TcpDnsQueryEncoder Class — netty Architecture

Source Code

codec-dns/src/main/java/io/netty/handler/codec/dns/TcpDnsQueryEncoder.java lines 23–63

@ChannelHandler.Sharable
public final class TcpDnsQueryEncoder extends MessageToByteEncoder<DnsQuery> {

    private final DnsQueryEncoder encoder;

    /**
     * Creates a new encoder with {@linkplain DnsRecordEncoder#DEFAULT the default record encoder}.
     */
    public TcpDnsQueryEncoder() {
        this(DnsRecordEncoder.DEFAULT);
    }

    /**
     * Creates a new encoder with the specified {@code recordEncoder}.
     */
    public TcpDnsQueryEncoder(DnsRecordEncoder recordEncoder) {
        super(DnsQuery.class);
        this.encoder = new DnsQueryEncoder(recordEncoder);
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, DnsQuery msg, ByteBuf out) throws Exception {
        // Length is two octets as defined by RFC-7766
        // See https://tools.ietf.org/html/rfc7766#section-8
        out.writerIndex(out.writerIndex() + 2);
        encoder.encode(msg, out);

        // Now fill in the correct length based on the amount of data that we wrote the ByteBuf.
        out.setShort(0, out.readableBytes() - 2);
    }

    @Override
    protected ByteBuf allocateBuffer(ChannelHandlerContext ctx, @SuppressWarnings("unused") DnsQuery msg,
                                     boolean preferDirect) {
        if (preferDirect) {
            return ctx.alloc().ioBuffer(1024);
        } else {
            return ctx.alloc().heapBuffer(1024);
        }
    }
}