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// Copyright (c) 2006-2009 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_SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_
#define CHROME_BROWSER_SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_
#pragma once
#include "chrome/browser/sync/engine/syncer_command.h"
namespace browser_sync {
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 {
public:
ModelChangingSyncerCommand() : work_session_(NULL) { }
virtual ~ModelChangingSyncerCommand() { }
// SyncerCommand implementation. Sets work_session to session.
virtual void ExecuteImpl(sessions::SyncSession* session);
// wrapper so implementations don't worry about storing work_session
void StartChangingModel() {
ModelChangingExecuteImpl(work_session_);
}
// Sometimes, a command has work to do that needs to touch global state
// belonging to multiple ModelSafeGroups, but in a way that is known to be
// safe. This will be called once, prior to ModelChangingExecuteImpl,
// *without* a ModelSafeGroup restriction in place on the SyncSession.
// Returns true on success, false on failure.
// TODO(tim): Remove this (bug 36594).
virtual bool ModelNeutralExecuteImpl(sessions::SyncSession* session) {
return true;
}
// 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 void ModelChangingExecuteImpl(sessions::SyncSession* session) = 0;
private:
// 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_;
DISALLOW_COPY_AND_ASSIGN(ModelChangingSyncerCommand);
};
} // namespace browser_sync
#endif // CHROME_BROWSER_SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_
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