#578 Do not buffer the request body by default when reading forms.

Author: Tratcher

src/Microsoft.AspNetCore.Http/BufferingHelper.cs

@@ -22,7 +22,7 @@ public static string TempDirectory
                 if (_tempDirectory == null)
                 {
                     // Look for folders in the following order.
-                    var temp = Environment.GetEnvironmentVariable("ASPNET_TEMP") ??     // ASPNET_TEMP - User set temporary location.
+                    var temp = Environment.GetEnvironmentVariable("ASPNETCORE_TEMP") ??     // ASPNETCORE_TEMP - User set temporary location.
                                Path.GetTempPath();                                      // Fall back.
 
                     if (!Directory.Exists(temp))
@@ -54,5 +54,26 @@ public static HttpRequest EnableRewind(this HttpRequest request, int bufferThres
             }
             return request;
         }
+
+        public static MultipartSection EnableRewind(this MultipartSection section, Action<IDisposable> registerForDispose, int bufferThreshold = DefaultBufferThreshold)
+        {
+            if (section == null)
+            {
+                throw new ArgumentNullException(nameof(section));
+            }
+            if (registerForDispose == null)
+            {
+                throw new ArgumentNullException(nameof(registerForDispose));
+            }
+
+            var body = section.Body;
+            if (!body.CanSeek)
+            {
+                var fileStream = new FileBufferingReadStream(body, bufferThreshold, _getTempDirectory);
+                section.Body = fileStream;
+                registerForDispose(fileStream);
+            }
+            return section;
+        }
     }
 }

src/Microsoft.AspNetCore.Http/Features/FormFeature.cs

@@ -118,8 +118,6 @@ private async Task<IFormCollection> InnerReadFormAsync(CancellationToken cancell
 
             cancellationToken.ThrowIfCancellationRequested();
 
-            _request.EnableRewind();
-
             FormCollection formFields = null;
             FormFileCollection files = null;
 
@@ -146,16 +144,27 @@ private async Task<IFormCollection> InnerReadFormAsync(CancellationToken cancell
                         ContentDispositionHeaderValue.TryParse(section.ContentDisposition, out contentDisposition);
                         if (HasFileContentDisposition(contentDisposition))
                         {
+                            // Enable buffering for the file if not already done for the full body
+                            section.EnableRewind(_request.HttpContext.Response.RegisterForDispose);
                             // Find the end
                             await section.Body.DrainAsync(cancellationToken);
 
                             var name = HeaderUtilities.RemoveQuotes(contentDisposition.Name) ?? string.Empty;
                             var fileName = HeaderUtilities.RemoveQuotes(contentDisposition.FileName) ?? string.Empty;
 
-                            var file = new FormFile(_request.Body, section.BaseStreamOffset.Value, section.Body.Length, name, fileName)
+                            FormFile file;
+                            if (section.BaseStreamOffset.HasValue)
+                            {
+                                // Relative reference to buffered request body
+                                file = new FormFile(_request.Body, section.BaseStreamOffset.Value, section.Body.Length, name, fileName);
+                            }
+                            else
                             {
-                                Headers = new HeaderDictionary(section.Headers),
-                            };
+                                // Individually buffered file body
+                                file = new FormFile(section.Body, 0, section.Body.Length, name, fileName);
+                            }
+                            file.Headers = new HeaderDictionary(section.Headers);
+
                             if (files == null)
                             {
                                 files = new FormFileCollection();
@@ -194,7 +203,10 @@ private async Task<IFormCollection> InnerReadFormAsync(CancellationToken cancell
             }
 
             // Rewind so later readers don't have to.
-            _request.Body.Seek(0, SeekOrigin.Begin);
+            if (_request.Body.CanSeek)
+            {
+                _request.Body.Seek(0, SeekOrigin.Begin);
+            }
 
             if (formFields != null)
             {

src/Microsoft.AspNetCore.Http/Features/HttpResponseFeature.cs

@@ -25,17 +25,17 @@ public HttpResponseFeature()
 
         public Stream Body { get; set; }
 
-        public bool HasStarted
+        public virtual bool HasStarted
         {
             get { return false; }
         }
 
-        public void OnStarting(Func<object, Task> callback, object state)
+        public virtual void OnStarting(Func<object, Task> callback, object state)
         {
             throw new NotImplementedException();
         }
 
-        public void OnCompleted(Func<object, Task> callback, object state)
+        public virtual void OnCompleted(Func<object, Task> callback, object state)
         {
             throw new NotImplementedException();
         }

test/Microsoft.AspNetCore.Http.Tests/FakeResponseFeature.cs

@@ -0,0 +1,30 @@
+// 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.Collections.Generic;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http.Features.Internal;
+
+namespace Microsoft.AspNetCore.Http.Features.Internal
+{
+    public class FakeResponseFeature : HttpResponseFeature
+    {
+        List<Tuple<Func<object, Task>, object>> _onCompletedCallbacks = new List<Tuple<Func<object, Task>, object>>();
+
+        public override void OnCompleted(Func<object, Task> callback, object state)
+        {
+            _onCompletedCallbacks.Add(new Tuple<Func<object, Task>, object>(callback, state));
+        }
+
+        public async Task CompleteAsync()
+        {
+            var callbacks = _onCompletedCallbacks;
+            _onCompletedCallbacks = null;
+            foreach (var callback in callbacks)
+            {
+                await callback.Item1(callback.Item2);
+            }
+        }
+    }
+}