thread.h

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    bool IsOk() const;

    // wait indefinitely, until the semaphore count goes beyond 0
    // and then decrement it and return (this method might have been called
    // Acquire())
    wxSemaError Wait();

    // same as Wait(), but does not block, returns wxSEMA_NO_ERROR if
    // successful and wxSEMA_BUSY if the count is currently zero
    wxSemaError TryWait();

    // same as Wait(), but as a timeout limit, returns wxSEMA_NO_ERROR if the
    // semaphore was acquired and wxSEMA_TIMEOUT if the timeout has ellapsed
    wxSemaError WaitTimeout(unsigned long milliseconds);

    // increments the semaphore count and signals one of the waiting threads
    wxSemaError Post();

private:
    wxSemaphoreInternal *m_internal;

    DECLARE_NO_COPY_CLASS(wxSemaphore)
};

// ----------------------------------------------------------------------------
// wxThread: class encapsulating a thread of execution
// ----------------------------------------------------------------------------

// there are two different kinds of threads: joinable and detached (default)
// ones. Only joinable threads can return a return code and only detached
// threads auto-delete themselves - the user should delete the joinable
// threads manually.

// NB: in the function descriptions the words "this thread" mean the thread
//     created by the wxThread object while "main thread" is the thread created
//     during the process initialization (a.k.a. the GUI thread)

// On VMS thread pointers are 64 bits (also needed for other systems???
#ifdef __VMS
   typedef unsigned long long wxThreadIdType;
#else
   typedef unsigned long wxThreadIdType;
#endif

class WXDLLIMPEXP_BASE wxThread
{
public:
    // the return type for the thread function
    typedef void *ExitCode;

    // static functions
        // Returns the wxThread object for the calling thread. NULL is returned
        // if the caller is the main thread (but it's recommended to use
        // IsMain() and only call This() for threads other than the main one
        // because NULL is also returned on error). If the thread wasn't
        // created with wxThread class, the returned value is undefined.
    static wxThread *This();

        // Returns true if current thread is the main thread.
    static bool IsMain();

        // Release the rest of our time slice leting the other threads run
    static void Yield();

        // Sleep during the specified period of time in milliseconds
        //
        // NB: at least under MSW worker threads can not call ::wxSleep()!
    static void Sleep(unsigned long milliseconds);

        // get the number of system CPUs - useful with SetConcurrency()
        // (the "best" value for it is usually number of CPUs + 1)
        //
        // Returns -1 if unknown, number of CPUs otherwise
    static int GetCPUCount();

        // Get the platform specific thread ID and return as a long.  This
        // can be used to uniquely identify threads, even if they are not
        // wxThreads.  This is used by wxPython.
   static wxThreadIdType GetCurrentId();

        // sets the concurrency level: this is, roughly, the number of threads
        // the system tries to schedule to run in parallel. 0 means the
        // default value (usually acceptable, but may not yield the best
        // performance for this process)
        //
        // Returns true on success, false otherwise (if not implemented, for
        // example)
    static bool SetConcurrency(size_t level);

    // constructor only creates the C++ thread object and doesn't create (or
    // start) the real thread
    wxThread(wxThreadKind kind = wxTHREAD_DETACHED);

    // functions that change the thread state: all these can only be called
    // from _another_ thread (typically the thread that created this one, e.g.
    // the main thread), not from the thread itself

        // create a new thread and optionally set the stack size on
        // platforms that support that - call Run() to start it
        // (special cased for watcom which won't accept 0 default)

    wxThreadError Create(unsigned int stackSize = 0);

        // starts execution of the thread - from the moment Run() is called
        // the execution of wxThread::Entry() may start at any moment, caller
        // shouldn't suppose that it starts after (or before) Run() returns.
    wxThreadError Run();

        // stops the thread if it's running and deletes the wxThread object if
        // this is a detached thread freeing its memory - otherwise (for
        // joinable threads) you still need to delete wxThread object
        // yourself.
        //
        // this function only works if the thread calls TestDestroy()
        // periodically - the thread will only be deleted the next time it
        // does it!
        //
        // will fill the rc pointer with the thread exit code if it's !NULL
    wxThreadError Delete(ExitCode *rc = (ExitCode *)NULL);

