// System.Net.Sockets.Socket.cs
//
// Authors:
//    Phillip Pearson (pp@myelin.co.nz)
//    Dick Porter <dick@ximian.com>
//
// Copyright (C) 2001, 2002 Phillip Pearson and Ximian, Inc.
//    http://www.myelin.co.nz
//

using System;
using System.Net;
using System.Collections;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Reflection;
using System.IO;

namespace System.Net.Sockets 
{
	public class Socket : IDisposable 
	{
		private sealed class SocketAsyncResult: IAsyncResult 
		{
			private object state;
			private WaitHandle waithandle;
			private bool completed_sync, completed;
			private Worker worker;
			private Exception delayedException = null;

			public SocketAsyncResult(object state) {
				this.state=state;
				completed_sync=completed=false;
			}

			public void SetDelayedException (Exception e) {
				delayedException = e;
			}

			public void CheckIfThrowDelayedException () {
				if (delayedException != null)
					throw delayedException;
			}

			public object AsyncState {
				get {
					return(state);
				}
			}

			public WaitHandle AsyncWaitHandle {
				get {
					lock (this) {
						if (waithandle == null)
							waithandle = new ManualResetEvent (completed);
					}

					return waithandle;
				}
				set {
					waithandle=value;
				}
			}

			public bool CompletedSynchronously {
				get {
					return(completed_sync);
				}
			}

			public bool IsCompleted {
				get {
					return(completed);
				}
				set {
					completed=value;
					lock (this) {
						if (waithandle != null && value) {
							((ManualResetEvent) waithandle).Set ();
						}
					}
				}
			}
			
			public Worker Worker {
				get {
					return(worker);
				}
				set {
					worker=value;
				}
			}
		}

		private sealed class Worker 
		{
			private AsyncCallback callback;
			private SocketAsyncResult result;
			private Socket socket;

			// Parameters
			private EndPoint endpoint;	// Connect,ReceiveFrom,SendTo
			private byte[] buffer;		// Receive,ReceiveFrom,Send,SendTo
			private int offset;		// Receive,ReceiveFrom,Send,SendTo
			private int size;		// Receive,ReceiveFrom,Send,SendTo
			private SocketFlags sockflags;	// Receive,ReceiveFrom,Send,SendTo

			// Return values
			private Socket acc_socket;
			private int total;
			

			// For Accept
			public Worker(Socket req_sock,
				      AsyncCallback req_callback,
				      SocketAsyncResult req_result)
				: this(req_sock, null, 0, 0, SocketFlags.None,
				       null, req_callback, req_result) {}

			// For Connect
			public Worker(Socket req_sock, EndPoint req_endpoint,
				      AsyncCallback req_callback,
				      SocketAsyncResult req_result)
				: this(req_sock, null, 0, 0, SocketFlags.None,
				       req_endpoint, req_callback,
				       req_result) {}

			// For Receive and Send
			public Worker(Socket req_sock, byte[] req_buffer,
				      int req_offset, int req_size,
				      SocketFlags req_sockflags,
				      AsyncCallback req_callback,
				      SocketAsyncResult req_result)
				: this(req_sock, req_buffer, req_offset,
				       req_size, req_sockflags, null,
				       req_callback, req_result) {}

			// For ReceiveFrom and SendTo
			public Worker(Socket req_sock, byte[] req_buffer,
				      int req_offset, int req_size,
				      SocketFlags req_sockflags,
				      EndPoint req_endpoint,
				      AsyncCallback req_callback,
				      SocketAsyncResult req_result) {
				socket=req_sock;
				buffer=req_buffer;
				offset=req_offset;
				size=req_size;
				sockflags=req_sockflags;
				endpoint=req_endpoint;
				callback=req_callback;
				result=req_result;
			}

			private void End() {
				result.IsCompleted=true;
				if (callback != null)
					callback(result);
			}
			
			public void Accept() {
				lock(result) {
					try {
						acc_socket=socket.Accept();
					} catch (Exception e) {
						result.SetDelayedException(e);
					}
					End();
				}
			}

			public void Connect() {
				lock(result) {
					if (socket.Blocking) {
						try {
							socket.Connect(endpoint);
						} catch (Exception e) {
							result.SetDelayedException(e);
						}
						End ();
						return;
					}

