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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

Low-Level HFS Routines / Opening Files

PBHOpenDF

You can use the PBHOpenDF function to open the data fork of a file.

FUNCTION PBHOpenDF (paramBlock: HParmBlkPtr; async: Boolean): 
                     OSErr;

paramBlock

A pointer to a basic HFS 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.
-->	ioNamePtr	StringPtr	A pointer to a pathname.
-->	ioVRefNum	Integer	A volume specification.
<--	ioRefNum	Integer	A file reference number.
-->	ioPermssn	SignedByte	The read/write permission.
-->	ioDirID	LongInt	A parent directory ID.

DESCRIPTION

The PBHOpenDF function creates an access path to the data fork of a file and returns a file reference number in the ioRefNum field. PBHOpenDF is exactly like the PBHOpen function except that PBHOpenDF allows you to open a file whose name begins with
a period (.).

You can open a path for writing even if it accesses a file on a locked volume, and no error is returned until a PBWrite, PBSetEOF, or PBAllocate call is made.

If you attempt to open a locked file for writing, PBHOpenDF returns the result code permErr. If you request exclusive read/write permission but another access path
is already open, PBHOpenDF returns the reference number of the existing access path
in ioRefNum and opWrErr as its function result. You should not use this reference
number unless your application originally opened the file.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for PBHOpenDF are

Trap macro	Selector
_HFSDispatch	$001A

RESULT CODES

noErr	0	No error
nsvErr	-35	No such volume
ioErr	-36	I/O error
bdNamErr	-37	Bad filename
tmfoErr	-42	Too many files open
fnfErr	-43	File not found
opWrErr	-49	File already open for writing
permErr	-54	Attempt to open locked file for writing
dirNFErr	-120	Directory not found or incomplete pathname
afpAccessDenied	-5000	User does not have the correct access to the file