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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

Low-Level File Access Routines / Manipulating the File Mark

PBGetFPos

You can use the PBGetFPos function to determine the current position of the file mark before reading from or writing to an open file.

FUNCTION PBGetFPos (paramBlock: ParmBlkPtr; async: Boolean): 
                     OSErr;

paramBlock

A pointer to a basic File Manager parameter block.

async

A Boolean value that specifies asynchronous (TRUE) or synchronous (FALSE) execution.

-->	ioCompletion	ProcPtr	A pointer to a completion routine.
<--	ioResult	OSErr	The result code of the function.
-->	ioRefNum	Integer	A file reference number.
<--	ioReqCount	LongInt	On output, set to 0.
<--	ioActCount	LongInt	On output, set to 0.
<--	ioPosMode	Integer	On output, set to 0.
<--	ioPosOffset	LongInt	The current position of the mark.

DESCRIPTION

The PBGetFPos function returns, in the ioPosOffset field, the mark of the specified file. The value returned in ioPosOffset is zero-based. Thus, a call to PBGetFPos returns 0 if you call it when the file mark is positioned at the beginning of the file.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro for PBGetFPos is _GetFPos.

RESULT CODES

noErr	0	No error
ioErr	-36	I/O error
fnOpnErr	-38	File not open
rfNumErr	-51	Bad reference number
gfpErr	-52	Error during PBGetFPos