I/O Streamlining and Cleanup

src/Microsoft.AspNet.Server.Kestrel/Filter/SocketInputStream.cs

@@ -74,11 +74,7 @@ public override void SetLength(long value)
 
         public override void Write(byte[] buffer, int offset, int count)
         {
-            var inputBuffer = _socketInput.IncomingStart(count);
-
-            Buffer.BlockCopy(buffer, offset, inputBuffer.Data.Array, inputBuffer.Data.Offset, count);
-
-            _socketInput.IncomingComplete(count, error: null);
+            _socketInput.IncomingData(buffer, offset, count);
         }
 
         public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken token)
@@ -90,7 +86,7 @@ public override Task WriteAsync(byte[] buffer, int offset, int count, Cancellati
         protected override void Dispose(bool disposing)
         {
             // Close _socketInput with a fake zero-length write that will result in a zero-length read.
-            _socketInput.IncomingComplete(0, error: null);
+            _socketInput.IncomingData(null, 0, 0);
             base.Dispose(disposing);
         }
     }

src/Microsoft.AspNet.Server.Kestrel/Filter/StreamSocketOutput.cs

@@ -51,11 +51,11 @@ public void ProducingComplete(MemoryPoolIterator2 end)
 
                 var returnBlock = block;
                 block = block.Next;
-                returnBlock.Pool?.Return(returnBlock);
+                returnBlock.Pool.Return(returnBlock);
             }
 
             _outputStream.Write(end.Block.Array, end.Block.Data.Offset, end.Index - end.Block.Data.Offset);
-            end.Block.Pool?.Return(end.Block);
+            end.Block.Pool.Return(end.Block);
         }
     }
 }

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

@@ -140,11 +140,11 @@ private static Libuv.uv_buf_t AllocCallback(UvStreamHandle handle, int suggested
 
         private Libuv.uv_buf_t OnAlloc(UvStreamHandle handle, int suggestedSize)
         {
-            var result = _rawSocketInput.IncomingStart(2048);
+            var result = _rawSocketInput.IncomingRawStart();
 
             return handle.Libuv.buf_init(
-                result.DataPtr,
-                result.Data.Count);
+                result.Pin + result.End,
+                result.Data.Offset + result.Data.Count - result.End);
         }
 
         private static void ReadCallback(UvStreamHandle handle, int status, object state)

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

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -472,33 +473,34 @@ public async Task WriteAsyncAwaited(ArraySegment<byte> data, CancellationToken c
 
         private void WriteChunked(ArraySegment<byte> data)
         {
-            SocketOutput.Write(BeginChunkBytes(data.Count), immediate: false);
+            var tenByteBuffer = ArrayPool<byte>.Shared.Rent(10);
+            SocketOutput.Write(BeginChunkBytes(data.Count, tenByteBuffer), immediate: false);
+            ArrayPool<byte>.Shared.Return(tenByteBuffer);
             SocketOutput.Write(data, immediate: false);
             SocketOutput.Write(_endChunkBytes, immediate: true);
         }
 
         private async Task WriteChunkedAsync(ArraySegment<byte> data, CancellationToken cancellationToken)
         {
-            await SocketOutput.WriteAsync(BeginChunkBytes(data.Count), immediate: false, cancellationToken: cancellationToken);
+            var tenByteBuffer = ArrayPool<byte>.Shared.Rent(10);
+            await SocketOutput.WriteAsync(BeginChunkBytes(data.Count, tenByteBuffer), immediate: false, cancellationToken: cancellationToken);
+            ArrayPool<byte>.Shared.Return(tenByteBuffer);
             await SocketOutput.WriteAsync(data, immediate: false, cancellationToken: cancellationToken);
             await SocketOutput.WriteAsync(_endChunkBytes, immediate: true, cancellationToken: cancellationToken);
         }
 