        // waits for a joinable thread to finish and returns its exit code
        //
        // Returns (ExitCode)-1 on error (for example, if the thread is not
        // joinable)
    ExitCode Wait();

        // kills the thread without giving it any chance to clean up - should
        // not be used in normal circumstances, use Delete() instead. It is a
        // dangerous function that should only be used in the most extreme
        // cases!
        //
        // The wxThread object is deleted by Kill() if the thread is
        // detachable, but you still have to delete it manually for joinable
        // threads.
    wxThreadError Kill();

        // pause a running thread: as Delete(), this only works if the thread
        // calls TestDestroy() regularly
    wxThreadError Pause();

        // resume a paused thread
    wxThreadError Resume();

    // priority
        // Sets the priority to "prio": see WXTHREAD_XXX_PRIORITY constants
        //
        // NB: the priority can only be set before the thread is created
    void SetPriority(unsigned int prio);

        // Get the current priority.
    unsigned int GetPriority() const;

    // thread status inquiries
        // Returns true if the thread is alive: i.e. running or suspended
    bool IsAlive() const;
        // Returns true if the thread is running (not paused, not killed).
    bool IsRunning() const;
        // Returns true if the thread is suspended
    bool IsPaused() const;

        // is the thread of detached kind?
    bool IsDetached() const { return m_isDetached; }

    // Get the thread ID - a platform dependent number which uniquely
    // identifies a thread inside a process
    wxThreadIdType GetId() const;

    // called when the thread exits - in the context of this thread
    //
    // NB: this function will not be called if the thread is Kill()ed
    virtual void OnExit() { }

    // Returns true if the thread was asked to terminate: this function should
    // be called by the thread from time to time, otherwise the main thread
    // will be left forever in Delete()!
    virtual bool TestDestroy();

    // dtor is public, but the detached threads should never be deleted - use
    // Delete() instead (or leave the thread terminate by itself)
    virtual ~wxThread();

protected:
    // exits from the current thread - can be called only from this thread
    void Exit(ExitCode exitcode = 0);

    // entry point for the thread - called by Run() and executes in the context
    // of this thread.
    virtual void *Entry() = 0;

private:
    // no copy ctor/assignment operator
    wxThread(const wxThread&);
    wxThread& operator=(const wxThread&);

    friend class wxThreadInternal;

    // the (platform-dependent) thread class implementation
    wxThreadInternal *m_internal;

    // protects access to any methods of wxThreadInternal object
    wxCriticalSection m_critsect;

    // true if the thread is detached, false if it is joinable
    bool m_isDetached;
};

// wxThreadHelperThread class
// --------------------------

class WXDLLIMPEXP_BASE wxThreadHelperThread : public wxThread
{
public:
    // constructor only creates the C++ thread object and doesn't create (or
    // start) the real thread
    wxThreadHelperThread(wxThreadHelper& owner)
        : wxThread(wxTHREAD_JOINABLE), m_owner(owner)
        { }

protected:
    // entry point for the thread -- calls Entry() in owner.
    virtual void *Entry();

private:
    // the owner of the thread
    wxThreadHelper& m_owner;

    // no copy ctor/assignment operator
    wxThreadHelperThread(const wxThreadHelperThread&);
    wxThreadHelperThread& operator=(const wxThreadHelperThread&);
};

// ----------------------------------------------------------------------------
// wxThreadHelper: this class implements the threading logic to run a
// background task in another object (such as a window).  It is a mix-in: just
// derive from it to implement a threading background task in your class.
// ----------------------------------------------------------------------------

class WXDLLIMPEXP_BASE wxThreadHelper
{
private:
    void KillThread()
    {
        if ( m_thread )
        {
            m_thread->Kill();
            delete m_thread;
        }
    }

public:
    // constructor only initializes m_thread to NULL
    wxThreadHelper() : m_thread(NULL) { }

    // destructor deletes m_thread
    virtual ~wxThreadHelper() { KillThread(); }

    // create a new thread (and optionally set the stack size on platforms that
    // support/need that), call Run() to start it
    wxThreadError Create(unsigned int stackSize = 0)
    {
        KillThread();

        m_thread = new wxThreadHelperThread(*this);

        return m_thread->Create(stackSize);
    }

    // entry point for the thread - called by Run() and executes in the context
    // of this thread.
    virtual void *Entry() = 0;