					Exception rethrow = null;
					try {
						socket.Connect (endpoint);
					} catch (SocketException e) {
						//WSAEINPROGRESS
						if (e.NativeErrorCode != 10036) {
							result.SetDelayedException(e);	
							End ();
							return;
						}

						socket.Poll (-1, SelectMode.SelectWrite);
						try {
							socket.Connect (endpoint);
						} catch (SocketException e2) {
							rethrow = e2;
						}
					} catch (Exception e3) {
						rethrow = e3;
					}
					
					if (rethrow != null)
						result.SetDelayedException(rethrow);
					End ();
				}
			}

			public void Receive() {
				lock(result) {
					if (socket.Blocking) {
						try {
							total=socket.Receive(buffer, offset,
									     size, sockflags);
						} catch (Exception e) {
	                                                result.SetDelayedException(e);
        	                                }
						End();
						return;
					}

					Exception rethrow = null;
					try {
						total = socket.Receive (buffer, offset, size, sockflags);
					} catch (SocketException e) {
						//WSAEWOULDBLOCK
						if (e.NativeErrorCode != 10035) {
							result.SetDelayedException(e);
							End ();
                                                        return;
						}

						socket.Poll (-1, SelectMode.SelectRead);
						try {
							total = socket.Receive (buffer, offset, size, sockflags);
						} catch (SocketException e2) {
							rethrow = e2;
						}
					} catch (Exception e3) {
						rethrow = e3;
					}

					if (rethrow != null)
						result.SetDelayedException(rethrow);
					End ();
				}
			}

			public void ReceiveFrom() {
				lock(result) {
					if (socket.Blocking) {
						try {
							total=socket.ReceiveFrom(buffer,
										 offset, size,
										 sockflags,
										 ref endpoint);
						} catch (Exception e) {
							result.SetDelayedException(e);
						}
						End();
						return;
					}

					Exception rethrow = null;
					try {
						total = socket.ReceiveFrom (buffer, offset, size,
									sockflags, ref endpoint);
					} catch (SocketException e) {
						//WSAEWOULDBLOCK
						if (e.NativeErrorCode != 10035) {
							result.SetDelayedException(e);
							End ();
                                                        return;
						}

						socket.Poll (-1, SelectMode.SelectRead);
						try {
							total = socket.ReceiveFrom (buffer, offset, size,
										sockflags, ref endpoint);
						} catch (SocketException e2) {
							rethrow = e2;
						}
					} catch (Exception e3) {
						rethrow = e3;
					}

					if (rethrow != null)
						result.SetDelayedException(rethrow);
					End ();
				}
			}

			public void Send() {
				lock(result) {
					if (socket.Blocking) {
						try {
							total=socket.Send(buffer, offset, size,
									  sockflags);
						} catch (Exception e) {
							result.SetDelayedException(e);
						}
						End();
						return;
					}

					Exception rethrow = null;
					try {
						total = socket.Send (buffer, offset, size, sockflags);
					} catch (SocketException e) {
						//WSAEWOULDBLOCK
						if (e.NativeErrorCode != 10035) {
							result.SetDelayedException(e);
							End ();
                                                        return;
						}

						socket.Poll (-1, SelectMode.SelectWrite);
						try {
							total = socket.Send (buffer, offset, size, sockflags);
						} catch (SocketException e2) {
							rethrow = e2;
						}
					} catch (Exception e3) {
						rethrow = e3;
					}

					if (rethrow != null)
						result.SetDelayedException(rethrow);
					End ();
				}
			}

			public void SendTo() {
				lock(result) {
					if (socket.Blocking) {
						try {
							total=socket.SendTo(buffer, offset,
									    size, sockflags,
									    endpoint);
						} catch (Exception e) {
							result.SetDelayedException(e);
						}
						End();
						return;
					}

					Exception rethrow = null;
					try {
						total = socket.SendTo (buffer, offset, size,
									sockflags, endpoint);
					} catch (SocketException e) {
						//WSAEWOULDBLOCK
						if (e.NativeErrorCode != 10035) {
							result.SetDelayedException(e);
							End ();
                                                        return;
						}

						socket.Poll (-1, SelectMode.SelectWrite);
						try {
							total = socket.SendTo (buffer, offset, size,
										sockflags, endpoint);
						} catch (SocketException e2) {
							rethrow = e2;
						}
					} catch (Exception e3) {
						rethrow = e3;
					}

					if (rethrow != null)
						result.SetDelayedException(rethrow);
					End ();
				}
			}

			public EndPoint EndPoint {
				get {
					return(endpoint);
				}
			}

			public Socket Socket {
				get {
					return(acc_socket);
				}
			}

			public int Total {
				get {
					return(total);
				}
			}
		}
			
		/* the field "socket" is looked up by name by the runtime */
		private IntPtr socket;
		private AddressFamily address_family;
		private SocketType socket_type;
		private ProtocolType protocol_type;
		private bool blocking=true;
		private int pendingEnds;
		private int closeDelayed;

		delegate void SocketAsyncCall ();
		/*
		 *	These two fields are looked up by name by the runtime, don't change
		 *  their name without also updating the runtime code.
		 */
		private static int ipv4Supported = -1, ipv6Supported = -1;

