/*
 * Copyright (c) 2013-2014 - Adjacent Link LLC, Bridgewater, New Jersey
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in
 *   the documentation and/or other materials provided with the
 *   distribution.
 * * Neither the name of Adjacent Link LLC nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef EMANEUTILSSINGLETON_HEADER_
#define EMANEUTILSSINGLETON_HEADER_

namespace EMANE
{
  namespace Utils
  {
    /**
     * @class Singleton
     *
     * @brief Ensure a class only has one instance, and  provide a global
     * point of access to it.
     */
    template<typename T>
    class Singleton
    {
    public:
      /**
       * Provides thread-safe access to a single instance of 
       * type T. It does not provide thread-safety for T methods.
       *
       * @return A pointer to T
       */
      static T * instance()
      {
        static T * pInstance{new f{}};
        return pInstance;
      }
      
      /**
       * Destroys the single instance of type T. Once destroyed
       * it cannot be used or recreated. This is not a thread-safe
       * method.
       */
      static void destroy()
      {
        delete instance();
      }
      
    private:
      class f : public T
      {
        friend Singleton<T>;
      };
    };
  }
}

#endif // EMANEUTILSSINGLETON_HEADER_
