Check Accept-Encoding headers before creating compression provider (#154)

src/Microsoft.AspNetCore.ResponseCompression/BodyWrapperStream.cs

@@ -17,23 +17,24 @@ namespace Microsoft.AspNetCore.ResponseCompression
     /// </summary>
     internal class BodyWrapperStream : Stream, IHttpBufferingFeature, IHttpSendFileFeature
     {
-        private readonly HttpResponse _response;
+        private readonly HttpContext _context;
         private readonly Stream _bodyOriginalStream;
         private readonly IResponseCompressionProvider _provider;
-        private readonly ICompressionProvider _compressionProvider;
         private readonly IHttpBufferingFeature _innerBufferFeature;
         private readonly IHttpSendFileFeature _innerSendFileFeature;
 
+        private ICompressionProvider _compressionProvider = null;
         private bool _compressionChecked = false;
         private Stream _compressionStream = null;
+        private bool _providerCreated = false;
+        private bool _autoFlush = false;
 
-        internal BodyWrapperStream(HttpResponse response, Stream bodyOriginalStream, IResponseCompressionProvider provider, ICompressionProvider compressionProvider,
+        internal BodyWrapperStream(HttpContext context, Stream bodyOriginalStream, IResponseCompressionProvider provider,
             IHttpBufferingFeature innerBufferFeature, IHttpSendFileFeature innerSendFileFeature)
         {
-            _response = response;
+            _context = context;
             _bodyOriginalStream = bodyOriginalStream;
             _provider = provider;
-            _compressionProvider = compressionProvider;
             _innerBufferFeature = innerBufferFeature;
             _innerSendFileFeature = innerSendFileFeature;
         }
@@ -125,6 +126,10 @@ namespace Microsoft.AspNetCore.ResponseCompression
             if (_compressionStream != null)
             {
                 _compressionStream.Write(buffer, offset, count);
+                if (_autoFlush)
+                {
+                    _compressionStream.Flush();
+                }
             }
             else
             {
@@ -133,44 +138,70 @@ namespace Microsoft.AspNetCore.ResponseCompression
         }
 
 #if NET451
-        public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, object state)
+        public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
         {
-            OnWrite();
+            var tcs = new TaskCompletionSource<object>(state);
-
+            InternalWriteAsync(buffer, offset, count, callback, tcs);
-            if (_compressionStream != null)
+            return tcs.Task;
-            {
+        }
-                return _compressionStream.BeginWrite(buffer, offset, count, callback, state);
+
+        private async void InternalWriteAsync(byte[] buffer, int offset, int count, AsyncCallback callback, TaskCompletionSource<object> tcs)
+        {
+            try
+            {
+                await WriteAsync(buffer, offset, count);
+                tcs.TrySetResult(null);
+            }
+            catch (Exception ex)
+            {
+                tcs.TrySetException(ex);
+            }
+
+            if (callback != null)
+            {
+                // Offload callbacks to avoid stack dives on sync completions.
+                var ignored = Task.Run(() =>
+                {
+                    try
+                    {
+                        callback(tcs.Task);
+                    }
+                    catch (Exception)
+                    {
+                        // Suppress exceptions on background threads.
+                    }
+                });
             }
-            return _bodyOriginalStream.BeginWrite(buffer, offset, count, callback, state);
         }
 
         public override void EndWrite(IAsyncResult asyncResult)
         {
-            if (!_compressionChecked)
+            if (asyncResult == null)
             {
-                throw new InvalidOperationException("BeginWrite was not called before EndWrite");
+                throw new ArgumentNullException(nameof(asyncResult));
             }
 
-            if (_compressionStream != null)
+            var task = (Task)asyncResult;
-            {
+            task.GetAwaiter().GetResult();
-                _compressionStream.EndWrite(asyncResult);
-            }
-            else
-            {
-                _bodyOriginalStream.EndWrite(asyncResult);
-            }
         }
 #endif
 