		/* When true, the socket was connected at the time of
		 * the last IO operation
		 */
		private bool connected=false;
		/* true if we called Close_internal */
		private bool closed;

		/* Used in LocalEndPoint and RemoteEndPoint if the
		 * Mono.Posix assembly is available
		 */
		private static object unixendpoint=null;
		private static Type unixendpointtype=null;
		
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void Select_internal(ref Socket[] read,
							   ref Socket[] write,
							   ref Socket[] err,
							   int timeout);

		public static void Select(IList read_list, IList write_list,
					  IList err_list, int time_us) {
			if(read_list==null &&
			   write_list==null &&
			   err_list==null) {
				throw new ArgumentNullException();
			}

			int read_count = 0, write_count = 0, err_count = 0;
			Socket[] read_arr = null;
			Socket[] write_arr = null;
			Socket[] err_arr = null;

			if (read_list!=null)
				read_count=read_list.Count;

			if (read_count != 0)
				read_arr=new Socket[read_count];

			if (write_list!=null)
				write_count=write_list.Count;

			if (write_count != 0)
				write_arr=new Socket[write_count];

			if (err_list!=null)
				err_count=err_list.Count;

			if (err_count != 0)
				err_arr=new Socket[err_count];
			
			int i;

			if (read_count != 0) {
				i=0;
				
				foreach (Socket s in read_list) {
					read_arr[i]=s;
					i++;
				}
			}

			if (write_count != 0) {
				i=0;
				foreach (Socket s in write_list) {
					write_arr[i]=s;
					i++;
				}
			}
			
			if (err_count != 0) {
				i=0;
				foreach (Socket s in err_list) {
					err_arr[i]=s;
					i++;
				}
			}

			Select_internal(ref read_arr, ref write_arr,
					ref err_arr, time_us);

			if(read_list!=null) {
				read_list.Clear();
				for(i=0; i<read_arr.Length; i++) {
					read_list.Add(read_arr[i]);
				}
			}
			
			if(write_list!=null) {
				write_list.Clear();
				for(i=0; i<write_arr.Length; i++) {
					write_list.Add(write_arr[i]);
				}
			}
			
			if(err_list!=null) {
				err_list.Clear();
				for(i=0; i<err_arr.Length; i++) {
					err_list.Add(err_arr[i]);
				}
			}
		}

		static Socket() {
			Assembly ass;
			
			try {
				ass=Assembly.Load("Mono.Posix");
			} catch (FileNotFoundException) {
				return;
			}
				
			unixendpointtype=ass.GetType("Mono.Posix.UnixEndPoint");

			/* The endpoint Create() method is an instance
			 * method :-(
			 */
			Type[] arg_types=new Type[1];
			arg_types[0]=typeof(string);
			ConstructorInfo cons=unixendpointtype.GetConstructor(arg_types);

			object[] args=new object[1];
			args[0]="";

			unixendpoint=cons.Invoke(args);
		}

		// private constructor used by Accept, which already
		// has a socket handle to use
		private Socket(AddressFamily family, SocketType type,
			       ProtocolType proto, IntPtr sock) {
			address_family=family;
			socket_type=type;
			protocol_type=proto;
			
			socket=sock;
			connected=true;
		}
		
		// Creates a new system socket, returning the handle
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern IntPtr Socket_internal(AddressFamily family,
						      SocketType type,
						      ProtocolType proto);
		
		public Socket(AddressFamily family, SocketType type,
			      ProtocolType proto) {
			address_family=family;
			socket_type=type;
			protocol_type=proto;
			
			socket=Socket_internal(family, type, proto);
		}

		public AddressFamily AddressFamily {
			get {
				return(address_family);
			}
		}

		// Returns the amount of data waiting to be read on socket
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static int Available_internal(IntPtr socket);
		
		public int Available {
			get {
				if (disposed && closed)
					throw new ObjectDisposedException (GetType ().ToString ());

				return(Available_internal(socket));
			}
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void Blocking_internal(IntPtr socket,
							    bool block);

		public bool Blocking {
			get {
				return(blocking);
			}
			set {
				Blocking_internal(socket, value);
				blocking=value;
			}
		}

		public bool Connected {
			get {
				return(connected);
			}
		}

		public IntPtr Handle {
			get {
				return(socket);
			}
		}

		// Returns the local endpoint details in addr and port
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static SocketAddress LocalEndPoint_internal(IntPtr socket);

