Make StreamCopyOperation public and update it to same as StaticFiles

src/Microsoft.AspNet.Http.Extensions/SendFileResponseExtensions.cs

@@ -5,6 +5,7 @@ using System;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.AspNet.Http.Extensions;
 using Microsoft.AspNet.Http.Features;
 
 namespace Microsoft.AspNet.Http
@@ -96,10 +97,7 @@ namespace Microsoft.AspNet.Http
             {
                 fileStream.Seek(offset, SeekOrigin.Begin);
 
-                // TODO: Use buffer pool
+                await StreamCopyOperation.CopyToAsync(fileStream, outputStream, length, cancel);
-                var buffer = new byte[bufferSize];
-
-                await StreamCopyOperation.CopyToAsync(fileStream, buffer, outputStream, length, cancel);
             }
         }
     }

src/Microsoft.AspNet.Http.Extensions/StreamCopyOperation.cs

@@ -2,19 +2,26 @@
 // 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.Diagnostics;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
 
-namespace Microsoft.AspNet.Http
+namespace Microsoft.AspNet.Http.Extensions
 {
     // FYI: In most cases the source will be a FileStream and the destination will be to the network.
-    internal static class StreamCopyOperation
+    public static class StreamCopyOperation
     {
-        internal static async Task CopyToAsync(Stream source, byte[] buffer, Stream destination, long? length, CancellationToken cancel)
+        private const int DefaultBufferSize = 4096;
+
+        public static async Task CopyToAsync(Stream source, Stream destination, long? length, CancellationToken cancel)
         {
             long? bytesRemaining = length;
+
+            var buffer = ArrayPool<byte>.Shared.Rent(DefaultBufferSize);
+            try
+            {
                 Debug.Assert(source != null);
                 Debug.Assert(destination != null);
                 Debug.Assert(!bytesRemaining.HasValue || bytesRemaining.Value >= 0);
@@ -53,5 +60,10 @@ namespace Microsoft.AspNet.Http
                     await destination.WriteAsync(buffer, 0, count, cancel);
                 }
             }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buffer);
+            }
+        }
     }
 }

src/Microsoft.AspNet.Http.Extensions/project.json

@@ -11,7 +11,8 @@
   },
   "dependencies": {
     "Microsoft.AspNet.Http.Abstractions": "1.0.0-*",
-    "Microsoft.Net.Http.Headers": "1.0.0-*"
+    "Microsoft.Net.Http.Headers": "1.0.0-*",
+    "System.Buffers": "4.0.0-*"
   },
   "frameworks": {
     "net451": {},