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Loading DLLs made easy

, 1 May 2001 263.1K 109
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How to load dynamic link librarys the easiest way instead of the long way

Introduction

Have you ever got tired of loading Dynamic Link Libraries the long way, with the usual steps LoadLibrary, and GetProcAddress, then you have to check for each function address if they are NULL, and don't mention about casting the function pointer and hard ways that make your brain strain. And wish there was an easier way to get around things? Well this will just do that in a way and is about the easiest way I know of actually

//GetProcAddresses
//Argument1: hLibrary - Handle for the Library Loaded
//Argument2: lpszLibrary - Library to Load
//Argument3: nCount - Number of functions to load
//[Arguments Format]
//Argument4: Function Address - Function address we want to store
//Argument5: Function Name -  Name of the function we want
//[Repeat Format]
//
//Returns: FALSE if failure
//Returns: TRUE if successful
BOOL GetProcAddresses( HINSTANCE *hLibrary, 
    LPCSTR lpszLibrary, INT nCount, ... )
{
    va_list va;
    va_start( va, nCount );

    if ( ( *hLibrary = LoadLibrary( lpszLibrary ) ) 
        != NULL )
    {
        FARPROC * lpfProcFunction = NULL;
        LPSTR lpszFuncName = NULL;
        INT nIdxCount = 0;
        while ( nIdxCount < nCount )
        {
            lpfProcFunction = va_arg( va, FARPROC* );
            lpszFuncName = va_arg( va, LPSTR );
            if ( ( *lpfProcFunction = 
                GetProcAddress( *hLibrary, 
                    lpszFuncName ) ) == NULL )
            {
                lpfProcFunction = NULL;
                return FALSE;
            }
            nIdxCount++;
        }
    }
    else
    {
        va_end( va );
        return FALSE;
    }
    va_end( va );
    return TRUE;
}

So since we now have the main core to this article, lets now look at how to use this with a short sample that was compiled as a Windows console application.

#include <windows.h>

typedef int ( WINAPI *MESSAGEBOX ) 
    ( HWND , LPCSTR, LPCSTR, DWORD );
typedef int ( WINAPI *MESSAGEBOXEX ) 
    ( HWND , LPCSTR, LPCSTR, DWORD , WORD );

void main(void)
{
    MESSAGEBOX lpfMsgBox = NULL;
    MESSAGEBOXEX lpfMsgBoxEx = NULL;
    HINSTANCE hLib;
    if(GetProcAddresses( &hLib, "User32.dll", 2,
        &lpfMsgBox, "MessageBoxA",
        &lpfMsgBoxEx, "MessageBoxExA" ) )
    {
        lpfMsgBox( 0, "Test1", "Test1", MB_OK );
        lpfMsgBoxEx( 0, "Test2", "Test2", MB_OK, 
            MAKELANGID( LANG_ENGLISH, SUBLANG_ENGLISH_US ) );
    }
    if ( hLib != NULL )
        FreeLibrary( hLib );
}

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Shoalin Panda
United States United States
No Biography provided

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Comments and Discussions

 
Questionwhy else? Pin
uur4-Oct-10 0:50
memberuur4-Oct-10 0:50 
AnswerRe: why else? Pin
Member 822898024-Jan-12 12:42
memberMember 822898024-Jan-12 12:42 
GeneralRe: why else? Pin
uur24-Jan-12 21:17
memberuur24-Jan-12 21:17 

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