Thread: Calling inpout32.dll for port control

You also forgot to define function. Your code also tries to execute function, whether it has been properly initialised or not. Beyond that, this is not a C++ question. It is (mostly) specific to the dll you are using, and windows.

If you are using inpout32.dll from logix4u.net .....

1) The function for out32 is named "Out32", not "out32". These things are case sensitive.

2) The return value from GetProcAddress() is a void pointer. In C++, there is no implicit conversion from a void pointer to other pointer types.

3) Inpout32.dll installs a kernel mode driver (usually as a result of calling one of the functions exported by the DLL). This means, the first time you use it, you need to be logged in to an account with administrative privileges (as that is what is required to install a kernel mode driver). If you don't do that, the dll cannot function. Once you have run it (at least) once from an account with administrative privileges, the dll (and programs using it) can be run from an account without admin privileges (unless your programs need admin privileges for other reasons).

4) When you have finished using the functions in the dll, it is usually a good idea to call FreeLibrary().

And Also , I am having problem compiling loadlibrary codes with dev c++. After you said that my problem is about windows and specific dll, I think that the compiler might be having problems recognizing LoadLibrary and Getp... functions. Could this be true? It doesnt even recognize HINSTANCE. Maybe I need additional libraries .

LoadLibrary() is a win32 function, so most compilers targeting windows will be able to use it. You need to include appropriate declarations (typically via a header file like <windows.h>, as suggested by tabstop) though.

When getting a pointer via GetProcAddress(oz, "Out32"), you need to convert the return value into a function pointer of the appropriate type (IIRC a stdcall function that accepts an argument of type short, and returns a short). Once you have such a pointer, you can use it until you call FreeLibrary() to release the DLL instance.

If my description above seems like gibberish to you, then ...... If you are still in the early stages of learning C++, you will probably want to do something a bit more elementary than loading dll functions. Loading dll functions is not difficult, but it does involve some specific techniques in C++. If you don't understand C++, it is really hard to understand how to work with dlls, using C++ code.

Thanks again. No I did not think feel that it was gibberish to me. Although I dont claim to be someone about c++. Anyway let's see If I can see the logic correctly then. I will create a stdcall function to be able to use Out32 with the new pointer function.

I will propose this code :

Code:

   HINSTANCE oz;  
  oz=LoadLibrary("inpout32.dll");

typedef short (_stdcall function)(char *a,short b);
function *func;
func=GetProcAddress(oz,"Out32");

I understand types of variables and functions above brief. However I might have some issues about them. Thats why we ask questions right : ). So What I understood is ,
I define a function definer with stdcall which has the same arguments with the function I want to call from the dll file, so that I can replicate it ?

When I use this code :

Code:

#include <windows.h>
#include <iostream>
#define Data 0x378
using namespace std;

int main(int argc, char *argv[])
{
    HINSTANCE oz;
    oz=LoadLibrary("inpout32.dll");
    typedef int (_stdcall function)(char *a,int b);
function *func;
func=GetProcAddress(oz,"Out32");
    func(Data,254);
    system("PAUSE");
    return EXIT_SUCCESS;
}

I get this error :

C:\Dev-Cpp\main.cpp In function `int main(int, char**)':
C:\Dev-Cpp\main.cpp In function `int main(int, char**)':
C:\Dev-Cpp\main.cpp In function `int main(int, char**)':
C:\Dev-Cpp\main.cpp In function `int main(int, char**)':


Now I have done this and I dont get any errors. Although I cant try coz this is a laptop .

Code:

#include <windows.h>
#include <iostream>
#define Data 0x378
using namespace std;

int main(int argc, char *argv[])
{
    HINSTANCE oz;
    oz=LoadLibrary("inpout32.dll");
    typedef int (_stdcall function)();
function *func;
func=GetProcAddress(oz,"Out32");
    
    system("PAUSE");
    return EXIT_SUCCESS;
}

However the code I want to apply is this :

Code:

#include <windows.h>
#include <iostream>
#define Data 0x378
using namespace std;

int main(int argc, char *argv[])
{
    HINSTANCE oz;
    oz=LoadLibrary("inpout32.dll");
    typedef int (_stdcall function)();
function *func;
func=GetProcAddress(oz,"Out32");
    func(Data,254);
    system("PAUSE");
    return EXIT_SUCCESS;
}

Because I only want pin 2 to go high in parallel port. However I get this error :
C:\Dev-Cpp\main.cpp In function `int main(int, char**)':
C:\Dev-Cpp\main.cpp In function `int main(int, char**)':
C:\Dev-Cpp\main.cpp In function `int main(int, char**)':

I feel like my first code makes sense as Out32(PORTvariable,value) is like this. Giving the value to the port adress which is 0x378, basically a char pointer ?

5) inpout32.dll was only meant to be a transitionary hack to allow somewhat easier upgrades of ancient DOS programs to run on a protected mode operating system.
If you're writing new code, you should really be using the provided OS API's for accessing devices.

Based on the documentation for inpout32, the typedef for function needs to be

Code:

   typedef short _stdcall (*function)(short, short);

In C++, the types of all arguments and return value of a function are important (unlike the deprecated feature of C where, if you specify an empty argument list, the compiler allows an arbitrary set of arguments). Note that the first argument is passed by value as a short, not as a pointer.

It still pays to check the return values from LoadLibrary() and GetProcAddress() to see if they succeeded. If they fail, and you proceed anyway, the results are rather unpredictable.