ring_buffer.cpp

	bool pop(T& obj) {
		for (;;) {
			const i32 pos = rd;
			Item* j = &objects[pos % CAPACITY];
			const i32 seq = j->seq;
			if (seq < pos + 1) {
				// nothing to pop
				return false;
			}
			else if (seq == pos + 1) {
				// try to pop
				if (rd.compareExchange(pos + 1, pos)) {
					obj = j->value;
					memoryBarrier();
					j->seq = pos + CAPACITY;
					return true;
				}
				// somebody popped before us, try again
			}
			else {
				// somebody popped before we got here, try again
				ASSERT(rd != pos);
			}
		}
	}

	void push(const T& obj, Lumix::Mutex* mutex) {
		for (;;) {
			const i32 pos = wr;
			Item* j = &objects[pos % CAPACITY];
			const i32 seq = j->seq;
			if (seq < pos) {
				// buffer full
				if (mutex) mutex->enter();
				m_fallback.push(obj);
				if (mutex) mutex->exit();
				return;
			}
			else if (seq == pos) {
				// we can try to push
				if (wr.compareExchange(pos + 1, pos)) {
					j->value = obj;
					memoryBarrier();
					j->seq = pos + 1;
					break;
				}
			}
			else {
				// somebody pushed before us, try again
				ASSERT(wr != pos);
			}
		}
	}