QHdrPtr

QHdr structure

#include <OSUtils.h>

typedef struct QHdr { Size Offset Description

short qFlags; 2 0 Various flags, differs per queue type

QElemPtr qHead; 4 2 Address of first queue element

QElemPtr qTail; 4 6 Address of last queue element

} QHdr; 10

typedef QHdr *QHdrPtr;

Notes: All standard Operating System queues have a QHdr structure which

contains pointers to the first and last queue elements. Use En queue and

De queue to manipulate queues created by your application. The various

managers handle their queues internally. The following calls return a

QHdrPtr:

GetDrvQHdr Drive queue elements are DrvQEl structures

GetEvQHdr Event queue elements are EvQEl structures

GetFSQHdr I/O queue elements are ParamBlockRec (et al.) structs

GetVBLQHdr Vertical retrace tasks are VBLTask structures

GetVCBQHdr Volume control blocks are VCB structures

The qFlags field is largely undocumented. We are told that in the vertical

retrace queue header, if qFlags bit 6 is set, a task is currently being

executed.