From milliseconds to hour, minutes, seconds and milliseconds

Question

I need to go from milliseconds to a tuple of (hour, minutes, seconds, milliseconds) representing the same amount of time. E.g.:

10799999ms = 2h 59m 59s 999ms

The following pseudo-code is the only thing I could come up with:

# The division operator below returns the result as a rounded down integer function to_tuple(x):     h = x / (60*60*1000)     x = x - h*(60*60*1000)     m = x / (60*1000)     x = x - m*(60*1000)     s = x / 1000     x = x - s*1000     return (h,m,s,x) 

I'm sure it must be possible to do it smarter/more elegant/faster/more compact.

Answer 1

Here is how I would do it in Java:

int seconds = (int) (milliseconds / 1000) % 60 ; int minutes = (int) ((milliseconds / (1000*60)) % 60); int hours   = (int) ((milliseconds / (1000*60*60)) % 24); 

Answer 2

Good question. Yes, one can do this more efficiently. Your CPU can extract both the quotient and the remainder of the ratio of two integers in a single operation. In <stdlib.h>, the function that exposes this CPU operation is called div(). In your psuedocode, you'd use it something like this:

function to_tuple(x):     qr = div(x, 1000)     ms = qr.rem     qr = div(qr.quot, 60)     s  = qr.rem     qr = div(qr.quot, 60)     m  = qr.rem     h  = qr.quot 

A less efficient answer would use the / and % operators separately. However, if you need both quotient and remainder, anyway, then you might as well call the more efficient div().