KQueueEventArray Class — netty Architecture

Source Code

transport-classes-kqueue/src/main/java/io/netty/channel/kqueue/KQueueEventArray.java lines 38–190

final class KQueueEventArray {
    private static final int KQUEUE_EVENT_SIZE = Native.sizeofKEvent();
    private static final int KQUEUE_IDENT_OFFSET = Native.offsetofKEventIdent();
    private static final int KQUEUE_FILTER_OFFSET = Native.offsetofKEventFilter();
    private static final int KQUEUE_FFLAGS_OFFSET = Native.offsetofKEventFFlags();
    private static final int KQUEUE_FLAGS_OFFSET = Native.offsetofKEventFlags();
    private static final int KQUEUE_DATA_OFFSET = Native.offsetofKeventData();
    private static final int KQUEUE_UDATA_OFFSET = Native.offsetofKeventUdata();

    private CleanableDirectBuffer memoryCleanable;
    private ByteBuffer memory;
    private long memoryAddress;
    private int size;
    private int capacity;

    KQueueEventArray(int capacity) {
        if (capacity < 1) {
            throw new IllegalArgumentException("capacity must be >= 1 but was " + capacity);
        }
        memoryCleanable = Buffer.allocateDirectBufferWithNativeOrder(calculateBufferCapacity(capacity));
        memory = memoryCleanable.buffer();
        memoryAddress = Buffer.memoryAddress(memory);
        this.capacity = capacity;
    }

    /**
     * Return the {@code memoryAddress} which points to the start of this {@link KQueueEventArray}.
     */
    long memoryAddress() {
        return memoryAddress;
    }

    /**
     * Return the capacity of the {@link KQueueEventArray} which represent the maximum number of {@code kevent}s
     * that can be stored in it.
     */
    int capacity() {
        return capacity;
    }

    int size() {
        return size;
    }

    void clear() {
        size = 0;
    }

    void evSet(int ident, short filter, short flags, int fflags, long data, long udata) {
        reallocIfNeeded();
        evSet(getKEventOffset(size++) + memoryAddress, ident, filter, flags, fflags, data, udata);
    }

    private void reallocIfNeeded() {
        if (size == capacity) {
            realloc(true);
        }
    }

    /**
     * Increase the storage of this {@link KQueueEventArray}.
     */
    void realloc(boolean throwIfFail) {
        // Double the capacity while it is "sufficiently small", and otherwise increase by 50%.
        int newLength = capacity <= 65536 ? capacity << 1 : capacity + capacity >> 1;

        try {
            int newCapacity = calculateBufferCapacity(newLength);
            CleanableDirectBuffer buffer = Buffer.allocateDirectBufferWithNativeOrder(newCapacity);
            // Copy over the old content of the memory and reset the position as we always act on the buffer as if
            // the position was never increased.
            memory.position(0).limit(size);
            buffer.buffer().put(memory);
            buffer.buffer().position(0);

            memoryCleanable.clean();
            memoryCleanable = buffer;
            memory = buffer.buffer();
            memoryAddress = Buffer.memoryAddress(memory);
        } catch (OutOfMemoryError e) {
            if (throwIfFail) {