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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

Low-Level HFS Routines / Exchanging the Data in Two Files

PBExchangeFiles

You can use the PBExchangeFiles function to exchange the data stored in two files on the same volume.

FUNCTION PBExchangeFiles (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.
-->	ioDestNamePtr	StringPtr	A pointer to the name of the destination file.
-->	ioDestDirID	LongInt	The destination file's parent directory ID.
-->	ioSrcDirID	LongInt	The source file's parent directory ID.

DESCRIPTION

The PBExchangeFiles function swaps the data in two files by changing some of the information in the volume catalog and, if the files are open, in the file control blocks. The PBExchangeFiles function uses the file ID parameter block.

You should use PBExchangeFiles to preserve the file ID when updating an existing file, in case the file is being tracked through its file ID.

Typically, you use PBExchangeFiles after creating a new file during a safe save.
You identify the names and parent directory IDs of the two files to be exchanged in
the fields ioNamePtr, ioDestNamePtr, ioSrcDirID, and ioDestDirID. The PBExchangeFiles function changes the fields in the catalog entries that record the location of the data and the modification dates. It swaps both the data forks and the resource forks.

The PBExchangeFiles function works on either open or closed files. If either file is open, PBExchangeFiles updates any file control blocks associated with the file. Exchanging the contents of two files requires essentially the same access privileges as opening both files for writing.

The PBExchangeFiles function does not require that file ID references exist for the files being exchanged.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for PBExchangeFiles are

Trap macro	Selector
_HFSDispatch	$0017

RESULT CODES

noErr	0	No error
nsvErr	-35	Volume not found
ioErr	-36	I/O error
fnfErr	-43	File not found
fLckdErr	-45	File is locked
vLckdErr	-46	Volume is locked or read-only
paramErr	-50	Function not supported by volume
volOfflinErr	-53	Volume is offline
wrgVolTypErr	-123	Not an HFS volume
diffVolErr	-1303	Files on different volumes
afpAccessDenied	-5000	User does not have the correct access
afpObjectTypeErr	-5025	Object is a directory, not a file
afpSameObjectErr	-5038	Source and destination are the same