Add new InternetAddress class with a static lookup function (including IPv6

sdk/lib/io/socket.dart

Index: sdk/lib/io/socket.dart
diff --git a/sdk/lib/io/socket.dart b/sdk/lib/io/socket.dart
index b8be4d6ac2df0b88be4fba1be11b958d95fa232b..fca699741fa34bcd35c5ce7138ccfa6bc27ed574 100644
--- a/sdk/lib/io/socket.dart
+++ b/sdk/lib/io/socket.dart
@@ -4,6 +4,73 @@
 
 part of dart.io;
 
+
+/**
+ * [InternetAddressType] is the type an [InternetAddress]. Currently, IPv4 and
+ * IPv6 are supported.
+ */
+class InternetAddressType {
+  static const InternetAddressType IPv4 = const InternetAddressType._(0);
+  static const InternetAddressType IPv6 = const InternetAddressType._(1);
+  static const InternetAddressType ANY = const InternetAddressType._(-1);
+
+  final int _value;
+
+  const InternetAddressType._(int this._value);
+
+  factory InternetAddressType._from(int value) {
+    if (value == 0) return IPv4;
+    if (value == 1) return IPv6;
+    throw new ArgumentError("Invalid type: $value");
+  }
+
+  /**
+   * Get the name of the type, e.g. "IPv4" or "IPv6".
+   */
+  String get name {
+    switch (_value) {
+      case -1: return "ANY";
+      case 0: return "IPv4";
+      case 1: return "IPv6";
+      default: throw new ArgumentError("Invalid InternetAddress");
+    }
+  }
+
+  String toString() => "InternetAddressType($name)";
+}
+
+
+/**
+ * The [InternetAddress] is an object reflecting either a remote or a local
+ * address, for wich a socket can be connected to or bound on.
+ *
+ */
+abstract class InternetAddress {
+  /**
+   * The [type] of the [InternetAddress] specified what IP procotol.
+   */
+  InternetAddressType type;
+
+  /**
+   * The resolved address of the host.
+   */
+  String get address;
+
+  /**
+   * The host used to lookup the address.
+   */
+  String get host;
+
+  /**
+   * Lookup a host, returning a Future of a list of [InternetAddress]s. If
+   * [type] is [InternetAddressType.ANY], it will lookup both IPv4 and IPv6
+   * addresses. The order of the list depends on the local machine and the DNS
+   * lookup performed, and can as such change over time.
+   */
+  external static Future<List<InternetAddress>> lookup(
+      String host, {InternetAddressType type: InternetAddressType.ANY});
+}
+
 /**
  * The RawServerSocket is a server socket, providing a stream of low-level
  * [RawSocket]s.
@@ -32,8 +99,8 @@ abstract class RawServerSocket implements Stream<RawSocket> {
    * the system.
    */
   external static Future<RawServerSocket> bind([String address = "127.0.0.1",
-                                               int port = 0,
-                                               int backlog = 0]);
+                                                int port = 0,
+                                                int backlog = 0]);
 
   /**
    * Returns the port used by this socket.
@@ -144,8 +211,12 @@ abstract class RawSocket implements Stream<RawSocketEvent> {
    * Creates a new socket connection to the host and port and returns a [Future]
    * that will complete with either a [RawSocket] once connected or an error
    * if the host-lookup or connection failed.
+   *
+   * [host] can either be a [String] or an [InternetAddress]. If [host] is a
+   * [String], [connect] will perform a [InternetAddress.lookup] and use
+   * the first value in the list.
    */
-  external static Future<RawSocket> connect(String host, int port);
+  external static Future<RawSocket> connect(host, int port);
 
   /**
    * Returns the number of received and non-read bytes in the socket that
@@ -181,9 +252,9 @@ abstract class RawSocket implements Stream<RawSocketEvent> {
   int get remotePort;
 
   /**
-   * Returns the host used to connect this socket.
+   * Returns the [InternetAddress] used to connect this socket.
    */
-  String get host;
+  InternetAddress get address;
 
   /**
    * Returns the remote host connected to by this socket.
@@ -238,8 +309,12 @@ abstract class Socket implements Stream<List<int>>, IOSink {
    * Creats a new socket connection to the host and port and returns a [Future]
    * that will complete with either a [Socket] once connected or an error
    * if the host-lookup or connection failed.
+   *
+   * [host] can either be a [String] or an [InternetAddress]. If [host] is a
+   * [String], [connect] will perform a [InternetAddress.lookup] and use
+   * the first value in the list.
    */
-  external static Future<Socket> connect(String host, int port);
+  external static Future<Socket> connect(host, int port);
 
   /**
    * Destroy the socket in both directions. Calling [destroy] will make the
@@ -270,9 +345,9 @@ abstract class Socket implements Stream<List<int>>, IOSink {
   int get remotePort;
 
   /**
-   * Returns the host used to connect this socket.
+   * Returns the [InternetAddress] used to connect this socket.
    */
-  String get host;
+  InternetAddress get address;
 
   /**
    * Returns the remote host connected to by this socket.