singletonholder.h

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#ifndef LOG4CXX_SINGLETON_HOLDER_H
#define LOG4CXX_SINGLETON_HOLDER_H
 
#include <log4cxx/helpers/object.h>
 
namespace LOG4CXX_NS
{
namespace helpers
{

template <class T>
class SingletonHolder : public Object
{
    using ThisType = SingletonHolder<T>;
    T m_data;
    struct Unused : public helpers::Class
    {
        LogString getName() const override { return LOG4CXX_STR("SingletonHolder"); }
    };
public: // Object method stubs
    const helpers::Class& getClass() const override { static Unused notUsed; return notUsed; }
    BEGIN_LOG4CXX_CAST_MAP()
    LOG4CXX_CAST_ENTRY(ThisType)
    END_LOG4CXX_CAST_MAP()
 
public: // ...structors
    SingletonHolder() {}
    template < typename Arg0, typename ... Args
             , typename = typename std::enable_if<!std::is_same<typename std::decay<Arg0>::type, SingletonHolder>::value>::type
             >
    SingletonHolder(Arg0 arg0, Args&& ... args)
        : m_data(arg0, std::forward<Args>(args) ... )
    {}
    // Prevent copying
    SingletonHolder(const SingletonHolder&) = delete;
    SingletonHolder(SingletonHolder&&) = delete;
 
public: // Accessors
    T& value() { return m_data; }
};
 
} // namespace helpers
} // namespace LOG4CXX_NS
 
#endif //LOG4CXX_SINGLETON_HOLDER_H