-        public static ArraySegment<byte> BeginChunkBytes(int dataCount)
+        public static ArraySegment<byte> BeginChunkBytes(int dataCount, byte[] tenByteBuffer)
         {
-            var bytes = new byte[10]
-            {
-                _hex[((dataCount >> 0x1c) & 0x0f)],
-                _hex[((dataCount >> 0x18) & 0x0f)],
-                _hex[((dataCount >> 0x14) & 0x0f)],
-                _hex[((dataCount >> 0x10) & 0x0f)],
-                _hex[((dataCount >> 0x0c) & 0x0f)],
-                _hex[((dataCount >> 0x08) & 0x0f)],
-                _hex[((dataCount >> 0x04) & 0x0f)],
-                _hex[((dataCount >> 0x00) & 0x0f)],
-                (byte)'\r',
-                (byte)'\n',
-            };
+            tenByteBuffer[0] = _hex[((dataCount >> 0x1c) & 0x0f)];
+            tenByteBuffer[1] = _hex[((dataCount >> 0x18) & 0x0f)];
+            tenByteBuffer[2] = _hex[((dataCount >> 0x14) & 0x0f)];
+            tenByteBuffer[3] = _hex[((dataCount >> 0x10) & 0x0f)];
+            tenByteBuffer[4] = _hex[((dataCount >> 0x0c) & 0x0f)];
+            tenByteBuffer[5] = _hex[((dataCount >> 0x08) & 0x0f)];
+            tenByteBuffer[6] = _hex[((dataCount >> 0x04) & 0x0f)];
+            tenByteBuffer[7] = _hex[((dataCount >> 0x00) & 0x0f)];
+            tenByteBuffer[8] = (byte)'\r';
+            tenByteBuffer[9] = (byte)'\n';
 
             // Determine the most-significant non-zero nibble
             int total, shift;
@@ -510,7 +512,7 @@ public static ArraySegment<byte> BeginChunkBytes(int dataCount)
             total |= (dataCount > 0x000f) ? 0x04 : 0x00;
 
             var offset = 7 - (total >> 2);
-            return new ArraySegment<byte>(bytes, offset, 10 - offset);
+            return new ArraySegment<byte>(tenByteBuffer, offset, 10 - offset);
         }
 
         private void WriteChunkedResponseSuffix()
@@ -922,7 +924,8 @@ public static bool TakeMessageHeaders(SocketInput input, FrameRequestHeaders req
                             continue;
                         }
 
-                        var name = beginName.GetArraySegment(endName);
+                        byte[] rentedBuffer;
+                        var name = beginName.GetArraySegment(endName, out rentedBuffer);
                         var value = beginValue.GetAsciiString(endValue);
                         if (wrapping)
                         {
@@ -931,6 +934,10 @@ public static bool TakeMessageHeaders(SocketInput input, FrameRequestHeaders req
 
                         consumed = scan;
                         requestHeaders.Append(name.Array, name.Offset, name.Count, value);
+                        if (rentedBuffer != null)
+                        {
+                            ArrayPool<byte>.Shared.Return(rentedBuffer);
+                        }
                         break;
                     }
                 }

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

@@ -18,7 +18,7 @@ public interface ISocketOutput
 
         /// <summary>
         /// Returns an iterator pointing to the tail of the response buffer. Response data can be appended
-        /// manually or by using <see cref="MemoryPoolIterator2.CopyFrom(ArraySegment{byte})"/>.
+        /// manually or by using <see cref="MemoryPoolIterator2.CopyFrom(ArraySegment{byte[], int, int})"/>.
         /// Be careful to ensure all appended blocks are backed by a <see cref="MemoryPoolSlab2"/>. 
         /// </summary>
         MemoryPoolIterator2 ProducingStart();

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

@@ -22,7 +22,7 @@ abstract public class ListenerPrimary : Listener
 
         // this message is passed to write2 because it must be non-zero-length, 
         // but it has no other functional significance
-        private readonly ArraySegment<ArraySegment<byte>> _dummyMessage = new ArraySegment<ArraySegment<byte>>(new[] { new ArraySegment<byte>(new byte[] { 1, 2, 3, 4 }) });
+        private readonly ArraySegment<byte> _dummyMessage = new ArraySegment<byte>(new byte[] { 1, 2, 3, 4 });
 
         protected ListenerPrimary(ServiceContext serviceContext) : base(serviceContext)
         {
@@ -86,7 +86,7 @@ protected override void DispatchConnection(UvStreamHandle socket)
             else
             {
                 var dispatchPipe = _dispatchPipes[index];
-                var write = new UvWriteReq(Log);
+                var write = new UvWrite2Req(Log);
                 write.Init(Thread.Loop);
                 write.Write2(
                     dispatchPipe,