Ichthyostega
20f3252892
Yet another chainsaw massacre. One of the most obnoxious annoyances with C++ metaprogramming is the need to insert `typename` and `template` qualifiers into most definitions, to help the compiler to cope with the syntax, which is not context-free. The recent standards adds several clarifications, so that most of these qualifiers are redundant now, at least at places where it is unambiguously clear that only a type can be given. GCC already supports most of these relaxing rules (Clang unfortunately lags way behind with support of newer language features...)
81 lines
2.7 KiB
C++
81 lines
2.7 KiB
C++
/*
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SYNC-CLASSLOCK.hpp - special case of object based locking tied directly to a type
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Copyright (C)
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2008, Hermann Vosseler <Ichthyostega@web.de>
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2023, Hermann Vosseler <Ichthyostega@web.de>
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**Lumiera** is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2 of the License, or (at your
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option) any later version. See the file COPYING for further details.
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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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** @note simply using the ClassLock may cause a Monitor object (with a mutex) to be
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** created at static initialisation and destroyed on application shutdown.
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** @see depend.hpp usage example
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** @see SyncClasslock_test
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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/nobug-init.hpp"
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#include "lib/zombie-check.hpp"
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#include "lib/meta/util.hpp"
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#include "lib/sync.hpp"
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namespace lib {
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/**
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* A synchronisation protection guard employing a lock scoped
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* to the parameter type as a whole, not an individual instance.
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* After creating an instance, every other access specifying the same
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* type is blocked.
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* @note the Lock is recursive, because several instances within the same
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* thread may want to acquire it at the same time without deadlock.
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* @note there is a design sloppiness, as two instantiations of the
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* ClassLock template with differing CONF count as different type.
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* Actually using two different configurations within for a single
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* class X should be detected and flagged as error, but actually
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* just two non-shared lock instances get created silently. Beware!
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* @see Sync::Lock the usual simple instance-bound variant
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*/
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template<class X, class CONF = RecursiveLock_NoWait>
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class ClassLock
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: public Sync<CONF>::Lock
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{
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using Lock = Sync<CONF>::Lock;
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using Monitor = sync::Monitor<CONF>;
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struct PerClassMonitor : Monitor {};
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Monitor&
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getPerClassMonitor()
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{
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static PerClassMonitor classMonitor;
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static ZombieCheck zombieCheck{util::typeStr(this)};
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zombieCheck();
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return classMonitor;
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}
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public:
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ClassLock()
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: Lock{getPerClassMonitor()}
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{ }
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};
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} // namespace lib
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#endif /*LIB_SYNC_CLASSLOCK_H*/
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