CallFormatIOProc
FormatIOVerb selector; is set to one of the edition opener verbs
selector is set to one of the format I/O verbs (ioHasFormat, ioReadFormat,
ioNewFormat, ioWriteFormat)
PB contains a format I/O parameter block record
routine is a pointer to a format I/O procedure.
noErr (0) No error
Notes: The I/O procedure is a routine that actually reads and writes the data. It
has an interface of a selector and a parameter block.
To override the standard reading and writing functions, create an I/O
function. Note that you also need to provide your own opener function to call
your I/O function. See Calling an Edition Opener Procedure under
Subscribing to Non-Edition Files for more information on writing
an opener function. See Calling a Format I/O Procedure under
Subscribing to Non-Edition Files for more information on writing a
format I/O procedure.