Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!bu-cs!dartvax!eleazar.dartmouth.edu!jskuskin
From: jskuskin@eleazar.dartmouth.edu (Jeffrey Kuskin)
Newsgroups: comp.sys.mac.programmer
Subject: Expanding System Heap
Message-ID: <13002@dartvax.Dartmouth.EDU>
Date: 11 Apr 89 19:04:19 GMT
Sender: news@dartvax.Dartmouth.EDU
Reply-To: jskuskin@eleazar.dartmouth.edu (Jeffrey Kuskin)
Distribution: na
Organization: Dartmouth College, Hanover, NH
Lines: 28


    I am in the process of writing an interrupt-handler which will
install itself into the SYSTEM heap.  The handler itself is not large
(300 bytes or so), but it requires a large data buffer (approx. 40K).
All this is for a 1 Meg SE, by the way.

    The problem:  The system heap does not have enough free space
        for me to be able to allocate a 40K block.  I have so far
        circumvented this problem by allocating a smaller buffer
        and filling/emptying it several times.  However, I would
        like to be able to use a full, 40K buffer.

    The questions:
        1)  Is there a way to increase the size of the system heap
            at run time?  That is, could the appication which installs
            the interrupt handler increase the size of the system heap?

        2)  If it turns out to be unfeasible to increase the size
            of the system heap, is there any danger in using most
            (say, 90%) of whatever free space remains in it?
            How well do the System/Finder cope with low-memory
            situations in the system heap?

    Thanks for any help.  Please E-mail responses.

    --  Jeff Kuskin, Dartmouth College

    EMAIL:  jskuskin@eleazar.dartmouth.edu