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Diffstat (limited to 'indra/llcommon/llsingleton.h')
| -rw-r--r-- | indra/llcommon/llsingleton.h | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/indra/llcommon/llsingleton.h b/indra/llcommon/llsingleton.h new file mode 100644 index 0000000000..7aee1bb85f --- /dev/null +++ b/indra/llcommon/llsingleton.h @@ -0,0 +1,201 @@ +/** + * @file llsingleton.h + * + * $LicenseInfo:firstyear=2002&license=viewerlgpl$ + * Second Life Viewer Source Code + * Copyright (C) 2010, Linden Research, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; + * version 2.1 of the License only. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA + * $/LicenseInfo$ + */ +#ifndef LLSINGLETON_H +#define LLSINGLETON_H + +#include "llerror.h" // *TODO: eliminate this + +#include <typeinfo> +#include <boost/noncopyable.hpp> + +/// @brief A global registry of all singletons to prevent duplicate allocations +/// across shared library boundaries +class LL_COMMON_API LLSingletonRegistry { + private: + typedef std::map<std::string, void *> TypeMap; + static TypeMap * sSingletonMap; + + static void checkInit() + { + if(sSingletonMap == NULL) + { + sSingletonMap = new TypeMap(); + } + } + + public: + template<typename T> static void * & get() + { + std::string name(typeid(T).name()); + + checkInit(); + + // the first entry of the pair returned by insert will be either the existing + // iterator matching our key, or the newly inserted NULL initialized entry + // see "Insert element" in http://www.sgi.com/tech/stl/UniqueAssociativeContainer.html + TypeMap::iterator result = + sSingletonMap->insert(std::make_pair(name, (void*)NULL)).first; + + return result->second; + } +}; + +// LLSingleton implements the getInstance() method part of the Singleton +// pattern. It can't make the derived class constructors protected, though, so +// you have to do that yourself. +// +// There are two ways to use LLSingleton. The first way is to inherit from it +// while using the typename that you'd like to be static as the template +// parameter, like so: +// +// class Foo: public LLSingleton<Foo>{}; +// +// Foo& instance = Foo::instance(); +// +// The second way is to use the singleton class directly, without inheritance: +// +// typedef LLSingleton<Foo> FooSingleton; +// +// Foo& instance = FooSingleton::instance(); +// +// In this case, the class being managed as a singleton needs to provide an +// initSingleton() method since the LLSingleton virtual method won't be +// available +// +// As currently written, it is not thread-safe. + +template <typename DERIVED_TYPE> +class LLSingleton : private boost::noncopyable +{ + +private: + typedef enum e_init_state + { + UNINITIALIZED, + CONSTRUCTING, + INITIALIZING, + INITIALIZED, + DELETED + } EInitState; + + static void deleteSingleton() + { + delete getData().mSingletonInstance; + getData().mSingletonInstance = NULL; + } + + // stores pointer to singleton instance + // and tracks initialization state of singleton + struct SingletonInstanceData + { + EInitState mInitState; + DERIVED_TYPE* mSingletonInstance; + + SingletonInstanceData() + : mSingletonInstance(NULL), + mInitState(UNINITIALIZED) + {} + + ~SingletonInstanceData() + { + deleteSingleton(); + } + }; + +public: + virtual ~LLSingleton() + { + SingletonInstanceData& data = getData(); + data.mSingletonInstance = NULL; + data.mInitState = DELETED; + } + + static SingletonInstanceData& getData() + { + // this is static to cache the lookup results + static void * & registry = LLSingletonRegistry::get<DERIVED_TYPE>(); + + // *TODO - look into making this threadsafe + if(NULL == registry) + { + static SingletonInstanceData data; + registry = &data; + } + + return *static_cast<SingletonInstanceData *>(registry); + } + + static DERIVED_TYPE* getInstance() + { + SingletonInstanceData& data = getData(); + + if (data.mInitState == CONSTRUCTING) + { + llerrs << "Tried to access singleton " << typeid(DERIVED_TYPE).name() << " from singleton constructor!" << llendl; + } + + if (data.mInitState == DELETED) + { + llwarns << "Trying to access deleted singleton " << typeid(DERIVED_TYPE).name() << " creating new instance" << llendl; + } + + if (!data.mSingletonInstance) + { + data.mInitState = CONSTRUCTING; + data.mSingletonInstance = new DERIVED_TYPE(); + data.mInitState = INITIALIZING; + data.mSingletonInstance->initSingleton(); + data.mInitState = INITIALIZED; + } + + return data.mSingletonInstance; + } + + // Reference version of getInstance() + // Preferred over getInstance() as it disallows checking for NULL + static DERIVED_TYPE& instance() + { + return *getInstance(); + } + + // Has this singleton been created uet? + // Use this to avoid accessing singletons before the can safely be constructed + static bool instanceExists() + { + return getData().mInitState == INITIALIZED; + } + + // Has this singleton already been deleted? + // Use this to avoid accessing singletons from a static object's destructor + static bool destroyed() + { + return getData().mInitState == DELETED; + } + +private: + virtual void initSingleton() {} +}; + +#endif |