Add new HTTP/2 and HPACK decoder in net/http2/.

net/http2/decoder/payload_decoders/headers_payload_decoder.h

Index: net/http2/decoder/payload_decoders/headers_payload_decoder.h
diff --git a/net/http2/decoder/payload_decoders/headers_payload_decoder.h b/net/http2/decoder/payload_decoders/headers_payload_decoder.h
new file mode 100644
index 0000000000000000000000000000000000000000..76e6a082c37cfe2b29e8ed5d0c26a780f89cf4d9
--- /dev/null
+++ b/net/http2/decoder/payload_decoders/headers_payload_decoder.h
@@ -0,0 +1,67 @@
+// 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.
+
+#ifndef NET_HTTP2_DECODER_PAYLOAD_DECODERS_HEADERS_PAYLOAD_DECODER_H_
+#define NET_HTTP2_DECODER_PAYLOAD_DECODERS_HEADERS_PAYLOAD_DECODER_H_
+
+// Decodes the payload of a HEADERS frame.
+
+#include "net/base/net_export.h"
+#include "net/http2/decoder/decode_buffer.h"
+#include "net/http2/decoder/decode_status.h"
+#include "net/http2/decoder/frame_decoder_state.h"
+#include "net/http2/http2_structures.h"
+
+namespace net {
+namespace test {
+class HeadersPayloadDecoderPeer;
+}  // namespace test
+
+class NET_EXPORT_PRIVATE HeadersPayloadDecoder {
+ public:
+  // States during decoding of a HEADERS frame, unless the fast path kicks
+  // in, in which case the state machine will be bypassed.
+  enum class PayloadState {
+    // The PADDED flag is set, and we now need to read the Pad Length field
+    // (the first byte of the payload, after the common frame header).
+    kReadPadLength,
+
+    // The PRIORITY flag is set, and we now need to read the fixed size priority
+    // fields (E, Stream Dependency, Weight) into priority_fields_.  Calls on
+    // OnHeadersPriority if completely decodes those fields.
+    kStartDecodingPriorityFields,
+
+    // The decoder passes the non-padding portion of the remaining payload
+    // (i.e. the HPACK block fragment) to the listener's OnHpackFragment method.
+    kReadPayload,
+
+    // The decoder has finished with the HPACK block fragment, and is now
+    // ready to skip the trailing padding, if the frame has any.
+    kSkipPadding,
+
+    // The fixed size fields weren't all available when the decoder first tried
+    // to decode them (state kStartDecodingPriorityFields); this state resumes
+    // the decoding when ResumeDecodingPayload is called later.
+    kResumeDecodingPriorityFields,
+  };
+
+  // Starts the decoding of a HEADERS frame's payload, and completes it if
+  // the entire payload is in the provided decode buffer.
+  DecodeStatus StartDecodingPayload(FrameDecoderState* state, DecodeBuffer* db);
+
+  // Resumes decoding a HEADERS frame's payload that has been split across
+  // decode buffers.
+  DecodeStatus ResumeDecodingPayload(FrameDecoderState* state,
+                                     DecodeBuffer* db);
+
+ private:
+  friend class test::HeadersPayloadDecoderPeer;
+
+  PayloadState payload_state_;
+  Http2PriorityFields priority_fields_;
+};
+
+}  // namespace net
+
+#endif  // NET_HTTP2_DECODER_PAYLOAD_DECODERS_HEADERS_PAYLOAD_DECODER_H_