TcpDnsResponseDecoder Class — netty Architecture

Source Code

codec-dns/src/main/java/io/netty/handler/codec/dns/TcpDnsResponseDecoder.java lines 24–70

public final class TcpDnsResponseDecoder extends LengthFieldBasedFrameDecoder {

    private final DnsResponseDecoder<SocketAddress> responseDecoder;

    /**
     * Creates a new decoder with {@linkplain DnsRecordDecoder#DEFAULT the default record decoder}.
     */
    public TcpDnsResponseDecoder() {
        this(DnsRecordDecoder.DEFAULT, 64 * 1024);
    }

    /**
     * Creates a new decoder with the specified {@code recordDecoder} and {@code maxFrameLength}
     */
    public TcpDnsResponseDecoder(DnsRecordDecoder recordDecoder, int maxFrameLength) {
        // Length is two octets as defined by RFC-7766
        // See https://tools.ietf.org/html/rfc7766#section-8
        super(maxFrameLength, 0, 2, 0, 2);

        this.responseDecoder = new DnsResponseDecoder<SocketAddress>(recordDecoder) {
            @Override
            protected DnsResponse newResponse(SocketAddress sender, SocketAddress recipient,
                                              int id, DnsOpCode opCode, DnsResponseCode responseCode) {
                return new DefaultDnsResponse(id, opCode, responseCode);
            }
        };
    }

    @Override
    protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
        ByteBuf frame = (ByteBuf) super.decode(ctx, in);
        if (frame == null) {
            return null;
        }

        try {
            return responseDecoder.decode(ctx.channel().remoteAddress(), ctx.channel().localAddress(), frame.slice());
        } finally {
            frame.release();
        }
    }

    @Override
    protected ByteBuf extractFrame(ChannelHandlerContext ctx, ByteBuf buffer, int index, int length) {
        return buffer.copy(index, length);
    }
}