Reading From and Writing to Files(IM:IC)

Inside Macintosh: Interapplication Communication /: Chapter 2 - Edition Manager / Subscribing to Non-Edition Files

Reading From and Writing to Files
The I/O procedure is a routine that actually reads and writes the data. It too 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" on page 2-64.
FUNCTION MyIO (selector: FormatIOVerb; 
               VAR PB: FormatIOParamBlock): OSErr;