Threads And Timers

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• Download source - 1.61 Kb

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