#include <ctime>
clock_t clock();

 // это инициализация
  #ifndef __linux__
       ::QueryPerformanceFrequency(&frequency);
       simplistic_synchronize(ref_point);
  #endif

 // это использование
        #ifdef __linux__
        // pt - типа boost::posix_time::ptime
        pt = microsec_clock::universal_time();  // это из boost - там под линём всё OK с таймерами
        #else
        pt = get_total_microseconds(); // под вендой начинаем извращаться через QueryPerformanceCounter
        #endif

typedef ptime time_type; // это boost::posix_time::ptime
struct reference_point
{
  FILETIME file_time;
  LARGE_INTEGER counter;
};

reference_point ref_point;
LARGE_INTEGER   frequency;
mutex           mtx;

void simplistic_synchronize(reference_point& ref_point)
{
  FILETIME      ft0 = { 0, 0 },
                ft1 = { 0, 0 };
  LARGE_INTEGER li;

  //
  // Spin waiting for a change in system time. Get the matching
  // performance counter value for that time.
  //
  ::GetSystemTimeAsFileTime(&ft0);
  do
  {
    ::GetSystemTimeAsFileTime(&ft1);
    ::QueryPerformanceCounter(&li);
  }
  while ((ft0.dwHighDateTime == ft1.dwHighDateTime) &&
         (ft0.dwLowDateTime == ft1.dwLowDateTime));

  ref_point.file_time = ft1;
  ref_point.counter = li;
}

void get_time(LARGE_INTEGER frequency, const reference_point&
    reference, FILETIME& current_time)
{
  LARGE_INTEGER li;

  ::QueryPerformanceCounter(&li);

  //
  // Calculate performance counter ticks elapsed
  //
  LARGE_INTEGER ticks_elapsed;

  ticks_elapsed.QuadPart = li.QuadPart -
      reference.counter.QuadPart;

  //
  // Translate to 100-nanoseconds intervals (FILETIME
  // resolution) and add to
  // reference FILETIME to get current FILETIME.
  //
  ULARGE_INTEGER filetime_ticks,
                 filetime_ref_as_ul;

  filetime_ticks.QuadPart =
      (ULONGLONG)((((double)ticks_elapsed.QuadPart/(double)
      frequency.QuadPart)*10000000.0)+0.5);
  filetime_ref_as_ul.HighPart = reference.file_time.dwHighDateTime;
  filetime_ref_as_ul.LowPart = reference.file_time.dwLowDateTime;
  filetime_ref_as_ul.QuadPart += filetime_ticks.QuadPart;

  //
  // Copy to result
  //
  current_time.dwHighDateTime = filetime_ref_as_ul.HighPart;
  current_time.dwLowDateTime = filetime_ref_as_ul.LowPart;
}

time_type create_time(FILETIME& ft) {
      // offset is difference (in 100-nanoseconds) from
      // 1970-Jan-01 to 1601-Jan-01
      boost::uint64_t c1 = 27111902;
      boost::uint64_t c2 = 3577643008UL; // 'UL' removes compiler warnings
      const boost::uint64_t OFFSET = (c1 << 32) + c2;

      boost::uint64_t filetime = ft.dwHighDateTime;
      filetime = filetime << 32;
      filetime += ft.dwLowDateTime;
      filetime -= OFFSET;
      // filetime now holds 100-nanoseconds since 1970-Jan-01

      // microseconds -- static casts supress warnings
      boost::uint32_t sub_sec = static_cast<boost::uint32_t>((filetime % 10000000) / 10);

      std::time_t t = static_cast<time_t>(filetime / 10000000); // seconds since epoch

      std::tm *curr_ptr = 0;
      curr_ptr = std::gmtime(&t);//, &curr);

      ptime::date_type d(curr_ptr->tm_year + 1900,
                  curr_ptr->tm_mon + 1,
                  curr_ptr->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 = static_cast<int>(ptime::time_duration_type::rep_type::res_adjust()/1000000);

      ptime::time_duration_type td(curr_ptr->tm_hour,
                            curr_ptr->tm_min,
                            curr_ptr->tm_sec,
                            sub_sec * adjust);
      return time_type(d,td);

    }


time_type get_total_microseconds(void)
{
     FILETIME  ft;
     {
        mutex::scoped_lock l(mtx);
        get_time(frequency, ref_point, ft);
     }
     return create_time(ft);
}

Цитата(Litkevich Yuriy @ 20.12.2009, 23:50)

Цитата(ViGOur @ 21.12.2009, 2:03)

потому тики будут точными на каждые 100 мс

для системного (низкоуровнего) счётчика, тики будут соответствовать точности кварцевого резонатора (с соответствующим коэфф. деления).

Меня не интересует ширпотребный таймер/часы. именно счётчик тиков

#include <sys/time.h>
unsigned long GetTickCount()
{
    struct timeval tv;
    gettimeofday(&tv,NULL);
    return (tv.tv_sec*1000+tv.tv_usec/1000);
}