		[MonoTODO("Support non-IP endpoints")]
		public EndPoint LocalEndPoint {
			get {
				if (disposed && closed)
					throw new ObjectDisposedException (GetType ().ToString ());

				SocketAddress sa;
				
				sa=LocalEndPoint_internal(socket);

				if(sa.Family==AddressFamily.InterNetwork || sa.Family==AddressFamily.InterNetworkV6) {
					// Stupidly, EndPoint.Create() is an
					// instance method
					return new IPEndPoint(0, 0).Create(sa);
				} else if (sa.Family==AddressFamily.Unix &&
					   unixendpoint!=null) {
					return((EndPoint)unixendpointtype.InvokeMember("Create", BindingFlags.InvokeMethod|BindingFlags.Instance|BindingFlags.Public, null, unixendpoint, new object[] {sa}));
				} else {
					throw new NotImplementedException();
				}
			}
		}

		public ProtocolType ProtocolType {
			get {
				return(protocol_type);
			}
		}

		// Returns the remote endpoint details in addr and port
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static SocketAddress RemoteEndPoint_internal(IntPtr socket);

		[MonoTODO("Support non-IP endpoints")]
		public EndPoint RemoteEndPoint {
			get {
				if (disposed && closed)
					throw new ObjectDisposedException (GetType ().ToString ());

				SocketAddress sa;
				
				sa=RemoteEndPoint_internal(socket);

				if(sa.Family==AddressFamily.InterNetwork || sa.Family==AddressFamily.InterNetworkV6 ) {
					// Stupidly, EndPoint.Create() is an
					// instance method
					return new IPEndPoint(0, 0).Create(sa);
				} else if (sa.Family==AddressFamily.Unix &&
					   unixendpoint!=null) {
					return((EndPoint)unixendpointtype.InvokeMember("Create", BindingFlags.InvokeMethod|BindingFlags.Instance|BindingFlags.Public, null, unixendpoint, new object[] {sa}));
				} else {
					throw new NotImplementedException();
				}
			}
		}

		public SocketType SocketType {
			get {
				return(socket_type);
			}
		}

#if NET_1_1
		public static bool SupportsIPv4 {
			get {
				CheckProtocolSupport();
				return ipv4Supported == 1;
			}
		}

		public static bool SupportsIPv6 {
			get {
				CheckProtocolSupport();
				return ipv6Supported == 1;
			}
		}
#else
		internal static bool SupportsIPv4 
		{
			get 
			{
				return true;
			}
		}

		internal static bool SupportsIPv6 
		{
			get 
			{
				return false;
			}
		}
#endif

		internal static void CheckProtocolSupport()
		{
			if(ipv4Supported == -1) {
				try  {
					Socket tmp = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
					tmp.Close();

					ipv4Supported = 1;
				}
				catch {
					ipv4Supported = 0;
				}
			}

			if(ipv6Supported == -1) {
				NetConfig config = (NetConfig)System.Configuration.ConfigurationSettings.GetConfig("system.net/settings");

				if(config != null)
					ipv6Supported = config.ipv6Enabled?-1:0;

				if(ipv6Supported != 0) {
					try {
						Socket tmp = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
						tmp.Close();

						ipv6Supported = 1;
					}
					catch { }
				}
			}
		}

		// Creates a new system socket, returning the handle
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static IntPtr Accept_internal(IntPtr sock);
		
		public Socket Accept() {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			IntPtr sock=Accept_internal(socket);
			
			return(new Socket(this.AddressFamily, this.SocketType,
					  this.ProtocolType, sock));
		}

		public IAsyncResult BeginAccept(AsyncCallback callback,
						object state) {

			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			Interlocked.Increment (ref pendingEnds);
			SocketAsyncResult req=new SocketAsyncResult(state);
			Worker worker=new Worker(this, callback, req);
			req.Worker=worker;
			SocketAsyncCall sac = new SocketAsyncCall (worker.Accept);
			sac.BeginInvoke (null, null);
			return(req);
		}

		public IAsyncResult BeginConnect(EndPoint end_point,
						 AsyncCallback callback,
						 object state) {

			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (end_point == null)
				throw new ArgumentNullException ("end_point");

			Interlocked.Increment (ref pendingEnds);
			SocketAsyncResult req=new SocketAsyncResult(state);
			Worker worker=new Worker(this, end_point, callback,
						 req);
			req.Worker=worker;
			SocketAsyncCall sac = new SocketAsyncCall (worker.Connect);
			sac.BeginInvoke (null, null);
			return(req);
		}

		public IAsyncResult BeginReceive(byte[] buffer, int offset,
						 int size,
						 SocketFlags socket_flags,
						 AsyncCallback callback,
						 object state) {

