Function Pointers, OCX, Demo

[Rick Fleming]

Hello,

I am interested in Purchasing PB/DLL, however there is one thing
that I haven't found listed in the features, which is what I am
looking for (among all the other goodies it already has )...

They are function pointers...

Example is:

Dim fpProc as (Whatever it would be, FPointer Of (Declared Function), etc...)
Dim lPointer as Long

lPointer = some function's address

fpProc = lPointer

then be able to call fpProc directly

result = fpProc(arg1, arg2, etc...)


This is a necessity for me, Microsoft Visual Basic doesn't have
this all they have is VarPtr and Address Of, with no way to do
this directly... The basis for this is to call a LoadLibrary
at runtime, and use functions from the library at runtime,
without having to directly know the dll name...

And while I know C, I hate it's syntax (it's only my
opinion) and would rather not use it to do this...
All my programs are C-Free hehe...

I looked at the Callback stuff with PB/DLL, however there isn't
any detailed description on this website about it...

Also, is it possible to create OCX (I know it's 'basically' just
a DLL, but...) controls with this?

Also, is there a Demo of this or anything? I don't like to
purchase programming products without at least demoing it first
to see if I'm comfortable with it ...

Thanks,

Rick Fleming

[Edwin Knoppert]

You can almost do anything if it's on an API level.
The pointers you described are certainly easy.
Forget copymemory in callbacks etc..

Using COM is hard but can be done.
If you can succesfully build OCX's, i don't have an example..

Jump to the 3th party section and look for the 'jazzage'.
He does all the COM stuff for PB.
VB is MUCH more easy to do such things, so i will not encourage COM in PB at the moment.


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[email protected]

[Michael Mattias]

Function pointers are obtained with the CODEPTR intrinsic if the function is located in the current source code module or using GetProcAddress if the function is in a loaded DLL.

You can call functions by pointer (address) using the CALL DWORD USING...TO... syntax.

MCM


[This message has been edited by Michael Mattias (edited September 09, 2000).]

[Rick Fleming]

Sweet...

In Visual Basic you can GetProcAddress (loadlibrary) or
Address Of (module proc) to get the function pointer,
but you can't do anything with it but pass it around...

Now only if there's a demo so I can see all the features
for myself then I will probably buy it...

Thanks,

Rick Fleming

[Lance Edmonds]

There is no demo available at this time, be we do offer a 30-day money-back guarantee on all products (except when delivered electronically). The following pages may give you more ideas about the capability of PowerBASIC:
http://www.powerbasic.com/products/pbdll32
https://www.powerbasic.com/shop
http://www.powerbasic.com/support/technote/basic.asp
http://www.powerbasic.com/products/compiler.asp

Thanks for asking!

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Philippe Monteil]

<<
Jump to the 3th party section and look for the 'jazzage'.
He does all the COM stuff for PB.
VB is MUCH more easy to do such things, so i will not encourage COM in PB at the moment.
>>
That is right, VB is the best development for ActiveX programming at the moment.
Our product do the best that can be done with the languages it supports.
For example, our addons for Xbase++ make that language almost 'compatible'
with VB for ActiveX client programming.

A few extensions to PB/DLL would make it much more COM/ActiveX aware,
but given the amount of misleading information spread in the PB
community about those 'bloated' technologies, I don't think that
the situation will change in a foresable future, even though announcements
were made about 18 months ago that future versions would support COM:
we will see what happens.

Philippe Monteil
[email protected]
JAZZAge Software



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[Steve Hutchesson]

Rick,

=======================================
lPointer = some function's address
fpProc = lPointer
then be able to call fpProc directly
result = fpProc(arg1, arg2, etc...)
=======================================

The things you require here are straight forward capacity in PowerBASIC.

fpProc = lPointer

is done with,

fpProc = CodePtr(FunctionName) ' get address of function

There is a high level syntax for calling a function by its address,

CALL DWORD var USING ....

The addressing techniques in PowerBASIC are powerful enough to do most
things,

address = StrPtr(basicString$) ' string addresses
address = VarPtr(variable) ' addresses of variables, UDTs etc...
address = CodePtr(Function/Sub) ' procedure address

PowerBASIC has a data type of PTR so you can pass an address and get its
actual value by using the POINTER operator [ @var ].

If you have a background in VB, the performance enhancing capacity in
PowerBASIC is very good when designing DLLs that must perform well. With
your background in C, PowerBASIC gives you the C style low level capacity
but with basic syntax.

If high speed compiler performance is still not good enough for what you
have to do, PowerBASIC supports a very good inline assembler so you can
target speed critical code.

The COM interface is another matter, it is currently a proprietry and
complex interface that is difficult to implement in low level code. The
current version of PowerBASIC does not provide a high level interface for
COM objects.

If your main experience in basic is VB, you will enjoy the sheer grunt of
PowerBASIC, it allows you to write code that is close to the speed of
assembler in normal basic syntax and if that is not fast enough for you,
you can write it in assembler in PowerBASIC. The API functions are
available as normal functions without having to mess around with extra
declarations.

Good luck with your choice and I hope you can get the swing of PowerBASIC.

Regards,

[email protected]


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