Imported Upstream version 5.16.0.100

Former-commit-id: 38faa55fb9669e35e7d8448b15c25dc447f25767

mcs/class/System/System.Net/BufferedReadStream.cs

@@ -0,0 +1,69 @@
+//
+// BufferedReadStream.cs
+//
+// Author:
+//       Martin Baulig <mabaul@microsoft.com>
+//
+// Copyright (c) 2018 Xamarin Inc. (http://www.xamarin.com)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+using System;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.Net
+{
+	class BufferedReadStream : WebReadStream
+	{
+		readonly BufferOffsetSize readBuffer;
+
+		public BufferedReadStream (WebOperation operation, Stream innerStream,
+		                           BufferOffsetSize readBuffer)
+			: base (operation, innerStream)
+		{
+			this.readBuffer = readBuffer;
+		}
+
+		protected override async Task<int> ProcessReadAsync (
+			byte[] buffer, int offset, int size,
+			CancellationToken cancellationToken)
+		{
+			cancellationToken.ThrowIfCancellationRequested ();
+
+			var remaining = readBuffer?.Size ?? 0;
+			if (remaining > 0) {
+				int copy = (remaining > size) ? size : remaining;
+				Buffer.BlockCopy (readBuffer.Buffer, readBuffer.Offset, buffer, offset, copy);
+				readBuffer.Offset += copy;
+				readBuffer.Size -= copy;
+				offset += copy;
+				size -= copy;
+				return copy;
+			}
+
+			if (InnerStream == null)
+				return 0;
+
+			return await InnerStream.ReadAsync (
+				buffer, offset, size, cancellationToken).ConfigureAwait (false);
+		}
+	}
+}
+