ATL / WTL / STL

   // Array of addresses.  Value of zero = no data,    > 0 = address of data to send
message_pointer    message_address_array[ 16 ];
…
// not shown: code to send the data and specify the event associated with that send.  The overlapped
// API is expected to set the event when the I/O is complete.  Presume an output is in progress or just 
// completed when this Wait is reached.
event_detected = WaitForMultipleObjects(
            EVENT_ARRAY_SIZE,
            mp_common_data->event_array,
            WAIT_FOR_ANY_EVENT,
            WAIT_TIMEOUT_VALUE );
// error checking and timeout checking not shown
Switch( event_detected )
{
   case EVENT_START_RUNNING:
      {…  break;}   // several events not shown
   case IO_EVENT_01:  // no break;
   case IO_EVENT_02:  // no break;  etc, etc
   case IO_EVENT_16:  // no break;
   {
      event_index = event_detected  –   IO_EVENT_01;
      message_address_array[ event_index ] = 0;  // zero = output completed
      break;
   }
   Default {…}    
}

event_index = event_detected  –   IO_EVENT_01;
if( event_index >= 0 && event_index <= LAST_EVENT )
    message_address_array[ event_index ] = 0;
else
    switch(…)  etc, etc

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