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Posted 25 Feb 2002


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CExpire - A C++ class that implements time and run based restrictions

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4.88/5 (37 votes)
28 Feb 2002Ms-PL3 min read
Shareware authors can use this class to limit the number of runs or the number of days that a program will function


This class is something I wrote to kill time. But by the time I finished it, I thought it might be pretty useful for shareware developers. It can be used to implement limited-number-of-runs and limited-time-period-only programs. Means if you want to allow only 25 runs, then this class will do that for you. Or if you want to restrict execution to 15 days from first run, this program will do that too. By the way, even if the user changes his system date back to the allowed-time-period after it has expired, he/she won't be able to run it. 


This is by no means a fool-proof protection scheme, but it serves its purpose at the intermediate level. And usually crackers manage to actually patch the executable to disable these checks or they manage to write key generators for your protected programs. But this class will save some time for you in the sense, it actually does what you would otherwise have to code on your own.

Protection Mechanism

It uses a combination of registry and file based protection mechanisms. You should be smart enough to pick the right innocent sounding registry keys and filenames to prevent the casual user from simply deleting a few odd keys and break the protection.

How to use the class.

You must instantiate an object of the class as early as possible. You may declare it as a global object if you would like to. In an SDK program, you might want to instantiate the class on the first line in your WinMain() and in an MFC program you might want to put it in your CWinApp derived class's InitInstance().

There are two ways in which you can use the class. In the first way you specify a specific number of times that the program can be run. In the second you set a number of days so that the program is active for that many days from the time of first execution. I shall demonstrate both methods below.

The constructor takes 4 parameters.

CExpire(const char*  ProgName,const char* KeyName, UINT Num, UINT ExpireType);

ProgName - This is a unique value that will be used to create the unique registry key for protection. It is a good idea to choose a GUID for this key. It will be placed in a location confusing enough for most of the average users of your program.

KeyName - This is again used as part of the unique registry key as well as in the generation of the special file. You can use a unique, but natural sounding name like MouseDrv98 or something that would not actually stand out.

Num - This is either the number of days from the date of execution or the total number of runs allowed. This value's interpretation depends upon the ExpireType parameter.

ExpireType - This can be one of two values as shown below

TYPERUNS - This implies run-count based protection
TYPEDAYS - This implies date-interval based protection

There are only three public functions that you'll need to call.

bool HasExpired();

It returns true if your program has expired and false if the user is still within his allowed limits.

UINT GetDaysLeft();

This returns the number of days left before the program expires. Use this if you have chosen ExpireType as TYPEDAYS

UINT GetRunsLeft();

This returns the number of runs left before the program expires. Use this if you have chosen ExpireType as TYPERUNS

Example Usage

SDK example

    CExpire Protector("{00000000-0000-0000-8888-00AA006D2EA4}",
            "This program has expired. Please buy the registered version.",
            "Fatal Error",0);
        char s[128];
        sprintf(s,"you have %d days left",Protector.GetDaysLeft());
    return 0;

MFC example

BOOL CTest_deleteApp::InitInstance()
    CExpire expire("JPEG-File-Viewer","FileStore",30,TYPERUNS);
        AfxMessageBox("This program will not run anymore...");
        return FALSE;
    char s[128];
    sprintf(s,"you have %d runs left",expire.GetRunsLeft());

#ifdef _AFXDLL

    CTest_deleteDlg dlg;
    m_pMainWnd = &dlg;
    int nResponse = dlg.DoModal();

    // Since the dialog has been closed, return FALSE so that we exit the
    //  application, rather than start the application's message pump.
    return FALSE;

Important Warning

DON'T choose a value for the KeyName parameter that might already define a file in the Windows System directory. It will be over-written. The best thing to do is to choose a filename and then add some numbers to the end like 32_32 or something natural sounding.

Thank you.


This article, along with any associated source code and files, is licensed under The Microsoft Public License (Ms-PL)


About the Author

Nish Nishant
United States United States
Nish Nishant is a Principal Software Architect based out of Columbus, Ohio. He has over 17 years of software industry experience in various roles including Lead Software Architect, Principal Software Engineer, and Product Manager. Nish was a Microsoft Visual C++ MVP between 2002 and 2015.

Nish is an industry acknowledged expert in the Microsoft technology stack. He authored C++/CLI in Action for Manning Publications in 2005, and had previously co-authored Extending MFC Applications with the .NET Framework for Addison Wesley in 2003. In addition, he has over 140 published technology articles on and another 250+ blog articles on his WordPress blog. Nish is vastly experienced in team management, mentoring teams, and directing all stages of software development.

