Listing 10 Extract from winstl_performance_counter.h

/* /////////////////////////////////////////////////////////////
 * ...
 *
 * Extract from winstl_performance_counter.h
 *
 * Copyright (C) 2002, Synesis Software Pty Ltd.
 * (Licensed under the Synesis Software Standard Source License:
 *  http://www.synesis.com.au/licenses/ssssl.html)
 *
 * ...
 * ////////////////////////////////////////////////////////// */

inline /* static */ performance_counter::interval_type performance_counter::_query_frequency()
{
    interval_type   frequency;

    // If no high-performance counter is available ...
    if( !::QueryPerformanceFrequency(reinterpret_cast<LARGE_INTEGER*>
        (&frequency)) ||
        frequency == 0)
    {
        // ... then set the divisor to be the frequency for GetTickCount(), 
        // which is 1000 since it returns intervals in milliseconds.
        frequency = 1000;
    }

    return frequency;
}

inline /* static */ performance_counter::interval_type performance_counter::_frequency()
{
    static interval_type    s_frequency = _query_frequency();

    return s_frequency;
}

inline /* static */ void performance_counter::_qpc(epoch_type &epoch)
{
    ::QueryPerformanceCounter(reinterpret_cast<LARGE_INTEGER*>(&epoch));
}

inline /* static */ void performance_counter::_gtc(epoch_type &epoch)
{
    epoch = ::GetTickCount();
}

inline /* static */ performance_counter::measure_fn_type 
  performance_counter::_get_measure_fn()
{
    measure_fn_type fn;
    epoch_type      frequency;

    if(QueryPerformanceFrequency(reinterpret_cast<LARGE_INTEGER*>(&frequency)))
    {
        fn = _qpc;
    }
    else
    {
        fn = _gtc;
    }

    return fn;
}

inline /* static */ void performance_counter::_measure(epoch_type &epoch)
{
    static measure_fn_type  fn  =   _get_measure_fn();

    fn(epoch);
}

// Operations
inline void performance_counter::start()
{
    _measure(m_start);
}

inline void performance_counter::stop()
{
    _measure(m_end);
}

// Attributes
inline performance_counter::interval_type performance_counter::get_period_count()
   const
{
    return static_cast<interval_type>(m_end - m_start);
}

inline performance_counter::interval_type performance_counter::get_seconds() 
   const
{
    return get_period_count() / _frequency();
}

inline performance_counter::interval_type performance_counter::get_milliseconds() 
   const
{
    interval_type   result;
    interval_type   count   =   get_period_count();

    if(count < __STLSOFT_GEN_SINT64_SUFFIX(0x20C49BA5E353F7))
    {
        result = (count * interval_type(1000)) / _frequency();
    }
    else
    {
        result = (count / _frequency()) * interval_type(1000);
    }

    return result;
}

inline performance_counter::interval_type performance_counter::get_microseconds() 
   const
{
    interval_type   result;
    interval_type   count   =   get_period_count();

    if(count < __STLSOFT_GEN_SINT64_SUFFIX(0x8637BD05AF6))
    {
        result = (count * interval_type(1000000)) / _frequency();
    }
    else
    {
        result = (count / _frequency()) * interval_type(1000000);
    }

    return result;
}