72 lines
2.6 KiB
C++
72 lines
2.6 KiB
C++
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/*
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SYNC-CLASSLOCK.hpp - special case of object based locking tied directly to a type
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Copyright (C) Lumiera.org
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2008, Christian Thaeter <ct@pipapo.org>
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Hermann Vosseler <Ichthyostega@web.de>
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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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/** @file sync-classlock.hpp
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** A special implementation of lib::Sync, where the storage of the object monitor
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** is associated directly to a type rather then to a single object instance. While
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** being problematic in conjunction with static startup/shutdown, doing so is sometimes
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** necessary to setup type based dispatcher tables, managing singleton creation etc.
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**
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** @see singletonfactory.hpp usage example
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*/
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#ifndef LIB_SYNC_CLASSLOCK_H
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#define LIB_SYNC_CLASSLOCK_H
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#include "lib/sync.hpp"
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namespace lib {
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template<class X, class CONF = NonrecursiveLock_NoWait>
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class ClassLock
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: public Sync<CONF>::Lock
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{
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typedef typename Sync<CONF>::Lock Lock;
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typedef typename Sync<CONF>::Monitor Monitor;
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static Monitor&
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getMonitor()
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{
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//TODO: a rather obscure race condition is hidden here:
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//TODO: depending on the build order, the dtor of this static variable may be called, while another thread is still holding an ClassLock.
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//TODO: An possible solution would be to use an shared_ptr to the Monitor in case of a ClassLock and to protect access with another Mutex.
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//TODO. But I am really questioning if we can't ignore this case and state: "don't hold a ClassLock when your code maybe still running in shutdown phase!"
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//TODO: probably best Idea is to detect this situation in DEBUG or ALPHA mode
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static scoped_ptr<Monitor> classMonitor_ (0);
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if (!classMonitor_) classMonitor_.reset (new Monitor ());
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return *classMonitor_;
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}
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public:
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ClassLock() : Lock (getMonitor()) {}
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};
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} // namespace lib
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#endif
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