Persist sessionStorage on disk.

webkit/dom_storage/session_storage_database.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 WEBKIT_DOM_STORAGE_SESSION_STORAGE_DATABASE_H_
 #define WEBKIT_DOM_STORAGE_SESSION_STORAGE_DATABASE_H_
 #pragma once
 
 #include <map>
 #include <string>
 
+#include "base/callback.h"
 #include "base/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/synchronization/lock.h"
 #include "third_party/leveldatabase/src/include/leveldb/status.h"
 #include "webkit/dom_storage/dom_storage_types.h"
 
 class GURL;
 
 namespace leveldb {
 class DB;
 class WriteBatch;
 }  // namespace leveldb
 
 namespace dom_storage {
 
 // SessionStorageDatabase holds the data from multiple namespaces and multiple
 // origins. All DomStorageAreas for session storage share the same
 // SessionStorageDatabase.
+
+// The namespace IDs used in the API (upper layer IDs) are different than the
+// namespace IDs used in the database (real IDs). All public functions deal with
+// upper layer IDs.
+
+// For private functions, the namespace IDs which are handled as int64 (named
+// namespace_id) are upper layer IDs. The namespaces IDs which are handled
+// as strings (named namesapce_id_str) are real IDs.
 class SessionStorageDatabase :
     public base::RefCountedThreadSafe<SessionStorageDatabase> {
  public:
   explicit SessionStorageDatabase(const FilePath& file_path);
 
+  typedef base::Callback<void(int64, int64)> SessionStorageAssociatedCallback;
+  SessionStorageDatabase(
+      const FilePath& file_path,
+      const SessionStorageAssociatedCallback& associated_callback);
+
   // Reads the (key, value) pairs for |namespace_id| and |origin|. |result| is
   // assumed to be empty and any duplicate keys will be overwritten. If the
   // database exists on disk then it will be opened. If it does not exist then
   // it will not be created and |result| will be unmodified.
   void ReadAreaValues(int64 namespace_id,
                       const GURL& origin,
                       ValuesMap* result);
 
   // Updates the data for |namespace_id| and |origin|. Will remove all keys
   // before updating the database if |clear_all_first| is set. Then all entries
   // in |changes| will be examined - keys mapped to a null NullableString16 will
   // be removed and all others will be inserted/updated as appropriate. It is
   // allowed to write data into a shallow copy created by CloneNamespace, and in
   // that case the copy will be made deep before writing the values.
   bool CommitAreaChanges(int64 namespace_id,
                          const GURL& origin,
                          bool clear_all_first,
                          const ValuesMap& changes);
 
   // Creates shallow copies of the areas for |namespace_id| and associates them
   // with |new_namespace_id|.
   bool CloneNamespace(int64 namespace_id, int64 new_namespace_id);
 
   // Deletes the data for |namespace_id| and |origin|.
   bool DeleteArea(int64 namespace_id, const GURL& origin);
 
   // Deletes the data for |namespace_id|.
   bool DeleteNamespace(int64 namespace_id);
 
+  // Reads all namespace ids from the database. The returned IDs will be upper
+  // level IDs. If there are some databases without an associated upper layer
+  // ID, this creates new, negative upper layer IDs for them.
+  bool ReadNamespaceIds(std::vector<int64>* namespace_ids);
+
+  // Associates |namespace_id| with |real_id|. Used by session restore.
+  void AssociateNamespaceId(int64 namespace_id, int64 real_id);
+
  private:
   friend class base::RefCountedThreadSafe<SessionStorageDatabase>;
   friend class SessionStorageDatabaseTest;
 
   ~SessionStorageDatabase();
 
   // Opens the database at file_path_ if it exists already and creates it if
   // |create_if_needed| is true. Returns true if the database was opened, false
   // if the opening failed or was not necessary (the database doesn't exist and
   // |create_if_needed| is false). The possible failures are:
@@ skipping 37 matching lines @@
                            std::map<std::string, std::string>* areas);
 
   // Adds an association between |origin| and |map_id| into the namespace
   // |namespace_id|.
   void AddAreaToNamespace(int64 namespace_id,
                           const std::string& origin,
                           const std::string& map_id,
                           leveldb::WriteBatch* batch);
 
