Win32 Performance Measurement Options

Listing 4 Extract from winstl_highperformance_counter.h

/* /////////////////////////////////////////////////////////////
 * ...
 *
 * Extract from winstl_highperformance_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 */ highperformance_counter::interval_type highperformance_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 maximum value, guaranteeing that 
        // the timed periods will always evaluate to 0.
        frequency = stlsoft_ns_qual(limit_traits)<interval_type>::maximum();
    }

    return frequency;
}

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

    return s_frequency;
}

// Operations
inline void highperformance_counter::start()
{
    ::QueryPerformanceCounter(reinterpret_cast<LARGE_INTEGER*>(&m_start));
}

inline void highperformance_counter::stop()
{
    ::QueryPerformanceCounter(reinterpret_cast<LARGE_INTEGER*>(&m_end));
}

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

inline highperformance_counter::interval_type highperformance_counter::get_milliseconds() const
{
    highperformance_counter::interval_type  result;
    highperformance_counter::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 highperformance_counter::interval_type highperformance_counter::get_microseconds() const
{
    highperformance_counter::interval_type  result;
    highperformance_counter::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;
}