How can a DLL function return a "String value" to the calling program ?

[Skan]

Dear friends,

It has been only a few hours since I discovered xblite. I have been
browsing through the fantastic examples bundled with this wonderful
program.

While there are many examples for w32 console, I could find only one
example ( api.x ) that demonstrates creation of DLL. Can somebody
point me how can a DLL function can return a "String value" to the
calling program ?


FUNCTION IntToBin ( num )
EXTERNAL STRING nu$
nu$ = BIN$(num)
RETURN nu$
END FUNCTION

Please help.

Best Regards, :)

[D.]

> Can somebody point me how can a DLL function can return
> a "String value" to the calling program ?
>
>
> FUNCTION IntToBin ( num )

> EXTERNAL STRING nu$ ' <<< you don't need this

> nu$ = BIN$(num)
> RETURN nu$
> END FUNCTION

Try defining the function with $ suffix, eg, :

FUNCTION IntToBin$ (num)

or, define the function return type as STRING, eg :

FUNCTION STRING IntToBin (num)

Don't forget to change the function declaration in the
PROLOG as well.

You don't need the line EXTERNAL STRING nu$.

ciao,
D.

[Skan]

Many thanks D., :D

[Skan]

Dear D.

I have one more problem.. The following is the whole program:

PROGRAM "skan"
VERSION "0.0090"

EXPORT
DECLARE FUNCTION STRING toHex ( num )
DECLARE FUNCTION STRING AllTrim ( istr$ )
END EXPORT

FUNCTION STRING toHex ( num )
nu$ = HEX$( num )
RETURN nu$
END FUNCTION

FUNCTION STRING AllTrim ( istr$ )
nist$ = TRIM$( istr$ )
RETURN nist$
END FUNCTION
END PROGRAM

I guess I am missing something very simple. toHex() works fine but
AllTrim() results in "Access Violation" from the calling program.

Please help.

Best Regards. :)

[D.]

I built your library. Both functions worked as expected.

How are you calling AllTrim? Can you provide your test code?

Also, you can shorten the above functions by using

RETURN HEX$ (num)

or

RETURN TRIM$ (istr$)

ciao,
D.

[Skan]

Dear D.

I am testing my DLL with AutoHotkey Scripting Language and the
following is the script:

Str0 := DllCall( "user32.dll\CharUpperA", Str,"skan", Str )
MsgBox, % Str0 "`nerrorlevel: " errorLevel

DllCall( "LoadLibrary", Str,"C:\xblite\Skan\skan.dll" )

Str1 := DllCall( "skan.dll\ToHex", UInt,1024, Str )
MsgBox, % Str1 "`nerrorlevel: " errorLevel

Str2 := Dllcall( "skan.dll\AllTrim", Str," sdsads ", Str )
MsgBox, % Str2 "`nerrorlevel: " errorLevel

If you like to test the above script:
No need to install AutoHotkey. Save the above script to a text file
( with .AHK extension ) and pass it as a parameter to AutoHotkey.exe
( which can be extracted from http://www.autohotkey.com/download/AutoHotkey.zip
).
AutoHotkey is an Interpreter and works similar to WSH

The call to User32.dll - CharUpperA() is to demonstrate that I am
using the parameters right. I am passing the string by value and
recieve the return value as String

Please help.

> Also, you can shorten the above functions by using
>
> RETURN HEX$ (num)
>
> or
>
> RETURN TRIM$ (istr$)

Thanks!

Best Regards.

[Skan]

.. and one more thing

the following works and return "Skan"

FUNCTION STRING AllTrim ( istr$ )

RETURN TRIM$ ( " Skan " )
END FUNCTION


.. but this returns only null

FUNCTION STRING AllTrim ( istr$ )

RETURN TRIM$ ( istr$ )
END FUNCTION

[D.]

Ok, your use of autohotkey explains the problems you
are seeing.

Two important things:

1. Autohotkey expects to pass all string parameters by address.

So we need to modify the xblite function to accept a string address:

DECLARE FUNCTION STRING AllTrim ( saddr )

FUNCTION STRING AllTrim (saddr)
nist$ = CSTRING$ (saddr) ' convert address into string
RETURN TRIM$ (nist$) ' return nist$
END FUNCTION

2. When calling an external function from autohotkey which expects
a string returned, you need to allocate enough space for the returned
string by calling VarSetCapacity:

VarSetCapacity(Str2, 6)

Str2 := Dllcall( "skan.dll\AllTrim", Str, " sdsads ", Str)
MsgBox, % Str2 "`nerrorlevel: " errorLevel

ciao,
D.

[Skan]

Dear D., :)

That was it, though the VarSetCapacity() is not needed.
You have been very kind and have saved me many hours of newbie
frustation.

Many thanks and best regards.