Inside Macintosh: Interapplication Communication /

Chapter 12 - Data Access Manager / Data Access Manager Reference

Data Access Manager Routines / Low-Level Interface: Retrieving Results

DBUnGetItem

The DBUnGetItem function reverses the effect of the last call to the DBGetItem function, in the sense that the next time you call the DBGetItem function it retrieves the same item a second time.

FUNCTION DBUnGetItem (sessID: LongInt; 
                      asyncPB: DBAsyncParmBlkPtr): OSErr;

sessID

The session ID that was returned by the DBInit function.

asyncPB

A pointer to an asynchronous parameter block. If you do not want to call the function asynchronously, set this parameter to NIL.

DESCRIPTION

The DBUnGetItem function does not remove the just-retrieved data item from the input buffer. This function can reverse the effect of only one call to the DBGetItem function; you cannot use it to step back through several previously retrieved data items.

SPECIAL CONSIDERATIONS

The DBUnGetItem function may move or purge memory. You should not call this routine from within an interrupt, such as in a completion routine or a VBL task.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the DBUnGetItem function are

Trap macro	Selector
_DBUnGetItem	$040D

RESULT CODES

noErr	0	No error
rcDBError	-802	Error executing function
rcDBBadSessID	-806	Session ID is invalid
rcDBAsyncNotSupp	-809	The database extension does not support asynchronous calls
rcDBPackNotInited	-813	The InitDBPack function has not yet been called

SEE ALSO

For a description of the asynchronous parameter block, see page 12-56. See page 12-84 for a description of the DBGetItem function.