Persist sessionStorage on disk.

webkit/dom_storage/session_storage_database.h

Index: webkit/dom_storage/session_storage_database.h
diff --git a/webkit/dom_storage/session_storage_database.h b/webkit/dom_storage/session_storage_database.h
index 822dbc3d43668726047e2d67d07ea5172f5cd704..777bdfdb7144f83365ccc48538a8811033288237 100644
--- a/webkit/dom_storage/session_storage_database.h
+++ b/webkit/dom_storage/session_storage_database.h
@@ -9,6 +9,7 @@
 #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"
@@ -28,11 +29,24 @@ 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
@@ -62,6 +76,14 @@ class SessionStorageDatabase :
   // 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;
@@ -119,12 +141,12 @@ class SessionStorageDatabase :
                           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.
@@ -177,16 +199,18 @@ class SessionStorageDatabase :
                     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);
@@ -205,13 +229,19 @@ class SessionStorageDatabase :
   // 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);
 };