Legacy Document

Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

Low-Level File Access Routines / Manipulating the File Mark

PBSetFPos

You can use the PBSetFPos function to position the file mark before reading from or writing to an open file.

FUNCTION PBSetFPos (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.
-->	ioPosMode	Integer	The positioning mode.
<->	ioPosOffset	LongInt	On input, the positioning offset. On output, the position at which the mark was actually set.

DECRIPTION

The PBSetFPos function sets the mark of the specified file to the position specified by the ioPosMode and ioPosOffset fields. If you try to set the mark past the logical end-of-file, PBSetFPos moves the mark to the end-of-file and returns eofErr as its function result.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro for PBSetFPos is _SetFPos.

RESULT CODES

noErr	0	No error
ioErr	-36	I/O error
fnOpnErr	-38	File not open
eofErr	-39	Logical end-of-file reached
posErr	-40	Attempt to position mark before start of file
rfNumErr	-51	Bad reference number
extFSErr	-58	External file system