// System.Net.Sockets.Socket.cs
//
// Authors:
//	Phillip Pearson (pp@myelin.co.nz)
//	Dick Porter <dick@ximian.com>
//	Gonzalo Paniagua Javier (gonzalo@ximian.com)
//
// Copyright (C) 2001, 2002 Phillip Pearson and Ximian, Inc.
//    http://www.myelin.co.nz
// (c) 2004 Novell, Inc. (http://www.novell.com)
//

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

namespace System.Net.Sockets 
{
	public class Socket : IDisposable 
	{
		[StructLayout (LayoutKind.Sequential)]
		private sealed class SocketAsyncResult: IAsyncResult 
		{
			/* Same structure in the runtime */
			public Socket Sock;
			IntPtr handle;
			object state;
			AsyncCallback callback;
			WaitHandle waithandle;

			Exception delayedException;

			public EndPoint EndPoint;	// Connect,ReceiveFrom,SendTo
			public byte [] Buffer;		// Receive,ReceiveFrom,Send,SendTo
			public int Offset;		// Receive,ReceiveFrom,Send,SendTo
			public int Size;		// Receive,ReceiveFrom,Send,SendTo
			public SocketFlags SockFlags;	// Receive,ReceiveFrom,Send,SendTo

			// Return values
			Socket acc_socket;
			int total;

			bool completed_sync;
			bool completed;
			AsyncCallback real_callback;
			int error;

			public SocketAsyncResult (Socket sock, object state, AsyncCallback callback)
			{
				this.Sock = sock;
				this.handle = sock.socket;
				this.state = state;
				this.real_callback = callback;
				SockFlags = SocketFlags.None;
			}

			public void CreateAsyncDelegate ()
			{
				if (real_callback != null)
					this.callback = new AsyncCallback (FakeCB);
			}

			static void FakeCB (IAsyncResult result)
			{
				SocketAsyncResult ares = (SocketAsyncResult) result;
				ares.real_callback.BeginInvoke (ares, null, null);
			}

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

				if (error != 0)
					throw new SocketException (error);
			}

			public void Complete ()
			{
				IsCompleted = true;
				if (real_callback != null)
					real_callback (this);
			}

			public void Complete (int total)
			{
				this.total = total;
				Complete ();
			}
			
			public void Complete (Exception e)
			{
				delayedException = e;
				Complete ();
			}

			public void Complete (Socket s)
			{
				acc_socket = s;
				Complete ();
			}

			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 Socket Socket {
				get {
					return acc_socket;
				}
			}

			public int Total {
				get {
					return total;
				}
			}
		}

		private sealed class Worker 
		{
			SocketAsyncResult result;

			public Worker (SocketAsyncResult ares)
			{
				this.result = ares;
			}

			public void Accept ()
			{
				lock (result) {
					Socket acc_socket = null;
					try {
						acc_socket = result.Sock.Accept ();
					} catch (Exception e) {
						result.Complete (e);
						return;
					}

					result.Complete (acc_socket);
				}
			}

			public void Connect ()
			{
				lock (result) {
					try {
						if (!result.Sock.blocking)
							result.Sock.Poll (-1, SelectMode.SelectWrite);

						result.Sock.Connect (result.EndPoint);
					} catch (Exception e) {
						result.Complete (e);
						return;
					}

					result.Complete ();
				}
			}

			public void Receive ()
			{
				lock (result) {
					int total = 0;
					try {
						if (!result.Sock.blocking)
							result.Sock.Poll (-1, SelectMode.SelectRead);

						total = result.Sock.Receive_nochecks (result.Buffer,
									     result.Offset,
									     result.Size,
									     result.SockFlags);
					} catch (Exception e) {
						result.Complete (e);
						return;
					}

					result.Complete (total);
				}
			}

			public void ReceiveFrom ()
			{
				lock (result) {
					int total = 0;
					try {
						if (!result.Sock.blocking)
							result.Sock.Poll (-1, SelectMode.SelectRead);

						total = result.Sock.ReceiveFrom_nochecks (result.Buffer,
										 result.Offset,
										 result.Size,
										 result.SockFlags,
										 ref result.EndPoint);
					} catch (Exception e) {
						result.Complete (e);
						return;
					}

					result.Complete (total);
				}
			}

			public void Send ()
			{
				lock (result) {
					int total = 0;
					try {
						if (!result.Sock.blocking)
							result.Sock.Poll (-1, SelectMode.SelectWrite);

