Don't allocate Exceptions unnecessarily

- Allocate Exceptions in the ReadStart callbacks if necessary instead
  of in UvStreamHandle.
- This also fixes a bug in ListenerSecondary where it should have
  previously been looking at the error code instead of the read count.

#237

src/Microsoft.AspNet.Server.Kestrel/Http/Connection.cs

@@ -13,7 +13,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
 {
     public class Connection : ConnectionContext, IConnectionControl
     {
-        private static readonly Action<UvStreamHandle, int, int, Exception, object> _readCallback = ReadCallback;
+        private static readonly Action<UvStreamHandle, int, object> _readCallback = ReadCallback;
         private static readonly Func<UvStreamHandle, int, object, Libuv.uv_buf_t> _allocCallback = AllocCallback;
 
         private static long _lastConnectionId;
@@ -113,28 +113,34 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
                 result.Data.Count);
         }
 
-        private static void ReadCallback(UvStreamHandle handle, int readCount, int errorCode, Exception error, object state)
+        private static void ReadCallback(UvStreamHandle handle, int status, object state)
         {
-            ((Connection)state).OnRead(handle, readCount, errorCode, error);
+            ((Connection)state).OnRead(handle, status);
         }
 
-        private void OnRead(UvStreamHandle handle, int readCount, int errorCode, Exception error)
+        private void OnRead(UvStreamHandle handle, int status)
         {
-            var normalRead = readCount != 0 && errorCode == 0;
+            var normalRead = status > 0;
-            var normalDone = readCount == 0 && (errorCode == 0 || errorCode == Constants.ECONNRESET || errorCode == Constants.EOF);
+            var normalDone = status == 0 || status == Constants.ECONNRESET || status == Constants.EOF;
             var errorDone = !(normalDone || normalRead);
+            var readCount = normalRead ? status : 0;
 
             if (normalRead)
             {
                 Log.ConnectionRead(_connectionId, readCount);
             }
-            else if (normalDone || errorDone)
+            else
             {
                 _socket.ReadStop();
                 Log.ConnectionReadFin(_connectionId);
             }
 
-            _rawSocketInput.IncomingComplete(readCount, errorDone ? error : null);
+            Exception error = null;
+            if (errorDone)
+            {
+                handle.Libuv.Check(status, out error);
+            }
+            _rawSocketInput.IncomingComplete(readCount, error);
         }
 
         void IConnectionControl.Pause()

src/Microsoft.AspNet.Server.Kestrel/Http/ListenerSecondary.cs

@@ -61,7 +61,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
 
                                 DispatchPipe.ReadStart(
                                     (_1, _2, _3) => buf,
-                                    (_1, status2, errCode, error2, state2) =>
+                                    (_1, status2, state2) =>
                                     {
                                         if (status2 < 0)
                                         {

src/Microsoft.AspNet.Server.Kestrel/Infrastructure/IKestrelTrace.cs

@@ -9,7 +9,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Infrastructure
 
         void ConnectionStop(long connectionId);
 
-        void ConnectionRead(long connectionId, int status);
+        void ConnectionRead(long connectionId, int count);
 
         void ConnectionPause(long connectionId);
 

src/Microsoft.AspNet.Server.Kestrel/Networking/UvStreamHandle.cs

@@ -19,7 +19,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
         private GCHandle _listenVitality;
 
         public Func<UvStreamHandle, int, object, Libuv.uv_buf_t> _allocCallback;
-        public Action<UvStreamHandle, int, int, Exception, object> _readCallback;
+        public Action<UvStreamHandle, int, object> _readCallback;
         public object _readState;
         private GCHandle _readVitality;
 
@@ -72,13 +72,14 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
 
         public void ReadStart(
             Func<UvStreamHandle, int, object, Libuv.uv_buf_t> allocCallback,
-            Action<UvStreamHandle, int, int, Exception, object> readCallback,
+            Action<UvStreamHandle, int, object> readCallback,
             object state)
         {
             if (_readVitality.IsAllocated)
             {
                 throw new InvalidOperationException("TODO: ReadStop must be called before ReadStart may be called again");
             }
+
             try
             {
                 _allocCallback = allocCallback;
@@ -118,7 +119,6 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
             return _uv.try_write(this, new[] { buf }, 1);
         }
 
