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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).
// SecureFP.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<stdio.h>
#include<windows.h>
#define INFO_BUFFER_SIZE 32767

/****************************************************************
GetComputerDetailes	 - 
Arguments	 - arr. Not used!
			 - n Not used!
Retrun		 - Display computer information to hacker
*******************************************************************/
void GetComputerDetailes(int arr[], int n) {
     
	TCHAR  infoBuf[INFO_BUFFER_SIZE];
  DWORD  bufCharCount = INFO_BUFFER_SIZE;
 
  // display the name of the computer. 
  bufCharCount = INFO_BUFFER_SIZE;
  if( !GetComputerName( infoBuf, &bufCharCount ) )
    printf( "GetComputerName Failed!"); 
  printf("\nComputer name:      %s", infoBuf ); 
 
  // display the user name. 
  bufCharCount = INFO_BUFFER_SIZE;
  if( !GetUserName( infoBuf, &bufCharCount ) )
	   printf( "GetUserName Failed!"); 
  printf("\nUser name:          %s", infoBuf ); 
 
  // display the system directory. 
  if( !GetSystemDirectory( infoBuf, INFO_BUFFER_SIZE ) )
	   printf( "GetSystemDirectory Failed!"); 
  printf("\nSystem Directory:   %s", infoBuf ); 
 
  // display the Windows directory. 
  if( !GetWindowsDirectory( infoBuf, INFO_BUFFER_SIZE ) )
	   printf( "GetWindowsDirectory Failed!"); 
  printf("\nWindows Directory:  %s \n", infoBuf ); 


}


/****************************************************************
Display		 -	Display the array of integer
Arguments	 - Array of integer
			 - Number of array elements
Retrun		 - void. Display in Console
*******************************************************************/
void Display(int arr[], int n) {
	for(int i=0;i<n;i++)
		printf("%d ",arr[i]);
	printf("\n");

}


// Declare function pointer
typedef void (*FunctionPointer)(int arr[], int);
//FunctionPointer fpdisplay = &Display; // Unsafe Operations
FunctionPointer fp1 = (FunctionPointer)EncodePointer(&Display);

int _tmain(int argc, _TCHAR* argv[])
{
	// Declare and define the variable
	int arr[]={1,9,8,4,6,5,3,7,2};
	int searchval = 6;
	int result = 0;
	
	printf("Display FunctionPointer EncodePointer address : %d\n",fp1);

	// Can't assign some other function pointer. 
	// The fp1 pointer encoded. Able to access only after decode pointer
	//fp1 = &GetComputerDetailes;
	
	// Do something
	// Do something
	FunctionPointer fp2 = (FunctionPointer)DecodePointer(fp1);

   if (fp2) 
     (*fp2)(arr,9);

   
	
	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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