[omnibox] Move private static functions/classes inside OnDeviceHeadModel

header into anonymous namespace.

For simplicity I did not make any changes other than moving
declarations, adjusting orders for these private functions/nested
classes.

Bug: 925072
Change-Id: Iafeaa2d71b18328061844721187e061bedeb32a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2444674Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: Ce Chen <cch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814118}

components/omnibox/browser/on_device_head_model.h

@@ -5,12 +5,8 @@
 #ifndef COMPONENTS_OMNIBOX_BROWSER_ON_DEVICE_HEAD_MODEL_H_
 #define COMPONENTS_OMNIBOX_BROWSER_ON_DEVICE_HEAD_MODEL_H_
 
-#include <fstream>
-#include <list>
-#include <memory>
 #include <string>
 #include <utility>
-#include <vector>
 
 // On device head suggest feature uses an on device model which encodes some
 // top queries into a radix tree (https://en.wikipedia.org/wiki/Radix_tree), to
@@ -65,9 +61,6 @@
 //
 // The size of score and address will be given in the first two bytes of the
 // model file.
-
-// TODO(crbug.com/925072): make some cleanups after converting this class into
-// a static class, e.g. move private class functions into anonymous namespace.
 class OnDeviceHeadModel {
  public:
   // Gets top "max_num_matches_to_return" suggestions and their scores which
@@ -76,124 +69,6 @@ class OnDeviceHeadModel {
       const std::string& model_filename,
       const uint32_t max_num_matches_to_return,
       const std::string& prefix);
-
- private:
-  // A useful data structure to keep track of the tree nodes should be and have
-  // been visited during tree traversal.
-  struct MatchCandidate {
-    // The sequences of characters from the start node to current node.
-    std::string text;
-
-    // Whether the text above can be returned as a suggestion; if false it is
-    // the prefix of some other complete suggestion.
-    bool is_complete_suggestion;
-
-    // If is_complete_suggestion is true, this is the score for the suggestion;
-    // Otherwise it will be set as max_score_as_root of the node.
-    uint32_t score;
-
-    // The address of the node in the model file. It is not required if
-    // is_complete_suggestion is true.
-    uint32_t address;
-  };
-
-  // Doubly linked list structure, which will be sorted based on candidates'
-  // scores (from low to high), to track nodes during tree search. We use two of
-  // this list to keep max_num_matches_to_return_ nodes in total with
-  // highest score during the search, and prune children and branches with low
-  // score.
-  // In theory, using RBTree might give a better search performance
-  // (i.e. log(n)) compared with linear from linked list here when inserting
-  // new candidates with high score into the struct, but since n is usually
-  // small, using linked list shall be okay.
-  using CandidateQueue = std::list<MatchCandidate>;
-
-  // A mini class holds all parameters needed to access the model on disk.
-  class OnDeviceModelParams {
-   public:
-    static std::unique_ptr<OnDeviceModelParams> Create(
-        const std::string& model_filename,
-        const uint32_t max_num_matches_to_return);
-
-    std::ifstream* GetModelFileStream() { return &model_filestream_; }
-    uint32_t score_size() const { return score_size_; }
-    uint32_t address_size() const { return address_size_; }
-    uint32_t max_num_matches_to_return() const {
-      return max_num_matches_to_return_;
-    }
-
-    ~OnDeviceModelParams();
-
-   private:
-    OnDeviceModelParams();
-    OnDeviceModelParams(const OnDeviceModelParams&) = delete;
-    OnDeviceModelParams& operator=(const OnDeviceModelParams&) = delete;
-
-    std::ifstream model_filestream_;
-    uint32_t score_size_;
-    uint32_t address_size_;
-    uint32_t max_num_matches_to_return_;
-  };
-
-  static void InsertCandidateToQueue(const MatchCandidate& candidate,
-                                     CandidateQueue* leaf_queue,
-                                     CandidateQueue* non_leaf_queue);
-
-  static uint32_t GetMinScoreFromQueues(OnDeviceModelParams* params,
-                                        const CandidateQueue& queue_1,
-                                        const CandidateQueue& queue_2);
-
-  // Finds start node which matches given prefix, returns true if found and
-  // the start node using param match_candidate.
-  static bool FindStartNode(OnDeviceModelParams* params,
-                            const std::string& prefix,
-                            MatchCandidate* match_candidate);
-
-  // Reads tree node from given match candidate, convert all possible
-  // suggestions and children of this node into structure MatchCandidate.
-  static std::vector<MatchCandidate> ReadTreeNode(
-      OnDeviceModelParams* params,
-      const MatchCandidate& current);
-
-  // Reads block max_score_as_root at the beginning of the node from the given
-  // address. If there is a leaf score at the end of the block, return the leaf
-  // score using param leaf_candidate;
-  static uint32_t ReadMaxScoreAsRoot(OnDeviceModelParams* params,
-                                     uint32_t address,
-                                     MatchCandidate* leaf_candidate,
-                                     bool* is_successful);
-
-  // Reads a child block and move ifstream cursor to next child; returns false
-  // when reaching the end of the node or ifstream read error happens.
-  static bool ReadNextChild(OnDeviceModelParams* params,
-                            MatchCandidate* candidate);
-
-  // Performs a search starting from the address specified by start_match and
-  // returns max_num_matches_to_return_ number of complete suggestions with
-  // highest scores.
-  static std::vector<std::pair<std::string, uint32_t>> DoSearch(
-      OnDeviceModelParams* params,
-      const MatchCandidate& start_match);
-
-  // Reads next num_bytes from the file stream.
-  static bool ReadNextNumBytes(OnDeviceModelParams* params,
-                               uint32_t num_bytes,
-                               char* buf);
-  static uint32_t ReadNextNumBytesAsInt(OnDeviceModelParams* params,
-                                        uint32_t num_bytes,
-                                        bool* is_successful);
-
-  // Checks if size of score and size of address read from the model file are
-  // valid.
-  // For score, we use size of 2 bytes (15 bits), 3 bytes (23 bits) or 4 bytes
-  // (31 bits); For address, we use size of 3 bytes (23 bits) or 4 bytes
-  // (31 bits).
-  static bool AreSizesValid(OnDeviceModelParams* params);
-
-  static bool OpenModelFileStream(OnDeviceModelParams* params,
-                                  const std::string& model_filename,
-                                  const uint32_t start_address);
-  static void MaybeCloseModelFileStream(OnDeviceModelParams* params);
 };
 
 #endif  // COMPONENTS_OMNIBOX_BROWSER_ON_DEVICE_HEAD_MODEL_H_