Actually, even "if (pos >= bufSize) { pos -= bufSize; }" is much faster than pos = pos % bufSize. Division (and modulo) are like the only basic math operations

Actually, even "if (pos >= bufSize) { pos -= bufSize; }" is much faster than pos = pos % bufSize. Division (and modulo) are like the only basic math operations that a modern wide ALU doesn't easily do three to four of per cycle (they are much more expensive), OTOH easily predicted branches are fairly cheap (or even compiled into conditional moves here).