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Inside Macintosh: Operating System Utilities /

Chapter 6 - Queue Utilities / Queue Utilities Reference

Data Structures

Queue Elements

A queue element is a single entry in a queue. The exact structure of an element in an operating-system queue depends on the type of the queue. The different queue types that are accessible to your application are defined by the QTypes data type.

TYPE QTypes =
   (dummyType,       {reserved}
   vType,            {vertical retrace queue type}
   ioQType,          {file I/O or driver I/O queue type}
   drvQType,         {drive queue type}
   evType,           {event queue type}
   fsQType,          {volume-control-block queue type}
   sIQType,          {slot interrupt queue type}
   dtQType,          {deferred task queue type}
   {nmType,}         {notification queue type}
   {slpQType}        {sleep queue type}
   );

Each of these enumerated queue types determines a different type of queue element. The QElem data type defines the available queue elements.

TYPE QElem = 
RECORD
   CASE QTypes OF
      vType:      (vblQElem:  VBLTask);
      ioQType:    (ioQElem:   ParamBlockRec);
      drvQType:   (drvQElem:  DrvQEl);
      evType:     (evQElem:   EvQEl);
      fsQType:    (vcbQElem:  VCB);
      dtQType:    (dtQElem:   DeferredTask);
      {siQType:   (siQElem:   SlotIntQElement);}
      {nmType:    (nmQElem:   NMRec);}
      {slpQType:  (slpQElem:  SleepQRec);}
END;
QElemPtr = ^QElem;