SocksCmdResponseDecoder Class — netty Architecture

Source Code

codec-socks/src/main/java/io/netty/handler/codec/socks/SocksCmdResponseDecoder.java lines 33–104

public class SocksCmdResponseDecoder extends ReplayingDecoder<State> {

    private SocksCmdStatus cmdStatus;
    private SocksAddressType addressType;

    public SocksCmdResponseDecoder() {
        super(State.CHECK_PROTOCOL_VERSION);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf byteBuf, List<Object> out) throws Exception {
        switch (state()) {
            case CHECK_PROTOCOL_VERSION: {
                if (byteBuf.readByte() != SocksProtocolVersion.SOCKS5.byteValue()) {
                    out.add(SocksCommonUtils.UNKNOWN_SOCKS_RESPONSE);
                    break;
                }
                checkpoint(State.READ_CMD_HEADER);
            }
            case READ_CMD_HEADER: {
                cmdStatus = SocksCmdStatus.valueOf(byteBuf.readByte());
                byteBuf.skipBytes(1); // reserved
                addressType = SocksAddressType.valueOf(byteBuf.readByte());
                checkpoint(State.READ_CMD_ADDRESS);
            }
            case READ_CMD_ADDRESS: {
                switch (addressType) {
                    case IPv4: {
                        String host = NetUtil.intToIpAddress(ByteBufUtil.readIntBE(byteBuf));
                        int port = ByteBufUtil.readUnsignedShortBE(byteBuf);
                        out.add(new SocksCmdResponse(cmdStatus, addressType, host, port));
                        break;
                    }
                    case DOMAIN: {
                        int fieldLength = byteBuf.readByte();
                        String host = byteBuf.readString(fieldLength, CharsetUtil.US_ASCII);
                        int port = ByteBufUtil.readUnsignedShortBE(byteBuf);
                        out.add(new SocksCmdResponse(cmdStatus, addressType, host, port));
                        break;
                    }
                    case IPv6: {
                        byte[] bytes = new byte[16];
                        byteBuf.readBytes(bytes);
                        String host = SocksCommonUtils.ipv6toStr(bytes);
                        int port = ByteBufUtil.readUnsignedShortBE(byteBuf);
                        out.add(new SocksCmdResponse(cmdStatus, addressType, host, port));
                        break;
                    }
                    case UNKNOWN: {
                        out.add(SocksCommonUtils.UNKNOWN_SOCKS_RESPONSE);
                        break;
                    }
                    default: {
                        throw new Error("Unexpected address type: " + addressType);
                    }
                }
                break;
            }
            default: {
                throw new Error("Unexpected response decoder type: " + state());
            }
        }
        ctx.pipeline().remove(this);
    }

    @UnstableApi
    public enum State {
        CHECK_PROTOCOL_VERSION,
        READ_CMD_HEADER,
        READ_CMD_ADDRESS
    }
}