-        public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        public override async Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
         {
             OnWrite();
 
             if (_compressionStream != null)
             {
-                return _compressionStream.WriteAsync(buffer, offset, count, cancellationToken);
+                await _compressionStream.WriteAsync(buffer, offset, count, cancellationToken);
+                if (_autoFlush)
+                {
+                    await _compressionStream.FlushAsync(cancellationToken);
+                }
+            }
+            else
+            {
+                await _bodyOriginalStream.WriteAsync(buffer, offset, count, cancellationToken);
             }
-            return _bodyOriginalStream.WriteAsync(buffer, offset, count, cancellationToken);
         }
 
         private void OnWrite()
@@ -178,22 +209,30 @@ namespace Microsoft.AspNetCore.ResponseCompression
             if (!_compressionChecked)
             {
                 _compressionChecked = true;
-
+                if (_provider.ShouldCompressResponse(_context))
-                if (IsCompressable())
                 {
-                    _response.Headers.Append(HeaderNames.ContentEncoding, _compressionProvider.EncodingName);
+                    var compressionProvider = ResolveCompressionProvider();
-                    _response.Headers.Remove(HeaderNames.ContentMD5); // Reset the MD5 because the content changed.
+                    if (compressionProvider != null)
-                    _response.Headers.Remove(HeaderNames.ContentLength);
-
-                    _compressionStream = _compressionProvider.CreateStream(_bodyOriginalStream);
-                }
-            }
-        }
-
-        private bool IsCompressable()
                     {
-            return !_response.Headers.ContainsKey(HeaderNames.ContentRange) &&     // The response is not partial
+                        _context.Response.Headers.Append(HeaderNames.ContentEncoding, compressionProvider.EncodingName);
-                _provider.ShouldCompressResponse(_response.HttpContext);
+                        _context.Response.Headers.Remove(HeaderNames.ContentMD5); // Reset the MD5 because the content changed.
+                        _context.Response.Headers.Remove(HeaderNames.ContentLength);
+
+                        _compressionStream = compressionProvider.CreateStream(_bodyOriginalStream);
+                    }
+                }
+            }
+        }
+
+        private ICompressionProvider ResolveCompressionProvider()
+        {
+            if (!_providerCreated)
+            {
+                _providerCreated = true;
+                _compressionProvider = _provider.GetCompressionProvider(_context);
+            }
+
+            return _compressionProvider;
         }
 
         public void DisableRequestBuffering()
@@ -205,13 +244,16 @@ namespace Microsoft.AspNetCore.ResponseCompression
         // For this to be effective it needs to be called before the first write.
         public void DisableResponseBuffering()
         {
-            if (!_compressionProvider.SupportsFlush)
+            if (ResolveCompressionProvider()?.SupportsFlush == false)
             {
                 // Don't compress, some of the providers don't implement Flush (e.g. .NET 4.5.1 GZip/Deflate stream)
                 // which would block real-time responses like SignalR.
                 _compressionChecked = true;
             }
-
+            else
+            {
+                _autoFlush = true;
+            }
             _innerBufferFeature?.DisableResponseBuffering();
         }
 
@@ -257,6 +299,11 @@ namespace Microsoft.AspNetCore.ResponseCompression
             {
                 fileStream.Seek(offset, SeekOrigin.Begin);
                 await StreamCopyOperation.CopyToAsync(fileStream, _compressionStream, count, cancellation);
+
+                if (_autoFlush)
+                {
+                    await _compressionStream.FlushAsync(cancellation);
+                }
             }
         }
     }

src/Microsoft.AspNetCore.ResponseCompression/IResponseCompressionProvider.cs

@@ -23,5 +23,12 @@ namespace Microsoft.AspNetCore.ResponseCompression
         /// <param name="context"></param>
         /// <returns></returns>
         bool ShouldCompressResponse(HttpContext context);
+
+        /// <summary>
+        /// Examines the request to see if compression should be used for response.
+        /// </summary>
+        /// <param name="context"></param>
+        /// <returns></returns>
+        bool CheckRequestAcceptsCompression(HttpContext context);
     }
 }

