Purge in-memory localStorage areas if the # of areas exceeds the limit

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>
@@ skipping 15 matching lines @@
 class Time;
 }
 
 namespace quota {
 class SpecialStoragePolicy;
 }
 
 namespace dom_storage {
 
 class DomStorageArea;
+class DomStorageHost;
 class DomStorageNamespace;
 class DomStorageSession;
 class DomStorageTaskRunner;
 class SessionStorageDatabase;
 struct LocalStorageUsageInfo;
 struct SessionStorageUsageInfo;
 
 // 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,
@@ skipping 114 matching lines @@
 
   // 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();
 
+  // Performs a quick check to see if the given item (of |key| and |value|
+  // fits in the cache/storage.
+  // This may trigger aggressive memory purge if the in-memory cache is
+  // getting tight.
+  bool CanSetItem(DomStorageHost* host,
+                  int connection_id,
+                  const string16& key,
+                  const string16& value);
+
  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();
 
+  // This forces the context to re-calculate the total area size next time
+  // GetInMemoryAreaSize() is called.
+  void InvalidateInMemoryAreaSize() {
+    total_area_size_ = -1;
+  }
+  int64 GetRemainingCacheSize();
+
   // Collection of namespaces keyed by id.
   StorageNamespaceMap namespaces_;
 
   // Where localstorage data is stored, maybe empty for the incognito use case.
   base::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.
   base::FilePath sessionstorage_directory_;
@@ skipping 17 matching lines @@
   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_;
 
   // Mapping between persistent namespace IDs and namespace IDs for
   // sessionStorage.
   std::map<std::string, int64> persistent_namespace_id_to_namespace_id_;
+
+  // Total in-memory map size.
+  int64 total_area_size_;
 };
 
 }  // namespace dom_storage
 
 #endif  // WEBKIT_DOM_STORAGE_DOM_STORAGE_CONTEXT_H_