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

net/http2/hpack/decoder/hpack_decoder_string_buffer.h

Index: net/http2/hpack/decoder/hpack_decoder_string_buffer.h
diff --git a/net/http2/hpack/decoder/hpack_decoder_string_buffer.h b/net/http2/hpack/decoder/hpack_decoder_string_buffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..a0917a2c16bc0447b903e7106fce098be7846e37
--- /dev/null
+++ b/net/http2/hpack/decoder/hpack_decoder_string_buffer.h
@@ -0,0 +1,82 @@
+// 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_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_
+#define NET_HTTP2_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_
+
+// HpackDecoderStringBuffer helps an HPACK decoder to avoid copies of a string
+// literal (name or value) except when necessary (e.g. when split across two
+// or more HPACK block fragments).
+
+#include <stddef.h>
+
+#include <ostream>
+#include <string>
+
+#include "base/macros.h"
+#include "base/strings/string_piece.h"
+#include "net/base/net_export.h"
+#include "net/http2/hpack/huffman/http2_hpack_huffman_decoder.h"
+
+namespace net {
+
+class NET_EXPORT_PRIVATE HpackDecoderStringBuffer {
+ public:
+  enum class State : uint8_t { RESET, COLLECTING, COMPLETE };
+  enum class Backing : uint8_t { RESET, UNBUFFERED, BUFFERED, STATIC };
+
+  HpackDecoderStringBuffer();
+  ~HpackDecoderStringBuffer();
+
+  void Reset();
+  void Set(base::StringPiece value, bool is_static);
+
+  // Note that for Huffman encoded strings the length of the string after
+  // decoding may be larger (expected), the same or even smaller; the latter
+  // are unlikely, but possible if the encoder makes odd choices.
+  void OnStart(bool huffman_encoded, size_t len);
+  bool OnData(const char* data, size_t len);
+  bool OnEnd();
+  void BufferStringIfUnbuffered();
+  size_t BufferedLength() const;
+
+  base::StringPiece str() const;
+
+  State state_for_testing() const { return state_; }
+  Backing backing_for_testing() const { return backing_; }
+  void OutputDebugStringTo(std::ostream& out) const;
+
+ private:
+  // Storage for the string being buffered, if buffering is necessary
+  // (e.g. if Huffman encoded, buffer_ is storage for the decoded string).
+  std::string buffer_;
+
+  // The StringPiece to be returned by HpackDecoderStringBuffer::str(). If a
+  // string has been collected, but not buffered, value_ points to that string.
+  base::StringPiece value_;
+
+  // The decoder to use if the string is Huffman encoded.
+  HpackHuffmanDecoder decoder_;
+
+  // Count of bytes not yet passed to OnData.
+  size_t remaining_len_ = 0;
+
+  // Is the HPACK string Huffman encoded?
+  bool is_huffman_encoded_ = false;
+
+  // State of the string decoding process.
+  State state_;
+
+  // Where is the string stored?
+  Backing backing_;
+
+  DISALLOW_COPY_AND_ASSIGN(HpackDecoderStringBuffer);
+};
+
+NET_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& out,
+                                            const HpackDecoderStringBuffer& v);
+
+}  // namespace net
+
+#endif  // NET_HTTP2_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_