On Tue, 2005-07-12 at 16:55 -0700, Andrew Morton wrote: > Steven Rostedt <[EMAIL PROTECTED]> wrote: > > > > I will also admit that my ring buffers lost one byte per page. Because > > I wanted to save on space with the accounting, and only had a start and > > end pointer per page. So when start and end were equal, the buffer was > > considered empty and when end was one less than start, it was considered > > full. But since end always pointed to an empty spot, it would still be > > empty when the buffer was full, thus wasting one byte per page. But to > > solve this, I would either have to add another variable in the buffer > > page descriptor (adding at least one byte, but probably 4 bytes) which > > would just be more waste, or I would have to make a complex system even > > more complex (ie. adding a flag on the end pointer at the MSB to > > differentiate between end being empty or filled). > > Nope. Just make the indices 32-bit numbers and let them wrap. > > Full: (tail - head) == size > Empty: (tail - head) == 0 > Add item: buf[head++ & (size-1)] = item; > Remove item: buf[tail++ & (size-1)]
You know I knew someone would have an answer. Look for version 0.2.1 comming soon :-) Thanks, -- Steve - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/