setting.h

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#ifndef SETTING_H_62B23520_7C8E_11DE_8A39_0800200C9A66_PM
#define SETTING_H_62B23520_7C8E_11DE_8A39_0800200C9A66_PM
 
#if defined(_MSC_VER) || (defined(__GNUC__) && (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4)) // GCC supports "pragma once" correctly since 3.4
#pragma once
#endif
 
 
#include <memory>
#include <vector>
#include "yaml-cpp-pm/noncopyable.h"
 
namespace YAML_PM
{
        class SettingChangeBase;
        
        template <typename T>
        class Setting
        {
        public:
                Setting(): m_value() {}
                
                const T get() const { return m_value; }
                std::auto_ptr <SettingChangeBase> set(const T& value);
                void restore(const Setting<T>& oldSetting) {
                        m_value = oldSetting.get();
                }
                
        private:
                T m_value;
        };
 
        class SettingChangeBase
        {
        public:
                virtual ~SettingChangeBase() {}
                virtual void pop() = 0;
        };
        
        template <typename T>
        class SettingChange: public SettingChangeBase
        {
        public:
                SettingChange(Setting<T> *pSetting): m_pCurSetting(pSetting) {
                        // copy old setting to save its state
                        m_oldSetting = *pSetting;
                }
                
                virtual void pop() {
                        m_pCurSetting->restore(m_oldSetting);
                }
 
        private:
                Setting<T> *m_pCurSetting;
                Setting<T> m_oldSetting;
        };
 
        template <typename T>
        inline std::auto_ptr <SettingChangeBase> Setting<T>::set(const T& value) {
                std::auto_ptr <SettingChangeBase> pChange(new SettingChange<T> (this));
                m_value = value;
                return pChange;
        }
        
        class SettingChanges: private noncopyable
        {
        public:
                SettingChanges() {}
                ~SettingChanges() { clear(); }
                
                void clear() {
                        restore();
                        
                        for(setting_changes::const_iterator it=m_settingChanges.begin();it!=m_settingChanges.end();++it)
                                delete *it;
                        m_settingChanges.clear();
                }
                
                void restore() {
                        for(setting_changes::const_iterator it=m_settingChanges.begin();it!=m_settingChanges.end();++it)
                                (*it)->pop();
                }
                
                void push(std::auto_ptr <SettingChangeBase> pSettingChange) {
                        m_settingChanges.push_back(pSettingChange.release());
                }
                
                // like std::auto_ptr - assignment is transfer of ownership
                SettingChanges& operator = (SettingChanges& rhs) {
                        if(this == &rhs)
                                return *this;
                        
                        clear();
                        m_settingChanges = rhs.m_settingChanges;
                        rhs.m_settingChanges.clear();
                        return *this;
                }
                
        private:
                typedef std::vector <SettingChangeBase *> setting_changes;
                setting_changes m_settingChanges;
        };
}
 
#endif // SETTING_H_62B23520_7C8E_11DE_8A39_0800200C9A66_PM