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)]
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