NetNews Usenet Archive 1992 #19/NN_1992_19.iso/spool/comp/sys/mac/programm/14959

Text File | 1992-09-03 | 4.4 KB | 169 lines

Newsgroups: comp.sys.mac.programmer
Path: sparky!uunet!sun-barr!ames!data.nas.nasa.gov!taligent![e-mail]
From: [e-mail] (Keith Rollin)
Subject: Re: Problem writing INIT/cdev
Message-ID: <[e-mail]>
Sender: [e-mail] (More Bytes Than You Can Read)
Organization: Taligent
References: <[e-mail]> <[e-mail]>
Distribution: comp
Date: Thu, 3 Sep 1992 20:08:55 GMT
Lines: 156

In article <[e-mail]>,
[e-mail] (Peter Landweber) writes:
>
>
>
>      I am working on an INIT/cdev combination to be used under System
> 7, and I've run into a problem.
>      At startup time, the INIT moves its resource map after the system
> resource map in the linked list, and it patches CloseResFile() to
> ignore the file.  The result is that my file stays open, and its
> resources are always available.  This is similar to what Suitcase II
> does with font suitcases.  So far everything has gone extremely well
> using this technique.
>      Now, I'm trying to add a "cdev".  The problem is that when the
> finder opens up my file as a Control Panel, it expects my file's
> resource map to be the first in the linked list.  Since the resource
> map is actually at the end of the linked list, the finder crashes.
>
> So, my questions are:
> 1)  Is there a way for the Finder to open up a Control Panel if the
> file is already open, and its resource map is not at the front of the
> linked list?
> 2)  Is there a way to open a file twice, with two separate resource
> maps?  That way, I could still have one resource map linked after the
> system resource map, and the other at the front of the linked list.
> One of the maps could be read-only if necessary.

I have an INIT/cdev that does the same thing. However, it takes a little
different approach than yours, and it seems to work.

First, I don't patch CloseResFile() to keep my file open. Instead, at INIT time,
I install my code, remember the file I came from, and patch InitAllPacks(). I
remember my file of origin with the following routine.


static void    RememberMe()
{
    FCBPBRec    pb;
    OSErr        err;

    pb.ioCompletion = nil;
    pb.ioNamePtr = gOurName;
    pb.ioVRefNum = 0;
    pb.ioRefNum = CurResFile();
    pb.ioFCBIndx = 0;

    err = PBGetFCBInfoSync(&pb);

    gOurVRefNum = pb.ioFCBVRefNum;
    gOurDirID = pb.ioFCBParID;
}


I patch InitAllPacks() so that I can re-open my resource fork just before the
first application is run:


static pascal void    MyInitAllPacks(void)
{
    SetUpA4();

    oldInitAllPacks();

    if (gMyRefNum == 0)
        OpenAndAddMe();

    RestoreA4();
}


OpenAndAddMe() opens the resource fork and shuffles it behind the System file:


typedef struct ResourceMap{
    long        dataOffset;
    long        mapOffset;
    long        dataLength;
    long        mapLength;
    struct ResourceMap    **nextMap;
    short        refNum;
    short        attributes;
    short        typesOffset;
    short        namesOffset;
} ResourceMap, *ResMapPtr, **ResMapHandle;

static void    OpenAndAddMe()
{
    THz                currentZone;

    short            oldFile;
    short            refNum;
    ResMapHandle    current = nil;
    ResMapHandle    previous = nil;
    ResMapHandle    ourParent = nil;
    ResMapHandle    us = nil;
    ResMapHandle    system = nil;

    currentZone = GetZone();
    SetZone(SystemZone());

    oldFile = CurResFile();
    refNum = InlineHOpenResFile(gOurVRefNum, gOurDirID, gOurName, fsRdPerm);
    UseResFile(oldFile);

    if (refNum != -1) {

        current = (ResMapHandle) TopMapHndl;

        // First, find us (we should be on top)

        while ((current != nil) && ((**current).refNum != refNum)) {
            previous = current;
            current = (**current).nextMap;
        }
        if (current != nil) {
            ourParent = previous;
            us = current;
        }

        // Second, find the System

        system = (ResMapHandle) SysMapHndl;

        if ((us == nil) || (system == nil)) {
            CloseResFile(refNum);
        } else {
            if (ourParent != system) {

            //
            // Be sure to perform all these steps so that the
            // resource chain is never inconsistant or circular.
            // If that happens, debuggers like TMON will detonate.
            //
                if ((ResMapHandle) TopMapHndl == us)
                    TopMapHndl = (void*) (**us).nextMap;
                if (ourParent)
                    (**ourParent).nextMap = (**us).nextMap;
                (**us).nextMap = (**system).nextMap;
                (**system).nextMap = us;
            }
            gMyRefNum = refNum;
        }
    }
    SetZone(currentZone);
}

I've checked the resource chain with this setup, and my INIT/cdev file appears
to get opened twice when the cdev is opened.

Hope this helps,

--
Keith Rollin
Phantom Programmer
Taligent, Inc.