Simplify InnerStart* pattern

The handling of async operations, and in particular the support for initializing it, is currently split across a bunch of methods, making it difficult to track what's happening where.  It's also largely unnecessary complexity.   Simplify it.

Author: stephentoub

src/System.Net.Sockets/src/System/Net/Sockets/Socket.cs

@@ -3757,14 +3757,10 @@ public bool AcceptAsync(SocketAsyncEventArgs e)
             SafeCloseSocket acceptHandle;
             e.AcceptSocket = GetOrCreateAcceptSocket(e.AcceptSocket, true, "AcceptSocket", out acceptHandle);
 
-            // Prepare for the native call.
-            e.StartOperationCommon(this);
+            // Prepare for and make the native call.
+            e.StartOperationCommon(this, SocketAsyncOperation.Accept);
             e.StartOperationAccept();
-
-            // Local variables for sync completion.
             SocketError socketError = SocketError.Success;
-
-            // Make the native call.
             try
             {
                 socketError = e.DoOperationAccept(this, _handle, acceptHandle);
@@ -3825,8 +3821,8 @@ public bool ConnectAsync(SocketAsyncEventArgs e)
 
                 MultipleConnectAsync multipleConnectAsync = new SingleSocketMultipleConnectAsync(this, true);
 
-                e.StartOperationCommon(this);
-                e.StartOperationWrapperConnect(multipleConnectAsync);
+                e.StartOperationCommon(this, SocketAsyncOperation.Connect);
+                e.StartOperationConnect(multipleConnectAsync);
 
                 pending = multipleConnectAsync.StartConnectAsync(e, dnsEP);
             }
@@ -3863,7 +3859,7 @@ public bool ConnectAsync(SocketAsyncEventArgs e)
                 }
 
                 // Prepare for the native call.
-                e.StartOperationCommon(this);
+                e.StartOperationCommon(this, SocketAsyncOperation.Connect);
                 e.StartOperationConnect();
 
                 // Make the native call.
@@ -3926,8 +3922,8 @@ public static bool ConnectAsync(SocketType socketType, ProtocolType protocolType
                     multipleConnectAsync = new SingleSocketMultipleConnectAsync(attemptSocket, false);
                 }
 
-                e.StartOperationCommon(attemptSocket);
-                e.StartOperationWrapperConnect(multipleConnectAsync);
+                e.StartOperationCommon(attemptSocket, SocketAsyncOperation.Connect);
+                e.StartOperationConnect(multipleConnectAsync);
 
                 pending = multipleConnectAsync.StartConnectAsync(e, dnsEP);
             }
@@ -3960,10 +3956,8 @@ public bool DisconnectAsync(SocketAsyncEventArgs e)
                 throw new ObjectDisposedException(GetType().FullName);
             }
 
-            // Prepare for the native call.
-            e.StartOperationCommon(this);
-            e.StartOperationDisconnect();
-
+            // Prepare for and make the native call.
+            e.StartOperationCommon(this, SocketAsyncOperation.Disconnect);
             SocketError socketError = SocketError.Success;
             try
             {
@@ -3995,14 +3989,9 @@ public bool ReceiveAsync(SocketAsyncEventArgs e)
                 throw new ArgumentNullException(nameof(e));
             }
 
-            // Prepare for the native call.
-            e.StartOperationCommon(this);
-            e.StartOperationReceive();
-
-            // Local vars for sync completion of native call.
+            // Prepare for and make the native call.
+            e.StartOperationCommon(this, SocketAsyncOperation.Receive);
             SocketError socketError;
-
-            // Wrap native methods with try/catch so event args object can be cleaned up.
             try
             {
                 socketError = e.DoOperationReceive(_handle, out _);
@@ -4053,13 +4042,9 @@ public bool ReceiveFromAsync(SocketAsyncEventArgs e)
             // e.m_SocketAddres for Create to work later.
             e.RemoteEndPoint = endPointSnapshot;
 
-            // Prepare for the native call.
-            e.StartOperationCommon(this);
-            e.StartOperationReceiveFrom();
-
-            // Make the native call.
+            // Prepare for and make the native call.
+            e.StartOperationCommon(this, SocketAsyncOperation.ReceiveFrom);
             SocketError socketError;
-
             try
             {
                 socketError = e.DoOperationReceiveFrom(_handle, out _);
@@ -4112,13 +4097,9 @@ public bool ReceiveMessageFromAsync(SocketAsyncEventArgs e)
 
             SetReceivingPacketInformation();
 