						total = result.Sock.Send_nochecks (result.Buffer,
									  result.Offset,
									  result.Size,
									  result.SockFlags);
					} catch (Exception e) {
						result.Complete (e);
						return;
					}

					result.Complete (total);
				}
			}

			public void SendTo() {
				lock (result) {
					int total = 0;
					try {
						if (!result.Sock.blocking)
							result.Sock.Poll (-1, SelectMode.SelectWrite);

						total = result.Sock.SendTo_nochecks (result.Buffer,
									    result.Offset,
									    result.Size,
									    result.SockFlags,
									    result.EndPoint);
					} catch (Exception e) {
						result.Complete (e);
						return;
					}

					result.Complete (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;
		internal bool blocking=true;
		private int pendingEnds;
		private int closeDelayed;
		static readonly bool supportsAsync = FakeGetSupportsAsync ();

		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,
							   out int error);

		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++;
				}
			}

			int error;
			
			Select_internal(ref read_arr, ref write_arr,
					ref err_arr, time_us, out error);

			if(error != 0) {
				throw new SocketException (error);
			}

			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,
						      out int error);
		
		public Socket(AddressFamily family, SocketType type,
			      ProtocolType proto) {
			address_family=family;
			socket_type=type;
			protocol_type=proto;
			
			int error;
			
			socket=Socket_internal(family, type, proto, out error);
			if (error != 0) {
				throw new SocketException (error);
			}
		}

		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,
							     out int error);
		
		public int Available {
			get {
				if (disposed && closed)
					throw new ObjectDisposedException (GetType ().ToString ());

				int ret, error;
				
				ret = Available_internal(socket, out error);

				if (error != 0) {
					throw new SocketException (error);
				}

				return(ret);
			}
		}

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

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

				if (error != 0) {
					throw new SocketException (error);
				}
				
				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, out int error);

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

				SocketAddress sa;
				int error;
				
				sa=LocalEndPoint_internal(socket, out error);

				if (error != 0) {
					throw new SocketException (error);
				}

				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, out int error);

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

				SocketAddress sa;
				int error;
				
				sa=RemoteEndPoint_internal(socket, out error);

				if (error != 0) {
					throw new SocketException (error);
				}

				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,
							     out int error);
		
		public Socket Accept() {
			if (disposed && closed)
				throw new ObjectDisposedException (GetType ().ToString ());

			int error;
			IntPtr sock=Accept_internal(socket, out error);

			if (error != 0) {
				throw new SocketException (error);
			}
			
			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 (this, state, callback);
			Worker worker = new Worker (req);
			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 (this, state, callback);
			req.EndPoint = end_point;
			Worker worker = new Worker (req);
			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 || offset > buffer.Length)
				throw new ArgumentOutOfRangeException ("offset");

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

			Interlocked.Increment (ref pendingEnds);
			SocketAsyncResult req = new SocketAsyncResult (this, state, callback);
			req.Buffer = buffer;
			req.Offset = offset;
			req.Size = size;
			req.SockFlags = socket_flags;
			if (supportsAsync && socket_type == SocketType.Stream) {
				int error;
				req.CreateAsyncDelegate ();
				KeepReference (req);
				AsyncReceiveInternal (req, out error);
				if (error != 10036) // WSAEINPROGRESS
					throw new SocketException (error);
			} else {
				Worker worker = new Worker (req);
				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 (this, state, callback);
			req.Buffer = buffer;
			req.Offset = offset;
			req.Size = size;
			req.SockFlags = socket_flags;
			req.EndPoint = remote_end;
			Worker worker = new Worker (req);
			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 (this, state, callback);
			req.Buffer = buffer;
			req.Offset = offset;
			req.Size = size;
			req.SockFlags = socket_flags;
			if (supportsAsync && socket_type == SocketType.Stream) {
				int error;
				req.CreateAsyncDelegate ();
				KeepReference (req);
				AsyncSendInternal (req, out error);
				if (error != 10036) // WSAEINPROGRESS
					throw new SocketException (error);
			} else {
				Worker worker = new Worker (req);
				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 (this, state, callback);
			req.Buffer = buffer;
			req.Offset = offset;
			req.Size = size;
			req.SockFlags = socket_flags;
			req.EndPoint = remote_end;
			Worker worker = new Worker(req);
			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,
							 out int error);

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

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

			if (error != 0) {
				throw new SocketException (error);
			}
		}

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

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

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

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

			int error;
			
			Connect_internal(socket, remote_end.Serialize(), out error);

			if (error != 0) {
				throw new SocketException (error);
			}
			
			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", "result");

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

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
			req.CheckIfThrowDelayedException();
			return req.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", "result");

