Blob support for IDB [Chromium]

content/browser/indexed_db/indexed_db_active_blob_registry.h

+// Copyright (c) 2013 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 "webkit/common/blob/shareable_file_reference.h"
+
+namespace content {
+
+class IndexedDBBackingStore;
+
+class IndexedDBActiveBlobRegistry {
+public:
+  IndexedDBActiveBlobRegistry(IndexedDBBackingStore* backing_store);
+  ~IndexedDBActiveBlobRegistry();
+
+  // These functions should be run on backing_store_->task_runner().
+  void MarkUsed(int64 database_id, int64 blob_key);
+  void MarkUnused(int64 database_id, int64 blob_key);
+  // Use DatabaseMetaDataKey::AllBlobsKey for "the whole database".
+  bool MarkDeletedCheckIfUsed(int64 database_id, int64 blob_key);
+
+  // These functions can be called from any thread, but GetMarkUsedCallback's
+  // return value should be called on the TaskRunner for backing_store_.
+  void MarkUnusedThreadSafe(int64 database_id, int64 blob_key,
+      const base::FilePath& unused);
+  webkit_blob::ShareableFileReference::FinalReleaseCallback
+      GetReleaseCallback(int64 database_id, int64 blob_key);
+  base::Closure GetMarkUsedCallback(int64 database_id, int64 blob_key);

[jsbell, 2013/09/13 00:12:21]

Add comment about the lifetime rules for this closure (which contains
base::Unretained(this))

[ericu, 2013/11/20 23:05:39]

Added a comment.  The reason it's safe is beyond the scope of this file: the
IndexedDBBackingStore keeps the IndexedDBActiveBlobRegistry alive, and we don't
process Get() requests after the backing store goes away.

+
+private:
+  // 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_counts_;
+  DeletedDBSet deleted_dbs_;
+  // Think of this as a scoped_refptr, but it's manually managed.  We'll hold a

[jsbell, 2013/09/13 00:12:21]

Reword - not clear what "this" refers to.

[ericu, 2013/11/20 23:05:39]

Done.

+  // reference as long as there's a blob registered in use_counts_, but not
+  // otherwise.  Ideally the blobs would hold the references themselves, but
+  // they live on the wrong thread.
+  IndexedDBBackingStore* backing_store_;
+  DISALLOW_COPY_AND_ASSIGN(IndexedDBActiveBlobRegistry);
+};
+
+} // namespace content
+
+#endif // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_ACTIVE_BLOB_REGISTRY_H_