qt-everywhere-src-5.14.1/qtbase/src/corelib/kernel/qelapsedtimer_win.cpp

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#include "qelapsedtimer.h"
#include "qdeadlinetimer.h"
#include "qdeadlinetimer_p.h"
#include <qt_windows.h>

QT_BEGIN_NAMESPACE

// Result of QueryPerformanceFrequency, 0 indicates that the high resolution timer is unavailable
static quint64 counterFrequency = 0;

static void resolveCounterFrequency()
{
    static bool done = false;
    if (done)
        return;

    // Retrieve the number of high-resolution performance counter ticks per second
    LARGE_INTEGER frequency;
    if (!QueryPerformanceFrequency(&frequency)) {
        qFatal("QueryPerformanceFrequency failed, even though Microsoft documentation promises it wouldn't.");
        counterFrequency = 0;
    } else {
        counterFrequency = frequency.QuadPart;
    }

    done = true;
}

static inline qint64 ticksToNanoseconds(qint64 ticks)
{
    if (counterFrequency > 0) {
        // QueryPerformanceCounter uses an arbitrary frequency
        qint64 seconds = ticks / counterFrequency;
        qint64 nanoSeconds = (ticks - seconds * counterFrequency) * 1000000000 / counterFrequency;
        return seconds * 1000000000 + nanoSeconds;
    }
    // GetTickCount(64) returns milliseconds
    return ticks * 1000000;
}


static quint64 getTickCount()
{
    resolveCounterFrequency();

    // This avoids a division by zero and disables the high performance counter if it's not available
    if (counterFrequency > 0) {
        LARGE_INTEGER counter;

        bool ok = QueryPerformanceCounter(&counter);
        Q_ASSERT_X(ok, "QElapsedTimer::start()",
                   "QueryPerformanceCounter failed, although QueryPerformanceFrequency succeeded.");
        Q_UNUSED(ok);
        return counter.QuadPart;
    }

    return GetTickCount64();
}

quint64 qt_msectime()
{
    return ticksToNanoseconds(getTickCount()) / 1000000;
}

QElapsedTimer::ClockType QElapsedTimer::clockType() noexcept
{
    resolveCounterFrequency();

    return counterFrequency > 0 ? PerformanceCounter : TickCounter;
}

bool QElapsedTimer::isMonotonic() noexcept
{
    return true;
}

void QElapsedTimer::start() noexcept
{
    t1 = getTickCount();
    t2 = 0;
}

qint64 QElapsedTimer::restart() noexcept
{
    qint64 oldt1 = t1;
    t1 = getTickCount();
    t2 = 0;
    return ticksToNanoseconds(t1 - oldt1) / 1000000;
}

qint64 QElapsedTimer::nsecsElapsed() const noexcept
{
    qint64 elapsed = getTickCount() - t1;
    return ticksToNanoseconds(elapsed);
}

qint64 QElapsedTimer::elapsed() const noexcept
{
    qint64 elapsed = getTickCount() - t1;
    return ticksToNanoseconds(elapsed) / 1000000;
}

qint64 QElapsedTimer::msecsSinceReference() const noexcept
{
    return ticksToNanoseconds(t1) / 1000000;
}

qint64 QElapsedTimer::msecsTo(const QElapsedTimer &other) const noexcept
{
    qint64 difference = other.t1 - t1;
    return ticksToNanoseconds(difference) / 1000000;
}

qint64 QElapsedTimer::secsTo(const QElapsedTimer &other) const noexcept
{
    return msecsTo(other) / 1000;
}

bool operator<(const QElapsedTimer &v1, const QElapsedTimer &v2) noexcept
{
    return (v1.t1 - v2.t1) < 0;
}

QDeadlineTimer QDeadlineTimer::current(Qt::TimerType timerType) noexcept
{
    Q_STATIC_ASSERT(!QDeadlineTimerNanosecondsInT2);
    QDeadlineTimer result;
    result.t1 = ticksToNanoseconds(getTickCount());
    result.type = timerType;
    return result;
}

QT_END_NAMESPACE