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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

File System Specification Routines / Opening Files

FSpOpenDF

You can use the FSpOpenDF function to open a file's data fork.

FUNCTION FSpOpenDF (spec: FSSpec; permission: SignedByte;
                     VAR refNum: Integer): OSErr;

spec

An FSSpec record specifying the file whose data fork is to be opened.

permission

A constant indicating the desired file access permissions.

refNum

A reference number of an access path to the file's data fork.

DESCRIPTION

The FSpOpenDF function opens the data fork of the file specified by the spec parameter and returns a file reference number in the refNum parameter. You can pass that reference number as a parameter to any of the low- or high-level file access routines.

The permission parameter specifies the kind of access permission mode you want.
In most cases, you can simply set the permission parameter to fsCurPerm. Some applications request fsRdWrPerm, to ensure that they can both read from and write
to a file. For more information about permissions, see "File Manipulation" on page 2-7. In shared environments, permission requests are translated into the deny mode permissions defined by AppleShare.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for FSpOpenDF are

Trap macro	Selector
_HighLevelHFSDispatch	$0002

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