141 lines
4.0 KiB
C++
141 lines
4.0 KiB
C++
/*
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Copyright (C) 2001-2006, William Joseph.
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All Rights Reserved.
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This file is part of GtkRadiant.
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GtkRadiant is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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GtkRadiant is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GtkRadiant; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#if !defined( INCLUDED_GENERIC_STATIC_H )
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#define INCLUDED_GENERIC_STATIC_H
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/// \file
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/// \brief Template techniques for instantiating singletons.
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#include <cstddef>
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class Null
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{
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};
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/// \brief A singleton which is statically initialised.
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///
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/// \param Type The singleton object type.
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/// \param Type The type distinguishing this instance from others of the same type.
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///
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/// \dontinclude generic/static.cpp
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/// \skipline Static example
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/// \until end example
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template<typename Type, typename Context = Null>
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class Static
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{
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static Type m_instance;
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public:
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static Type& instance(){
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return m_instance;
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}
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};
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template<typename Type, typename Context>
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Type Static<Type, Context>::m_instance;
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/// \brief A singleton which is lazily initialised.
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/// The instance is constructed the first time it is referenced, and is never destroyed.
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///
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/// \param Type The singleton object type.
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/// \param Type The type distinguishing this instance from others of the same type.
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///
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/// \dontinclude generic/static.cpp
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/// \skipline LazyStatic example
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/// \until end example
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template<typename Type, typename Context = Null>
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class LazyStatic
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{
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static Type* m_instance; // this will be initialised to 0 by the CRT, according to the c++ standard
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public:
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static Type& instance(){
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if ( m_instance == 0 ) {
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m_instance = new Type; // allocate using 'new' to get the correct alignment
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}
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return *m_instance;
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}
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};
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template<typename Type, typename Context>
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Type * LazyStatic<Type, Context>::m_instance;
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/// \brief A singleton which keeps a count of the number of times it is referenced.
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///
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/// The instance is constructed when its reference count changes from 0 to 1 and destroyed when its reference count changes from 1 to 0.
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/// Use with SmartStatic.
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///
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/// \param Type The singleton object type.
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/// \param Type The type distinguishing this instance from others of the same type.
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template<typename Type, typename Context = Null>
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class CountedStatic
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{
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static std::size_t m_refcount; // this will be initialised to 0 by the CRT, according to the c++ standard
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static Type* m_instance;
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public:
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static Type& instance(){
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return *m_instance;
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}
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static void capture(){
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if ( ++m_refcount == 1 ) {
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m_instance = new Type; // allocate using 'new' to get the correct alignment
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}
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}
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static void release(){
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if ( --m_refcount == 0 ) {
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delete m_instance;
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}
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}
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};
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template<typename Type, typename Context>
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std::size_t CountedStatic<Type, Context>::m_refcount; // this will be initialised to 0 by the CRT, according to the c++ standard
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template<typename Type, typename Context>
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Type * CountedStatic<Type, Context>::m_instance;
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/// \brief A reference to a CountedStatic.
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/// Guarantees that CountedStatic<Type> will be constructed for the lifetime of this object.
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///
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/// \param Type The type parameter of the CountedStatic to reference.
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/// \param Type The type distinguishing this instance from others of the same type.
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///
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/// \dontinclude generic/static.cpp
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/// \skipline SmartStatic example
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/// \until end example
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template<typename Type, typename Context = Null>
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class SmartStatic
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{
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public:
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SmartStatic(){
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CountedStatic<Type, Context>::capture();
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}
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~SmartStatic(){
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CountedStatic<Type, Context>::release();
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}
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Type& instance(){
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return CountedStatic<Type, Context>::instance();
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}
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};
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#endif
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