[mkgmap-dev] Rounding bug in splitter?

Tue Aug 11 06:56:58 BST 2009

On Mon, Aug 10, 2009 at 09:37:44PM +0000, Chris Miller wrote:
> Assuming my understanding above is correct, here's how I think the rounding 
> methods should be implemented to give the correct rounding in all situations:
> 
> private int roundDown(int val) {
>   return val >> SHIFT << SHIFT;
> }

I would write this as

  return val & ~(1 << SHIFT);

> private int roundUp(int val) {
>   return (val + (1 << SHIFT) - 1) >> SHIFT << SHIFT;
> }

And this one as

  return (val + ((1 << SHIFT) - 1))) & ~(1 << SHIFT);

It's probably not a big deal, but if SHIFT is a compile-time constant
and the compiler performs constant folding, the run-time code should
be shorter and faster.

	Marko