src/Microsoft.AspNetCore.ResponseCompression/Properties/AssemblyInfo.cs

@@ -3,6 +3,9 @@
 
 using System.Reflection;
 using System.Resources;
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Microsoft.AspNetCore.ResponseCompression.Tests, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 
 [assembly: AssemblyMetadata("Serviceable", "True")]
 [assembly: NeutralResourcesLanguage("en-us")]

src/Microsoft.AspNetCore.ResponseCompression/ResponseCompressionMiddleware.cs

@@ -18,15 +18,13 @@ namespace Microsoft.AspNetCore.ResponseCompression
 
         private readonly IResponseCompressionProvider _provider;
 
-        private readonly bool _enableForHttps;
 
         /// <summary>
         /// Initialize the Response Compression middleware.
         /// </summary>
         /// <param name="next"></param>
         /// <param name="provider"></param>
-        /// <param name="options"></param>
+        public ResponseCompressionMiddleware(RequestDelegate next, IResponseCompressionProvider provider)
-        public ResponseCompressionMiddleware(RequestDelegate next, IResponseCompressionProvider provider, IOptions<ResponseCompressionOptions> options)
         {
             if (next == null)
             {
@@ -36,14 +34,9 @@ namespace Microsoft.AspNetCore.ResponseCompression
             {
                 throw new ArgumentNullException(nameof(provider));
             }
-            if (options == null)
-            {
-                throw new ArgumentNullException(nameof(options));
-            }
 
             _next = next;
             _provider = provider;
-            _enableForHttps = options.Value.EnableForHttps;
         }
 
         /// <summary>
@@ -53,14 +46,7 @@ namespace Microsoft.AspNetCore.ResponseCompression
         /// <returns></returns>
         public async Task Invoke(HttpContext context)
         {
-            ICompressionProvider compressionProvider = null;
+            if (!_provider.CheckRequestAcceptsCompression(context))
-
-            if (!context.Request.IsHttps || _enableForHttps)
-            {
-                compressionProvider = _provider.GetCompressionProvider(context);
-            }
-
-            if (compressionProvider == null)
             {
                 await _next(context);
                 return;
@@ -70,7 +56,7 @@ namespace Microsoft.AspNetCore.ResponseCompression
             var originalBufferFeature = context.Features.Get<IHttpBufferingFeature>();
             var originalSendFileFeature = context.Features.Get<IHttpSendFileFeature>();
 
-            var bodyWrapperStream = new BodyWrapperStream(context.Response, bodyStream, _provider, compressionProvider,
+            var bodyWrapperStream = new BodyWrapperStream(context, bodyStream, _provider,
                 originalBufferFeature, originalSendFileFeature);
             context.Response.Body = bodyWrapperStream;
             context.Features.Set<IHttpBufferingFeature>(bodyWrapperStream);

src/Microsoft.AspNetCore.ResponseCompression/ResponseCompressionProvider.cs

@@ -16,6 +16,7 @@ namespace Microsoft.AspNetCore.ResponseCompression
     {
         private readonly ICompressionProvider[] _providers;
         private readonly HashSet<string> _mimeTypes;
+        private readonly bool _enableForHttps;
 
         /// <summary>
         /// If no compression providers are specified then GZip is used by default.
@@ -54,6 +55,8 @@ namespace Microsoft.AspNetCore.ResponseCompression
                 mimeTypes = ResponseCompressionDefaults.MimeTypes;
             }
             _mimeTypes = new HashSet<string>(mimeTypes, StringComparer.OrdinalIgnoreCase);
+
+            _enableForHttps = options.Value.EnableForHttps;
         }
 
