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Useful synchronization MACROs for multithreaded applications

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  • Useful synchronization MACROs for multithreaded applications

    Code:
    '______________________________________________________________________________
    '
    '  WorkerThread Example
    '
    '  Spawns a second "worker" thread and demonstrates synchronizing variables
    '  between each thread using a critical section object and a couple of MACROs.
    '
    '  Posted By Kev Peel (www.kgpsoftware.com), Dec 2007.
    '______________________________________________________________________________
    #Compile Exe
    #Dim All
    #Register None
    %USEMACROS = 1                      ' Cuts code size.
    #Include "WIN32API.INC"             ' Includes required API definitions.
    Global gCS As CRITICAL_SECTION      ' Thread synchronization object.
    Global gnEndApp As Long             ' Set to TRUE to exit the application.
    
    '------------------------------------------------------------------------------
    ' Safely reads any variable type to a temporary variable and returns it.
    ' This function uses the global critical section variable.
    '------------------------------------------------------------------------------
    Macro Function SafeReadVar(vVar, vType)
      MacroTemp vTmp
      Local vTmp As vType
      EnterCriticalSection gCS
      vTmp = vVar
      LeaveCriticalSection gCS
    End Macro = vTmp
    
    '------------------------------------------------------------------------------
    ' Safely writes any value to the specified variable.
    ' This function uses the global critical section variable.
    '------------------------------------------------------------------------------
    Macro SafeWriteVar(vVar, vValue)
      EnterCriticalSection gCS
      vVar = vValue
      LeaveCriticalSection gCS
    End Macro
    
    '------------------------------------------------------------------------------
    ' Sample "worker thread" Does background stuff.
    '------------------------------------------------------------------------------
    Function WorkerThread(ByVal dummy As Long) As Long
      Do
         If MessageBox(%HWND_DESKTOP, "Close the app?", "WorkerThread Example", %MB_OKCANCEL Or %MB_ICONINFORMATION) = %IDOK Then
            ' Safely assign the flag...
            SafeWriteVar(gnEndApp, %TRUE)
            ' End the thread...
            Exit Function
         End If
      Loop
      
    End Function
     
    '------------------------------------------------------------------------------
    ' Creates a worker thread and enters a sample message loop.
    '------------------------------------------------------------------------------
    Function PBMain
      Local dummy As Long
      gnEndApp = %FALSE
      InitializeCriticalSection gCS
      ' Spawn worker thread...
      Thread Create WorkerThread(0) To dummy
      ' Sample message loop...
      Do Until SafeReadVar(gnEndApp, Long) <> %FALSE
         Dialog DoEvents
      Loop
      DeleteCriticalSection gCS
    End Function
    kgpsoftware.com | Slam DBMS | PrpT Control | Other Downloads | Contact Me
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