Rename domain_security_preload_generator.

net/tools/domain_security_preload_generator/huffman/huffman_frequency_tracker.h

-// Copyright (c) 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_TOOLS_DOMAIN_SECURITY_PRELOAD_GENERATOR_HUFFMAN_FREQUENCY_TRACKER_H_
-#define NET_TOOLS_DOMAIN_SECURITY_PRELOAD_GENERATOR_HUFFMAN_FREQUENCY_TRACKER_H_
-
-#include <stdint.h>
-
-#include <map>
-#include <memory>
-#include <vector>
-
-namespace net {
-
-namespace transport_security_state {
-
-namespace {
-class HuffmanNode;
-}  // namespace
-
-struct HuffmanRepresentation {
-  uint32_t bits;
-  uint32_t number_of_bits;
-};
-
-// A HuffmanRepresentationTable maps the original characters to their Huffman
-// representation. The Huffman representation consists of the number of bits
-// needed to represent the character and the actual bits.
-using HuffmanRepresentationTable = std::map<uint8_t, HuffmanRepresentation>;
-using HuffmanRepresentationPair = std::pair<uint8_t, HuffmanRepresentation>;
-
-// This class tracks the number of times each character is used and calculates
-// a space efficient way to represent all tracked characters by constructing a
-// Huffman tree based on the number of times each character is seen.
-class HuffmanFrequencyTracker {
- public:
-  HuffmanFrequencyTracker();
-  ~HuffmanFrequencyTracker();
-
-  // Will increase the count for |character| by one, indicating it has been
-  // used.
-  void RecordUsage(uint8_t character);
-
-  // Returns a HuffmanRepresentationTable based on the usage data collected
-  // through RecordUsage().
-  HuffmanRepresentationTable ToTable();
-
-  // Outputs the Huffman representation as a vector of uint8_t's in a format
-  // Chromium can use to reconstruct the tree.
-  //
-  // The nodes of the tree are pairs of uint8s. The last node in the array is
-  // the root of the tree. Each pair is two uint8_t values, the first is "left"
-  // and the second is "right". If a uint8_t value has the MSB set then it
-  // represents a literal leaf value. Otherwise it's a pointer to the n'th
-  // element of the array.
-  std::vector<uint8_t> ToVector();
-
- private:
-  // Determines the Huffman representation of the characters under |node| and
-  // inserts them into |*table|. |bits| and |number_of_bits| are used as a
-  // prefix.
-  void TreeToTable(HuffmanNode* node,
-                   uint32_t bits,
-                   uint32_t number_of_bits,
-                   HuffmanRepresentationTable* table);
-
-  // Converts the tree under |*node| into a byte representation in |*vector|.
-  // See ToVector() for more information on the format.
-  uint32_t WriteToVector(HuffmanNode* node, std::vector<uint8_t>* vector);
-
-  // Constructs a Huffman tree based on |counts_|.
-  std::unique_ptr<HuffmanNode> BuildTree();
-
-  // Holds usage information for the tracked characters. Maps the character to
-  // the number of times its usage has been recorded through RecordUsage().
-  std::map<uint8_t, uint32_t> counts_;
-};
-
-}  // namespace transport_security_state
-
-}  // namespace net
-
-#endif  // NET_TOOLS_DOMAIN_SECURITY_PRELOAD_GENERATOR_HUFFMAN_FREQUENCY_TRACKER_H_