-            // Prepare for the native call.
-            e.StartOperationCommon(this);
-            e.StartOperationReceiveMessageFrom();
-
-            // Make the native call.
+            // Prepare for and make the native call.
+            e.StartOperationCommon(this, SocketAsyncOperation.ReceiveMessageFrom);
             SocketError socketError;
-
             try
             {
                 socketError = e.DoOperationReceiveMessageFrom(this, _handle);
@@ -4149,14 +4130,9 @@ public bool SendAsync(SocketAsyncEventArgs e)
                 throw new ArgumentNullException(nameof(e));
             }
 
-            // Prepare for the native call.
-            e.StartOperationCommon(this);
-            e.StartOperationSend();
-
-            // Local vars for sync completion of native call.
+            // Prepare for and make the native call.
+            e.StartOperationCommon(this, SocketAsyncOperation.Send);
             SocketError socketError;
-
-            // Wrap native methods with try/catch so event args object can be cleaned up.
             try
             {
                 socketError = e.DoOperationSend(_handle);
@@ -4196,33 +4172,18 @@ public bool SendPacketsAsync(SocketAsyncEventArgs e)
                 throw new NotSupportedException(SR.net_notconnected);
             }
 
-            // Prepare for the native call.
-            e.StartOperationCommon(this);
-            e.StartOperationSendPackets();
-
-            // Make the native call.
+            // Prepare for and make the native call.
+            e.StartOperationCommon(this, SocketAsyncOperation.SendPackets);
             SocketError socketError;
-
-            Debug.Assert(e.SendPacketsDescriptorCount != null);
-
-            if (e.SendPacketsDescriptorCount > 0)
+            try
             {
-                try
-                {
-                    socketError = e.DoOperationSendPackets(this, _handle);
-                }
-                catch (Exception)
-                {
-                    // Clear in-use flag on event args object.
-                    e.Complete();
-                    throw;
-                }
+                socketError = e.DoOperationSendPackets(this, _handle);
             }
-            else
+            catch (Exception)
             {
-                // No buffers or files to send.
-                e.FinishOperationSyncSuccess(0, SocketFlags.None);
-                socketError = SocketError.Success;
+                // Clear in-use flag on event args object.
+                e.Complete();
+                throw;
             }
 
             bool pending = (socketError == SocketError.IOPending);
@@ -4252,14 +4213,9 @@ public bool SendToAsync(SocketAsyncEventArgs e)
             EndPoint endPointSnapshot = e.RemoteEndPoint;
             e._socketAddress = SnapshotAndSerialize(ref endPointSnapshot);
 
-            // Prepare for the native call.
-            e.StartOperationCommon(this);
-            e.StartOperationSendTo();
-
-            // Make the native call.
+            // Prepare for and make the native call.
+            e.StartOperationCommon(this, SocketAsyncOperation.SendTo);
             SocketError socketError;
-
-            // Wrap native methods with try/catch so event args object can be cleaned up.
             try
             {
                 socketError = e.DoOperationSendTo(_handle);

src/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Unix.cs

@@ -15,8 +15,6 @@ public partial class SocketAsyncEventArgs : EventArgs, IDisposable
         private SocketFlags _receivedFlags;
         private Action<int, byte[], int, SocketFlags, SocketError> _transferCompletionCallback;
 
-        internal int? SendPacketsDescriptorCount => _sendPacketsElements?.Length;
-
         private void InitializeInternals()
         {
             // No-op for *nix.
@@ -53,11 +51,6 @@ private void FinishOperationSync(SocketError socketError, int bytesTransferred,
             }
         }
 
-        private void InnerStartOperationAccept()
-        {
-            _acceptedFileDescriptor = (IntPtr)(-1);
-        }
-
         private void AcceptCompletionCallback(IntPtr acceptedFileDescriptor, byte[] socketAddress, int socketAddressSize, SocketError socketError)
         {
             CompleteAcceptOperation(acceptedFileDescriptor, socketAddress, socketAddressSize, socketError);
@@ -79,6 +72,8 @@ internal unsafe SocketError DoOperationAccept(Socket socket, SafeCloseSocket han
                 throw new PlatformNotSupportedException(SR.net_sockets_accept_receive_notsupported);
             }
 
+            _acceptedFileDescriptor = (IntPtr)(-1);
+
             Debug.Assert(acceptHandle == null, $"Unexpected acceptHandle: {acceptHandle}");
 
             IntPtr acceptedFd;
@@ -94,11 +89,6 @@ internal unsafe SocketError DoOperationAccept(Socket socket, SafeCloseSocket han
             return socketError;
         }
 
