DLL Help

  
// this loads the named DLL file into memory


HMODULE LoadLibrary(LPCTSTR *szLibrary);

// you then need to load each DLL export you want to use, you can load it by name or ''ordinal'' - 

// basically a function number, a 16 bit number, but you''ll need to cast it as a LPCTSTR (2nd arg)


FARPROC GetProcAddress(HMODULE hModule, LPCTSTR lpProcName);

// when you''ve finished using the DLL unload it with this:


BOOL FreeLibrary(HMODULE hModule);
  

  
// this creates a variable type that will operate as a pointer to the MessageBox Funcntion

typedef int (*PFNMSGBOX)(HWND, LPCTSTR, LPCTSTR, UINT);

// a variable can be declared, eg:

PFNMSGBOX  pfnMessageBox = NULL; // good idea to init it to a known value

HMODULE hDll = NULL;

// example function to load the user32.dll file & the function


bool LoadDll(void) {
 
 // load the library & return false on failure

 hDll = LoadLibrary("user32.dll");
 if(!hDll) return false;

 // get the proceedure address, note the type cast on the

 // returned value & also that windows has 2 varients of many string functions

 // suffixed with W and A for Widestring & Ascii strings

 
 pfnMessageBox = (PFNMSGBOX) GetProcAddress(hDll, "MessageBoxA");

 if( pfnMessageBox ) return true;

 // loaded badly, clear up

 FreeLibrary(hDll);
 hDll = NULL;
}

// example of using the function


void ShowMessageBox(void)
{
 if(pfnMessageBox) pfnMessageBox(NULL, "Dynamically loaded from USER32.DLL", "Hello",MB_OK);
}