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#include "qperformancetimer_p.h"

#if defined(Q_OS_MAC)
#include <sys/time.h>
#include <unistd.h>
#include <mach/mach_time.h>
#elif defined(Q_OS_UNIX)
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
#elif defined(Q_OS_WIN)
#include <windows.h>
#endif

// mac/unix code heavily copied from QElapsedTimer

QT_BEGIN_NAMESPACE

////////////////////////////// Mac //////////////////////////////
#if defined(Q_OS_MAC)

static mach_timebase_info_data_t info = {0,0};
static qint64 absoluteToNSecs(qint64 cpuTime)
{
    if (info.denom == 0)
        mach_timebase_info(&info);
    qint64 nsecs = cpuTime * info.numer / info.denom;
    return nsecs;
}

void QPerformanceTimer::start()
{
    t1 = mach_absolute_time();
}

qint64 QPerformanceTimer::elapsed() const
{
    qint64 cpu_time = mach_absolute_time();
    return absoluteToNSecs(cpu_time - t1);
}

// return number of nsecs elapsed from timer start time till absoluteMonotonicTimeNs
// elapsedToAbsoluteTime(0) returns negative value of absolute time (ns) when the timer was started
qint64 QPerformanceTimer::elapsedToAbsoluteTime(qint64 absoluteMonotonicTimeNs) const
{
    qint64 absolute_t1_ns = absoluteToNSecs(t1);
    return absoluteMonotonicTimeNs - absolute_t1_ns;
}

////////////////////////////// Unix //////////////////////////////
#elif defined(Q_OS_UNIX)

#if defined(QT_NO_CLOCK_MONOTONIC) || defined(QT_BOOTSTRAPPED)
// turn off the monotonic clock
# ifdef _POSIX_MONOTONIC_CLOCK
#  undef _POSIX_MONOTONIC_CLOCK
# endif
# define _POSIX_MONOTONIC_CLOCK -1
#endif

#if (_POSIX_MONOTONIC_CLOCK-0 != 0)
static const bool monotonicClockChecked = true;
static const bool monotonicClockAvailable = _POSIX_MONOTONIC_CLOCK > 0;
#else
static int monotonicClockChecked = false;
static int monotonicClockAvailable = false;
#endif

#ifdef Q_CC_GNU
# define is_likely(x) __builtin_expect((x), 1)
#else
# define is_likely(x) (x)
#endif
#define load_acquire(x) ((volatile const int&)(x))
#define store_release(x,v) ((volatile int&)(x) = (v))

static void unixCheckClockType()
{
#if (_POSIX_MONOTONIC_CLOCK-0 == 0)
    if (is_likely(load_acquire(monotonicClockChecked)))
        return;

# if defined(_SC_MONOTONIC_CLOCK)
    // detect if the system support monotonic timers
    long x = sysconf(_SC_MONOTONIC_CLOCK);
    store_release(monotonicClockAvailable, x >= 200112L);
# endif

    store_release(monotonicClockChecked, true);
#endif
}

static inline void do_gettime(qint64 *sec, qint64 *frac)
{
#if (_POSIX_MONOTONIC_CLOCK-0 >= 0)
    unixCheckClockType();
    if (is_likely(monotonicClockAvailable)) {
        timespec ts;
        clock_gettime(CLOCK_MONOTONIC, &ts);
        *sec = ts.tv_sec;
        *frac = ts.tv_nsec;
        return;
    }
#endif
    *sec = 0;
    *frac = 0;
}

void QPerformanceTimer::start()
{
    do_gettime(&t1, &t2);
}

qint64 QPerformanceTimer::elapsed() const
{
    qint64 sec, frac;
    do_gettime(&sec, &frac);
    sec = sec - t1;
    frac = frac - t2;

    return sec * Q_INT64_C(1000000000) + frac;
}

qint64 QPerformanceTimer::elapsedToAbsoluteTime(qint64 absoluteMonotonicTimeNs) const
{
    qint64 sec = absoluteMonotonicTimeNs / Q_INT64_C(1000000000);
    qint64 frac = absoluteMonotonicTimeNs % Q_INT64_C(1000000000);
    sec = sec - t1;
    frac = frac - t2;

    return sec * Q_INT64_C(1000000000) + frac;
}

////////////////////////////// Windows //////////////////////////////
#elif defined(Q_OS_WIN)

static qint64 getTimeFromTick(quint64 elapsed)
{
    static LARGE_INTEGER freq;
    if (!freq.QuadPart)
        QueryPerformanceFrequency(&freq);
    return 1000000000 * elapsed / freq.QuadPart;
}

void QPerformanceTimer::start()
{
    LARGE_INTEGER li;
    QueryPerformanceCounter(&li);
    t1 = li.QuadPart;
}

qint64 QPerformanceTimer::elapsed() const
{
    LARGE_INTEGER li;
    QueryPerformanceCounter(&li);
    return getTimeFromTick(li.QuadPart - t1);
}

qint64 QPerformanceTimer::elapsedToAbsoluteTime(qint64 absoluteMonotonicTimeNs) const
{
    qint64 absolute_t1_ns = getTimeFromTick(t1);
    return absoluteMonotonicTimeNs - absolute_t1_ns;
}

////////////////////////////// Default //////////////////////////////
#else

// default implementation (no hi-perf timer) does nothing
void QPerformanceTimer::start()
{
}

qint64 QPerformanceTimer::elapsed() const
{
    return 0;
}

qint64 QPerformanceTimer::elapsedToAbsoluteTime(qint64 absoluteMonotonicTimeNs) const
{
    Q_UNUSED(absoluteMonotonicTimeNs);
    return 0;
}

#endif

QT_END_NAMESPACE


