Add the IndexedDBActiveBlobRegistry, currently unused, to enable future blob

content/browser/indexed_db/indexed_db_active_blob_registry.h

+// Copyright (c) 2014 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 CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_ACTIVE_BLOB_REGISTRY_H_
+#define CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_ACTIVE_BLOB_REGISTRY_H_
+
+#include <map>
+#include <set>
+#include <utility>
+#include "base/basictypes.h"
+#include "base/files/file_path.h"
+#include "base/memory/weak_ptr.h"
+#include "content/common/content_export.h"
+#include "webkit/common/blob/shareable_file_reference.h"
+
+namespace content {
+
+class IndexedDBBackingStore;
+
+class CONTENT_EXPORT IndexedDBActiveBlobRegistry {
+ public:
+  IndexedDBActiveBlobRegistry(IndexedDBBackingStore* backing_store);
+  ~IndexedDBActiveBlobRegistry();
+
+  // Most methods of this class, and the closure returned by
+  // GetAddBlobRefCallback, should only be called on the backing_store's task
+  // runner.  The exception is the closure returned by GetFinalReleaseCallback,
+  // which just calls ReleaseBlobRefThreadSafe.
+
+  // Use DatabaseMetaDataKey::AllBlobsKey for "the whole database".
+  bool MarkDeletedCheckIfUsed(int64 database_id, int64 blob_key);
+
+  webkit_blob::ShareableFileReference::FinalReleaseCallback
+      GetFinalReleaseCallback(int64 database_id, int64 blob_key);
+  // This closure holds a raw pointer to the IndexedDBActiveBlobRegistry,
+  // and may not be called after it is deleted.
+  base::Closure GetAddBlobRefCallback(int64 database_id, int64 blob_key);
+  // Call this to force the registry to drop its use counts, permitting the
+  // factory to drop any blob-related refcount for the backing store.
+  // This will also turn any outstanding callbacks into no-ops.
+  void ForceShutdown();
+
+ private:
+  void AddBlobRef(int64 database_id, int64 blob_key);
+  void ReleaseBlobRef(int64 database_id, int64 blob_key);
+  static void ReleaseBlobRefThreadSafe(
+      scoped_refptr<base::TaskRunner> task_runner,
+      base::WeakPtr<IndexedDBActiveBlobRegistry> weak_ptr,
+      int64 database_id,
+      int64 blob_key,
+      const base::FilePath& unused);
+
+  // Maps blob_key -> IsDeleted; if the record's absent, it's not in active use
+  // and we don't care if it's deleted.
+  typedef std::map<int64, bool> SingleDBMap;
+  // Maps DB ID -> SingleDBMap
+  typedef std::map<int64, SingleDBMap> AllDBsMap;
+  typedef std::set<int64> DeletedDBSet;
+
+  AllDBsMap use_tracker_;
+  DeletedDBSet deleted_dbs_;
+  // As long as we've got blobs registered in use_tracker_,
+  // backing_store_->factory() will keep backing_store_ alive for us.  And
+  // backing_store_ owns us, so we'll stay alive as long as we're needed.
+  IndexedDBBackingStore* backing_store_;
+  base::WeakPtrFactory<IndexedDBActiveBlobRegistry> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(IndexedDBActiveBlobRegistry);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_ACTIVE_BLOB_REGISTRY_H_