הנה הקוד :
הקוד נכתב בתכנות ++C קונבנציונאלי : לקוח מתוך
קוד גורו (קישור)
Library Source: DLL_Callback.h #ifndef _DLL_CALLBACK_ #define _DLL_CALLBACK_ // All declarations which are needed resides in "windows.h" #include <windows.h> // Placeholder for function-export macros #define LIBRARY_EXPORT __declspec(dllexport) __cdecl // Function Declarations for Static Export extern "C" { long LIBRARY_EXPORT GetDBData(void); long LIBRARY_EXPORT SetCallbackProcAddr(long); } // Function Declaration for Callback function // of the Calling App typedef void (* TDataReadNotify)(long); #endif DLL_Callback.cpp // Comment out the line below, if you want STDCALL // for the VB-Example. #define CDECL_CALLING_CONVENTION #ifdef CDECL_CALLING_CONVENTION #include "DLL_Callback.h" #else #include "DLL_Callback_StdCall.h" #endif // Vars for Imported Functions TDataReadNotify DataReadNotify; HANDLE hThread; DWORD pThreadId; DWORD DoTheWork(LPVOID lpParameter) { long lDBData; // Doing stuff that takes 5 sec., i.e. reading DB Data. // ... Sleep(5000); lDBData = 123; // ... // Notify the caller app via CB-function. if (DataReadNotify != NULL) DataReadNotify(lDBData); return 0; }; long LIBRARY_EXPORT GetDBData(void) { long lProcAdr; // Get ProcAddress for Thread-Func and create/run the thread. lProcAdr = (long)(&DoTheWork); hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)lProcAdr, NULL, 0, &pThreadId); // Return to caller app. return 0; }; long LIBRARY_EXPORT SetCallbackProcAddr(long lProcAddress) { long Result = 0; // Set the Proc-Address for the notify-func of // the caller app. DataReadNotify = (TDataReadNotify)lProcAddress; if (DataReadNotify != NULL) Result = 1; return Result; }; C++ Sample Source: Callback_Sample.h #ifndef _CALLBACK_SAMPLE_ #define _CALLBACK_SAMPLE_ // All declarations which are needed resides // in "windows.h" #include <windows.h> // Placeholder for function-import macros #define LIBRARY_IMPORT __declspec(dllimport) __cdecl // Function Declarations for Static // Import (aka "Implicied Linking") // This requires the Output-LIB of the DLL_Callback Library. extern "C" { int LIBRARY_IMPORT GetDBData(void); int LIBRARY_IMPORT SetCallbackProcAddr(long); } #endif Callback_Sample.cpp #include "Callback_Sample.h" int iWait = 1; char sDBData[11]; char sMessage[64]; void DataReadNotify(long lDBData) { _ltoa(lDBData, sDBData, 10); strcpy(sMessage, "DBData from DLL is: "); strcat(sMessage, sDBData); ::MessageBox(0, sMessage, "Sample App", MB_OK + MB_ICONINFORMATION); // Set Wait to 0, so that WinMain can go further. iWait = 0; }; int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { long lProcAdr; // Get Address-Pointer of the CB-function lProcAdr = (long)(&DataReadNotify); // Send Address-Pointer Information to the DLL SetCallbackProcAddr(lProcAdr); // Call the function of the DLL, which reads DB-Info // or something else. GetDBData(); // Do other work while the DLL reads the DBData // ... // I.e.: Show a splash-screen, write values to an // INI-File or whatever // ... // if the DLL-function is still busy, loop until // the DLL notifies via the CALLBACK-function "DataReadNotify()". while (iWait) {}; return 0; };
