Path: utzoo!attcan!uunet!unisoft!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Resource path: getting the really most recently opened file?
Message-ID: <11098@hoptoad.uucp>
Date: 13 Apr 90 14:41:59 GMT
Organization: Eclectic Software, San Francisco
Lines: 31

Here's something I thought would be easy, but I can't figure it out
from disassembling the ROM.

We all know about resource file search paths, and how you can use
UseResFile to set which file is the first to be searched, so that any
files opened after the one you specify will not be searched.  Fine and
dandy.  But somewhere, the system must keep track of the temporarily
unused part of the search path.  For one thing, it needs to get back at
the resource map when you UseResFile on the real most recently opened
file to expand the search path back to its former state.  For another,
it has to be able to close all open resource files when you
ExitToShell.  And so on.

So where is this information stored?  It's not stored in TopMapHndl, at
least not in any obvious way.  TopMapHndl is the map currently at the
start of the search path, not the file at the beginning of the total
search path.  And the RM code in the ROM doesn't reference any low
memory globals other than the documented ones, which don't contain
this information.

I do realize that wherever this information is stored may change in
future system versions.  I'll make a decision on whether this is any
better or worse than my current fallback solution, which involves
searching the FCB table for all open resource files.  (Hint: even if
it's bad, it's probably better....)
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com

"Satanic is merely the name they give to the behavior of those who would
 disrupt the orderly way in which men want to live."
    -- Gabrielle, THE VAMPIRE LESTAT, Anne Rice