IPAddress::empty()

Summary: Checks if IPAddress has not been initialized.

Test Plan: unit test

Reviewed By: tudorb@fb.com

Subscribers: tudorb

FB internal diff: D1459525

folly/IPAddress.h

@@ -251,6 +251,12 @@ class IPAddress : boost::totally_ordered<IPAddress> {
     return isV6() && asV6().isIPv4Mapped();
   }
 
+  // @return true if address is uninitialized
+  bool empty() const { return (family_ == AF_UNSPEC); }
+
+  // @return true if address is initialized
+  explicit operator bool() { return !empty(); }
+
   // @return true if this is an IPAddressV4 instance
   bool isV4() const { return (family_ == AF_INET); }
 

folly/test/IPAddressTest.cpp

@@ -31,14 +31,20 @@ TEST(IPAddress, CodeExample) {
   EXPECT_EQ(4, sizeof(IPAddressV4));
   EXPECT_EQ(16, sizeof(IPAddressV6));
   EXPECT_EQ(20, sizeof(IPAddress));
+  IPAddress uninitaddr;
   IPAddress v4addr("192.0.2.129");
   IPAddress v6map("::ffff:192.0.2.129");
+  ASSERT_TRUE(uninitaddr.empty());
+  ASSERT_FALSE(v4addr.empty());
+  ASSERT_FALSE(v6map.empty());
   EXPECT_TRUE(v4addr.inSubnet("192.0.2.0/24"));
   EXPECT_TRUE(v4addr.inSubnet(IPAddress("192.0.2.0"), 24));
   EXPECT_TRUE(v4addr.inSubnet("192.0.2.128/30"));
   EXPECT_FALSE(v4addr.inSubnet("192.0.2.128/32"));
   EXPECT_EQ(2164392128, v4addr.asV4().toLong());
   EXPECT_EQ(3221226113, v4addr.asV4().toLongHBO());
+  ASSERT_FALSE(uninitaddr.isV4());
+  ASSERT_FALSE(uninitaddr.isV6());
   ASSERT_TRUE(v4addr.isV4());
   ASSERT_TRUE(v6map.isV6());
   EXPECT_TRUE(v4addr == v6map);