DecompressionHandler: Set cancellation token for SerializeToStreamAsync override

The virtual method available in .NET Standard 2.1 does not include the cancellation token parameter, so we use an alternative method to set it in advance.

Author: TalAloni

StandardSocketsHttpHandler/Net/Http/DecompressionHandler.cs

@@ -59,10 +59,12 @@ protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage
                 if (GZipEnabled && last == s_gzip)
                 {
                     response.Content = new GZipDecompressedContent(response.Content);
+                    ((GZipDecompressedContent)response.Content).SetDefaultCancellationToken(cancellationToken);
                 }
                 else if (DeflateEnabled && last == s_deflate)
                 {
                     response.Content = new DeflateDecompressedContent(response.Content);
+                    ((DeflateDecompressedContent)response.Content).SetDefaultCancellationToken(cancellationToken);
                 }
             }
 
@@ -82,6 +84,7 @@ protected override void Dispose(bool disposing)
         private abstract class DecompressedContent : HttpContent
         {
             HttpContent _originalContent;
+            private CancellationToken _cancellationToken;
             bool _contentConsumed;
 
             public DecompressedContent(HttpContent originalContent)
@@ -106,13 +109,24 @@ public DecompressedContent(HttpContent originalContent)
                 }
             }
 
+            public void SetDefaultCancellationToken(CancellationToken cancellationToken)
+            {
+                Debug.Assert(cancellationToken != null);
+
+                _cancellationToken = cancellationToken;
+            }
+
             protected abstract Stream GetDecompressedStream(Stream originalStream);
 
-            protected override async Task SerializeToStreamAsync(Stream stream, TransportContext context)
+            protected override Task SerializeToStreamAsync(Stream stream, TransportContext context) =>
+                SerializeToStreamAsyncInternal(stream, context, _cancellationToken);
+
+            internal async Task SerializeToStreamAsyncInternal(Stream stream, TransportContext context, CancellationToken cancellationToken)
             {
                 using (Stream decompressedStream = await CreateContentReadStreamAsync().ConfigureAwait(false))
                 {
-                    await decompressedStream.CopyToAsync(stream).ConfigureAwait(false);
+                    const int BufferSize = 81920; // Stream.DefaultCopyBufferSize
+                    await decompressedStream.CopyToAsync(stream, BufferSize, cancellationToken).ConfigureAwait(false);
                 }
             }