Move InMemoryURLIndex Caching Operations to FILE Thread

chrome/browser/history/in_memory_url_index.h

 // Copyright (c) 2012 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 CHROME_BROWSER_HISTORY_IN_MEMORY_URL_INDEX_H_
 #define CHROME_BROWSER_HISTORY_IN_MEMORY_URL_INDEX_H_
 #pragma once
 
 #include <functional>
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
-#include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "base/string16.h"
 #include "chrome/browser/autocomplete/autocomplete_match.h"
 #include "chrome/browser/autocomplete/history_provider_util.h"
 #include "chrome/browser/cancelable_request.h"
 #include "chrome/browser/history/history.h"
 #include "chrome/browser/history/history_types.h"
 #include "chrome/browser/history/in_memory_url_index_types.h"
-#include "chrome/browser/history/in_memory_url_index_cache.pb.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "sql/connection.h"
 
 class HistoryQuickProviderTest;
 class Profile;
 
 namespace base {
 class Time;
 }
 
 namespace in_memory_url_index {
 class InMemoryURLIndexCacheItem;
 }
 
 namespace history {
 
 namespace imui = in_memory_url_index;
 
 class HistoryDatabase;
+class RefCountedURLIndexPrivateDataPtr;
 class URLIndexPrivateData;
 struct URLVisitedDetails;
 struct URLsModifiedDetails;
 struct URLsDeletedDetails;
 
 // The URL history source.
 // Holds portions of the URL database in memory in an indexed form.  Used to
 // quickly look up matching URLs for a given query string.  Used by
 // the HistoryURLProvider for inline autocomplete and to provide URL
 // matches to the omnibox.
 //
 // Note about multi-byte codepoints and the data structures in the
 // InMemoryURLIndex class: One will quickly notice that no effort is made to
 // insure that multi-byte character boundaries are detected when indexing the
 // words and characters in the URL history database except when converting
 // URL strings to lowercase. Multi-byte-edness makes no difference when
 // indexing or when searching the index as the final filtering of results
 // is dependent on the comparison of a string of bytes, not individual
 // characters. While the lookup of those bytes during a search in the
 // |char_word_map_| could serve up words in which the individual char16
 // occurs as a portion of a composite character the next filtering step
 // will eliminate such words except in the case where a single character
 // is being searched on and which character occurs as the second char16 of a
 // multi-char16 instance.
-class InMemoryURLIndex : public content::NotificationObserver {
+class InMemoryURLIndex : public content::NotificationObserver,
+                         public base::SupportsWeakPtr<InMemoryURLIndex> {
  public:
+  // Defines an abstract class which is notified upon completion of restoring
+  // the index's private data either by reading from the cache file or by
+  // rebuilding from the history database.
+  class RestoreCacheObserver {
+   public:
+    virtual ~RestoreCacheObserver();
+
+    // Callback that lets the observer know that the restore operation has
+    // completed. |succeeded| indicates if the restore was successful. This is
+    // called on the UI thread.
+    virtual void OnCacheRestoreFinished(bool succeeded) = 0;
+  };
+
+  // Defines an abstract class which is notified upon completion of saving
+  // the index's private data to the cache file.
+  class SaveCacheObserver {
+   public:
+    virtual ~SaveCacheObserver();
+
+    // Callback that lets the observer know that the save succeeded.
+    // This is called on the UI thread.
+    virtual void OnCacheSaveFinished(bool succeeded) = 0;
+  };
+
   // |profile|, which may be NULL during unit testing, is used to register for
   // history changes. |history_dir| is a path to the directory containing the
   // history database within the profile wherein the cache and transaction
   // journals will be stored. |languages| gives a list of language encodings by
   // which URLs and omnibox searches are broken down into words and characters.
   InMemoryURLIndex(Profile* profile,
                    const FilePath& history_dir,
                    const std::string& languages);
   virtual ~InMemoryURLIndex();
 
   // Opens and prepares the index of historical URL visits. If the index private
   // data cannot be restored from its cache file then it is rebuilt from the
   // history database.
   void Init();
 
   // Signals that any outstanding initialization should be canceled and
   // flushes the cache to disk.
   void ShutDown();
 
   // Scans the history index and returns a vector with all scored, matching
   // history items. This entry point simply forwards the call on to the
   // URLIndexPrivateData class. For a complete description of this function
   // refer to that class.
   ScoredHistoryMatches HistoryItemsForTerms(const string16& term_string);
 
+  // Sets the optional observers for completion of restoral and saving of the
+  // index's private data.
+  void set_restore_cache_observer(
+      RestoreCacheObserver* restore_cache_observer) {
+    restore_cache_observer_ = restore_cache_observer;
+  }
+  void set_save_cache_observer(SaveCacheObserver* save_cache_observer) {
+    save_cache_observer_ = save_cache_observer;
+  }
+
  private:
   friend class ::HistoryQuickProviderTest;
   friend class InMemoryURLIndexTest;
+  friend class InMemoryURLIndexCacheTest;
   FRIEND_TEST_ALL_PREFIXES(LimitedInMemoryURLIndexTest, Initialization);
-  FRIEND_TEST_ALL_PREFIXES(InMemoryURLIndexCacheTest, CacheFilePath);
 
   // Creating one of me without a history path is not allowed (tests excepted).
   InMemoryURLIndex();
 
