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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

Low-Level File Access Routines / Manipulating the End-of-File

PBSetEOF

You can use the PBSetEOF function to set the logical end-of-file of an open file.

FUNCTION PBSetEOF (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.
-->	ioMisc	Ptr	The logical end-of-file.

DESCRIPTION

The PBSetEOF function sets the logical end-of-file of the open file, whose access path is specified by ioRefNum, to ioMisc. Because the ioMisc field is of type Ptr, you must coerce the desired value from type LongInt to type Ptr.

If you attempt to set the logical end-of-file beyond the current physical end-of-file, another allocation block is added to the file; if there isn't enough space on the volume,
no change is made and PBSetEOF returns dskFulErr as its function result.

If the value of the ioMisc field is 0, all space occupied by the file on the volume is released. The file still exists, but it contains 0 bytes. Setting a file fork's end-of-file to 0
is therefore not the same as deleting the file (which removes both file forks at once).

ASSEMBLY-LANGUAGE INFORMATION

The trap macro for PBSetEOF is _SetEOF.

RESULT CODES

noErr	0	No error
dskFulErr	-34	Disk full
ioErr	-36	I/O error
fnOpnErr	-38	File not open
wPrErr	-44	Hardware volume lock
fLckdErr	-45	File is locked
vLckdErr	-46	Software volume lock
rfNumErr	-51	Bad reference number
wrPermErr	-61	Read/write permission doesn't allow writing