Implementing DllMain

To work with an instance of a resource type, a Resource Monitor needs to have the resource DLL that supports the type loaded into its process. If the DLL is already loaded, the Resource Monitor calls the appropriate entry point function. If not, the Resource Monitor calls LoadLibrary and triggers the DllMain entry point.

To implement DllMain

1. Recommended: Call the function DisableThreadLibraryCalls in response to DLL_PROCESS_ATTACH. Refer to the description of the function for the performance benefits.
2. Optional: Initialize semaphores, mutexes, critical sections, classes, COM objects, or any other objects used by the DLL.
3. Recommended. For optimal performance, take no more than 300 milliseconds to return a value.

Resource DLLs that support multiple resource types typically define a single DllMain entry point for the entire DLL, and define an entry point for each <Name> resource type supported by the DLL. This is illustrated in the following example.

Example

The following example demonstrates a DllMain implementation in a resource DLL that supports two resource types, MyTypeAlpha and MyTypeBeta. For additional examples see Resource DLL Examples.

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BOOLEAN WINAPI DllMain( IN HINSTANCE hDllHandle, 
         IN DWORD     nReason, 
         IN LPVOID    Reserved )
 {
  BOOLEAN bSuccess = TRUE;


  //  Perform global initialization.

  switch ( nReason )
   {
    case DLL_PROCESS_ATTACH:

      //  For optimization.

      DisableThreadLibraryCalls( hDllHandle );

      break;

    case DLL_PROCESS_DETACH:

      break;
   }


  //  Perform type-specific initialization.

  if(    MyTypeAlphaDllMain( hDllHandle, nReason, Reserved )
      && MyTypeBetaDllMain(  hDllHandle, nReason, Reserved ) )
   {
    bSuccess = TRUE;
   }
  else
   {
    bSuccess = FALSE;
   }


  return bSuccess;

 }
//  end DllMain

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BOOLEAN WINAPI MyTypeAlphaDllMain( IN HINSTANCE hDllHandle, 
                    IN DWORD nReason, 
                    IN LPVOID Reserved )
 {
  switch ( nReason )
   {
    case DLL_PROCESS_ATTACH:

      g_hSIS = CreateSemaphoreW( NULL, 0, 1, SIS_ALPHA );

      if( g_hSIS == NULL ) return FALSE;

      //  Set initial count to 1.

      if( GetLastError() != ERROR_ALREADY_EXISTS )
         ReleaseSemaphore( g_hSIS, 1, NULL );

      break;

    case DLL_PROCESS_DETACH:

      if ( g_hSIS != NULL )
       {
        CloseHandle( g_hSIS );
        g_hSIS = NULL;
       }

      break;

   }

  return TRUE;

 }
//  end MyTypeAlphaDllMain

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BOOLEAN WINAPI MyTypeBetaDllMain( IN HINSTANCE hDllHandle, 
                   IN DWORD nReason, 
                   IN LPVOID Reserved )
 {

  //  MyTypeBeta needs no processing at this time.

  switch ( nReason )
   {
    case DLL_PROCESS_ATTACH:

      break;

    case DLL_PROCESS_DETACH:

      break;

   }

  return TRUE;

 }
//  end MyTypeBetaDllMain

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