HashedWheelBucket Class — netty Architecture

Source Code

common/src/main/java/io/netty/util/HashedWheelTimer.java lines 760–864

    private static final class HashedWheelBucket {
        // Used for the linked-list datastructure
        private HashedWheelTimeout head;
        private HashedWheelTimeout tail;

        /**
         * Add {@link HashedWheelTimeout} to this bucket.
         */
        public void addTimeout(HashedWheelTimeout timeout) {
            assert timeout.bucket == null;
            timeout.bucket = this;
            if (head == null) {
                head = tail = timeout;
            } else {
                tail.next = timeout;
                timeout.prev = tail;
                tail = timeout;
            }
        }

        /**
         * Expire all {@link HashedWheelTimeout}s for the given {@code deadline}.
         */
        public void expireTimeouts(long deadline) {
            HashedWheelTimeout timeout = head;

            // process all timeouts
            while (timeout != null) {
                HashedWheelTimeout next = timeout.next;
                if (timeout.remainingRounds <= 0) {
                    if (timeout.deadline <= deadline) {
                        timeout.expire();
                    } else {
                        // The timeout was placed into a wrong slot. This should never happen.
                        throw new IllegalStateException(String.format(
                                "timeout.deadline (%d) > deadline (%d)", timeout.deadline, deadline));
                    }
                } else if (!timeout.isCancelled()) {
                    timeout.remainingRounds --;
                }
                timeout = next;
            }
        }

        public HashedWheelTimeout remove(HashedWheelTimeout timeout) {
            HashedWheelTimeout prev = timeout.prev;
            HashedWheelTimeout next = timeout.next;

            // remove timeout that was either processed or cancelled by updating the linked-list
            if (prev != null) {
                prev.next = next;
            }
            if (next != null) {
                next.prev = prev;
            }

            if (timeout == head) {
                head = next;
            }
            if (timeout == tail) {
                tail = prev;
            }
            // null out prev, next and bucket to allow for GC.
            timeout.prev = null;
            timeout.next = null;
            timeout.bucket = null;
            return next;
        }

        /**
         * Clear this bucket and return all not expired / cancelled {@link Timeout}s.
         */
        public void clearTimeouts(Set<Timeout> set) {
            for (;;) {
                HashedWheelTimeout timeout = pollTimeout();
                if (timeout == null) {
                    return;
                }
                if (timeout.isExpired() || timeout.isCancelled()) {
                    continue;
                }