			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", "result");

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

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
			req.CheckIfThrowDelayedException();
			return req.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", "result");

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

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
 			req.CheckIfThrowDelayedException();
			end_point = req.EndPoint;
			return req.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", "result");

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

			Interlocked.Decrement (ref pendingEnds);
			CheckIfClose ();
			req.CheckIfThrowDelayedException();
			return req.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", "result");

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

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

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

				int error;
				
				Close_internal(socket, out error);

				if (error != 0) {
					throw new SocketException (error);
				}
			}
		}

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

		public object GetSocketOption(SocketOptionLevel level,
					      SocketOptionName name) {
			object obj_val;
			int error;
			
			GetSocketOption_obj_internal(socket, level, name,
						     out obj_val, out error);

			if (error != 0) {
				throw new SocketException (error);
			}
			
			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;
			int error;
			
			GetSocketOption_arr_internal(socket, level, name,
						     ref opt_value, out error);

			if (error != 0) {
				throw new SocketException (error);
			}
		}

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

			if (error != 0) {
				throw new SocketException (error);
			}

			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,
					    out int error);

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

			int error;
			int result = WSAIoctl (socket, ioctl_code, in_value,
					       out_value, out error);

			if (error != 0) {
				throw new SocketException (error);
			}
			
			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,
							   out int error);

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

			if (error != 0) {
				throw new SocketException (error);
			}
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		extern static bool Poll_internal (IntPtr socket, SelectMode mode, int timeout, out int error);

		public bool Poll (int time_us, SelectMode mode)
		{
			if (mode != SelectMode.SelectRead &&
			    mode != SelectMode.SelectWrite &&
			    mode != SelectMode.SelectError)
				throw new NotSupportedException ("'mode' parameter is not valid.");

			int error;
			bool result = Poll_internal (socket, mode, time_us, out error);
			if (error != 0)
				throw new SocketException (error);

			return result;
		}
		
		public int Receive (byte [] buf)
		{
			if (buf == null)
				throw new ArgumentNullException ("buf");

			return Receive_nochecks (buf, 0, buf.Length, SocketFlags.None);
		}

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

			return Receive_nochecks (buf, 0, buf.Length, flags);
		}

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

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

			return Receive_nochecks (buf, 0, size, flags);
		}

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

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

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

			if (size < 0 || offset + size > buf.Length)
				throw new ArgumentOutOfRangeException ("size");
			
			return Receive_nochecks (buf, offset, size, flags);
		}

		int Receive_nochecks (byte [] buf, int offset, int size, SocketFlags flags)
		{
			int ret, error;
			
			ret = Receive_internal (socket, buf, offset, size, flags, out error);

			if (error != 0) {
				connected = false;
				throw new SocketException (error);
			}
			
			connected = true;

			return ret;
		}
		
		public int ReceiveFrom (byte [] buf, ref EndPoint remote_end)
		{
			if (buf == null)
				throw new ArgumentNullException ("buf");

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

			return ReceiveFrom_nochecks (buf, 0, buf.Length, SocketFlags.None, ref remote_end);
		}

		public int ReceiveFrom (byte [] buf, SocketFlags flags, ref EndPoint remote_end)
		{
			if (buf == null)
				throw new ArgumentNullException ("buf");

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


			return ReceiveFrom_nochecks (buf, 0, buf.Length, flags, ref remote_end);
		}

		public int ReceiveFrom (byte [] buf, int size, SocketFlags flags,
					ref EndPoint remote_end)
		{
			if (buf == null)
				throw new ArgumentNullException ("buf");

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

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

			return ReceiveFrom_nochecks (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,
							    out int error);

		public int ReceiveFrom (byte [] buf, int offset, int size, SocketFlags flags,
					ref EndPoint remote_end)
		{
			if (buf == null)
				throw new ArgumentNullException ("buf");

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

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

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

			return ReceiveFrom_nochecks (buf, offset, size, flags, ref remote_end);
		}

		int ReceiveFrom_nochecks (byte [] buf, int offset, int size, SocketFlags flags,
					  ref EndPoint remote_end)
		{
			SocketAddress sockaddr = remote_end.Serialize();
			int cnt, error;

			cnt = RecvFrom_internal (socket, buf, offset, size, flags, ref sockaddr, out error);

			if (error != 0) {
				connected = false;
				throw new SocketException (error);
			}

			connected = true;
			
