#ifndef CALL_ONCE_H
#define CALL_ONCE_H

#include <QtCore/QtGlobal>
#include <QtCore/QAtomicInt>
#include <QtCore/QMutex>
#include <QtCore/QWaitCondition>
#include <QtCore/QThreadStorage>
#include <QtCore/QThread>

namespace CallOnce {
    enum ECallOnce {
        CO_Request,
        CO_InProgress,
        CO_Finished
    };

    Q_GLOBAL_STATIC(QThreadStorage<QAtomicInt*>, once_flag)
}

template <class Function>
        inline static void qCallOnce(Function func, QBasicAtomicInt& flag)
{
    using namespace CallOnce;
    int protectFlag = flag.fetchAndStoreAcquire((int)flag);
    if (protectFlag == CO_Finished)
        return;
    if (protectFlag == CO_Request && flag.testAndSetRelaxed(protectFlag,
                                                            CO_InProgress)) {
        func();
        flag.fetchAndStoreRelease(CO_Finished);
    }
    else {
        do {
            QThread::yieldCurrentThread();
        }
        while (!flag.testAndSetAcquire(CO_Finished, CO_Finished));
    }
}

template <class Function>
        inline static void qCallOncePerThread(Function func)
{
    using namespace CallOnce;
    if (!once_flag()->hasLocalData()) {
        once_flag()->setLocalData(new QAtomicInt(CallOnce::CO_Request));
        qCallOnce(func, *once_flag()->localData());
    }
}

#endif // CALL_ONCE_H

#include <QtCore/QtGlobal>
#include <QtCore/QtDebug>

#include <QtCore/QTimer>

#include <QtCore/QTime>

#include <QtCore/QVector>
#include <QtCore/QThread>
#include <QtCore/QtConcurrentMap>
#include <QtCore/QtConcurrentFilter>
#include <QtCore/QCoreApplication>

#include <algorithm>

#include "call_once.h"

enum {Max = 100};

struct run_once
{
    void operator()()
    {
        qDebug() << "Functor: This only once...";
    }
};

void func_run_once()
{
    qDebug() << "Function: This only once...";
}

struct inc_functor
{
    inc_functor() : counter(0) {}
    inline int operator()() {return counter++;}
    int counter;
};

struct setPriorityFunctor
{
    setPriorityFunctor(QThread::Priority priority = QThread::NormalPriority)
        : m_priority(priority) {}
    inline void operator()()
    {
        QThread* thread = QThread::currentThread();
        thread->setPriority(m_priority);
    }
    QThread::Priority m_priority;
};

void setLowestPriorityFunction()
{
    QThread* thread = QThread::currentThread();
    thread->setPriority(QThread::LowestPriority);

    qDebug("Current thread %x. Thread set to Lowest priority",
           (quintptr)thread);
}

void setHighestPriorityFunction()
{
    QThread* thread = QThread::currentThread();
    thread->setPriority(QThread::HighestPriority);

    qDebug("Current thread %x. Thread set to Highest priority",
           (quintptr)thread);
}

int calculate(const int& num)
{
#if 0 // Test once call per thread with function
    #if 0 // Set lowest thread priority
        qCallOncePerThread(setLowestPriorityFunction);
    #else // Set highest thread priority
        qCallOncePerThread(setHighestPriorityFunction);
    #endif
#else // Test once call per thread with functor
    #if 0
        qCallOncePerThread(setPriorityFunctor(QThread::HighestPriority));
    #else
        qCallOncePerThread(setPriorityFunctor(QThread::LowestPriority));
    #endif
#endif

    return ~num;
}

static QBasicAtomicInt flag = Q_BASIC_ATOMIC_INITIALIZER(CallOnce::CO_Request);

int parityFilter(const int& num)
{
    qCallOnce(run_once(), flag);

    return num % 2 ? false : true;
}

static QBasicAtomicInt testflag = Q_BASIC_ATOMIC_INITIALIZER(CallOnce::CO_Request);

int main(int argc, char* argv[])
{
    QCoreApplication a(argc, argv);