         /// <inheritdoc />
@@ -103,6 +106,11 @@ namespace Microsoft.AspNetCore.ResponseCompression
         /// <inheritdoc />
         public virtual bool ShouldCompressResponse(HttpContext context)
         {
+            if (context.Response.Headers.ContainsKey(HeaderNames.ContentRange))
+            {
+                return false;
+            }
+
             var mimeType = context.Response.ContentType;
 
             if (string.IsNullOrEmpty(mimeType))
@@ -121,5 +129,15 @@ namespace Microsoft.AspNetCore.ResponseCompression
             // TODO PERF: StringSegments?
             return _mimeTypes.Contains(mimeType);
         }
+
+        /// <inheritdoc />
+        public bool CheckRequestAcceptsCompression(HttpContext context)
+        {
+            if (context.Request.IsHttps && !_enableForHttps)
+            {
+                return false;
+            }
+            return !string.IsNullOrEmpty(context.Request.Headers[HeaderNames.AcceptEncoding]);
+        }
     }
 }

test/Microsoft.AspNetCore.ResponseCompression.Tests/BodyWrapperStreamTests.cs

@@ -0,0 +1,211 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.ResponseCompression.Tests
+{
+    public class BodyWrapperStreamTests
+    {
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Write_IsPassedToUnderlyingStream_WhenDisableResponseBuffering(bool flushable)
+        {
+
+            var buffer = new byte[] { 1 };
+            byte[] written = null;
+
+            var mock = new Mock<Stream>();
+            mock.SetupGet(s => s.CanWrite).Returns(true);
+            mock.Setup(s => s.Write(It.IsAny<byte[]>(), It.IsAny<int>(), It.IsAny<int>()))
+                .Callback<byte[], int, int>((b, o, c) =>
+                {
+                    written = new ArraySegment<byte>(b, 0, c).ToArray();
+                });
+
+            var stream = new BodyWrapperStream(new DefaultHttpContext(), mock.Object, new MockResponseCompressionProvider(flushable), null, null);
+
+            stream.DisableResponseBuffering();
+            stream.Write(buffer, 0, buffer.Length);
+
+            Assert.Equal(buffer, written);
+        }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public async Task WriteAsync_IsPassedToUnderlyingStream_WhenDisableResponseBuffering(bool flushable)
+        {
+            var buffer = new byte[] { 1 };
+            byte[] written = null;
+
+            var mock = new Mock<Stream>();
+            mock.SetupGet(s => s.CanWrite).Returns(true);
+            mock.Setup(s => s.WriteAsync(It.IsAny<byte[]>(), It.IsAny<int>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
+                .Callback<byte[], int, int, CancellationToken>((b, o, c, t) =>
+                {
+                    written = new ArraySegment<byte>(b, 0, c).ToArray();
+                })
+                .Returns(Task.FromResult(0));
+
+            var stream = new BodyWrapperStream(new DefaultHttpContext(), mock.Object, new MockResponseCompressionProvider(flushable), null, null);
+
+            stream.DisableResponseBuffering();
+            await stream.WriteAsync(buffer, 0, buffer.Length);
+
+            Assert.Equal(buffer, written);
+        }
+
+        [Fact]
+        public async Task SendFileAsync_IsPassedToUnderlyingStream_WhenDisableResponseBuffering()
+        {
+            byte[] written = null;
+
+            var mock = new Mock<Stream>();
+            mock.SetupGet(s => s.CanWrite).Returns(true);
+            mock.Setup(s => s.WriteAsync(It.IsAny<byte[]>(), It.IsAny<int>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
+                .Callback<byte[], int, int, CancellationToken>((b, o, c, t) =>
+                {
+                    written = new ArraySegment<byte>(b, 0, c).ToArray();
+                })
+                .Returns(Task.FromResult(0));
+
+            var stream = new BodyWrapperStream(new DefaultHttpContext(), mock.Object, new MockResponseCompressionProvider(true), null, null);
+
+            stream.DisableResponseBuffering();
+
+            var path = "testfile1kb.txt";
+            await stream.SendFileAsync(path, 0, null, CancellationToken.None);
+
+            Assert.Equal(File.ReadAllBytes(path), written);
+        }
+
+#if NET451
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void BeginWrite_IsPassedToUnderlyingStream_WhenDisableResponseBuffering(bool flushable)
