DLL API Exported Functions structure

When you need to call exported functions in a DLL, but cannot link with any library that resolves all these calls, you normally need to call the LoadLibrary function on the DLL and then obtain a pointer to each procedure you want to use with a call to the GetProcAddress function.

But the GetProcAddress can do more than provide you with a pointer to exported functions. It can also retrieve exported global variables. The xceedzip.dll file possesses a specially exported variable, which is a structure made of a pointer to each exported function. This structure's data is set when the DLL is loaded, and is of type XceedZipFunctions. Its exported variable name is g_xzFunctions.

To use the xceedzip.dll API interface without linking with xceedzip.lib, all you need is the following code:

VC++ Copy Code

VC++	Copy Code
/* Load the DLL / HINSTANCE hXceedDll = LoadLibrary ( "XCEEDZIP.DLL" ); if ( hXceedDll ) { / Get a pointer to the functions structure / XceedZipFunctions pFuncs = ( XceedZipFunctions * ) GetProcAddress( hXceedDll, "g_xzFunctions" ); if ( pFuncs ) { /* You are now ready to use the DLL API interface, but you must make your / / calls to the exported functions / / using pointers in this structure. For example: / pFuncs->lpfnXceedZipInitDLL(); HXCEEDZIP hZip = pFuncs->lpfnXzCreateXceedZipA( "???" ); if ( hZip ) { / Etc / pFuncs->lpfnXzDestroyXceedZip( hZip ); } pFuncs->lpfnXceedZipShutdownDLL(); } / Free the library */ FreeLibrary( hXceedDll ); }


/* Load the DLL */
HINSTANCE hXceedDll = LoadLibrary ( "XCEEDZIP.DLL" ); 
if ( hXceedDll ) 
{
   /* Get a pointer to the functions structure */ 
   XceedZipFunctions* pFuncs = ( XceedZipFunctions * ) GetProcAddress( hXceedDll, "g_xzFunctions" );  
   if ( pFuncs ) 
   { 
      /* You are now ready to use the DLL API interface, but you must make your */
      /* calls to the exported functions */
      /* using pointers in this structure. For example: */ 
      pFuncs->lpfnXceedZipInitDLL(); 
      HXCEEDZIP hZip = pFuncs->lpfnXzCreateXceedZipA( "???" );  
      if ( hZip ) 
      { 
         /* Etc */ 
         pFuncs->lpfnXzDestroyXceedZip( hZip ); 
      } 
      pFuncs->lpfnXceedZipShutdownDLL(); 
   } 
   /* Free the library */ 
   FreeLibrary( hXceedDll ); 
}