Attempt to make dll wrapper, compiles no errors, but no success.

[aonyn]

Hi All,

Good news, I think I have a solution, my initial test works as expected.
I tried unicode, and that still did not work correctly.
The key was, UTF8 as the expected string format.
I am using a helper dll which I am writing in purebasic with pseudotypes.

Here is the code in purebasic.

Code (glbasic) Select Expand


Prototype pbp_xAppTitle(title.p-utf8)

ProcedureDLL xAppTitle(title.s)
If OpenLibrary(0, "xors3d.dll")
pb_xAppTitle.pbp_xAppTitle = GetFunction(0, "_xAppTitle@4")
pb_xAppTitle(title)
CloseLibrary(0)
EndIf
EndProcedure


Then I declare the helper dll this way in GLBasic.

Code (glbasic) Select Expand


DECLARE_ALIAS(glb_xAppTitle, "xors3d_TextConvert.dll", "xAppTitle", (const char*), void);


And finally I wrap it in a GLBasic function.

Code (glbasic) Select Expand


FUNCTION xAppTitle: title$
INLINE
if(glb_xAppTitle)
glb_xAppTitle(title_Str.c_str());
ENDINLINE
ENDFUNCTION


And EUREKA, it works!!!
Perhaps there is a more efficient way to do it, but for now, I am just happy to have solved the problem, and can continue wrapping xors3d. 

Thanks everyone for all your input.
Without the hints, I would probably still be stuck on step 1.

regards,
Dave

[aonyn]

Well, sending arguments to UTF8 is solved 
however, receiving the return back to ascii, not so much 

Well, I will figure it out, I at least know what the problem is. 
I will post back as I make progress.

Regards,
Dave

[aonyn]

Hi Ocean,

Thanks, the tip was very helpful.

Some built in method of communicating with different string encodings would be very useful indeed.

Purebasic handles it with pseudotypes, but from what I can tell, pseudotypes only work with parameters, not returns.
I think I will have to write a function to manually decode the return.

It appears that the best way to do this will involve allocating memory, and a lot of peak/poke.
This is all new territory for me, but I will certainly learn a lot doing it.

regards,
Dave

[aonyn]

Hi All,

EUREKA! It works, finally!   
I am passing strings both to and from the xors3d dll, with a bit of help from PureBasic.

Here is how I am passing strings to:

PureBasic DLL

Code (glbasic) Select Expand


Prototype pbp_xChangeDir(path.p-utf8)

ProcedureDLL xChangeDir(path.s)
If OpenLibrary(0, "xors3d.dll")
pb_xChangeDir.pbp_xChangeDir = GetFunction(0, "_xChangeDir@4")
CloseLibrary(0)
EndIf
EndProcedure


GLBasic Wrapper

Code (glbasic) Select Expand


INLINE
extern "C"
{
DECLARE_ALIAS(glb_xChangeDir, "xors3d_TextConvert.dll", "xChangeDir", (const char*), void);
}
ENDINLINE

FUNCTION xChangeDir: path$
INLINE
if(glb_xChangeDir)
glb_xChangeDir(path_Str.c_str());
ENDINLINE
ENDFUNCTION


And here is how I am receiving strings from:

PureBasic DLL

Code (glbasic) Select Expand


Prototype.i pbp_xCurrentDir()

ProcedureDLL.s xCurrentDir()
If OpenLibrary(0, "xors3d.dll")
pb_xCurrentDir.pbp_xCurrentDir = GetFunction(0, "_xCurrentDir@0")
outputString$ = PeekS(pb_xCurrentDir())
CloseLibrary(0)
ProcedureReturn outputString$
EndIf
EndProcedure


GLBasic Wrapper

Code (glbasic) Select Expand


INLINE
extern "C"
{
DECLARE_ALIAS(glb_xChangeDir, "xors3d_TextConvert.dll", "xChangeDir", (const char*), void);
}
ENDINLINE

FUNCTION xCurrentDir$:
LOCAL currentDir$
INLINE
if(glb_xCurrentDir)
currentDir_Str = glb_xCurrentDir();
ENDINLINE
RETURN currentDir$
ENDFUNCTION


Now the part which baffles me a bit is, the dll function is supposed to return a const char* according to the documentation.
However, to get the return, I had to receive the return as an integer, then used the function as the argument for the PeekS command.
This argument refers to a memory address, so it appears the function returns a memory address to the string, and I am grabbing the string from memory, and saving it to a variable which finally I am returning to GLBasic.

Is this expected behavior for a const char* return, or is the function acting differently than it is documented?

No matter though, because what I have done is now working as expected, and I am moving forward with the wrapper. I would still like to know why this works as it does though, to satisfy my own curiosity, so feedback is appreciated.

Thanks everyone for your help, and of course I will provide this wrapper to the community (including the PureBasic source code) when it is ready, although I can't promise I will be done quickly, as I am doing this for amusement, and have real world responsibilities which must come first. Also, I am still on the coding learning curve, so I can't say whether I will hit more stumbling blocks along the way, but I am sure I will have fun solving problems, and learning new skills.

regards,
Dave

[MrTAToad]

Dont forget that a const char pointer is a pointer to a memory address, so that would be more or less correct.

[aonyn]

Thanks MrTAToad,

Explained that way, it does make sense.

regards,
Dave