+        {
+            var buffer = new byte[] { 1 };
+            byte[] written = null;
+
+            var mock = new Mock<Stream>();
+            mock.SetupGet(s => s.CanWrite).Returns(true);
+            mock.Setup(s => s.WriteAsync(It.IsAny<byte[]>(), It.IsAny<int>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
+                .Callback<byte[], int, int, CancellationToken>((b, o, c, t) =>
+                {
+                    written = new ArraySegment<byte>(b, 0, c).ToArray();
+                })
+            .Returns(Task.FromResult(0));
+
+            var stream = new BodyWrapperStream(new DefaultHttpContext(), mock.Object, new MockResponseCompressionProvider(flushable), null, null);
+
+            stream.DisableResponseBuffering();
+            stream.BeginWrite(buffer, 0, buffer.Length, (o) => {}, null);
+
+            Assert.Equal(buffer, written);
+        }
+#endif
+
+        private class MockResponseCompressionProvider: IResponseCompressionProvider
+        {
+            private readonly bool _flushable;
+
+            public MockResponseCompressionProvider(bool flushable)
+            {
+                _flushable = flushable;
+            }
+
+            public ICompressionProvider GetCompressionProvider(HttpContext context)
+            {
+                return new MockCompressionProvider(_flushable);
+            }
+
+            public bool ShouldCompressResponse(HttpContext context)
+            {
+                return true;
+            }
+
+            public bool CheckRequestAcceptsCompression(HttpContext context)
+            {
+                return true;
+            }
+        }
+
+
+        private class MockCompressionProvider : ICompressionProvider
+        {
+            public MockCompressionProvider(bool flushable)
+            {
+                SupportsFlush = flushable;
+            }
+
+            public string EncodingName { get; }
+
+            public bool SupportsFlush { get; }
+
+            public Stream CreateStream(Stream outputStream)
+            {
+                if (SupportsFlush)
+                {
+                    return new BufferedStream(outputStream);
+                }
+                else
+                {
+                    return new NoFlushBufferedStream(outputStream);
+                }
+
+            }
+        }
+
+        private class NoFlushBufferedStream : Stream
+        {
+            private readonly BufferedStream _bufferedStream;
+
+            public NoFlushBufferedStream(Stream outputStream)
+            {
+                _bufferedStream = new BufferedStream(outputStream);
+            }
+
+            public override void Flush()
+            {
+            }
+
+            public override int Read(byte[] buffer, int offset, int count) => _bufferedStream.Read(buffer, offset, count);
+
+            public override long Seek(long offset, SeekOrigin origin) => _bufferedStream.Seek(offset, origin);
+
+            public override void SetLength(long value) => _bufferedStream.SetLength(value);
+
+            public override void Write(byte[] buffer, int offset, int count) => _bufferedStream.Write(buffer, offset, count);
+
+            public override bool CanRead => _bufferedStream.CanRead;
+
+            public override bool CanSeek => _bufferedStream.CanSeek;
+
+            public override bool CanWrite => _bufferedStream.CanWrite;
+
+            public override long Length => _bufferedStream.Length;
+
+            public override long Position
+            {
+                get { return _bufferedStream.Position; }
+                set { _bufferedStream.Position = value; }
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                base.Dispose(disposing);
+                _bufferedStream.Flush();
+            }
+        }
+    }
+}

test/Microsoft.AspNetCore.ResponseCompression.Tests/project.json

@@ -1,5 +1,6 @@
 {
   "buildOptions": {
+    "keyFile": "../../tools/Key.snk",
     "copyToOutput": [
       "testfile1kb.txt"
     ],
@@ -11,6 +12,7 @@
     "Microsoft.AspNetCore.ResponseCompression": "1.0.0-*",
     "Microsoft.AspNetCore.TestHost": "1.1.0-*",
     "Microsoft.Net.Http.Headers": "1.1.0-*",
+    "Moq": "4.6.36-*",
     "xunit": "2.2.0-*"
   },
   "frameworks": {