Add endHeader flag to QPACK decode (#62059)

Co-authored-by: Tratcher <Tratcher@users.noreply.github.com>
Co-authored-by: James Newton-King <james@newtonking.com>

Author: 3 people

src/libraries/Common/src/System/Net/Http/aspnetcore/Http3/QPack/QPackDecoder.cs

@@ -176,15 +176,15 @@ public void Reset()
             _state = State.RequiredInsertCount;
         }
 
-        public void Decode(in ReadOnlySequence<byte> headerBlock, IHttpHeadersHandler handler)
+        public void Decode(in ReadOnlySequence<byte> headerBlock, bool endHeaders, IHttpHeadersHandler handler)
         {
             foreach (ReadOnlyMemory<byte> segment in headerBlock)
             {
-                Decode(segment.Span, handler);
+                Decode(segment.Span, endHeaders: false, handler);
             }
         }
 
-        public void Decode(ReadOnlySpan<byte> headerBlock, IHttpHeadersHandler handler)
+        public void Decode(ReadOnlySpan<byte> headerBlock, bool endHeaders, IHttpHeadersHandler handler)
         {
             foreach (byte b in headerBlock)
             {

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http3RequestStream.cs

@@ -839,8 +839,9 @@ private async ValueTask ReadHeadersAsync(long headersLength, CancellationToken c
                 }
 
                 int processLength = (int)Math.Min(headersLength, _recvBuffer.ActiveLength);
+                bool endHeaders = headersLength == processLength;
 
-                _headerDecoder.Decode(_recvBuffer.ActiveSpan.Slice(0, processLength), this);
+                _headerDecoder.Decode(_recvBuffer.ActiveSpan.Slice(0, processLength), endHeaders, this);
                 _recvBuffer.Discard(processLength);
                 headersLength -= processLength;
             }