ThreadLocalInstance.hpp

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// @formatter:off
//
// Balau core C++ library
//
// Copyright (C) 2008 Bora Software (contact@borasoftware.com)
//
// Licensed under the Boost Software License - Version 1.0 - August 17th, 2003.
// See the LICENSE file for the full license text.
//


#ifndef COM_BORA_SOFTWARE__BALAU_CONCURRENT__THREAD_LOCAL_INSTANCE
#define COM_BORA_SOFTWARE__BALAU_CONCURRENT__THREAD_LOCAL_INSTANCE

#include <boost/thread/tss.hpp>

namespace Balau::Concurrent {

template <typename T, typename Enable = void> class ThreadLocalInstance;

template <typename T>
class ThreadLocalInstance<T, typename std::enable_if<std::is_default_constructible<T>::value>::type> {
    public: T & operator () () {
        if (!instance.get()) {
            instance.reset(new T);
        }

        return *instance.get();
    }

    public: T & operator () (std::function<T * ()> instantiate) {
        if (!instance.get()) {
            instance.reset(instantiate());
        }

        return *instance.get();
    }


    private: boost::thread_specific_ptr<T> instance;
};

template <typename T>
class ThreadLocalInstance<T, std::negation<typename std::enable_if<std::is_default_constructible<T>::value>::type>> {
    public: T & operator () (std::function<T * ()> instantiate) {
        if (instance.get()) {
            instance.reset(instantiate());
        }

        return *instance.get();
    }


    private: boost::thread_specific_ptr<T> instance;
};

} // namespace Balau::Concurrent

#endif // COM_BORA_SOFTWARE__BALAU_CONCURRENT__THREAD_LOCAL_INSTANCE