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// 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.
#include "base/compiler_specific.h"
#include "sync/engine/syncer_command.h"
#include "sync/internal_api/public/engine/model_safe_worker.h"
namespace syncer {
namespace sessions {
class SyncSession;
// An abstract SyncerCommand which dispatches its Execute step to the
// model-safe worker thread. Classes derived from ModelChangingSyncerCommand
// instead of SyncerCommand must implement ModelChangingExecuteImpl instead of
// ExecuteImpl, but otherwise, the contract is the same.
// A command should derive from ModelChangingSyncerCommand instead of
// SyncerCommand whenever the operation might change any client-visible
// fields on any syncable::Entry. If the operation involves creating a
// WriteTransaction, this is a sign that ModelChangingSyncerCommand is likely
// necessary.
class ModelChangingSyncerCommand : public SyncerCommand {
ModelChangingSyncerCommand() : work_session_(NULL) { }
virtual ~ModelChangingSyncerCommand() { }
// SyncerCommand implementation. Sets work_session to session.
virtual SyncerError ExecuteImpl(sessions::SyncSession* session) OVERRIDE;
// Wrapper so implementations don't worry about storing work_session.
SyncerError StartChangingModel() {
return ModelChangingExecuteImpl(work_session_);
std::set<ModelSafeGroup> GetGroupsToChangeForTest(
const sessions::SyncSession& session) const {
return GetGroupsToChange(session);
// This should return the set of groups in |session| that need to be
// changed. The returned set should be a subset of
// session.GetEnabledGroups(). Subclasses can guarantee this either
// by calling one of the session.GetEnabledGroups*() functions and
// filtering that, or using GetGroupForModelType() (which handles
// top-level/unspecified nodes) to project from model types to
// groups.
virtual std::set<ModelSafeGroup> GetGroupsToChange(
const sessions::SyncSession& session) const = 0;
// Abstract method to be implemented by subclasses to handle logic that
// operates on the model. This is invoked with a SyncSession ModelSafeGroup
// restriction in place so that bits of state belonging to data types
// running on an unsafe thread are siloed away.
virtual SyncerError ModelChangingExecuteImpl(
sessions::SyncSession* session) = 0;
// ExecuteImpl is expected to be run by SyncerCommand to set work_session.
// StartChangingModel is called to start this command running.
// Implementations will implement ModelChangingExecuteImpl and not
// worry about storing the session or setting it. They are given work_session.
sessions::SyncSession* work_session_;
} // namespace syncer