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1996-09-26
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159 lines
Short: Patches SetFunction() to new better one.
Uploader: mbars@bluejay.creighton.edu
author: mc6489@mclink.it
SetFunction Manager
SetMan / SetManager V1.0
Copyright © 1991,1992 by
Nicola Salmoria
Via Piemonte 11
53100 Siena ITALY
Internet: mc6489@mclink.it
This program is FREEWARE. It is NOT, and will never be, public domain.
Copy it as much as you can (provided no charge is made and the archive is left
intact). It cannot be included in any commercial program without the written
permission of the author.
NOVICE USERS
------------
The program 'SetMan' should be put in C: and executed as the first command in
the startup-sequence. When I say first, I mean FIRST!! Run it even before
SetPatch.
If you're not expert with the Amiga operating system, all you need to know about
SetMan is that it will, under certain circumstances, avoid GURUs. Read on for
more infos.
EXPERT USERS
------------
Let's go into details. There's a function in exec.library, whose name is
SetFunction(). You know that Amiga libraries contain a 'jump table', where are
stored the addresses of every function in the library. Library functions are
always executed via the jump table, and NEVER through absolute addressing.
SetFunction() allows the user to modify the jump table, in order to insert a
custom routine in place of the standard one.
For example, one could modify the DisplayBeep() vector to play a sound instead
of flashing the screen.
SetFunction() is a very useful feature of the Amiga operating system, but it has
the major drawback that there's no system supervising of concurrent use of the
same vector by different tasks. Under certain circumstances, that can be deadly.
Before removing its custom vector, a program should check that it was not
modified again. However, very few do that, and so if you do not terminate such
program in REVERSE order of when you executed them, you'll probably get a system
crash.
Another fault of KickStart 1.x is that the dos.library vectors cannot be
modified by SetFunction(), 'cos they do not follow the conventions estabilished
by Commodore itself.
SetMan modifies the SetFunction() vector, and inserts a custom routine which
solves both of the previous problems. It keeps a linked list of all changes to
the jump tables, and allows any program to remove its vector at any time.
Moreover, it allows to modify dos.library vectors in a transparent, upward
compatible, way.
In this archive there's another free gift, whose name is SetManager. SetManager
displays the list of all modified vectors, with the name of the program which
inserted a custom routine, the address of that routine, and the current status.
Status will usually be 'active'; if you click on the function name, you can
disable it, thus removing the custom function. The third possible state is
'removed', which only occurs when you don't quit programs in the correct order
I explained later. It's there for your information, but is absolutely no
problem. When you exit the other program which uses the same vector, both will
disappear from the list.
NOTE: modified vectors are shown as 'offset' 'library name'. However, SetManager
is able to read the standard 'xxx_lib.fd' files, provided by Commodore on the
'Extras' disk. just assign the name 'FD:' to a directory containing the .fd
files, and they will be read and interpreted when you load SetManager. That way,
you will get the true function names, instead of offsets.
PROGRAMMERS
-----------
You are strongly suggested to use SetMan facilities to modify the dos.library
vectors.
To know if SetMan is running, all you have to do is search for a public MsgPort
named "SetMan". You need that only under KickStart 1.x, 'cos since version 2.0
of the operating system dos.library has joined the rest of us. However, SetMan
is smart enough to use the custom routine for dos.library only if it's really
the non-standard one.
Here is an example of how to proceed:
-----------------------
if (DOSBase->dl_lib.lib_Version < 36 && !FindPort("SetMan"))
{
printf("You need SetMan to execute this program!\n");
exit(RETURN_WARN);
}
else
{
TrueFunction = SetFunction((struct Library *)DOSBase,FUNCOFFSET,NewFunction);
etc etc.....
}
-----------------------
BUGS AND INCOMPATIBILITIES
--------------------------
There are no known bugs in this version of SetMan.
A few more words should be spent on compatibility problems.
Due to the very different procedures followed by the original SetFunction() and
by SetMan, it's not possible to guarantee a 100% compatibility with every
program around. Every effort has been made to avoid every possible problem;
SetMan handles correctly every strange behaviour I could think about; the only
way to confuse SetMan should be using two differnt programs communicating
through a message port and doing very strange things. I'm almost sure such
things things should never happen.
I've encountered a problem with a program called 'TurboTopaz', which refuses to
quit saying that 'Vector has been changed'. That's true, 'cos SetMan puts a
function of its own ahead of the custom one; if TurboTopaz used SetFunction(),
it would receive in return the value it expects, but it reads directly the jump
table, something I believe is not supported by Commodore.
I use a lot of programs which call SetFunction(), and none of them has problems
with SetMan.
ACKNOWLODGEMENT
---------------
I'd like to thank Marco Ciuchini who pointed out an important incompatibility
problem which I have been able to completely remove.
============================= Archive contents =============================
Original Packed Ratio Date Time Name
-------- ------- ----- --------- -------- -------------
1920 913 52.4% 27-Jun-93 22:11:12 SetMan10g/changes.doc
1872 1297 30.7% 26-Jun-93 14:57:18 SetMan10g/SetMan
5504 2565 53.3% 11-Nov-92 20:59:18 SetMan10g/setman.doc
6121 2743 55.1% 11-Nov-92 20:58:48 SetMan10g/setman.ita
7848 4383 44.1% 11-Nov-92 20:43:38 SetMan10g/SetManager
2724 1468 46.1% 11-Nov-92 21:18:48 SetMan10g/SetManager.info
-------- ------- ----- --------- --------
25989 13369 48.5% 20-Apr-94 11:26:56 6 files