Reference no: EM132493987

You have written a piece of code which runs for a very long time.

Let's say on the fastest single processor you can find, the code runs for days if not weeks. There's isn't, for the sake of this question, any opportunity to multi-thread the applications.

In order to preserve as much progress as you application can, you would like to introduce a snapshot routine. All this routine does is creeate all of the state data that your application would require should it need to restart at this particular step. As an example, say you have a loop in your code that needs to be executed a thousand times. Each time through the loop takes several hours. At the top of every loop, you want your code to call snapshot(). This will allow you to re-load the program state in case your program crashes (or there's a power failure etc).

Since you don't want to lose hours of processing, the snapshot() routine can be considered a critical section of code. To ensure that nothing interrupts your snapshot code, you want to disable most of the signals your code might receive from the keyboard (just in case your cat walk across the keyboard when you aren't looking). Once you are done processing the snapshot, it would be nice to re-enable keyboard signals just in case you need to temporarily halt your code (Microsoft is going to reboot your machine whether you like it or not).

Without worrying about the details of saving all of your variables, in 10 lines of code or less, how would you implement the snapshot routine using only signals?