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Secure Function Pointer and Callbacks in Windows Programming

, 4 May 2011 CPOL
This article explains the usage of function pointer and callback in Windows application programming Interface (API).
// Win32DLLClient.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<windows.h>

typedef int (__cdecl *MYPROC)(); 
typedef int (__cdecl *SORTDISPLAYPROC)(int arr[],int); 
typedef int (__cdecl *SEARCHPROC)(int arr[],int,int,int); 

int _tmain(int argc, _TCHAR* argv[])
{
	int arr[]={11,99,88,44,66,55,33,77,22,10,9,6};
	int s = 12;
	int svalue = 33;

	int sResult = 0;

	HINSTANCE hinstLib; 
    MYPROC ProcAdd; 
	SORTDISPLAYPROC ProcSort, ProcDisplay;
	SEARCHPROC lSearch, bSearch;
    BOOL fFreeResult;
 
    // Get a handle to the DLL module.
     hinstLib = LoadLibrary(TEXT("Win32DLL")); 
 

	 // If the handle is valid, try to get the function address.
     if (hinstLib != NULL) 
    { 

        ProcAdd = (MYPROC) GetProcAddress(hinstLib, "InitBubbleSort"); 
		ProcDisplay = (SORTDISPLAYPROC) GetProcAddress(hinstLib, "Display"); 
		ProcSort = (SORTDISPLAYPROC) GetProcAddress(hinstLib, "BubbleSort"); 

		lSearch = (SEARCHPROC) GetProcAddress(hinstLib, "LinearSearch"); 
		bSearch = (SEARCHPROC) GetProcAddress(hinstLib, "BinarySearch"); 


		int *ipArr = (int*) GetProcAddress(hinstLib, "arr");
		int *Size = (int*) GetProcAddress(hinstLib, "nSize");
		int *sv = (int*) GetProcAddress(hinstLib, "searchval");

		ipArr=arr;
		Size = &s;
		sv = &svalue;

        // If the function address is valid, call the function.
         if (NULL != ProcAdd){
            (ProcAdd)(); 
        }


		printf("\nDisply the array of elements before BubbleSort \n");
		 // If the function address is valid, call the function.
         if (NULL != ProcDisplay){
            (ProcDisplay)(arr,s); 
        }

		
		 // If the function address is valid, call the function.
         if (NULL != ProcSort){
            (ProcSort)(arr,s); 
        }


		 printf("\nDisply the array of elements After BubbleSort \n");
		   // If the function address is valid, call the function.
         if (NULL != ProcDisplay){
            (ProcDisplay)(arr,s); 
        }

	  printf("\nSearch using LinearSearch \n");
		if (NULL != lSearch){
            sResult = (lSearch)(arr,svalue,0,s); 
        }
		
		if(sResult == -1)
			printf("Search element not found!\n");
		else
			printf("Element %d found in %d position!\n", svalue,sResult);

		

        // Free the DLL module.
         fFreeResult = FreeLibrary(hinstLib); 
    } 
 
	return 0;
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

R.selvam
Software Developer (Senior)
India India
Selvam has worked on several technologies like Core Java, VC++, MFC, Windows API and Weblogic server. He takes a lot of interest in reading technical articles and enjoy writing them too. He has been awarded as a Microsoft Community Star in 2004, MVP in 2005-06, SCJP 5.0 in 2009, Microsoft Community Contributor(MCC) 2011.

Github : https://github.com/selvamselvam
Web site: http://www.careerdrill.com

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