Implement an initial extension settings API.

chrome/browser/extensions/extension_settings.h

+// Copyright (c) 2011 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 CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_H_
+#pragma once
+
+#include "base/callback.h"
+#include "base/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "chrome/browser/extensions/extension_settings_storage.h"
+
+// Manages ExtensionSettingsStorage objects for extensions.
+class ExtensionSettings : public base::RefCountedThreadSafe<ExtensionSettings> {
+ public:
+  // File path is the base of the extension settings directory.
+  // The databases will be at base_path/extension_id.
+  explicit ExtensionSettings(const FilePath& base_path);
+
+  // Callback from the GetStorage() methods.
+  typedef base::Callback<void(ExtensionSettingsStorage*)> Callback;
+
+  // Gets the storage area for a given extension.  Only valid for the duration
+  // of the callback.
+  // By default this will be of a cached LEVELDB storage, but on failure to
+  // create a leveldb instance will fall back to cached NOOP storage.
+  // Callbacks will happen asynchronously regardless of whether they need to go
+  // to the FILE thread, but will always be called on the UI thread.
+  void GetStorage(const std::string& extension_id, const Callback& callback);
+
+  // Gets a storage area for a given extension with a specific type.
+  // and whether it should be wrapped in a cache.
+  // Use this for testing; if the given type fails to be created (e.g. if
+  // leveldb creation fails) then a DCHECK will fail.
+  // Callback objects will be deleted when used.
+  void GetStorageForTesting(
+      ExtensionSettingsStorage::Type type,
+      bool cached,
+      const std::string& extension_id,
+      const Callback& callback);
+
+ private:
+  friend class base::RefCountedThreadSafe<ExtensionSettings>;
+  ~ExtensionSettings();
+
+  // Attempts to get and callback with an existing storage area.  Returns
+  // whether storage existed and the callback run.
+  bool GetExistingStorage(
+      const std::string& extension_id, const Callback& callback);
+
+  // Runs a Callback with a storage argument, then deletes the callback.
+  void RunWithStorage(Callback* callback, ExtensionSettingsStorage* storage);
+
+  // Starts the process of creation of a storage area.
+  // Must be run on the UI thread.
+  void StartCreationOfStorage(
+      const std::string& extension_id,
+      ExtensionSettingsStorage::Type type,
+      ExtensionSettingsStorage::Type fallback_type,
+      bool cached,
+      const Callback& callback);
+
+  // Creates a new storage area of a given type, with a fallback type if
+  // creation fails, and optionally wrapped in a cache.
+  // Must be run on the FILE thread.
+  void CreateStorageOnFileThread(
+      const std::string& extension_id,
+      ExtensionSettingsStorage::Type type,
+      ExtensionSettingsStorage::Type fallback_type,
+      bool cached,
+      const Callback& callback);
+
+  // Creates a storage area of a given type, optionally wrapped in a cache.
+  // Returns NULL if creation fails.
+  ExtensionSettingsStorage* CreateStorage(
+      const std::string& extension_id,
+      ExtensionSettingsStorage::Type type,
+      bool cached);
+
+  // End the creation of a storage area.
+  // Must be run on the UI thread.
+  void EndCreationOfStorage(
+      const std::string& extension_id,
+      ExtensionSettingsStorage* storage,
+      const Callback& callback);
+
+  // The base file path to create any leveldb databases at.
+  const FilePath base_path_;
+
+  // A cache of ExtensionSettingsStorage objects that have already been created.
+  // Ensure that there is only ever one created per extension.
+  std::map<std::string, ExtensionSettingsStorage*> storage_objs_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtensionSettings);
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_H_