#ifndef DATE_TIME_HIGHRES_TIME_CLOCK_HPP___

#define DATE_TIME_HIGHRES_TIME_CLOCK_HPP___

/* Copyright (c) 2002,2003,2005 CrystalClear Software, Inc.

 * Use, modification and distribution is subject to the

 * Boost Software License, Version 1.0. (See accompanying

 * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)

 * Author: Jeff Garland, Bart Garst

 * $Date: 2008-11-23 06:13:35 -0500 (Sun, 23 Nov 2008) $

 */

/*! @file microsec_time_clock.hpp

  This file contains a high resolution time clock implementation.

*/

#include <boost/cstdint.hpp>

#include <boost/shared_ptr.hpp>

#include <boost/detail/workaround.hpp>

#include <boost/date_time/compiler_config.hpp>

#include <boost/date_time/c_time.hpp>

#include <boost/date_time/time_clock.hpp>

#include <boost/date_time/filetime_functions.hpp>

#ifdef BOOST_DATE_TIME_HAS_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.

   */

  template<class time_type>

  class microsec_clock

  {

  private:

    //! Type for the function used to convert time_t to tm

    typedef std::tm* (*time_converter)(const std::time_t*, std::tm*);

  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 a local time object for the given zone, based on computer clock

    //JKG -- looks like we could rewrite this against universal_time

    template<class time_zone_type>

    static time_type local_time(shared_ptr<time_zone_type> tz_ptr)

    {

      typedef typename time_type::utc_time_type utc_time_type;

      typedef second_clock<utc_time_type> second_clock;

      // we'll need to know the utc_offset this machine has

      // in order to get a utc_time_type set to utc

      utc_time_type utc_time = second_clock::universal_time();

      time_duration_type utc_offset = second_clock::local_time() - utc_time;

      // use micro clock to get a local time with sub seconds

      // and adjust it to get a true utc time reading with sub seconds

      utc_time = microsec_clock<utc_time_type>::local_time() - utc_offset;

      return time_type(utc_time, tz_ptr);

    }

    //! Returns the local time based on computer clock settings

    static time_type local_time()

    {

      return create_time(&c_time::localtime);

    }

    //! Returns the UTC time based on computer settings

    static time_type universal_time()

    {

      return create_time(&c_time::gmtime);

    }

  private:

    static time_type create_time(time_converter converter)

    {

#ifdef BOOST_HAS_GETTIMEOFDAY

      timeval tv;

      gettimeofday(&tv, 0); //gettimeofday does not support TZ adjust on Linux.

      std::time_t t = tv.tv_sec;

      boost::uint32_t sub_sec = tv.tv_usec;

#elif defined(BOOST_HAS_FTIME)

      winapi::file_time ft;

      winapi::get_system_time_as_file_time(ft);

      uint64_t micros = winapi::file_time_to_microseconds(ft); // it will not wrap, since ft is the current time

                                                               // and cannot be before 1970-Jan-01

      std::time_t t = static_cast<time_t>(micros / 1000000UL); // seconds since epoch

      // microseconds -- static casts supress warnings

      boost::uint32_t sub_sec = static_cast<boost::uint32_t>(micros % 1000000UL);

#else

#error Internal Boost.DateTime error: BOOST_DATE_TIME_HAS_HIGH_PRECISION_CLOCK is defined, however neither gettimeofday nor FILETIME support is detected.

#endif

      std::tm curr;

      std::tm* curr_ptr = converter(&t, &curr);

      date_type d(curr_ptr->tm_year + 1900,

                  curr_ptr->tm_mon + 1,

                  curr_ptr->tm_mday);

      //The following line will adjust 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 = static_cast< int >(resolution_traits_type::res_adjust() / 1000000);

      time_duration_type td(curr_ptr->tm_hour,

                            curr_ptr->tm_min,

                            curr_ptr->tm_sec,

                            sub_sec * adjust);

      return time_type(d,td);

    }

  };

} } //namespace date_time

#endif //BOOST_DATE_TIME_HAS_HIGH_PRECISION_CLOCK

#endif