qt-everywhere-src-5.14.1/qtbase/src/corelib/thread/qthread.h

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** Copyright (C) 2016 The Qt Company Ltd.
** Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
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#ifndef QTHREAD_H
#define QTHREAD_H

#include <QtCore/qobject.h>

// For QThread::create. The configure-time test just checks for the availability
// of std::future and std::async; for the C++17 codepath we perform some extra
// checks here (for std::invoke and C++14 lambdas).
#if QT_CONFIG(cxx11_future)
#  include <future> // for std::async
#  include <functional> // for std::invoke; no guard needed as it's a C++98 header

#  if defined(__cpp_lib_invoke) && __cpp_lib_invoke >= 201411 \
      && defined(__cpp_init_captures) && __cpp_init_captures >= 201304 \
      && defined(__cpp_generic_lambdas) &&  __cpp_generic_lambdas >= 201304
#    define QTHREAD_HAS_VARIADIC_CREATE
#  endif
#endif

#include <limits.h>

QT_BEGIN_NAMESPACE


class QThreadData;
class QThreadPrivate;
class QAbstractEventDispatcher;

class Q_CORE_EXPORT QThread : public QObject
{
    Q_OBJECT
public:
    static Qt::HANDLE currentThreadId() noexcept Q_DECL_PURE_FUNCTION;
    static QThread *currentThread();
    static int idealThreadCount() noexcept;
    static void yieldCurrentThread();

    explicit QThread(QObject *parent = nullptr);
    ~QThread();

    enum Priority {
        IdlePriority,

        LowestPriority,
        LowPriority,
        NormalPriority,
        HighPriority,
        HighestPriority,

        TimeCriticalPriority,

        InheritPriority
    };

    void setPriority(Priority priority);
    Priority priority() const;

    bool isFinished() const;
    bool isRunning() const;

    void requestInterruption();
    bool isInterruptionRequested() const;

    void setStackSize(uint stackSize);
    uint stackSize() const;

    void exit(int retcode = 0);

    QAbstractEventDispatcher *eventDispatcher() const;
    void setEventDispatcher(QAbstractEventDispatcher *eventDispatcher);

    bool event(QEvent *event) override;
    int loopLevel() const;

#ifdef Q_CLANG_QDOC
    template <typename Function, typename... Args>
    static QThread *create(Function &&f, Args &&... args);
    template <typename Function>
    static QThread *create(Function &&f);
#else
#  if QT_CONFIG(cxx11_future)
#    ifdef QTHREAD_HAS_VARIADIC_CREATE
    template <typename Function, typename... Args>
    static QThread *create(Function &&f, Args &&... args);
#    else
    template <typename Function>
    static QThread *create(Function &&f);
#    endif // QTHREAD_HAS_VARIADIC_CREATE
#  endif // QT_CONFIG(cxx11_future)
#endif // Q_CLANG_QDOC

public Q_SLOTS:
    void start(Priority = InheritPriority);
    void terminate();
    void quit();

public:
    // default argument causes thread to block indefinetely
    bool wait(unsigned long time = ULONG_MAX);

    static void sleep(unsigned long);
    static void msleep(unsigned long);
    static void usleep(unsigned long);

Q_SIGNALS:
    void started(QPrivateSignal);
    void finished(QPrivateSignal);

protected:
    virtual void run();
    int exec();

    static void setTerminationEnabled(bool enabled = true);

protected:
    QThread(QThreadPrivate &dd, QObject *parent = nullptr);

private:
    Q_DECLARE_PRIVATE(QThread)

#if QT_CONFIG(cxx11_future)
    static QThread *createThreadImpl(std::future<void> &&future);
#endif

    friend class QCoreApplication;
    friend class QThreadData;
};

#if QT_CONFIG(cxx11_future)

#if defined(QTHREAD_HAS_VARIADIC_CREATE) || defined(Q_CLANG_QDOC)
// C++17: std::thread's constructor complying call
template <typename Function, typename... Args>
QThread *QThread::create(Function &&f, Args &&... args)
{
    using DecayedFunction = typename std::decay<Function>::type;
    auto threadFunction =
        [f = static_cast<DecayedFunction>(std::forward<Function>(f))](auto &&... largs) mutable -> void
        {
            (void)std::invoke(std::move(f), std::forward<decltype(largs)>(largs)...);
        };

    return createThreadImpl(std::async(std::launch::deferred,
                                       std::move(threadFunction),
                                       std::forward<Args>(args)...));
}
#elif defined(__cpp_init_captures) && __cpp_init_captures >= 201304
// C++14: implementation for just one callable
template <typename Function>
QThread *QThread::create(Function &&f)
{
    using DecayedFunction = typename std::decay<Function>::type;
    auto threadFunction =
        [f = static_cast<DecayedFunction>(std::forward<Function>(f))]() mutable -> void
        {
            (void)f();
        };

    return createThreadImpl(std::async(std::launch::deferred, std::move(threadFunction)));
}
#else
// C++11: same as C++14, but with a workaround for not having generalized lambda captures
namespace QtPrivate {
template <typename Function>
struct Callable
{
    explicit Callable(Function &&f)
        : m_function(std::forward<Function>(f))
    {
    }

    // Apply the same semantics of a lambda closure type w.r.t. the special
    // member functions, if possible: delete the copy assignment operator,
    // bring back all the others as per the RO5 (cf. §8.1.5.1/11 [expr.prim.lambda.closure])
    ~Callable() = default;
    Callable(const Callable &) = default;
    Callable(Callable &&) = default;
    Callable &operator=(const Callable &) = delete;
    Callable &operator=(Callable &&) = default;

    void operator()()
    {
        (void)m_function();
    }

    typename std::decay<Function>::type m_function;
};
} // namespace QtPrivate

template <typename Function>
QThread *QThread::create(Function &&f)
{
    return createThreadImpl(std::async(std::launch::deferred, QtPrivate::Callable<Function>(std::forward<Function>(f))));
}
#endif // QTHREAD_HAS_VARIADIC_CREATE

#endif // QT_CONFIG(cxx11_future)

QT_END_NAMESPACE

#endif // QTHREAD_H