			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (buffer == null)
				throw new ArgumentNullException ("buffer");

			if (offset < 0)
				throw new ArgumentOutOfRangeException ("offset must be >= 0");

			if (size < 0)
				throw new ArgumentOutOfRangeException ("size must be >= 0");

			if (offset + size > buffer.Length)
				throw new ArgumentOutOfRangeException ("offset + size exceeds the buffer length");

			Interlocked.Increment (ref pendingEnds);
			SocketAsyncResult req=new SocketAsyncResult(state);
			Worker worker=new Worker(this, buffer, offset, size,
						 socket_flags, callback, req);
			req.Worker=worker;
			SocketAsyncCall sac = new SocketAsyncCall (worker.Receive);
			sac.BeginInvoke (null, null);
			return(req);
		}

		public IAsyncResult BeginReceiveFrom(byte[] buffer, int offset,
						     int size,
						     SocketFlags socket_flags,
						     ref EndPoint remote_end,
						     AsyncCallback callback,
						     object state) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (buffer == null)
				throw new ArgumentNullException ("buffer");

			if (offset < 0)
				throw new ArgumentOutOfRangeException ("offset must be >= 0");

			if (size < 0)
				throw new ArgumentOutOfRangeException ("size must be >= 0");

			if (offset + size > buffer.Length)
				throw new ArgumentOutOfRangeException ("offset + size exceeds the buffer length");

			Interlocked.Increment (ref pendingEnds);
			SocketAsyncResult req=new SocketAsyncResult(state);
			Worker worker=new Worker(this, buffer, offset, size,
						 socket_flags, remote_end,
						 callback, req);
			req.Worker=worker;
			SocketAsyncCall sac = new SocketAsyncCall (worker.ReceiveFrom);
			sac.BeginInvoke (null, null);
			return(req);
		}

		public IAsyncResult BeginSend(byte[] buffer, int offset,
					      int size,
					      SocketFlags socket_flags,
					      AsyncCallback callback,
					      object state) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (buffer == null)
				throw new ArgumentNullException ("buffer");

			if (offset < 0)
				throw new ArgumentOutOfRangeException ("offset must be >= 0");

			if (size < 0)
				throw new ArgumentOutOfRangeException ("size must be >= 0");

			if (offset + size > buffer.Length)
				throw new ArgumentOutOfRangeException ("offset + size exceeds the buffer length");

			Interlocked.Increment (ref pendingEnds);
			SocketAsyncResult req=new SocketAsyncResult(state);
			Worker worker=new Worker(this, buffer, offset, size,
						 socket_flags, callback, req);
			req.Worker=worker;
			SocketAsyncCall sac = new SocketAsyncCall (worker.Send);
			sac.BeginInvoke (null, null);
			return(req);
		}

		public IAsyncResult BeginSendTo(byte[] buffer, int offset,
						int size,
						SocketFlags socket_flags,
						EndPoint remote_end,
						AsyncCallback callback,
						object state) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (buffer == null)
				throw new ArgumentNullException ("buffer");

			if (offset < 0)
				throw new ArgumentOutOfRangeException ("offset must be >= 0");

			if (size < 0)
				throw new ArgumentOutOfRangeException ("size must be >= 0");

			if (offset + size > buffer.Length)
				throw new ArgumentOutOfRangeException ("offset + size exceeds the buffer length");

			Interlocked.Increment (ref pendingEnds);
			SocketAsyncResult req=new SocketAsyncResult(state);
			Worker worker=new Worker(this, buffer, offset, size,
						 socket_flags, remote_end,
						 callback, req);
			req.Worker=worker;
			SocketAsyncCall sac = new SocketAsyncCall (worker.SendTo);
			sac.BeginInvoke (null, null);
			return(req);
		}

		// Creates a new system socket, returning the handle
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void Bind_internal(IntPtr sock,
							 SocketAddress sa);

		public void Bind(EndPoint local_end) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if(local_end==null) {
				throw new ArgumentNullException("local_end");
			}
			
			Bind_internal(socket, local_end.Serialize());
		}

		// Closes the socket
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void Close_internal(IntPtr socket);
		
		public void Close() {
			((IDisposable) this).Dispose ();
		}

		// Connects to the remote address
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void Connect_internal(IntPtr sock,
							    SocketAddress sa);

		public void Connect(EndPoint remote_end) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if(remote_end==null) {
				throw new ArgumentNullException("remote_end");
			}

