Sync shared code from runtime

src/Shared/runtime/Http3/QPack/QPackEncoder.cs

@@ -340,6 +340,7 @@ private static bool EncodeHeaderBlockPrefix(Span<byte> destination, out int byte
             return true;
         }
 
+        // TODO these are fairly hard coded for the first two bytes to be zero.
         public bool BeginEncode(IEnumerable<KeyValuePair<string, string>> headers, Span<byte> buffer, out int length)
         {
             _enumerator = headers.GetEnumerator();
@@ -350,11 +351,7 @@ public bool BeginEncode(IEnumerable<KeyValuePair<string, string>> headers, Span<
             buffer[0] = 0;
             buffer[1] = 0;
 
-            bool doneEncode = Encode(buffer.Slice(2), out length);
-
-            // Add two for the first two bytes.
-            length += 2;
-            return doneEncode;
+            return Encode(buffer.Slice(2), out length);
         }
 
         public bool BeginEncode(int statusCode, IEnumerable<KeyValuePair<string, string>> headers, Span<byte> buffer, out int length)

src/Shared/runtime/Quic/Implementations/MsQuic/Internal/MsQuicApi.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
@@ -143,6 +143,12 @@ static MsQuicApi()
 
             OperatingSystem ver = Environment.OSVersion;
 
+            if (ver.Platform == PlatformID.Win32NT && ver.Version < new Version(10, 0, 19041, 0))
+            {
+                IsQuicSupported = false;
+                return;
+            }
+
             // TODO: try to initialize TLS 1.3 in SslStream.
 
             try

src/Shared/runtime/Quic/Implementations/MsQuic/MsQuicStream.cs

@@ -402,15 +402,15 @@ internal override int Read(Span<byte> buffer)
         {
             ThrowIfDisposed();
 
-            return ReadAsync(buffer.ToArray()).GetAwaiter().GetResult();
+            return ReadAsync(buffer.ToArray()).AsTask().GetAwaiter().GetResult();
         }
 
         internal override void Write(ReadOnlySpan<byte> buffer)
         {
             ThrowIfDisposed();
 
             // TODO: optimize this.
-            WriteAsync(buffer.ToArray()).GetAwaiter().GetResult();
+            WriteAsync(buffer.ToArray()).AsTask().GetAwaiter().GetResult();
         }
 
         // MsQuic doesn't support explicit flushing