How to deal with a wrapping counter in embedded C

Question

I need to deal with a counter that gives me ticks for my application. The counter is 32bits so what i need to know is how to deal with it when it wraps. for example:

I h

Answer 1

If you use unsigned variables to store your counter and timer expiry time, then you can simply use this test:

if (current_time - expiry_time < 0x80000000UL)
    /* timer has expired */

This assumes that you test for expiry at least once every 0x80000000 ticks, and that your longest timer is set to expire less than 0x80000000 ticks into the future.