Previously, ring buffer had capacity of provided buffer size - 1. This
trick was used to distinguish between empty and full states. It had one
drawback: ring buffer could not be used as a pool of equal sized buffers
(using ring_buf_put_claim and ring_buf_get_claim).
Reworked internals to use non wrapping head and tail. Since they are
non wrapping, there is no issue with distinguishing between empty and
full. Since this appraoch would be vulnerable to wrapping on 32 bit
boundary, added a mechanism which periodically reduces all indexes to
avoid 32 bit wrapping.
After this rework, buffer has one byte more capacity. Simple test shows
slight performance improvement.
Updated tests to reflect increased capacity and added test to check if
it is possible to continuesly allocated 2 buffers of half ring buffer
size.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
1e46bb3bb5