@Override
    public final void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        ByteBuf buf = internalBuffer();
        int readable = buf.readableBytes();
        if (readable > 0) {
            ByteBuf bytes = buf.readBytes(readable);
            buf.release();
            ctx.fireChannelRead(bytes);
        } else {
            buf.release();
        }
        cumulation = null;
        numReads = 0;
        ctx.fireChannelReadComplete();
        handlerRemoved0(ctx);
    }
Returns the internal cumulative buffer of this decoder. You usually
do not need to access the internal buffer directly to write a decoder.
Use it only when you must use it at your own risk.
src/main/java/com/alipay/remoting/codec/AbstractBatchDecoder.java