CodecOutputList Class — netty Architecture

Source Code

codec-base/src/main/java/io/netty/handler/codec/CodecOutputList.java lines 29–236

final class CodecOutputList extends AbstractList<Object> implements RandomAccess {

    private static final CodecOutputListRecycler NOOP_RECYCLER = new CodecOutputListRecycler() {
        @Override
        public void recycle(CodecOutputList object) {
            // drop on the floor and let the GC handle it.
        }
    };

    private static final FastThreadLocal<CodecOutputLists> CODEC_OUTPUT_LISTS_POOL =
            new FastThreadLocal<CodecOutputLists>() {
                @Override
                protected CodecOutputLists initialValue() throws Exception {
                    // 16 CodecOutputList per Thread are cached.
                    return new CodecOutputLists(16);
                }
            };

    private interface CodecOutputListRecycler {
        void recycle(CodecOutputList codecOutputList);
    }

    private static final class CodecOutputLists implements CodecOutputListRecycler {
        private final CodecOutputList[] elements;
        private final int mask;

        private int currentIdx;
        private int count;

        CodecOutputLists(int numElements) {
            elements = new CodecOutputList[MathUtil.safeFindNextPositivePowerOfTwo(numElements)];
            for (int i = 0; i < elements.length; ++i) {
                // Size of 16 should be good enough for the majority of all users as an initial capacity.
                elements[i] = new CodecOutputList(this, 16);
            }
            count = elements.length;
            currentIdx = elements.length;
            mask = elements.length - 1;
        }

        public CodecOutputList getOrCreate() {
            if (count == 0) {
                // Return a new CodecOutputList which will not be cached. We use a size of 4 to keep the overhead
                // low.
                return new CodecOutputList(NOOP_RECYCLER, 4);
            }
            --count;

            int idx = (currentIdx - 1) & mask;
            CodecOutputList list = elements[idx];
            currentIdx = idx;
            return list;
        }

        @Override
        public void recycle(CodecOutputList codecOutputList) {
            int idx = currentIdx;
            elements[idx] = codecOutputList;
            currentIdx = (idx + 1) & mask;
            ++count;
            assert count <= elements.length;
        }
    }

    static CodecOutputList newInstance() {
        return CODEC_OUTPUT_LISTS_POOL.get().getOrCreate();
    }

    private final CodecOutputListRecycler recycler;
    private int size;
    private int maxSeenSize;
    private Object[] array;
    private boolean insertSinceRecycled;

    private CodecOutputList(CodecOutputListRecycler recycler, int size) {
        this.recycler = recycler;
        array = new Object[size];
    }

    @Override
    public Object get(int index) {