142 lines
4 KiB
C++
142 lines
4 KiB
C++
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/*
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SINGLETONPOLICIES.hpp - how to manage creation, lifecycle and multithreading
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Copyright (C) CinelerraCV
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2007, Christian Thaeter <ct@pipapo.org>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program 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 this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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====================================================================
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This code is heavily inspired by
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The Loki Library (loki-lib/trunk/include/loki/Singleton.h)
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Copyright (c) 2001 by Andrei Alexandrescu
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This Loki code accompanies the book:
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Alexandrescu, Andrei. "Modern C++ Design: Generic Programming
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and Design Patterns Applied".
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Copyright (c) 2001. Addison-Wesley. ISBN 0201704315
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*/
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#ifndef CINELERRA_SINGLETON_H
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#define CINELERRA_SINGLETON_H
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#include "common/error.hpp"
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namespace cinelerra
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{
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namespace singleton
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{
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/* == several Policies usable in conjunction with cinelerra::Singleton == */
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/**
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* Policy for creating the Singleton instance statically
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*/
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template<class S>
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struct Static
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{
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static S* create ()
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{
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#ifdef DEBUG
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static uint callCount (0);
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ASSERT ( 0 == callCount++ );
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#endif
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static S _theSingle_;
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return &_theSingle_;
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}
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static void destroy (S*)
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{
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S->~S();
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}
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};
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/**
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* Policy for creating the Singleton instance heap allocated
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*/
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template<class S>
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struct Heap
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{
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static S* create () { return new S; }
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static void destroy (S* pS) { delete pS; }
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};
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/**
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* Policy relying on the compiler/runtime system for Singleton Lifecycle
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*/
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template<class S>
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struct Automatic
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{
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/** implements the Singleton removal by calling
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* the provided deleter function at application shutdown,
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* relying on the runtime system calling destructors of
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* static objects
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*/
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static void scheduleDelete (void (*deleter) (void))
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{
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struct DeleteTrigger
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{
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~DeleteTrigger() { *deleter (); }
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};
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static DeleteTrigger trigger;
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REQUIRE (deleter);
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}
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static void onDeadReference ()
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{
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throw error::Logic ("Trying to access the a Singleton instance that has "
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"already been released or finished its lifecycle.");
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}
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};
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/**
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* Policy for handling multithreaded access to the singleton instance
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* @todo actually implement this policy using the cinelerra databackend.
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*/
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template<class S>
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struct Multithreaded
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{
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typedef volatile S* VolatileType;
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class Lock
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{
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public:
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Lock() { UNIMPLEMENTED ("aquire Thread Lock"); }
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~Lock() { UNIMPLEMENTED ("release Thread Lock"); }
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};
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};
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/**
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* Policy just ignoring thread safety
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*/
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template<class S>
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struct IgnoreThreadsafety
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{
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typedef S VolatileType;
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struct Lock {};
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};
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} // namespace singleton
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} // namespace cinelerra
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#endif
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