Contact Nish : If you are interested in hiring Nish as a consultant, you can reach him via his google email id voidnish.

Company Website :

Comments and Discussions

GeneralRe: Another Suggestions - Set Hidden File Time Pin
over-cast30-Dec-03 18:14
sussover-cast30-Dec-03 18:14 
GeneralExcellent Pin
5-Mar-02 10:20
suss5-Mar-02 10:20 
GeneralArticle Updated [Mar 02 2002] Pin
Nish Nishant1-Mar-02 18:02
sitebuilderNish Nishant1-Mar-02 18:02 
GeneralSuggestion Pin
Mauricio Ritter27-Feb-02 2:35
MemberMauricio Ritter27-Feb-02 2:35 
GeneralRe: Suggestion Pin
Nish Nishant27-Feb-02 3:49
sitebuilderNish Nishant27-Feb-02 3:49 
GeneralRe: Suggestion Pin
Nish Nishant1-Mar-02 18:07
sitebuilderNish Nishant1-Mar-02 18:07 
GeneralRe: Suggestion Pin
Mauricio Ritter2-Mar-02 11:30
MemberMauricio Ritter2-Mar-02 11:30 
GeneralBad style (in other cases it could be bug) Pin
limax26-Feb-02 22:16
Memberlimax26-Feb-02 22:16 
bool CExpire::CreateProgKey(const char*  ProgName, const char* KeyName)
	char *SubKey = new char [sizeof ProgName+sizeof KeyName+300];

sizeof ProgName == sizeof KeyName == sizeof AnyPointer == 4 for Win32;
It is pointless to take sizeof pointer to char. Either remove these sizeofs (to make buffer const length = 300) or get real length with strlen();
Of course second is better;
GeneralRe: Bad style (in other cases it could be bug) Pin
Nish Nishant1-Mar-02 18:10
sitebuilderNish Nishant1-Mar-02 18:10 
Generalanother cp solution Pin
26-Feb-02 21:58
suss26-Feb-02 21:58 
GeneralRe: another cp solution Pin
Juan Carlos Cobas14-Jun-03 5:17
MemberJuan Carlos Cobas14-Jun-03 5:17 
GeneralRe: another cp solution Pin
Tibor Blazko15-Jun-03 22:00
MemberTibor Blazko15-Jun-03 22:00 
GeneralRe: another cp solution Pin
Juan Carlos Cobas15-Jun-03 22:15
MemberJuan Carlos Cobas15-Jun-03 22:15 
QuestionBad Form? Pin
William Bartholomew26-Feb-02 11:14
MemberWilliam Bartholomew26-Feb-02 11:14 
AnswerRe: Bad Form? Pin
Maximilien26-Feb-02 12:15
MemberMaximilien26-Feb-02 12:15 
GeneralRe: Bad Form? Pin
Nish Nishant26-Feb-02 12:33
sitebuilderNish Nishant26-Feb-02 12:33 
GeneralRe: Bad Form? Pin
Uwe Keim26-Feb-02 13:35
sitebuilderUwe Keim26-Feb-02 13:35 
GeneralRe: Bad Form? Pin
Nish Nishant26-Feb-02 14:14
sitebuilderNish Nishant26-Feb-02 14:14 
GeneralRe: Bad Form? Pin
Neville Franks26-Feb-02 23:49
MemberNeville Franks26-Feb-02 23:49 
GeneralRe: Bad Form? Pin
Bruce Duncan27-Feb-02 8:24
MemberBruce Duncan27-Feb-02 8:24 
GeneralRe: Bad Form? Pin
2-Mar-02 0:40
suss2-Mar-02 0:40 
GeneralRe: Bad Form? Pin
Nish Nishant2-Mar-02 0:51
sitebuilderNish Nishant2-Mar-02 0:51 
AnswerRe: Bad Form? Pin
Nish Nishant26-Feb-02 12:32
sitebuilderNish Nishant26-Feb-02 12:32 
AnswerRe: Bad Form? Pin
Joe USer27-Feb-02 7:54
MemberJoe USer27-Feb-02 7:54 
GeneralDoesn't work with restricted users... Pin
Maximilien26-Feb-02 10:26
MemberMaximilien26-Feb-02 10:26 

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