giobradja
23rd February 2007 08:20 UTC

System::Call problem
Hello everyone.

I'm using the System::Call to call a function from a DLL and get back some output. I've succesfully get back ulong values but I can't get back a byte array. the syntax i use is:

System::Call "${ROCKDLLNAME}::Rockey(i,*i,*l,*l,*i,*i,*i,*i,*t)i (${RY_READ},r4,,,0,24,,,r5) .r0"

The prototype of the function that is called is

WORD Rockey(WORD function, WORD* handle, DWORD* lp1, DWORD* lp2, WORD* p1, WORD* p2, WORD* p3, WORD* p4, BYTE* buffer);

In the past I have done the same thing with success when calling an other DLL. The only difference is that in that case buffer was declared as "ULONG* buffer". Has this enything to do?

Any help will be appreciated!

Thanx
Giorgio

kichik
23rd February 2007 11:58 UTC

You shouldn't use `*t` for `BYTE*`. That's for `char **`. If it's really a byte array and not a string, you should allocate a buffer and pass its address as `i`.

giobradja
23rd February 2007 14:03 UTC

The buffer IS actually a string. I store information in it and I can get them back from PowerBuilder (RAD) where the function prototype is declared as character array.
Anyway if I allocate a buffer and pass its address as i, how can I convert it to a string? It is sure that the contents of the buffer are 24 numbers, something like '0126582254...'.

Thanx for your time.

kichik
23rd February 2007 14:13 UTC

If it's a string, simply use `t .r5` instead of `*t r5`. It's a pointer to a buffer, not a pointer to a pointer and you want the output and not the input.

giobradja
23rd February 2007 14:29 UTC

You are a MAJOR player. After 24 hours of pain, finally there is a spark in the dark.

Thanx for your help.