-        private void InnerStartOperationConnect()
-        {
-            // No-op for *nix.
-        }
-
         private void ConnectCompletionCallback(SocketError socketError)
         {
             CompletionCallback(0, SocketFlags.None, socketError);
@@ -138,14 +128,11 @@ private void CompleteTransferOperation(int bytesTransferred, byte[] socketAddres
             _receivedFlags = receivedFlags;
         }
 
-        private void InnerStartOperationReceive()
+        internal unsafe SocketError DoOperationReceive(SafeCloseSocket handle, out SocketFlags flags)
         {
             _receivedFlags = System.Net.Sockets.SocketFlags.None;
             _socketAddressSize = 0;
-        }
 
-        internal unsafe SocketError DoOperationReceive(SafeCloseSocket handle, out SocketFlags flags)
-        {
             int bytesReceived;
             SocketError errorCode;
             if (_bufferList == null)
@@ -166,14 +153,11 @@ internal unsafe SocketError DoOperationReceive(SafeCloseSocket handle, out Socke
             return errorCode;
         }
 
-        private void InnerStartOperationReceiveFrom()
+        internal unsafe SocketError DoOperationReceiveFrom(SafeCloseSocket handle, out SocketFlags flags)
         {
             _receivedFlags = System.Net.Sockets.SocketFlags.None;
             _socketAddressSize = 0;
-        }
 
-        internal unsafe SocketError DoOperationReceiveFrom(SafeCloseSocket handle, out SocketFlags flags)
-        {
             SocketError errorCode;
             int bytesReceived = 0;
             int socketAddressLen = _socketAddress.Size;
@@ -195,13 +179,6 @@ internal unsafe SocketError DoOperationReceiveFrom(SafeCloseSocket handle, out S
             return errorCode;
         }
 
-        private void InnerStartOperationReceiveMessageFrom()
-        {
-            _receiveMessageFromPacketInfo = default(IPPacketInformation);
-            _receivedFlags = System.Net.Sockets.SocketFlags.None;
-            _socketAddressSize = 0;
-        }
-
         private void ReceiveMessageFromCompletionCallback(int bytesTransferred, byte[] socketAddress, int socketAddressSize, SocketFlags receivedFlags, IPPacketInformation ipPacketInformation, SocketError errorCode)
         {
             CompleteReceiveMessageFromOperation(bytesTransferred, socketAddress, socketAddressSize, receivedFlags, ipPacketInformation, errorCode);
@@ -221,6 +198,10 @@ private void CompleteReceiveMessageFromOperation(int bytesTransferred, byte[] so
 
         internal unsafe SocketError DoOperationReceiveMessageFrom(Socket socket, SafeCloseSocket handle)
         {
+            _receiveMessageFromPacketInfo = default(IPPacketInformation);
+            _receivedFlags = System.Net.Sockets.SocketFlags.None;
+            _socketAddressSize = 0;
+
             bool isIPv4, isIPv6;
             Socket.GetIPProtocolInformation(socket.AddressFamily, _socketAddress, out isIPv4, out isIPv6);
 
@@ -237,14 +218,11 @@ internal unsafe SocketError DoOperationReceiveMessageFrom(Socket socket, SafeClo
             return socketError;
         }
 
-        private void InnerStartOperationSend()
+        internal unsafe SocketError DoOperationSend(SafeCloseSocket handle)
         {
             _receivedFlags = System.Net.Sockets.SocketFlags.None;
             _socketAddressSize = 0;
-        }
 
-        internal unsafe SocketError DoOperationSend(SafeCloseSocket handle)
-        {
             int bytesSent;
             SocketError errorCode;
             if (_bufferList == null)
@@ -265,11 +243,6 @@ internal unsafe SocketError DoOperationSend(SafeCloseSocket handle)
             return errorCode;
         }
 
-        private void InnerStartOperationSendPackets()
-        {
-            // nop
-        }
-
         internal SocketError DoOperationSendPackets(Socket socket, SafeCloseSocket handle)
         {
             Debug.Assert(_sendPacketsElements != null);
@@ -329,14 +302,11 @@ internal SocketError DoOperationSendPackets(Socket socket, SafeCloseSocket handl
             return SocketError.IOPending;
         }
 
-        private void InnerStartOperationSendTo()
+        internal SocketError DoOperationSendTo(SafeCloseSocket handle)
         {
             _receivedFlags = System.Net.Sockets.SocketFlags.None;
             _socketAddressSize = 0;
-        }
 
-        internal SocketError DoOperationSendTo(SafeCloseSocket handle)
-        {
             int bytesSent;
             int socketAddressLen = _socketAddress.Size;
             SocketError errorCode;