			Connect_internal(socket, remote_end.Serialize());
			connected=true;
		}
		
		public Socket EndAccept(IAsyncResult result) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (result == null)
				throw new ArgumentNullException ("result");

			SocketAsyncResult req = result as SocketAsyncResult;
			if (req == null)
				throw new ArgumentException ("Invalid IAsyncResult");

			if (!result.IsCompleted)
				result.AsyncWaitHandle.WaitOne();

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
			req.CheckIfThrowDelayedException();
			return(req.Worker.Socket);
		}

		public void EndConnect(IAsyncResult result) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (result == null)
				throw new ArgumentNullException ("result");

			SocketAsyncResult req = result as SocketAsyncResult;
			if (req == null)
				throw new ArgumentException ("Invalid IAsyncResult");

			if (!result.IsCompleted)
				result.AsyncWaitHandle.WaitOne();

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
			req.CheckIfThrowDelayedException();
		}

		public int EndReceive(IAsyncResult result) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (result == null)
				throw new ArgumentNullException ("result");

			SocketAsyncResult req = result as SocketAsyncResult;
			if (req == null)
				throw new ArgumentException ("Invalid IAsyncResult");

			if (!result.IsCompleted)
				result.AsyncWaitHandle.WaitOne();

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
			req.CheckIfThrowDelayedException();
			return(req.Worker.Total);
		}

		public int EndReceiveFrom(IAsyncResult result,
					  ref EndPoint end_point) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (result == null)
				throw new ArgumentNullException ("result");

			SocketAsyncResult req = result as SocketAsyncResult;
			if (req == null)
				throw new ArgumentException ("Invalid IAsyncResult");

			if (!result.IsCompleted)
				result.AsyncWaitHandle.WaitOne();

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
 			req.CheckIfThrowDelayedException();
			end_point=req.Worker.EndPoint;
			return(req.Worker.Total);
		}

		public int EndSend(IAsyncResult result) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (result == null)
				throw new ArgumentNullException ("result");

			SocketAsyncResult req = result as SocketAsyncResult;
			if (req == null)
				throw new ArgumentException ("Invalid IAsyncResult");

			if (!result.IsCompleted)
				result.AsyncWaitHandle.WaitOne();

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
			req.CheckIfThrowDelayedException();
			return(req.Worker.Total);
		}

		public int EndSendTo(IAsyncResult result) {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			if (result == null)
				throw new ArgumentNullException ("result");

			SocketAsyncResult req = result as SocketAsyncResult;
			if (req == null)
				throw new ArgumentException ("Invalid IAsyncResult");

			if (!result.IsCompleted)
				result.AsyncWaitHandle.WaitOne();

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
			req.CheckIfThrowDelayedException();
			return(req.Worker.Total);
		}

		void CheckIfClose ()
		{
			if (Interlocked.CompareExchange (ref closeDelayed, 0, 1) == 1 &&
			    Interlocked.CompareExchange (ref pendingEnds, 0, 0) == 0) {
				closed = true;
				Close_internal(socket);
			}
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void GetSocketOption_obj_internal(IntPtr socket, SocketOptionLevel level, SocketOptionName name, out object obj_val);
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void GetSocketOption_arr_internal(IntPtr socket, SocketOptionLevel level, SocketOptionName name, ref byte[] byte_val);

		public object GetSocketOption(SocketOptionLevel level,
					      SocketOptionName name) {
			object obj_val;
			
			GetSocketOption_obj_internal(socket, level, name,
						     out obj_val);
			
			if(name==SocketOptionName.Linger) {
				return((LingerOption)obj_val);
			} else if (name==SocketOptionName.AddMembership ||
				   name==SocketOptionName.DropMembership) {
				return((MulticastOption)obj_val);
			} else {
				return((int)obj_val);
			}
		}

		public void GetSocketOption(SocketOptionLevel level,
					    SocketOptionName name,
					    byte[] opt_value) {
			int opt_value_len=opt_value.Length;
			
			GetSocketOption_arr_internal(socket, level, name,
						     ref opt_value);
		}

		public byte[] GetSocketOption(SocketOptionLevel level,
					      SocketOptionName name,
					      int length) {
			byte[] byte_val=new byte[length];
			