   // Helpers for deleting data for |namespace_id| and |origin|.
-  bool DeleteArea(int64 namespace_id,
-                  const std::string& origin,
-                  leveldb::WriteBatch* batch);
-  bool DeleteArea(const std::string& namespace_id_str,
-                  const std::string& origin,
-                  leveldb::WriteBatch* batch);
+  bool DeleteAreaHelper(int64 namespace_id,
+                        const std::string& origin,
+                        leveldb::WriteBatch* batch);
+  bool DeleteAreaHelper(const std::string& namespace_id_str,
+                        const std::string& origin,
+                        leveldb::WriteBatch* batch);
 
   // Retrieves the map id for |namespace_id| and |origin|. It's not an error if
   // the map doesn't exist.
   bool GetMapForArea(int64 namespace_id,
                      const GURL& origin,
                      bool* exists,
                      std::string* map_id);
   bool GetMapForArea(const std::string& namespace_id_str,
                      const std::string& origin,
                      bool* exists,
@@ skipping 32 matching lines @@
 
   // Breaks the association between (|namespace_id|, |origin|) and |map_id| and
   // creates a new map for (|namespace_id|, |origin|). Copies the data from the
   // old map if |copy_data| is true.
   bool DeepCopyArea(int64 namespace_id,
                     const GURL& origin,
                     bool copy_data,
                     std::string* map_id,
                     leveldb::WriteBatch* batch);
 
+  // Helper functions for ID conversions.
+  bool AllocateNamespaceId(int64* namespace_id);
+  bool GetRealId(int64 namespace_id, int64* real_id);
+
   // Helper functions for creating the keys needed for the schema.
   static std::string NamespaceStartKey(const std::string& namespace_id_str);
-  static std::string NamespaceStartKey(int64 namespace_id,
-                                       int64 namespace_offset);
+  std::string NamespaceStartKey(int64 namespace_id);
   static std::string NamespaceKey(const std::string& namespace_id_str,
                                   const std::string& origin);
-  static std::string NamespaceKey(int64 namespace_id,
-                                  int64 namespace_offset,
-                                  const GURL& origin);
-  static std::string NamespaceIdStr(int64 namespace_id, int64 namespace_offset);
+  std::string NamespaceKey(int64 namespace_id,
+                           const GURL& origin);
+  std::string NamespaceIdStr(int64 namespace_id);
   static const char* NamespacePrefix();
   static std::string MapRefCountKey(const std::string& map_id);
   static std::string MapKey(const std::string& map_id, const std::string& key);
   static const char* MapPrefix();
   static const char* NextNamespaceIdKey();
   static const char* NextMapIdKey();
 
   scoped_ptr<leveldb::DB> db_;
   FilePath file_path_;
 
   // For protecting the database opening code.
   base::Lock db_lock_;
 
   // True if a database error has occurred (e.g., cannot read data).
   bool db_error_;
   // True if the database is in an inconsistent state.
   bool is_inconsistent_;
 
-  // On startup, we read the next ununsed namespace id from the database. It
-  // will be the offset for namespace ids. The actual id of a namespace in the
-  // database will be: id passed to the API function + namespace_offset_. The
-  // namespace ids which are handled as int64 (named namespace_id) don't contain
-  // the offset yet. The namespaces ids which are handled as strings (named
-  // namesapce_id_str) contain the offset.
-  int64 namespace_offset_;
+  // To track in-memory namespace id allocations (which don't necessarily end up
+  // in the db).
+  int64 next_namespace_id_;
+
+  // To track created upper layer namespace IDs.
+  int64 next_negative_namespace_id_;
+
+  // Track the correspondence between the upper layer IDs (used in the API) and
+  // the IDs in the database.
+  std::map<int64, int64> id_to_real_id_;
+  std::map<int64, int64> real_id_to_id_;
+
+  SessionStorageAssociatedCallback associated_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionStorageDatabase);
 };
 
 }  // namespace dom_storage
 
 #endif  // WEBKIT_DOM_STORAGE_SESSION_STORAGE_DATABASE_H_