#ifndef DATE_TIME_HIGHRES_TIME_CLOCK_HPP___
#define DATE_TIME_HIGHRES_TIME_CLOCK_HPP___

/*! @file highres_time_clock.hpp
  This file contains the interface for clock devices
*/

#include "boost/date_time/c_time.hpp"
#ifdef BOOST_DATE_TIME_HAS_GETTIMEOFDAY_HIGH_PRECISION_CLOCK

namespace boost {
namespace date_time {


  //! A clock providing microsecond level resolution 
  /*! A high precision clock that measures the local time
   *  at a resolution up to microseconds and adjusts to the
   *  resolution of the time system.  For example, for the
   *  a library configuration with nano second resolution,
   *  the last 3 places of the fractional seconds will always
   *  be 000 since there are 1000 nano-seconds in a micro second.
   *
   *  This clock is only available on platforms with a gettimeofday
   *  function.
   */
  template<class time_type> 
  class microsec_clock
  {
  public:
    typedef typename time_type::date_type date_type;
    typedef typename time_type::time_duration_type time_duration_type;
    typedef typename time_duration_type::rep_type resolution_traits_type;

    //! Return the local time based on computer clock settings
    static time_type local_time() {
      timeval tv;
      gettimeofday(&tv, 0); //gettimeofday does not support TZ adjust on Linux.
      return create_time(&tv);
    }
    
  private:
    static time_type create_time(timeval* tv) {
      time_t t = tv->tv_sec;
      boost::uint32_t fs = tv->tv_usec;
      ::std::time(&t); 
      tm* curr = localtime(&t);
      date_type d(curr->tm_year + 1900, 
		  curr->tm_mon + 1, 
		  curr->tm_mday);
      //The following line will adjusts the fractional second tick in terms
      //of the current time system.  For example, if the time system
      //doesn't support fractional seconds then res_adjust returns 0
      //and all the fractional seconds return 0.
      int adjust = resolution_traits_type::res_adjust()/1000000;

      time_duration_type td(curr->tm_hour,
			    curr->tm_min,
                            curr->tm_sec,
			    fs*adjust);
      return time_type(d,td);
      
    }

    
  };

  
} } //namespace date_time

#endif //BOOST_DATE_TIME_HAS_GETTIMEOFDAY_HIGH_PRECISION_CLOCK

#endif