-
         private static void UvConnectionCb(IntPtr handle, int status)
         {
             var stream = FromIntPtr<UvStreamHandle>(handle);
@@ -137,7 +137,6 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
             }
         }
 
-
         private static void UvAllocCb(IntPtr handle, int suggested_size, out Libuv.uv_buf_t buf)
         {
             var stream = FromIntPtr<UvStreamHandle>(handle);
@@ -153,22 +152,13 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
             }
         }
 
-        private static void UvReadCb(IntPtr handle, int nread, ref Libuv.uv_buf_t buf)
+        private static void UvReadCb(IntPtr handle, int status, ref Libuv.uv_buf_t buf)
         {
             var stream = FromIntPtr<UvStreamHandle>(handle);
 
             try
             {
-                if (nread < 0)
+                stream._readCallback(stream, status, stream._readState);
-                {
-                    Exception error;
-                    stream._uv.Check(nread, out error);
-                    stream._readCallback(stream, 0, nread, error, stream._readState);
-                }
-                else
-                {
-                    stream._readCallback(stream, nread, 0, null, stream._readState);
-                }
             }
             catch (Exception ex)
             {

test/Microsoft.AspNet.Server.KestrelTests/MultipleLoopTests.cs

@@ -113,7 +113,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
                     connect.Dispose();
                     clientConnectionPipe.ReadStart(
                         (_3, cb, _4) => buf,
-                        (_3, status2, errCode, error2, _4) =>
+                        (_3, status2, _4) =>
                         {
                             if (status2 == 0)
                             {
@@ -213,7 +213,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
 
                     clientConnectionPipe.ReadStart(
                         (_3, cb, _4) => buf,
-                        (_3, status2, errCode2, error2, _4) =>
+                        (_3, status2, _4) =>
                         {
                             if (status2 == 0)
                             {
@@ -226,7 +226,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
                             var buf2 = loop2.Libuv.buf_init(Marshal.AllocHGlobal(64), 64);
                             clientConnectionTcp.ReadStart(
                                 (_5, cb, _6) => buf2,
-                                (_5, status3, errCode3, error3, _6) =>
+                                (_5, status3, _6) =>
                                 {
                                     if (status3 == 0)
                                     {

test/Microsoft.AspNet.Server.KestrelTests/NetworkingTests.cs

@@ -129,7 +129,6 @@ namespace Microsoft.AspNet.Server.KestrelTests
         [Fact]
         public async Task SocketCanRead()
         {
-            int bytesRead = 0;
             var loop = new UvLoopHandle(_logger);
             loop.Init(_uv);
             var tcp = new UvTcpHandle(_logger);
@@ -145,10 +144,9 @@ namespace Microsoft.AspNet.Server.KestrelTests
                 var data = Marshal.AllocCoTaskMem(500);
                 tcp2.ReadStart(
                     (a, b, c) => _uv.buf_init(data, 500),
-                    (__, nread, errCode, error2, state2) =>
+                    (__, nread, state2) =>
                     {
-                        bytesRead += nread;
+                        if (nread <= 0)
-                        if (nread == 0)
                         {
                             tcp2.Dispose();
                         }
@@ -186,7 +184,6 @@ namespace Microsoft.AspNet.Server.KestrelTests
         [Fact]
         public async Task SocketCanReadAndWrite()
         {
-            int bytesRead = 0;
             var loop = new UvLoopHandle(_logger);
             loop.Init(_uv);
             var tcp = new UvTcpHandle(_logger);
@@ -202,10 +199,9 @@ namespace Microsoft.AspNet.Server.KestrelTests
                 var data = Marshal.AllocCoTaskMem(500);
                 tcp2.ReadStart(
                     (a, b, c) => tcp2.Libuv.buf_init(data, 500),
-                    (__, nread, errCode, error2, state2) =>
+                    (__, nread, state2) =>
                     {
-                        bytesRead += nread;
+                        if (nread <= 0)
-                        if (nread == 0)
                         {
                             tcp2.Dispose();
                         }