path: root/src/corelib/thread/qthread.h

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#ifndef QTHREAD_H
#define QTHREAD_H

#include <QtCore/qobject.h>

// The implementation of QThread::create uses various C++14/C++17 facilities;
// we must check for their presence. Specifically for glibcxx bundled in MinGW
// with win32 threads, we check the condition found in its <future> header
// since _GLIBCXX_HAS_GTHREADS might then not be defined.
// For std::async (used in all codepaths)
// there is no SG10 feature macro; just test for the header presence.
// For the C++17 codepath do some more throughout checks for std::invoke and
// C++14 lambdas availability.
#if QT_HAS_INCLUDE(<future>) \
    && (!defined(__GLIBCXX__) || (defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)))
#  define QTHREAD_HAS_CREATE
#  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;

#ifndef QT_NO_THREAD
class Q_CORE_EXPORT QThread : public QObject
{
    Q_OBJECT
public:
    static Qt::HANDLE currentThreadId() Q_DECL_NOTHROW Q_DECL_PURE_FUNCTION;
    static QThread *currentThread();
    static int idealThreadCount() Q_DECL_NOTHROW;
    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 QTHREAD_HAS_CREATE
#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
#endif

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)

    friend class QCoreApplication;
    friend class QThreadData;
};

#ifdef QTHREAD_HAS_CREATE
namespace QtPrivate {

class QThreadCreateThread : public QThread
{
public:
#if defined(QTHREAD_HAS_VARIADIC_CREATE)
    // C++17: std::thread's constructor complying call
    template <typename Function, typename... Args>
    explicit QThreadCreateThread(Function &&f, Args &&... args)
        : m_future(std::async(std::launch::deferred,
                   [f = static_cast<typename std::decay<Function>::type>(std::forward<Function>(f))](auto &&... largs) mutable -> void
                   {
                       (void)std::invoke(std::move(f), std::forward<decltype(largs)>(largs)...);
                   }, std::forward<Args>(args)...))
    {
    }
#elif defined(__cpp_init_captures) && __cpp_init_captures >= 201304
    // C++14: implementation for just one callable
    template <typename Function>
    explicit QThreadCreateThread(Function &&f)
        : m_future(std::async(std::launch::deferred,
                   [f = static_cast<typename std::decay<Function>::type>(std::forward<Function>(f))]() mutable -> void
                   {
                       (void)f();
                   }))
    {
    }
#else
private:
    // C++11: same as C++14, but with a workaround for not having generalized lambda captures
    template <typename Function>
    struct Callable
    {
        explicit Callable(Function &&f)
            : m_function(std::forward<Function>(f))
        {
        }

#if defined(Q_COMPILER_DEFAULT_MEMBERS) && defined(Q_COMPILER_DELETE_MEMBERS)
        // 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;
#endif

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

        typename std::decay<Function>::type m_function;
    };

public:
    template <typename Function>
    explicit QThreadCreateThread(Function &&f)
        : m_future(std::async(std::launch::deferred, Callable<Function>(std::forward<Function>(f))))
    {
    }
#endif // QTHREAD_HAS_VARIADIC_CREATE

private:
    void run() override
    {
        m_future.get();
    }

    std::future<void> m_future;
};

} // namespace QtPrivate

#ifdef QTHREAD_HAS_VARIADIC_CREATE
template <typename Function, typename... Args>
QThread *QThread::create(Function &&f, Args &&... args)
{
    return new QtPrivate::QThreadCreateThread(std::forward<Function>(f), std::forward<Args>(args)...);
}
#else
template <typename Function>
QThread *QThread::create(Function &&f)
{
    return new QtPrivate::QThreadCreateThread(std::forward<Function>(f));
}
#endif // QTHREAD_HAS_VARIADIC_CREATE

#endif // QTHREAD_HAS_CREATE

#else // QT_NO_THREAD

class Q_CORE_EXPORT QThread : public QObject
{
public:
    static Qt::HANDLE currentThreadId() { return Qt::HANDLE(currentThread()); }
    static QThread* currentThread();

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

private:
    explicit QThread(QObject *parent = nullptr);
    static QThread *instance;

    friend class QCoreApplication;
    friend class QThreadData;
    friend class QAdoptedThread;
    Q_DECLARE_PRIVATE(QThread)
};

#endif // QT_NO_THREAD

QT_END_NAMESPACE

#endif // QTHREAD_H