Inside Macintosh: Operating System Utilities /

Chapter 6 - Queue Utilities / Queue Utilities Reference

Data Structures

Queue Headers

A queue header is a block of data that contains information about a queue. The QHdr data type defines the structure of a queue header.

TYPE QHdr =
RECORD
   qFlags:     Integer;       {information on queue}
   qHead:      QElemPtr;      {pointer to first queue entry}
   qTail:      QElemPtr;      {pointer to last queue entry}
END;

Field Description

qFlags

Queue flags. This field contains information that is different for each queue type. Ordinarily, these flags are reserved for use by system software.

qHead

A pointer to the first element in the queue. If a queue has no elements, this field is set to NIL.

qTail

A pointer to the last element in the queue. If a queue has no elements, this field is set to NIL.