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Inside Macintosh: More Macintosh Toolbox /

Chapter 1 - Resource Manager / Resource Manager Reference

Resource Manager Routines / Writing to Resource Forks

UpdateResFile

You can use the UpdateResFile procedure to update the resource map and resource data for a resource fork without closing it.

PROCEDURE UpdateResFile (refNum: Integer);

refNum

A file reference number for a resource fork.

DESCRIPTION

Given the reference number of a file whose resource fork is open, UpdateResFile performs three tasks. The first task is to change, add, or remove resource data in the
file's resource fork to match the resource map in memory. Changed resource data for each resource is written only if that resource's resChanged bit has been set by a successful call to ChangedResource or AddResource. The UpdateResFile procedure calls the WriteResource procedure to write changed or added resources to the resource fork.

The second task is to compact the resource fork, closing up any empty space created when a resource was removed, made smaller, or made larger. If a resource is made larger, the Resource Manager writes it at the end of the resource fork rather than at its original location. It then compacts the space occupied by the original resource data. The actual size of the resource fork is adjusted when a resource is removed or made larger, but not when a resource is made smaller.

The third task is to write the resource map in memory to the resource fork if your application has called the ChangedResource procedure for any resource listed in the resource map or if it has added or removed a resource. All changes to resource information in the resource map become permanent at this time; if you want any of these changes to be temporary, you must restore the original information before calling UpdateResFile.

If there's no open resource fork with the given reference number, UpdateResFile
does nothing, and the ResError function returns the result code resNotFound. If the value of the refNum parameter is 0, it represents the System file's resource fork. If you call UpdateResFile but the mapReadOnly attribute of the resource fork is set, UpdateResFile does nothing, and the ResError function returns the result code resAttrErr.

Because the CloseResFile procedure calls UpdateResFile before it closes the resource fork, you need to call UpdateResFile directly only if you want to update the file without closing it.

RESULT CODES

noErr	0	No error
resNotFound	-192	Resource not found
resAttrErr	-198	Attribute inconsistent with operation

SEE ALSO

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

For an example of the use of UpdateResFile, see Listing 1-11 on page 1-32. For descriptions of the ChangedResource, AddResource, and CloseResFile procedures, see page 1-83, page 1-85, and page 1-104, respectively. The
WriteResource procedure is described next.