			GetSocketOption_arr_internal(socket, level, name,
						     ref byte_val);

			return(byte_val);
		}

		// See Socket.IOControl, WSAIoctl documentation in MSDN. The
		// common options between UNIX and Winsock are FIONREAD,
		// FIONBIO and SIOCATMARK. Anything else will depend on the
		// system.
		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		extern static int WSAIoctl (IntPtr sock, int ioctl_code, byte [] input, byte [] output);

		public int IOControl (int ioctl_code, byte [] in_value, byte [] out_value)
		{
			if (disposed)
				throw new ObjectDisposedException (GetType ().ToString ());

			int result = WSAIoctl (socket, ioctl_code, in_value, out_value);
			if (result == -1)
				throw new InvalidOperationException ("Must use Blocking property instead.");

			return result;
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void Listen_internal(IntPtr sock,
							   int backlog);

		public void Listen(int backlog) {
			Listen_internal(socket, backlog);
		}

		/* The docs for Poll() are a bit lightweight too, but
		 * it seems to be just a simple wrapper around Select.
		 */
		public bool Poll(int time_us, SelectMode mode) {
			Socket [] socketlist = new Socket []{this};
			Socket [] n = null;

			switch(mode) {
			case SelectMode.SelectError:
				Select_internal (ref n, ref n, ref socketlist, time_us);
				break;
			case SelectMode.SelectRead:
				Select_internal (ref socketlist, ref n, ref n, time_us);
				break;
			case SelectMode.SelectWrite:
				Select_internal (ref n, ref socketlist, ref n, time_us);
				break;
			default:
				throw new NotSupportedException();
			}

			return (socketlist.Length == 1);
		}
		
		public int Receive(byte[] buf) {
			return(Receive(buf, 0, buf.Length, SocketFlags.None));
		}

		public int Receive(byte[] buf, SocketFlags flags) {
			return(Receive(buf, 0, buf.Length, flags));
		}

		public int Receive(byte[] buf, int size, SocketFlags flags) {
			return(Receive(buf, 0, size, flags));
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static int Receive_internal(IntPtr sock,
							   byte[] buffer,
							   int offset,
							   int count,
							   SocketFlags flags);

		public int Receive(byte[] buf, int offset, int size,
				   SocketFlags flags) {
			if(buf==null) {
				throw new ArgumentNullException("buffer is null");
			}
			if(offset<0 || offset > buf.Length) {
				throw new ArgumentOutOfRangeException("offset exceeds the size of buffer");
			}
			if(size<0 || offset+size > buf.Length) {
				throw new ArgumentOutOfRangeException("offset+size exceeds the size of buffer");
			}
			
			int ret;
			
			try {
				ret=Receive_internal(socket, buf, offset,
						     size, flags);
			} catch(SocketException) {
				connected=false;
				throw;
			}
			connected=true;

			return(ret);
		}
		
		public int ReceiveFrom(byte[] buf, ref EndPoint remote_end) {
			return(ReceiveFrom(buf, 0, buf.Length,
					   SocketFlags.None, ref remote_end));
		}

		public int ReceiveFrom(byte[] buf, SocketFlags flags,
				       ref EndPoint remote_end) {
			return(ReceiveFrom(buf, 0, buf.Length, flags,
					   ref remote_end));
		}

		public int ReceiveFrom(byte[] buf, int size, SocketFlags flags,
				       ref EndPoint remote_end) {
			return(ReceiveFrom(buf, 0, size, flags,
					   ref remote_end));
		}


		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static int RecvFrom_internal(IntPtr sock,
							    byte[] buffer,
							    int offset,
							    int count,
							    SocketFlags flags,
							    ref SocketAddress sockaddr);

		public int ReceiveFrom(byte[] buf, int offset, int size,
				       SocketFlags flags,
				       ref EndPoint remote_end) {
			if(buf==null) {
				throw new ArgumentNullException("buffer is null");
			}
			if(remote_end==null) {
				throw new ArgumentNullException("remote endpoint is null");
			}
			if(offset<0 || offset>buf.Length) {
				throw new ArgumentOutOfRangeException("offset exceeds the size of buffer");
			}
			if(size<0 || offset+size>buf.Length) {
				throw new ArgumentOutOfRangeException("offset+size exceeds the size of buffer");
			}

			SocketAddress sockaddr=remote_end.Serialize();
			int count;

			try {
				count=RecvFrom_internal(socket, buf, offset,
							size, flags,
							ref sockaddr);
			} catch(SocketException) {
				connected=false;
				throw;
			}
			connected=true;
			
