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Threads And Timers

, 26 Jan 2004
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Adding a WM_TIMER message to CWinThreads.

Introduction

In this project and in the source files, there is a base class to CWinThread class that will provide you with WM_TIMER messages to your threads. Since WM_TIMER messages are reserved for window objects only, this is a bit tricky to perform. I did this because I was in need of threads that could react to timers but I had lots of threads (100's) to manage and they all read there configuration from the database and set timers based on that configuration. Some threads had 1 timer and other threads had 100's of timers. I needed a way to manage all these timers and events.

Using the code

This class is derived from the standard MFC CWinThread class. m_autoremove will remove all the timers outstanding if you don't. You can turn it off by setting the m_autoremove to false. There are 2 methods AddTimer() and RemoveTimer(). Simple!

// WinTimerThread.h
class CWinTimerThread : public CWinThread
{
    public:
        DECLARE_DYNCREATE(CWinTimerThread)
        //
        CWinTimerThread();
        ~CWinTimerThread();

        //
        bool    m_autoremove;
        //
        UINT_PTR AddTimer(UINT uElapse);
        BOOL RemoveTimer(UINT_PTR idEvent);

};
// WinTimerThread.cpp
...
// Static declarations
static CMapPtrToPtr g_MapTimerID_TO_CWinThreadPtr;

static void CALLBACK TimerProc(
    HWND hwnd,         // handle to window
    UINT uMsg,         // WM_TIMER message
    UINT_PTR idEvent,  // timer identifier
    DWORD dwTime       // current system time 
    )
{
    CWinThread* pThread;

    if (g_MapTimerID_TO_CWinThreadPtr.Lookup((void *) idEvent, (void*&) pThread))
    {
        pThread->PostThreadMessage(WM_TIMER, idEvent, dwTime);
    }
}
// Class 
IMPLEMENT_DYNCREATE(CWinTimerThread, CWinThread)

CWinTimerThread::CWinTimerThread()
{
    m_autoremove = true;
}

CWinTimerThread::~CWinTimerThread()
{
    // check if autoremove is activated
    if (!m_autoremove)
        return;
    // declare local variables
    POSITION pos;
    UINT_PTR idEvent;
    CWinThread* pThread;

    //get the starting point in the list of timer events
    pos = g_MapTimerID_TO_CWinThreadPtr.GetStartPosition();
    //loop while there are list items
    while (pos)
    {
        // get timer event entry
        g_MapTimerID_TO_CWinThreadPtr.GetNextAssoc(pos, 
            (void *&) idEvent, (void*&) pThread);
        // check if the idevent is refering to this object
        if (pThread == this)
        {
           RemoveTimer(idEvent);
        }
    }
}


UINT_PTR CWinTimerThread::AddTimer(UINT uElapse)
{
    UINT_PTR idEvent;

    idEvent = ::SetTimer(NULL, NULL, uElapse, (TIMERPROC) TimerProc);
    g_MapTimerID_TO_CWinThreadPtr.SetAt((void *) idEvent, this);
    return idEvent;
}
BOOL CWinTimerThread::RemoveTimer(UINT_PTR idEvent)
{
    ::KillTimer(NULL, idEvent);
    return g_MapTimerID_TO_CWinThreadPtr.RemoveKey((void *) idEvent);
}

Below is how to use the new CWinTimerThread.

// MyThread.h
#include "WinTimerThread.h"

#if !defined(MYTHREAD_H)
#define MYTHREAD_H
#pragma once

class CMyThread : public CWinTimerThread
{
    public:
        DECLARE_DYNCREATE(CMyThread)
        //
        CMyThread();
        ~CMyThread();

        virtual BOOL InitInstance();
        virtual int ExitInstance();

        void SetLogWindow(CWnd* pWnd);

    protected:
        // 
        CWnd* m_pLogWnd;
        //
        void LogMessage(CString& logmsg);
        void OnTimer(WPARAM idEvent, LPARAM dwTime);
        //
        DECLARE_MESSAGE_MAP()};

#endif // MYTHREAD_H

Notice that all you have to do is call AddTimer() anywhere in the thread and specify the amount of milliseconds, and you're done. The clean up is done for you so you don't even have to worry about it.

// MyThread.cpp
//
#include "stdafx.h"
#include "MyThread.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#endif

IMPLEMENT_DYNCREATE(CMyThread, CWinTimerThread)

CMyThread::CMyThread()
{
}

CMyThread::~CMyThread()
{
}
BEGIN_MESSAGE_MAP(CMyThread, CWinTimerThread)
    ON_THREAD_MESSAGE(WM_TIMER,    OnTimer)
END_MESSAGE_MAP()

BOOL CMyThread::InitInstance()
{
    ...
    //
    AddTimer(1000);
    return TRUE;
}
...

Points of Interest

Posting the WM_TIMER message to the thread should be safe since the numeric value is 0x113, well below WM_USER = 0x400. This is very compatible to the original SetTimer(), KillTimer() and OnTimer(idEvent, dwTime).

Also note that the message to the thread is ON_THREAD_MESSAGE() not the ON_MESSAGE() macro.

History

Version 1.0

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

David A. Jones
Web Developer
Canada Canada
No Biography provided

Comments and Discussions

 
GeneralExcellent article; one small quibble on thread safety PinmemberHal Berman29-May-08 6:06 
Generalfrequency of running process Pinmembermehmetned17-Jul-06 22:53 
GeneralRe: frequency of running process PinmemberDavid A. Jones18-Jul-06 4:23 
are you going to have a lot of threads? I think that you should have a pool of threads that are initialized and waiting on a queue or mutex. I think that the queue or mutex would then provide some information about what to service. You will have to tune the number of threads and queues to optimize your service requests. Spawning threads will be expensive so they should already be initialized and waiting for something to do.
 
I hope this helps.
 
Cheers,
 
David.
GeneralCWinThread and SetTimer Pinmemberkumar_subrahmanya7-Jul-06 1:58 
GeneralRe: CWinThread and SetTimer [modified] PinmemberDavid A. Jones12-Jul-06 5:20 
Generalerror while creating class derived from CWinThread PinsussVC++error11-Jul-05 10:47 
GeneralOnTimer() Pinmembermedlar12-Jun-05 22:27 
GeneralChanging the AddTimer PinmemberTom Wright10-Mar-05 10:10 
GeneralRe: Changing the AddTimer PinmemberTom Wright10-Mar-05 11:00 
GeneralRequired in Visual Studio 6.0 Env. Pinmembersudiptam29-Sep-04 1:27 
GeneralRe: Required in Visual Studio 6.0 Env. PinmemberDavid A. Jones1-Oct-04 15:12 
QuestionIs it really possible to create 100's of Timers? PinmemberPersia26-Feb-04 2:17 
AnswerRe: Is it really possible to create 100's of Timers? PinmemberDavid A. Jones26-Feb-04 4:43 
Generalversion 7.10 PinsussGopal Krishna15-Apr-04 3:46 
GeneralRe: version 7.10 PinmemberDavid A. Jones16-Apr-04 2:53 
AnswerRe: Is it really possible to create 100's of Timers? PinmemberDavid A. Jones1-Oct-04 15:09 

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