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Inside Macintosh: More Macintosh Toolbox /

Chapter 1 - Resource Manager / Resource Manager Reference

Resource Manager Routines / Opening Resource Forks

OpenResFile

If the FSpOpenResFile function is not available, you can use the OpenResFile function to open a resource fork.

FUNCTION OpenResFile (fileName: Str255): Integer;

fileName

The name of the file whose resource fork is to be opened.

DESCRIPTION

The OpenResFile function opens the resource fork of the file with the name specified by the fileName parameter in the application's default directory--that is, the directory in which the application is located. It also makes this file the current resource file.

Like the OpenRFPerm function, the OpenResFile function takes a filename and opens the resource fork for the file with that name. Unlike OpenRFPerm, OpenResFile does not let you specify the read/write permission of the resource fork the first time it is opened. The OpenResFile function is an earlier version of the OpenRFPerm function.

If it finds the specified file in your application's default directory, OpenResFile reads the file's resource map into memory and returns a file reference number for the file. It also reads into memory every resource in the resource fork whose resPreload attribute is set.

You can use the file reference number returned by OpenResFile to refer to the file in other Resource Manager routines. If the file's resource fork is already open, OpenResFile returns the file reference number but does not make that file the current resource file.

If the OpenResFile function fails to open the specified file's resource fork (for instance, because there's no file with the given name), it returns -1 as the file reference number. Use the ResError function to determine what kind of error occurred.

You don't have to call OpenResFile to open the System file's resource fork or an application file's resource fork. These resource forks are opened automatically when the system and the application start up, respectively. To get the file reference number for your application, call the CurResFile function after the application starts up and before you open the resource forks for any other files.

The OpenResFile function checks that the information in the resource map is internally consistent. If it isn't, ResError returns the result code mapReadErr.

To open a resource fork just for block-level operations, such as copying files without reading the resource map into memory, use the File Manager function OpenRF.

SPECIAL CONSIDERATIONS

The OpenResFile function may move or purge memory blocks in the application heap. Your application should not call this function at interrupt time.

If you want to open the resource fork for another application (or any resource fork other than your application's that includes 'CODE' resources), you must bracket your calls to OpenResFile with calls to SetResLoad with the load parameter set to FALSE and then to TRUE. You must also avoid making intersegment calls while the other application's resource fork is open. The discussion of this issue in relation to FSpOpenResFile (page 1-56) also applies to OpenResFile.

ASSEMBLY-LANGUAGE INFORMATION

A handle to the resource map for the most recently opened resource fork is stored in the global variable TopMapHndl.

RESULT CODES

noErr	0	No error
nsvErr	-35	No such volume
ioErr	-36	I/O error
bdNamErr	-37	Bad filename or volume name (perhaps zero length)
eofErr	-39	End of file
tmfoErr	-42	Too many files open
fnfErr	-43	File not found
opWrErr	-49	File already open with write permission
permErr	-54	Attempt to open locked file for writing
extFSErr	-58	Volume belongs to an external file system
memFullErr	-108	Not enough room in heap zone
dirNFErr	-120	Directory not found
mapReadErr	-199	Map inconsistent with operation

SEE ALSO

To check for errors, call the ResError function as described on page 1-47.