCTION FROM PRIMITIVE INTEGERS
+
+/* Initialize this BigUnsigned from the given primitive integer. The same
+ * pattern works for all primitive integer types, so I put it into a template to
+ * reduce code duplication. (Don't worry: this is protected and we instantiate
+ * it only with primitive integer types.) Type X could be signed, but x is
+ * known to be nonnegative. */
+template <class X>
+void BigUnsigned::initFromPrimitive(X x) {
+ if (x == 0)
+ ; // NumberlikeArray already initialized us to zero.
+ else {
+ // Create a single block. blk is NULL; no need to delete it.
+ cap = 1;
+ blk = new Blk[1];
+ len = 1;
+ blk[0] = Blk(x);
+ }
+}
+
+/* Ditto, but first check that x is nonnegative. I could have put the check in
+ * initFromPrimitive and let the compiler optimize it out for unsigned-type
+ * instantiations, but I wanted to avoid the warning stupidly issued by g++ for
+ * a condition that is constant in *any* instantiation, even if not in all. */
+template <class X>
+void BigUnsigned::initFromSignedPrimitive(X x) {
+ if (x < 0)
+ throw "BigUnsigned constructor: "
+ "Cannot construct a BigUnsigned from a negative number";
+ else
+ initFromPrimitive(x);
+}
+
+// CONVERSION TO PRIMITIVE INTEGERS
+
+/* Template with the same idea as initFromPrimitive. This might be slightly
+ * slower than the previous version with the masks, but it's much shorter and
+ * clearer, which is the library's stated goal. */
+template <class X>
+X BigUnsigned::convertToPrimitive() const {
+ if (len == 0)
+ // The number is zero; return zero.
+ return 0;
+ else if (len == 1) {
+ // The single block might fit in an X. Try the conversion.
+ X x = X(blk[0]);
+ // Make sure the result accurately represents the block.
+ if (Blk(x) == blk[0])
+ // Successful conversion.
+ return x;
+ // Otherwise fall through.
+ }
+ throw "BigUnsigned::to<Primitive>: "
+ "Value is too big to fit in the requested type";
+}
+
+/* Wrap the above in an x >= 0 test to make sure we got a nonnegative result,
+ * not a negative one that happened to convert back into the correct nonnegative
+ * one. (E.g., catch incorrect conversion of 2^31 to the long -2^31.) Again,
+ * separated to avoid a g++ warning. */
+template <class X>
+X BigUnsigned::convertToSignedPrimitive() const {
+ X x = convertToPrimitive<X>();
+ if (x >= 0)
+ return x;
+ else
+ throw "BigUnsigned::to(Primitive): "
+ "Value is too big to fit in the requested type";
+}
+