Timed Auto Saving - input output files in c++

[Despairy]

I cant seem to find anything useful on the web except adding outside libraries for this one
help is required.

I wrote a program that you can say builds a database of users and their passwords.
the program loads the users from an existing file already into a hashtable.
now if i run the program for 2 days it wont update the file and if the pc crash
i will lose the whole data inside the program.

i wrote a function save() that opens the output file and copies the hashtable to it
now i want to call this function every 5 minutes .
is there any way of doing this?

workspace is vs2008 windows.

thanks , Despairy.

[vijayan121]

> I cant seem to find anything useful on the web except adding outside libraries for this one

With a conforming implementation, nothing more than the standard C++ library is needed. Something like this:

#include <thread>
#include <atomic>
#include <chrono>

void save_file( const std::string& path, int minutes,
                std::atomic<bool>& keep_saving /* , hashtable */ )
{
    const std::chrono::duration<int> duration( minutes * 60 ) ; // seconds
    do
    {
        std::this_thread::sleep_for(duration) ;
        // TODO: save hashtable to the file
        // NOTE: synchronized read access to the hashtable would be required.
    }
    while(keep_saving) ;
}

int main()
{
    std::string path_to_file = "whatever" ;
    std::atomic<bool> keep_saving_file(true) ;
    std::thread thread_to_save_file( save_file, path_to_file, 5, keep_saving
                                     /* , hashtable */ ) ;

    // do other stuff
    // ...

    // quit program now
    keep_saving_file.store(false) ;
    thread_to_save_file.join() ;

}

> workspace is vs2008 windows

With VS2008, there is no support for C++11 features; an external library would be required. Boost.Threads is an option; this would give the closest possible mapping to standard C++ threads. http://www.boost.org/doc/libs/1_48_0/doc/html/thread.html

[rubberman]

You may also want to write in a mutex so that the thread that saves the file doesn't try to do so when the in-memory data is being modified, and vice-versa.

[Despairy]

Thanks for answering. i asked my teacher and she said they run automated
testings on vs 2008 without any additional libraries.
so looking for another idea if you got any :( thanks

[rubberman]

You can use a timer with an interrupt handler for the timer expiring event (ETIME). This was the old way to do it, and should work with VS 2008 just fine.

[Caligulaminus]

See: http://www.daniweb.com/software-development/cpp/threads/364890/1563056#post1563056