    // returns a pointer to the thread which can be used to call Run()
    wxThread *GetThread() const { return m_thread; }

protected:
    wxThread *m_thread;
};

// call Entry() in owner, put it down here to avoid circular declarations
inline void *wxThreadHelperThread::Entry()
{
    return m_owner.Entry();
}

// ----------------------------------------------------------------------------
// Automatic initialization
// ----------------------------------------------------------------------------

// GUI mutex handling.
void WXDLLIMPEXP_BASE wxMutexGuiEnter();
void WXDLLIMPEXP_BASE wxMutexGuiLeave();

// macros for entering/leaving critical sections which may be used without
// having to take them inside "#if wxUSE_THREADS"
#define wxENTER_CRIT_SECT(cs)   (cs).Enter()
#define wxLEAVE_CRIT_SECT(cs)   (cs).Leave()
#define wxCRIT_SECT_DECLARE(cs) static wxCriticalSection cs
#define wxCRIT_SECT_DECLARE_MEMBER(cs) wxCriticalSection cs
#define wxCRIT_SECT_LOCKER(name, cs)  wxCriticalSectionLocker name(cs)

// function for checking if we're in the main thread which may be used whether
// wxUSE_THREADS is 0 or 1
inline bool wxIsMainThread() { return wxThread::IsMain(); }

#else // !wxUSE_THREADS

// no thread support
inline void WXDLLIMPEXP_BASE wxMutexGuiEnter() { }
inline void WXDLLIMPEXP_BASE wxMutexGuiLeave() { }

// macros for entering/leaving critical sections which may be used without
// having to take them inside "#if wxUSE_THREADS"
#define wxENTER_CRIT_SECT(cs)
#define wxLEAVE_CRIT_SECT(cs)
#define wxCRIT_SECT_DECLARE(cs)
#define wxCRIT_SECT_DECLARE_MEMBER(cs)
#define wxCRIT_SECT_LOCKER(name, cs)

// if there is only one thread, it is always the main one
inline bool wxIsMainThread() { return true; }

#endif // wxUSE_THREADS/!wxUSE_THREADS

// mark part of code as being a critical section: this macro declares a
// critical section with the given name and enters it immediately and leaves
// it at the end of the current scope
//
// example:
//
//      int Count()
//      {
//          static int s_counter = 0;
//
//          wxCRITICAL_SECTION(counter);
//
//          return ++s_counter;
//      }
//
// this function is MT-safe in presence of the threads but there is no
// overhead when the library is compiled without threads
#define wxCRITICAL_SECTION(name) \
    wxCRIT_SECT_DECLARE(s_cs##name);  \
    wxCRIT_SECT_LOCKER(cs##name##Locker, s_cs##name)

// automatically lock GUI mutex in ctor and unlock it in dtor
class WXDLLIMPEXP_BASE wxMutexGuiLocker
{
public:
    wxMutexGuiLocker() { wxMutexGuiEnter(); }
   ~wxMutexGuiLocker() { wxMutexGuiLeave(); }
};

// -----------------------------------------------------------------------------
// implementation only until the end of file
// -----------------------------------------------------------------------------

#if wxUSE_THREADS

#if defined(__WXMSW__) || defined(__WXMAC__) || defined(__WXPM__) || defined(__EMX__)
    // unlock GUI if there are threads waiting for and lock it back when
    // there are no more of them - should be called periodically by the main
    // thread
    extern void WXDLLIMPEXP_BASE wxMutexGuiLeaveOrEnter();

    // returns true if the main thread has GUI lock
    extern bool WXDLLIMPEXP_BASE wxGuiOwnedByMainThread();

#ifndef __WXPM__
    // wakes up the main thread if it's sleeping inside ::GetMessage()
    extern void WXDLLIMPEXP_BASE wxWakeUpMainThread();
#endif // !OS/2

    // return true if the main thread is waiting for some other to terminate:
    // wxApp then should block all "dangerous" messages
    extern bool WXDLLIMPEXP_BASE wxIsWaitingForThread();
#endif // MSW, Mac, OS/2

#endif // wxUSE_THREADS

#endif // _WX_THREAD_H_