    QTime t; t.start();
    for (int i = 0; i < 1000 * 1000 * 100; ++i)
        qCallOnce(run_once(), testflag);
    qDebug("%d ms", t.elapsed());

    QVector<int> ints;

    std::generate_n(std::back_insert_iterator<QVector<int> >(ints),
                                                (int)Max, inc_functor());

// Test qCallOnce
    {
        QVector<int> results = QtConcurrent::blockingMapped(ints, calculate);
        qDebug() << results;
    }

// Test qCallOncePerThread
    {
        QtConcurrent::blockingFilter(ints, parityFilter);
        qDebug() << ints;
    }

    return 0;
}

QPushButton {
/*top right bottom left (clockwise)*/
background-color: #d6d3ce;
border-width: 2px 3px 3px 2px;
border-style: solid;
border-color:
qlineargradient(spread:pad, x1:1, y1:1, x2:1, y2:0, stop:0 white, stop:0.5 white, stop:0.51 #848284, stop:1 #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:0, y2:1, stop:0 white, stop:0.33 white, stop:0.34 black, stop:0.67 black, stop:0.68 #848284, stop:1.0  #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:1, y2:0, stop:0 white, stop:0.33 white, stop:0.34 black, stop:0.67 black, stop:0.68 #848284, stop:1.0 #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:0, y2:1, stop:0 white, stop:0.5 white, stop:0.51 #848284, stop:1 #848284);
}

QPushButton:default{
border-width: 3px 4px 4px 3px;
border-color: 
qlineargradient(spread:pad, x1:1, y1:1, x2:1, y2:0, stop:0 white, stop:0.33 white, stop:0.34 black, stop:0.67 black, stop:0.68 #848284, stop:1.0 #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:0, y2:1, stop:0 white, stop:0.25 white, stop:0.26 black, stop:0.50 black, stop:0.51 black, stop:0.75 black, stop:0.76 #848284, stop:1 #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:1, y2:0, stop:0 white, stop:0.25 white, stop:0.26 black, stop:0.50 black, stop:0.51 black, stop:0.75 black, stop:0.76 #848284, stop:1 #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:0, y2:1, stop:0 white, stop:0.33 white, stop:0.34 black, stop:0.67 black, stop:0.68 #848284, stop:1.0  #848284);
}

QPushButton:pressed{
border-width: 3px;
border-color:
qlineargradient(spread:pad, x1:1, y1:1, x2:1, y2:0, stop:0 #848284, stop:0.33 #848284, stop:0.34 black, stop:0.67 black, stop:0.68 #848284, stop:1.0 #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:0, y2:1, stop:0 white, stop:0.33 white, stop:0.34 black, stop:0.67 black, stop:0.68 #848284, stop:1.0  #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:1, y2:0, stop:0 white, stop:0.33 white, stop:0.34 black, stop:0.67 black, stop:0.68 #848284, stop:1.0 #848284)
qlineargradient(spread:pad, x1:1, y1:1, x2:0, y2:1, stop:0 #848284, stop:0.33 #848284, stop:0.34 black, stop:0.67 black, stop:0.68 #848284, stop:1.0  #848284);
}

QPushButton {
font-weight: bold;
border: 1px solid black;
border-radius: 7px;
color: white;
background-color: 
qradialgradient(spread:pad, cx:0.51, cy:-1.0, radius:2, fx:0.50, fy:0.0, stop:0.53 #81beff, stop:0.54 #268fff, stop:1 #268fff);
}

QPushButton:hover {
color: qlineargradient(spread:pad, x1:1, y1:1, x2:1, y2:0, stop:0 black, stop:0.5 white);
}

QPushButton:pressed {
padding: 3px 0px 0px 3px;
background-color:
qradialgradient(spread:pad, cx:0.51, cy:-1.0, radius:2, fx:0.50, fy:0.0, stop:0.51 #0061ff, stop:0.52 #268fff, stop:1 #268fff);
}

QPushButton:default {
border-width: 2px;
}

QPushButton:focus {
border: 4px double black;
}