[-Fabez-]

Sorry, I should have added more information. I initially asked how to create .Dll's as they seemed a good way to modularize my code, making it easier to handle, and because most programs seem to use them. After completing the initial examples given to me by Mt2002, I started looking at what else .Dll's could do. My research indicated that they could be used for global hooks, which I though would be usefull for a global hotkey program, however the documentation is unclear as to which functions go where, and my code does not produce any errors or give any output. Below is the code for the program.

#include <windows.h>
#include <iostream>
#include <fstream>

using namespace std;


int main(){
    HOOKPROC KeyProc;
    HINSTANCE MyDll;
    HHOOK MyHook;

    MyDll = LoadLibrary("GlobalHotkey.dll");
    if (MyDll == NULL){
        cout << "MyDll: Loading Failed" << endl;
        return -1;
    }

    KeyProc = (HOOKPROC)GetProcAddress(MyDll, "KeyboardProc@12");
    if (KeyProc == NULL){
        cout << "KeyProc: Loading Failed" << endl;
        return -1;
    }

    MyHook = SetWindowsHookEx(WH_KEYBOARD,KeyProc,MyDll,0);
    if (MyHook == NULL){
        cout << "KeyProc: Loading Failed" << endl;
        return -1;
    }

    cout << "MyDll is loaded at: " << MyDll << endl;
    cout << "KeyProc is loaded at: " << KeyProc << endl;
    cout << "MyHook: " << MyHook << endl;

    cin.ignore();
}

And this is the code for my .Dll

#include <windows.h>
#include <iostream>
#include <fstream>

using namespace std;

fstream KeyInfo;

extern "C" __declspec(dllexport) void MainFunction(){
    cout << "Dll: Main Function" << endl;
}

extern "C" __declspec(dllexport) LRESULT CALLBACK KeyboardProc(int code,WPARAM wParam,LPARAM lParam){

    cout << "Code: " << code << endl;
    cout << "WPARAM: " << wParam << endl;
    cout << "LPARAM: " << lParam << endl;

    KeyInfo.open ("C:\\KeyInfo.txt", fstream::in | fstream::out | fstream::app);
    KeyInfo << "Code: " << code << endl;
    KeyInfo << "WPARAM: " << wParam << endl;
    KeyInfo << "LPARAM: " << lParam << endl;

    return CallNextHookEx(0, code, wParam, lParam);
}

As stated before, the above code does not produce any errors, neither does it produce any output. Can you see anything wrong with the code, or where the functions are ? Thanks -Fabez-

[mt2002]

I started looking at what else .Dll's could do. My research indicated that they could be used for global hooks

.
They can be, yes. The most common method that I have seen and used them for is an extension to the original program. ie, kind of like a plugin library to extend the functionaily of the original program.

To make things simple for now, lets focus on you being able to call the MainFunction function from the DLL. You do not have to use the symbolic name for the function. So, to get the address of MainFunction, just use GetProcAddress (MyDll, "MainFunction");

Please let me know if it gets called.

[-Fabez-]

Using the following code, the MainFunction executed without any errors.

FARPROC Something = GetProcAddress(MyDll, "MainFunction");
if (Something == NULL){
    cout << "MainFunction: Loading Failed" << endl;
    return -1;
}
(Something)();

Just a quick question though, what does FARPROC stand for ?

[mt2002]

Just a quick question though, what does FARPROC stand for ?

typedef int (FAR WINAPI *FARPROC)()

It identifies a function pointer of the form int (_stdcall *FARPROC) () (FAR is defined as either nothing or the far keyword on some older compiliers that support far (32 bit linear) pointers, and WINAPI is defined as _stdcall calling convention in most cases.)

In your code, it creates a function pointer, something that points to the function from within the loaded DLL to be called.

k, we have verified that MainFunction right now works? If so, we can focus on the other routine. I am still uncertain if that will work, however, as you are using a C++ calling convention but exporting it as a C routine. I'll have to double check that one...

[burnthepc]

Just wanted to say, great post mt2002!

I've wondered how it's done

[-Fabez-]

Agreed, it certainly helped

[-Fabez-]

I have yet another question for you If I have the string containing a function name, is it possible to execute the function contained in the string ? Also how do I check if I have read or write permissions to a certain area, such as the users My Documents area to create a settings folder and to create and output folder for the screenshots.

[mt2002]

Originally Posted by -Fabez-

I have yet another question for you If I have the string containing a function name, is it possible to execute the function contained in the string ?

You can only indirectly call a function by either i) import/export tables or ii) directly via function pointers (GetProcAddress does this by a function name lookup via the tables) If the only information that you have is the function name, then no you cannot do it directly unless you use one of the above methods.

Also how do I check if I have read or write permissions to a certain area, such as the users My Documents area to create a settings folder and to create and output folder for the screenshots.

This one I am not to sure of...Im sure there is something in the Win32 API for it though. Ill post it if I find anything...