			// Stupidly, EndPoint.Create() is an
			// instance method
			remote_end = remote_end.Create (sockaddr);

			return cnt;
		}

		public int Send (byte [] buf)
		{
			if (buf == null)
				throw new ArgumentNullException ("buf");

			return Send_nochecks (buf, 0, buf.Length, SocketFlags.None);
		}

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

			return Send_nochecks (buf, 0, buf.Length, flags);
		}

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

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

			return Send_nochecks (buf, 0, size, flags);
		}

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

		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");

			return Send_nochecks (buf, offset, size, flags);
		}

		int Send_nochecks (byte [] buf, int offset, int size, SocketFlags flags)
		{
			if (size == 0)
				return 0;

			int ret, error;

			ret = Send_internal (socket, buf, offset, size, flags, out error);

			if (error != 0) {
				connected = false;
				throw new SocketException (error);
			}

			connected = true;

			return ret;
		}

		public int SendTo (byte [] buffer, EndPoint remote_end)
		{
			if (buffer == null)
				throw new ArgumentNullException ("buffer");

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

			return SendTo_nochecks (buffer, 0, buffer.Length, SocketFlags.None, remote_end);
		}

		public int SendTo (byte [] buffer, SocketFlags flags, EndPoint remote_end)
		{
			if (buffer == null)
				throw new ArgumentNullException ("buffer");

			if (remote_end == null)
				throw new ArgumentNullException ("remote_end");
				
			return SendTo_nochecks (buffer, 0, buffer.Length, flags, remote_end);
		}

		public int SendTo (byte [] buffer, int size, SocketFlags flags, EndPoint remote_end)
		{
			if (buffer == null)
				throw new ArgumentNullException ("buffer");

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

			if (size < 0 || size > buffer.Length)
				throw new ArgumentOutOfRangeException ("size");

			return SendTo_nochecks (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,
							  out int error);

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

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

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

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

			return SendTo_nochecks (buffer, offset, size, flags, remote_end);
		}

		int SendTo_nochecks (byte [] buffer, int offset, int size, SocketFlags flags,
				   EndPoint remote_end)
		{
			SocketAddress sockaddr = remote_end.Serialize ();

			int ret, error;

			ret = SendTo_internal (socket, buffer, offset, size, flags, sockaddr, out error);

			if (error != 0) {
				connected = false;
				throw new SocketException (error);
			}

			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,
								     out int error);

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

			if (error != 0) {
				throw new SocketException (error);
			}
		}

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

			if (error != 0) {
				throw new SocketException (error);
			}
		}

		public void SetSocketOption(SocketOptionLevel level,
					    SocketOptionName name,
					    object opt_value) {
			if(opt_value==null) {
				throw new ArgumentNullException();
			}
			
			int error;
			
			/* 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;
				int int_val = (bool_val) ? 1 : 0;
				
				SetSocketOption_internal (socket, level, name, null, null, int_val, out error);
			} else {
				SetSocketOption_internal (socket, level, name, opt_value, null, 0, out error);
			}

			if (error != 0) {
				throw new SocketException (error);
			}
		}

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

			if (error != 0) {
				throw new SocketException (error);
			}
		}

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

		private bool disposed;
		
		protected virtual void Dispose(bool explicitDisposing) {
			if (!disposed) {
				int error;
				
				disposed = true;
				connected = false;
				if (!explicitDisposing) {
					closed = true;
					Close_internal (socket, out error);

					if (error != 0) {
						throw new SocketException (error);
					}
					
					return;
				}
			
				if (Interlocked.CompareExchange (ref pendingEnds, 0, 0) == 0) {
					closed = true;
					Close_internal (socket, out error);

					if (error != 0) {
						throw new SocketException (error);
					}
				} else {
					Interlocked.CompareExchange (ref closeDelayed, 1, 0);
				}
			}
		}

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

		static Hashtable asyncObjects;

		static void KeepReference (object o)
		{
			lock (typeof (Socket)) {
				if (asyncObjects == null)
					asyncObjects = new Hashtable ();

				asyncObjects [o] = o;
			}
		}

		static void RemoveReference (object o)
		{
			lock (typeof (Socket)) {
				if (asyncObjects == null)
					return;

				asyncObjects.Remove (o);
			}
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		extern static bool GetSupportsAsync ();

		static bool FakeGetSupportsAsync ()
		{
			if (Environment.GetEnvironmentVariable ("MONO_ENABLE_SOCKET_AIO") != null)
				return GetSupportsAsync ();
			
			return false;
		}

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		extern static void AsyncReceiveInternal (SocketAsyncResult ares, out int error);

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		extern static void AsyncSendInternal (SocketAsyncResult ares, out int error);
	}
}