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** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
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// ask for the latest POSIX, just in case
#define _POSIX_C_SOURCE 200809L

#include "qelapsedtimer.h"
#include <sys/time.h>
#include <time.h>
#include <unistd.h>

#include "private/qcore_unix_p.h"

#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

QT_BEGIN_NAMESPACE

#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

#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 (Q_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 qint64 fractionAdjustment()
{
    return 1000*1000ull;
}

bool QElapsedTimer::isMonotonic() Q_DECL_NOTHROW
{
    unixCheckClockType();
    return monotonicClockAvailable;
}

QElapsedTimer::ClockType QElapsedTimer::clockType() Q_DECL_NOTHROW
{
    unixCheckClockType();
    return monotonicClockAvailable ? MonotonicClock : SystemTime;
}

static inline void do_gettime(qint64 *sec, qint64 *frac)
{
#if (_POSIX_MONOTONIC_CLOCK-0 >= 0)
    unixCheckClockType();
    if (Q_LIKELY(monotonicClockAvailable)) {
        timespec ts;
        clock_gettime(CLOCK_MONOTONIC, &ts);
        *sec = ts.tv_sec;
        *frac = ts.tv_nsec;
        return;
    }
#endif
#ifdef CLOCK_REALTIME
    // even if we don't have a monotonic clock,
    // we can use clock_gettime -> nanosecond resolution
    timespec ts;
    clock_gettime(CLOCK_REALTIME, &ts);
    *sec = ts.tv_sec;
    *frac = ts.tv_nsec;
#else
    // use gettimeofday
    timeval tv;
    ::gettimeofday(&tv, 0);
    *sec = tv.tv_sec;
    *frac = tv.tv_usec * 1000;
#endif
}

// used in qcore_unix.cpp and qeventdispatcher_unix.cpp
timeval qt_gettime() Q_DECL_NOTHROW
{
    qint64 sec, frac;
    do_gettime(&sec, &frac);

    timeval tv;
    tv.tv_sec = sec;
    tv.tv_usec = frac / 1000;

    return tv;
}

void qt_nanosleep(timespec amount)
{
    // We'd like to use clock_nanosleep.
    //
    // But clock_nanosleep is from POSIX.1-2001 and both are *not*
    // affected by clock changes when using relative sleeps, even for
    // CLOCK_REALTIME.
    //
    // nanosleep is POSIX.1-1993

    int r;
    EINTR_LOOP(r, nanosleep(&amount, &amount));
}

static qint64 elapsedAndRestart(qint64 sec, qint64 frac,
                                qint64 *nowsec, qint64 *nowfrac)
{
    do_gettime(nowsec, nowfrac);
    sec = *nowsec - sec;
    frac = *nowfrac - frac;
    return sec * Q_INT64_C(1000) + frac / fractionAdjustment();
}

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

qint64 QElapsedTimer::restart() Q_DECL_NOTHROW
{
    return elapsedAndRestart(t1, t2, &t1, &t2);
}

qint64 QElapsedTimer::nsecsElapsed() const Q_DECL_NOTHROW
{
    qint64 sec, frac;
    do_gettime(&sec, &frac);
    sec = sec - t1;
    frac = frac - t2;
    return sec * Q_INT64_C(1000000000) + frac;
}

qint64 QElapsedTimer::elapsed() const Q_DECL_NOTHROW
{
    qint64 sec, frac;
    return elapsedAndRestart(t1, t2, &sec, &frac);
}

qint64 QElapsedTimer::msecsSinceReference() const Q_DECL_NOTHROW
{
    return t1 * Q_INT64_C(1000) + t2 / fractionAdjustment();
}

qint64 QElapsedTimer::msecsTo(const QElapsedTimer &other) const Q_DECL_NOTHROW
{
    qint64 secs = other.t1 - t1;
    qint64 fraction = other.t2 - t2;
    return secs * Q_INT64_C(1000) + fraction / fractionAdjustment();
}

qint64 QElapsedTimer::secsTo(const QElapsedTimer &other) const Q_DECL_NOTHROW
{
    return other.t1 - t1;
}

bool operator<(const QElapsedTimer &v1, const QElapsedTimer &v2) Q_DECL_NOTHROW
{
    return v1.t1 < v2.t1 || (v1.t1 == v2.t1 && v1.t2 < v2.t2);
}

QT_END_NAMESPACE