DeflateDecoder Class — netty Architecture

Source Code

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/extensions/compression/DeflateDecoder.java lines 42–166

abstract class DeflateDecoder extends WebSocketExtensionDecoder {

    static final ByteBuf FRAME_TAIL = Unpooled.unreleasableBuffer(
            Unpooled.wrappedBuffer(new byte[] {0x00, 0x00, (byte) 0xff, (byte) 0xff}))
            .asReadOnly();

    static final ByteBuf EMPTY_DEFLATE_BLOCK = Unpooled.unreleasableBuffer(
            Unpooled.wrappedBuffer(new byte[] { 0x00 }))
            .asReadOnly();

    private final boolean noContext;
    private final WebSocketExtensionFilter extensionDecoderFilter;
    private final int maxAllocation;

    private EmbeddedChannel decoder;

    /**
     * Constructor
     *
     * @param noContext true to disable context takeover.
     * @param extensionDecoderFilter extension decoder filter.
     */
    DeflateDecoder(boolean noContext, WebSocketExtensionFilter extensionDecoderFilter, int maxAllocation) {
        this.noContext = noContext;
        this.extensionDecoderFilter = checkNotNull(extensionDecoderFilter, "extensionDecoderFilter");
        this.maxAllocation = maxAllocation;
    }

    /**
     * Returns the extension decoder filter.
     */
    protected WebSocketExtensionFilter extensionDecoderFilter() {
        return extensionDecoderFilter;
    }

    protected abstract boolean appendFrameTail(WebSocketFrame msg);

    protected abstract int newRsv(WebSocketFrame msg);

    @Override
    protected void decode(ChannelHandlerContext ctx, WebSocketFrame msg, List<Object> out) throws Exception {
        final ByteBuf decompressedContent = decompressContent(ctx, msg);

        final WebSocketFrame outMsg;
        if (msg instanceof TextWebSocketFrame) {
            outMsg = new TextWebSocketFrame(msg.isFinalFragment(), newRsv(msg), decompressedContent);
        } else if (msg instanceof BinaryWebSocketFrame) {
            outMsg = new BinaryWebSocketFrame(msg.isFinalFragment(), newRsv(msg), decompressedContent);
        } else if (msg instanceof ContinuationWebSocketFrame) {
            outMsg = new ContinuationWebSocketFrame(msg.isFinalFragment(), newRsv(msg), decompressedContent);
        } else {
            throw new CodecException("unexpected frame type: " + msg.getClass().getName());
        }

        out.add(outMsg);
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        cleanup();
        super.handlerRemoved(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        cleanup();
        super.channelInactive(ctx);
    }

    private ByteBuf decompressContent(ChannelHandlerContext ctx, WebSocketFrame msg) {
        if (decoder == null) {
            if (!(msg instanceof TextWebSocketFrame) && !(msg instanceof BinaryWebSocketFrame)) {
                throw new CodecException("unexpected initial frame type: " + msg.getClass().getName());
            }
            decoder = EmbeddedChannel.builder()
                    .handlers(ZlibCodecFactory.newZlibDecoder(ZlibWrapper.NONE, maxAllocation))
                    .build();
        }

        boolean readable = msg.content().isReadable();
        boolean emptyDeflateBlock = EMPTY_DEFLATE_BLOCK.equals(msg.content());