Persist sessionStorage on disk.

webkit/dom_storage/dom_storage_context.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_DOM_STORAGE_CONTEXT_H_
 #define WEBKIT_DOM_STORAGE_DOM_STORAGE_CONTEXT_H_
 
 #include <map>
+#include <set>
 #include <vector>
 
 #include "base/atomic_sequence_num.h"
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
 #include "base/time.h"
 #include "googleurl/src/gurl.h"
 
 class FilePath;
 class NullableString16;
 
 namespace base {
 class Time;
 }
 
 namespace quota {
 class SpecialStoragePolicy;
 }
 
 namespace dom_storage {
 
 class DomStorageArea;
 class DomStorageNamespace;
 class DomStorageSession;
 class DomStorageTaskRunner;
+class SessionStorageDatabase;
 
 // The Context is the root of an object containment hierachy for
 // Namespaces and Areas related to the owning profile.
 // One instance is allocated in the main process for each profile,
 // instance methods should be called serially in the background as
 // determined by the task_runner. Specifcally not on chrome's non-blocking
 // IO thread since these methods can result in blocking file io.
 //
 // In general terms, the DomStorage object relationships are...
 //   Contexts (per-profile) own Namespaces which own Areas which share Maps.
@@ skipping 105 matching lines @@
 
   std::string AllocatePersistentSessionId();
 
   // Must be called on the background thread.
   void CreateSessionNamespace(int64 namespace_id,
                               const std::string& persistent_namespace_id);
   void DeleteSessionNamespace(int64 namespace_id, bool should_persist_data);
   void CloneSessionNamespace(int64 existing_id, int64 new_id,
                              const std::string& new_persistent_id);
 
+  // Starts backing sessionStorage on disk. This function must be called right
+  // after DomStorageContext is created, before it's used.
+  void SetSaveSessionStorageOnDisk();
+
+  // Deletes all namespaces which don't have an associated DomStorageNamespace
+  // alive. This function is used for deleting possible leftover data after an
+  // unclean exit.
+  void StartScavengingUnusedSessionStorage();
+
  private:
   friend class DomStorageContextTest;
   FRIEND_TEST_ALL_PREFIXES(DomStorageContextTest, Basics);
   friend class base::RefCountedThreadSafe<DomStorageContext>;
   typedef std::map<int64, scoped_refptr<DomStorageNamespace> >
       StorageNamespaceMap;
 
   ~DomStorageContext();
 
   void ClearSessionOnlyOrigins();
 
+  // For scavenging unused sessionStorages.
+  void FindUnusedNamespaces();
+  void FindUnusedNamespacesInCommitSequence(
+      const std::set<std::string>& namespace_ids_in_use,
+      const std::set<std::string>& protected_persistent_session_ids);
+  void DeleteNextUnusedNamespace();
+  void DeleteNextUnusedNamespaceInCommitSequence();
+
   // Collection of namespaces keyed by id.
   StorageNamespaceMap namespaces_;
 
   // Where localstorage data is stored, maybe empty for the incognito use case.
   FilePath localstorage_directory_;
 
   // Where sessionstorage data is stored, maybe empty for the incognito use
   // case. Always empty until the file-backed session storage feature is
   // implemented.
   FilePath sessionstorage_directory_;
 
   // Used to schedule sequenced background tasks.
   scoped_refptr<DomStorageTaskRunner> task_runner_;
 
   // List of objects observing local storage events.
   ObserverList<EventObserver> event_observers_;
 
   // We use a 32 bit identifier for per tab storage sessions.
   // At a tab per second, this range is large enough for 68 years.
   base::AtomicSequenceNumber session_id_sequence_;
 
   bool is_shutdown_;
   bool force_keep_session_state_;
   scoped_refptr<quota::SpecialStoragePolicy> special_storage_policy_;
+  scoped_refptr<SessionStorageDatabase> session_storage_database_;
+
+  // For cleaning up unused namespaces gradually.
+  bool scavenging_started_;
+  std::vector<std::string> deletable_persistent_namespace_ids_;
+
+  // Persistent namespace IDs to protect from gradual deletion (they will
+  // be needed for session restore).
+  std::set<std::string> protected_persistent_session_ids_;
 };
 
 }  // namespace dom_storage
 
 #endif  // WEBKIT_DOM_STORAGE_DOM_STORAGE_CONTEXT_H_