   // HistoryDBTask used to rebuild our private data from the history database.
   class RebuildPrivateDataFromHistoryDBTask : public HistoryDBTask {
    public:
     explicit RebuildPrivateDataFromHistoryDBTask(InMemoryURLIndex* index);
     virtual ~RebuildPrivateDataFromHistoryDBTask();
 
@@ skipping 12 matching lines @@
   // Initializes all index data members in preparation for restoring the index
   // from the cache or a complete rebuild from the history database.
   void ClearPrivateData();
 
   // Constructs a file path for the cache file within the same directory where
   // the history database is kept and saves that path to |file_path|. Returns
   // true if |file_path| can be successfully constructed. (This function
   // provided as a hook for unit testing.)
   bool GetCacheFilePath(FilePath* file_path);
 
+  // Sets the directory wherein the cache file will be maintained.
+  // For unit test usage only.
+  void set_history_dir(const FilePath& dir_path) { history_dir_ = dir_path; }
+
   // Restores the index's private data from the cache file stored in the
   // profile directory.
-  void RestoreFromCacheFile();
-
-  // Restores private_data_ from the given |path|. Runs on the UI thread.
-  // Provided for unit testing so that a test cache file can be used.
-  void DoRestoreFromCacheFile(const FilePath& path);
+  void PostRestoreFromCacheFileTask();
 
   // Schedules a history task to rebuild our private data from the history
   // database.
   void ScheduleRebuildFromHistory();
 
   // Callback used by RebuildPrivateDataFromHistoryDBTask to signal completion
   // or rebuilding our private data from the history database. |data| points to
   // a new instance of the private data just rebuilt. This callback is only
   // called upon a successful restore from the history database.
   void DoneRebuidingPrivateDataFromHistoryDB(URLIndexPrivateData* data);
 
   // Rebuilds the history index from the history database in |history_db|.
   // Used for unit testing only.
   void RebuildFromHistory(HistoryDatabase* history_db);
 
-  // Caches the index private data and writes the cache file to the profile
-  // directory.
-  void SaveToCacheFile();
+  // Posts a task to cache the index private data and write the cache file to
+  // the profile directory.
+  void PostSaveToCacheFileTask();
 
   // Saves private_data_ to the given |path|. Runs on the UI thread.
   // Provided for unit testing so that a test cache file can be used.
   void DoSaveToCacheFile(const FilePath& path);
 
+  // Notifies the observer, if any, of the success of the private data caching.
+  // |succeeded| is true on a successful save.
+  void OnCacheSaveDone(scoped_refptr<RefCountedBool> succeeded);
+
+  // Callback used by RebuildPrivateDataFromHistoryDBTask to signal completion
+  // or rebuilding our private data from the history database. |succeeded|
+  // will be true if the rebuild was successful. |data| will point to a new
+  // instanceof the private data just rebuilt.
+  void DoneRebuidingPrivateDataFromHistoryDB(bool succeeded,
+                                             URLIndexPrivateData* data);
+
+  // Rebuilds the history index from the history database in |history_db|.
+  // Used for unit testing only.
+  void RebuildFromHistory(URLDatabase* history_db);
+
+  // Determines if the private data was successfully reloaded from the cache
+  // file or if the private data must be rebuilt from the history database.
+  // |private_data_ptr|'s data will be NULL if the cache file load failed.
+  void OnCacheLoadDone(
+    scoped_refptr<RefCountedURLIndexPrivateDataPtr> private_data_ptr);
+
+  // Callback function that sets the private data from the just-restored-from-
+  // file |private_data| if |succeeded| otherwise clears the private data.
+  // Notifies any |restore_cache_observer_| of success status.
+  void OnCacheRestored(URLIndexPrivateData* private_data, bool succeeded);
+
+  // Notifications -------------------------------------------------------------
+
   // Handles notifications of history changes.
   virtual void Observe(int notification_type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
   // Notification handlers.
   void OnURLVisited(const URLVisitedDetails* details);
   void OnURLsModified(const URLsModifiedDetails* details);
   void OnURLsDeleted(const URLsDeletedDetails* details);
 
   // Returns a pointer to our private data. For unit testing only.
   URLIndexPrivateData* private_data() { return private_data_.get(); }
 
   // The profile, may be null when testing.
   Profile* profile_;
 
   // Directory where cache file resides. This is, except when unit testing,
   // the same directory in which the profile's history database is found. It
   // should never be empty.
   FilePath history_dir_;
 
   // The index's durable private data.
   scoped_ptr<URLIndexPrivateData> private_data_;
 
+  // Observers to notify upon restoral or save of the private data cache.
+  RestoreCacheObserver* restore_cache_observer_;
+  SaveCacheObserver* save_cache_observer_;
+
+  CancelableRequestConsumer cache_reader_consumer_;
+  content::NotificationRegistrar registrar_;
+
   // Set to true once the shutdown process has begun.
   bool shutdown_;
 
-  CancelableRequestConsumer cache_reader_consumer_;
-  content::NotificationRegistrar registrar_;
-
   // Set to true when changes to the index have been made and the index needs
   // to be cached. Set to false when the index has been cached. Used as a
   // temporary safety check to insure that the cache is saved before the
   // index has been destructed.
   // TODO(mrossetti): Eliminate once the transition to SQLite has been done.
   // http://crbug.com/83659
   bool needs_to_be_cached_;
 
   DISALLOW_COPY_AND_ASSIGN(InMemoryURLIndex);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_IN_MEMORY_URL_INDEX_H_