Add HpackDecoderState and HpackDecoderListener.

net/http2/hpack/decoder/hpack_decoder_listener.h

Index: net/http2/hpack/decoder/hpack_decoder_listener.h
diff --git a/net/http2/hpack/decoder/hpack_decoder_listener.h b/net/http2/hpack/decoder/hpack_decoder_listener.h
new file mode 100644
index 0000000000000000000000000000000000000000..a5facd6ddb3a72fcd652b8f4c07372c375e5cb16
--- /dev/null
+++ b/net/http2/hpack/decoder/hpack_decoder_listener.h
@@ -0,0 +1,65 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Defines HpackDecoderListener, the base class of listeners for HTTP header
+// lists decoded from an HPACK block.
+
+#ifndef NET_HTTP2_HPACK_DECODER_HPACK_DECODER_LISTENER_H_
+#define NET_HTTP2_HPACK_DECODER_HPACK_DECODER_LISTENER_H_
+
+#include "base/strings/string_piece.h"
+#include "net/base/net_export.h"
+#include "net/http2/hpack/hpack_string.h"
+#include "net/http2/hpack/http2_hpack_constants.h"
+
+namespace net {
+
+class NET_EXPORT HpackDecoderListener {
+ public:
+  HpackDecoderListener();
+  virtual ~HpackDecoderListener();
+
+  // OnHeaderListStart is called at the start of decoding an HPACK block into
+  // an HTTP/2 header list. Will only be called once per block, even if it
+  // extends into CONTINUATION frames.
+  virtual void OnHeaderListStart() = 0;
+
+  // Called for each header name-value pair that is decoded, in the order they
+  // appear in the HPACK block. Multiple values for a given key will be emitted
+  // as multiple calls to OnHeader.
+  virtual void OnHeader(HpackEntryType entry_type,
+                        const HpackString& name,
+                        const HpackString& value) = 0;
+
+  // OnHeaderListEnd is called after successfully decoding an HPACK block into
+  // an HTTP/2 header list. Will only be called once per block, even if it
+  // extends into CONTINUATION frames.
+  virtual void OnHeaderListEnd() = 0;
+
+  // OnHeaderErrorDetected is called if an error is detected while decoding.
+  // error_message may be used in a GOAWAY frame as the Opaque Data.
+  virtual void OnHeaderErrorDetected(base::StringPiece error_message) = 0;
+};
+
+// A no-op implementation of HpackDecoderListener, useful for ignoring
+// callbacks once an error is detected.
+class NET_EXPORT HpackDecoderNoOpListener : public HpackDecoderListener {
+ public:
+  HpackDecoderNoOpListener();
+  ~HpackDecoderNoOpListener() override;
+
+  void OnHeaderListStart() override;
+  void OnHeader(HpackEntryType entry_type,
+                const HpackString& name,
+                const HpackString& value) override;
+  void OnHeaderListEnd() override;
+  void OnHeaderErrorDetected(base::StringPiece error_message) override;
+
+  // Returns a listener that ignores all the calls.
+  static HpackDecoderNoOpListener* NoOpListener();
+};
+
+}  // namespace net
+
+#endif  // NET_HTTP2_HPACK_DECODER_HPACK_DECODER_LISTENER_H_