Add HttpRequestRewindExtensions

- dotnet/aspnetcore#2684
- makes the `BufferingHelper` methods used in MVC and WebHooks `public`

Author: dougbu

src/Microsoft.AspNetCore.Http/Extensions/HttpRequestRewindExtensions.cs

@@ -0,0 +1,91 @@
+// 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 Microsoft.AspNetCore.Http.Internal;
+
+namespace Microsoft.AspNetCore.Http
+{
+    /// <summary>
+    /// Extension methods for enabling buffering in an <see cref="HttpRequest"/>.
+    /// </summary>
+    public static class HttpRequestRewindExtensions
+    {
+        /// <summary>
+        /// Ensure the <paramref name="request"/> <see cref="HttpRequest.Body"/> can be read multiple times. Normally
+        /// buffers request bodies in memory; writes requests larger than 30K bytes to disk.
+        /// </summary>
+        /// <param name="request">The <see cref="HttpRequest"/> to prepare.</param>
+        /// <remarks>
+        /// Temporary files for larger requests are written to the location named in the <c>ASPNETCORE_TEMP</c>
+        /// environment variable, if any. If that environment variable is not defined, these files are written to the
+        /// current user's temporary folder. Files are automatically deleted at the end of their associated requests.
+        /// </remarks>
+        public static void EnableBuffering(this HttpRequest request)
+        {
+            BufferingHelper.EnableRewind(request);
+        }
+
+        /// <summary>
+        /// Ensure the <paramref name="request"/> <see cref="HttpRequest.Body"/> can be read multiple times. Normally
+        /// buffers request bodies in memory; writes requests larger than <paramref name="bufferThreshold"/> bytes to
+        /// disk.
+        /// </summary>
+        /// <param name="request">The <see cref="HttpRequest"/> to prepare.</param>
+        /// <param name="bufferThreshold">
+        /// The maximum size in bytes of the in-memory <see cref="System.Buffers.ArrayPool{Byte}"/> used to buffer the
+        /// stream. Larger request bodies are written to disk.
+        /// </param>
+        /// <remarks>
+        /// Temporary files for larger requests are written to the location named in the <c>ASPNETCORE_TEMP</c>
+        /// environment variable, if any. If that environment variable is not defined, these files are written to the
+        /// current user's temporary folder. Files are automatically deleted at the end of their associated requests.
+        /// </remarks>
+        public static void EnableBuffering(this HttpRequest request, int bufferThreshold)
+        {
+            BufferingHelper.EnableRewind(request, bufferThreshold);
+        }
+
+        /// <summary>
+        /// Ensure the <paramref name="request"/> <see cref="HttpRequest.Body"/> can be read multiple times. Normally
+        /// buffers request bodies in memory; writes requests larger than 30K bytes to disk.
+        /// </summary>
+        /// <param name="request">The <see cref="HttpRequest"/> to prepare.</param>
+        /// <param name="bufferLimit">
+        /// The maximum size in bytes of the request body. An attempt to read beyond this limit will cause an
+        /// <see cref="System.IO.IOException"/>.
+        /// </param>
+        /// <remarks>
+        /// Temporary files for larger requests are written to the location named in the <c>ASPNETCORE_TEMP</c>
+        /// environment variable, if any. If that environment variable is not defined, these files are written to the
+        /// current user's temporary folder. Files are automatically deleted at the end of their associated requests.
+        /// </remarks>
+        public static void EnableBuffering(this HttpRequest request, long bufferLimit)
+        {
+            BufferingHelper.EnableRewind(request, bufferLimit: bufferLimit);
+        }
+
+        /// <summary>
+        /// Ensure the <paramref name="request"/> <see cref="HttpRequest.Body"/> can be read multiple times. Normally
+        /// buffers request bodies in memory; writes requests larger than <paramref name="bufferThreshold"/> bytes to
+        /// disk.
+        /// </summary>
+        /// <param name="request">The <see cref="HttpRequest"/> to prepare.</param>
+        /// <param name="bufferThreshold">
+        /// The maximum size in bytes of the in-memory <see cref="System.Buffers.ArrayPool{Byte}"/> used to buffer the
+        /// stream. Larger request bodies are written to disk.
+        /// </param>
+        /// <param name="bufferLimit">
+        /// The maximum size in bytes of the request body. An attempt to read beyond this limit will cause an
+        /// <see cref="System.IO.IOException"/>.
+        /// </param>
+        /// <remarks>
+        /// Temporary files for larger requests are written to the location named in the <c>ASPNETCORE_TEMP</c>
+        /// environment variable, if any. If that environment variable is not defined, these files are written to the
+        /// current user's temporary folder. Files are automatically deleted at the end of their associated requests.
+        /// </remarks>
+        public static void EnableBuffering(this HttpRequest request, int bufferThreshold, long bufferLimit)
+        {
+            BufferingHelper.EnableRewind(request, bufferThreshold, bufferLimit);
+        }
+    }
+}