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/* Authors: Jonathan Gammell */

#ifndef OMPL_GEOMETRIC_PLANNERS_BITSTAR_DATASTRUCTURES_IDGENERATOR_
#define OMPL_GEOMETRIC_PLANNERS_BITSTAR_DATASTRUCTURES_IDGENERATOR_

//I am member class of the BITstar class, so I need to include it's definition to be aware of the class BITstar. It has a forward declaration to me.
#include "ompl/geometric/planners/bitstar/BITstar.h"

//For locking the ID generator:
#include <boost/thread/mutex.hpp>
//For boost::scoped_ptr
#include <boost/scoped_ptr.hpp>
//For the boost::once_flag and other tools for making sure an init function is only called once.
#include <boost/thread/once.hpp>
//For boost::lock_guard
#include <boost/thread/locks.hpp>

namespace ompl
{
    namespace geometric
    {
        /** @anchor IdGenerator
        @par Short description
        A class to generate unique IDs for the \ref gVertex "Vertex" class.
        */

        /** \brief An ID generator class for vertex IDs.*/
        class BITstar::IdGenerator
        {
        public:
            IdGenerator()
                :  nextId_(0u)
            {
            }

            /** \brief Generator a new id and increment the global/static counter of IDs. */
            BITstar::VertexId getNewId()
            {
                //Create a scoped mutex copy of idMutex that unlocks when it goes out of scope:
                boost::lock_guard<boost::mutex> lockGuard(idMutex_);

                //Return the next id, purposefully post-decrementing:
                return nextId_++;
            }

        private:
            //Variables:
            //The next ID to be returned:
            BITstar::VertexId nextId_;
            //The mutex
            boost::mutex idMutex_;
        };
    } //geometric
} //ompl


//An anonymous namespace to hide the instance:
namespace
{
    //Global variables:
    //The initialization flag stating that the ID generator has been created:
    static boost::once_flag g_IdInited = BOOST_ONCE_INIT;
    //A pointer to the actual ID generator
    static boost::scoped_ptr<ompl::geometric::BITstar::IdGenerator> g_IdGenerator;

    //A function to initialize the ID generator pointer:
    void initIdGenerator()
    {
        g_IdGenerator.reset(new ompl::geometric::BITstar::IdGenerator());
    }

    //A function to get the current ID generator:
    ompl::geometric::BITstar::IdGenerator& getIdGenerator()
    {
        boost::call_once(&initIdGenerator, g_IdInited);
        return *g_IdGenerator;
    }
}
#endif //OMPL_GEOMETRIC_PLANNERS_BITSTAR_DATASTRUCTURES_IDGENERATOR_