			// Stupidly, EndPoint.Create() is an
			// instance method
			remote_end=remote_end.Create(sockaddr);

			return(count);
		}

		public int Send(byte[] buf) {
			return(Send(buf, 0, buf.Length, SocketFlags.None));
		}

		public int Send(byte[] buf, SocketFlags flags) {
			return(Send(buf, 0, buf.Length, flags));
		}

		public int Send(byte[] buf, int size, SocketFlags flags) {
			return(Send(buf, 0, size, flags));
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static int Send_internal(IntPtr sock,
							byte[] buf, int offset,
							int count,
							SocketFlags flags);

		public int Send (byte[] buf, int offset, int size, SocketFlags flags)
		{
			if (buf == null)
				throw new ArgumentNullException ("buffer");

			if (offset < 0 || offset > buf.Length)
				throw new ArgumentOutOfRangeException ("offset");

			if (size < 0 || offset + size > buf.Length)
				throw new ArgumentOutOfRangeException ("size");

			if (size == 0)
				return 0;

			int ret;

			try {
				ret = Send_internal (socket, buf, offset, size, flags);
			} catch (SocketException) {
				connected = false;
				throw;
			}
			connected = true;

			return ret;
		}

		public int SendTo(byte[] buffer, EndPoint remote_end) {
			return(SendTo(buffer, 0, buffer.Length,
				      SocketFlags.None, remote_end));
		}

		public int SendTo(byte[] buffer, SocketFlags flags,
				  EndPoint remote_end) {
			return(SendTo(buffer, 0, buffer.Length, flags,
				      remote_end));
		}

		public int SendTo(byte[] buffer, int size, SocketFlags flags,
				  EndPoint remote_end) {
			return(SendTo(buffer, 0, size, flags, remote_end));
		}


		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static int SendTo_internal(IntPtr sock,
							  byte[] buffer,
							  int offset,
							  int count,
							  SocketFlags flags,
							  SocketAddress sa);

		public int SendTo(byte[] buffer, int offset, int size,
				  SocketFlags flags, EndPoint remote_end) {
			if(buffer==null) {
				throw new ArgumentNullException("buffer is null");
			}
			if(remote_end==null) {
				throw new ArgumentNullException("remote endpoint is null");
			}
			if(offset<0 || offset>buffer.Length) {
				throw new ArgumentOutOfRangeException("offset exceeds the size of buffer");
			}
			if(size<0 || offset+size>buffer.Length) {
				throw new ArgumentOutOfRangeException("offset+size exceeds the size of buffer");
			}

			SocketAddress sockaddr=remote_end.Serialize();

			int ret;

			try {
				ret=SendTo_internal(socket, buffer, offset,
						    size, flags, sockaddr);
			}
			catch(SocketException) {
				connected=false;
				throw;
			}
			connected=true;

			return(ret);
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void SetSocketOption_internal(IntPtr socket, SocketOptionLevel level, SocketOptionName name, object obj_val, byte[] byte_val, int int_val);

		public void SetSocketOption(SocketOptionLevel level,
					    SocketOptionName name,
					    byte[] opt_value) {
			SetSocketOption_internal(socket, level, name, null,
						 opt_value, 0);
		}

		public void SetSocketOption(SocketOptionLevel level,
					    SocketOptionName name,
					    int opt_value) {
			SetSocketOption_internal(socket, level, name, null,
						 null, opt_value);
		}

		public void SetSocketOption(SocketOptionLevel level,
					    SocketOptionName name,
					    object opt_value) {
			if(opt_value==null) {
				throw new ArgumentNullException();
			}
			
			/* Passing a bool as the third parameter to
			 * SetSocketOption causes this overload to be
			 * used when in fact we want to pass the value
			 * to the runtime as an int.
			 */
			if(opt_value is System.Boolean) {
				bool bool_val=(bool)opt_value;
				
				/* Stupid casting rules :-( */
				if(bool_val==true) {
					SetSocketOption_internal(socket, level,
								 name, null,
								 null, 1);
				} else {
					SetSocketOption_internal(socket, level,
								 name, null,
								 null, 0);
				}
			} else {
				SetSocketOption_internal(socket, level, name,
							 opt_value, null, 0);
			}
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private extern static void Shutdown_internal(IntPtr socket, SocketShutdown how);
		
		public void Shutdown(SocketShutdown how) {
			Shutdown_internal(socket, how);
		}

		public override int GetHashCode ()
		{ 
			return (int) socket; 
		}

		private bool disposed;
		
		protected virtual void Dispose(bool explicitDisposing) {
			if (!disposed) {
				disposed = true;
				connected = false;
				if (!explicitDisposing) {
					closed = true;
					Close_internal (socket);
					return;
				}
			
				if (Interlocked.CompareExchange (ref pendingEnds, 0, 0) == 0) {
					closed = true;
					Close_internal (socket);
				} else {
					Interlocked.CompareExchange (ref closeDelayed, 1, 0);
				}
			}
		}

		void IDisposable.Dispose ()
		{
			Dispose (true);
			GC.SuppressFinalize (this);
		}
		
		~Socket () {
			Dispose(false);
		}
	}
}