Author: Dave Lyons
Year: 1989
... explains how to write a user tool set and why writing a user tool set is better than stealing a system tool set number.
Apple II
Technical Notes
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Developer Technical Support
Apple IIgs
#73: Using User Tool Sets
Revised by: Dave "Flag Bits" Lyons July 1991
Written by: Dave Lyons November 1989
This Technical Note explains how to write a user tool set and why writing a
user tool set is better than stealing a system tool set number.
Changes since January 1991: Expanded recommendation on where to keep user
tool set files on disk and clarified SetTSPtr information.
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The Apple IIgs Toolbox Reference describes system tool sets, which are
usually called through the system tool dispatcher vectors 1 ($E10000) and 2
($E10004).
There are 255 possible system tool set numbers (1 through 255). All of these
are reserved for definition by the system. If your program is "borrowing" a
system tool set number, please feel guilty and switch over to the user tool
set numbers. There are 255 of them too, and they're called through user tool
dispatcher vectors 1 ($E10008) and 2 ($E1000C). All 255 user tool set
numbers are available for the current application to use as it chooses.
(Desk accessories are forbidden to use user tool sets.)
Of the four tool dispatcher vectors, only the first one ($E10000) has
received a lot of publicity. $E10008 works just like $E10000, except that
it passes control to a user tool set instead of a system tool set.
The second vector of each pair ($E10004 and $E1000C) works just like the
first, except that one extra RTL address must be pushed onto the stack after
any parameters are pushed. This way you can have a subroutine to do some or
all of your toolbox dispatching, and that subroutine can do extra processing
before or after the tool call, or both.
How Can I Write a User Tool Set?
Appendix A of Toolbox Reference, Volume 2, shows how to write a user tool
set. Your tool set's Work Area Pointer is a four-byte value you can set with
SetWAP and get with GetWAP. The WAP value is already loaded into the Y and A
registers every time one of your tool set's functions gets control. The
traditional use for the WAP is to keep track of an area of memory owned by
your tool set.
If you do use the WAP in a conventional way, your xxxStatus function should
return TRUE if the WAP is nonzero; your xxxStartUp function should set the
WAP to a non-zero value pointing to some memory space you own (provided by
the caller, or allocated with NewHandle using a memory ID provided by the
caller); and your xxxShutDown function should set the WAP back to zero.
Since the X register contains the tool set and function number when one of
your functions gets control, it is not necessary for a tool set to be written
to be used as a predetermined user tool set number. At execution time, your
tool set can compute the proper error codes and values to send to GetWAP and
SetWAP.
Note: At the bottom of page A-8 of the Apple IIgs Toolbox Reference,
Volume 2, "lda #$90" should read "lda #$8100" for version 1.0 prototype. On
page A-10, the figure should show two RTL addresses (6 bytes) on the stack.
ToStrip and ToBusyStrip Vectors
These two vectors are for tool sets to jump to when a function exits.
ToBusyStrip $E10180
ToStrip $E10184
Inputs: X = error code (0 if no error)
Y = number of bytes of input parameters to strip
When your function is ready to exit, set up the registers and jump to
ToStrip. It shifts the six bytes of RTL addresses up by Y bytes, sets up A
and the carry flag appropriately, and returns to whomever called the tool.
If the system busy flag needs to be decremented, jump to ToBusyStrip instead
of ToStrip.
How Can I Load My Tool Set From Disk?
One way to load your tool set from disk is to use InitialLoad or
InitialLoad2, supplying a pathname like "9:MyToolset" (prefix 9 is initially
set to the directory containing your application; prefix 1 also works, but
its length is limited to 64 characters). You can then use SetTSPtr to tell
the Tool Locator about your tool set, as shown in Appendix A.
Note that SetTSPtr calls your xxxBootInit function. Even if there is no
useful work to be done at BootInit time, you still need to have a BootInit
function (function number 1) that returns $0000 in the Accumulator and the
carry flag cleared..
When you're done with your tool set, call UserShutdown on the memory ID
returned by InitialLoad, so the memory it's using is disposed of or made
purgeable. (You can shut it down and allow it to remain in memory in a
purgeable state; if you do this, you should try to revive your tool set with
Restart before you try InitialLoad or InitialLoad2.)
To allow several applications to share one copy of a user tool set file, you
may want to keep your user tool set in the user's *:System:Tools folder. To
avoid duplicate file names, leave the ToolXXX names for System tool sets, and
give your user tool set a descriptive name.
If your tool set is not found in the *:System:Tools folder, you can then
check the 9: folder. This way users do not need to burden their
*:System:Tools folders if few of their applications use a particular user
tool set or if space on their boot volume is limited.
When your application quits and calls TLShutDown, the system disconnects your
tool set from the user tool set TPT. If the UserShutDown is not followed
immediately by the TLShutDown, you may wish to use SetTSPtr to cleanly remove
your tool set from the system (set the tool set pointer so that it points at
a zero word).
Note: Because of the way the tool dispatcher transfers control to toolbox
functions, a function's entry point must not be at the first byte of a bank
($xx0000). This is normally not an issue, since it's common to put the
actual code right after the function pointer table, all in one load segment.
Just make sure no function begins at the first byte of a load segment, and
you're safe.
Further Reference
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o Apple IIgs Toolbox Reference, Volume 2
o GS/OS Reference