HPACK optimal Huffman code instrumentation and UMA collection.

net/spdy/hpack_encoder.h

 // Copyright 2014 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_SPDY_HPACK_ENCODER_H_
 #define NET_SPDY_HPACK_ENCODER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 38 matching lines @@
       const std::map<std::string, std::string>& header_set,
       std::string* output);
 
   // Called upon a change to SETTINGS_HEADER_TABLE_SIZE. Specifically, this
   // is to be called after receiving (and sending an acknowledgement for) a
   // SETTINGS_HEADER_TABLE_SIZE update from the remote decoding endpoint.
   void ApplyHeaderTableSizeSetting(size_t size_setting) {
     header_table_.SetSettingsHeaderTableSize(size_setting);
   }
 
+  // Sets externally-owned storage for aggregating character counts of emitted
+  // literal representations.
+  void SetCharCountsStorage(std::vector<size_t>* char_counts,
+                            size_t* total_char_counts);
+
  private:
   typedef std::pair<base::StringPiece, base::StringPiece> Representation;
   typedef std::vector<Representation> Representations;
 
   // Emits a static/dynamic indexed representation (Section 4.2).
   void EmitDynamicIndex(HpackEntry* entry);
   void EmitStaticIndex(HpackEntry* entry);
 
   // Emits a literal representation (Section 4.3).
   void EmitIndexedLiteral(const Representation& representation);
   void EmitNonIndexedLiteral(const Representation& representation);
   void EmitLiteral(const Representation& representation);
 
   // Emits a Huffman or identity string (whichever is smaller).
   void EmitString(base::StringPiece str);
 
+  void UpdateCharacterCounts(base::StringPiece str);
+
   // Determines the representation delta required to encode |header_set| in
   // the current header table context. Entries in the reference set are
   // enumerated and marked with membership in the current |header_set|.
   // Representations which must be explicitly emitted are returned.
   Representations DetermineEncodingDelta(
       const std::map<std::string, std::string>& header_set);
 
   static void CookieToCrumbs(const Representation& cookie,
                              Representations* crumbs_out);
 
   HpackHeaderTable header_table_;
   HpackOutputStream output_stream_;
 
   bool allow_huffman_compression_;
   const HpackHuffmanTable& huffman_table_;
 
+  // Externally-owned, nullable storage for character counts of literals.
+  std::vector<size_t>* char_counts_;
+  size_t* total_char_counts_;
+
   DISALLOW_COPY_AND_ASSIGN(HpackEncoder);
 };
 
 }  // namespace net
 
 #endif  // NET_SPDY_HPACK_ENCODER_H_