public void login()
                throws IOException, LoginFailureException, CorruptStreamException
            {
                out.streamStart(connection.domain, connection.resource);
                System.err.println("sent stream start");
                sendFeatures();
                System.err.println("sent features");
                sendAuth();
                System.err.println("sent auth");
                in.streamStart();
                System.err.println("read stream start");
                String challengeData = readFeaturesAndChallenge();
                System.err.println("read features and challenge");
                sendResponse(challengeData);
                System.err.println("sent response");
                readSuccess();
            }

            private void sendFeatures()
                throws IOException
            {
                out.write(new ProtocolTreeNode("stream:features", null, connection.supports_receipt_acks ? (new ProtocolTreeNode[] {
                    new ProtocolTreeNode("receipt_acks", null)
                }) : null), false);
            }

            private void sendAuth()
                throws IOException
            {
                ProtocolTreeNode node = new ProtocolTreeNode("auth", new KeyValue[] {
                    new KeyValue("xmlns", "urn:ietf:params:xml:ns:xmpp-sasl"), new KeyValue("mechanism", "DIGEST-MD5-1")
                });
                out.write(node);
            }

            private String readFeaturesAndChallenge()
                throws IOException, CorruptStreamException
            {
label0:
                {
                    ProtocolTreeNode root;
                    boolean server_supports_receipt_acks;
label1:
                    do
                    {
                        for(server_supports_receipt_acks = false; (root = in.nextTree()) != null; server_supports_receipt_acks = root.getChild("receipt_acks") != null)
                            if(!ProtocolTreeNode.tagEquals(root, "stream:features"))
                                continue label1;

                        break label0;
                    } while(!ProtocolTreeNode.tagEquals(root, "challenge"));
                    connection.supports_receipt_acks = connection.supports_receipt_acks && server_supports_receipt_acks;
                    String data = new String(Base64.decode(root.data.getBytes()));
                    return data;
                }
                throw new CorruptStreamException("fell out of loop in readFeaturesAndChallenge");
            }

            private void sendResponse(String challengeData)
                throws IOException
            {
                String response = getResponse(challengeData);
                ProtocolTreeNode node = new ProtocolTreeNode("response", new KeyValue[] {
                    new KeyValue("xmlns", "urn:ietf:params:xml:ns:xmpp-sasl")
                }, new String(Base64.encode(response.getBytes())));
                out.write(node);
            }

            private void readSuccess()
                throws CorruptStreamException, IOException, LoginFailureException
            {
                ProtocolTreeNode node = in.nextTree();
                if(ProtocolTreeNode.tagEquals(node, "failure"))
                    throw new LoginFailureException(0);
                ProtocolTreeNode.require(node, "success");
                String expiration = node.getAttributeValue("expiration");
                if(expiration != null)
                    try
                    {
                        connection.expire_date = Long.parseLong(expiration);
                    }
                    catch(NumberFormatException xxx)
                    {
                        throw new IOException("invalid expire date: " + expiration);
                    }
                String kind = node.getAttributeValue("kind");
                if("paid".equals(kind))
                    connection.account_kind = 1;
                else
                if("free".equals(kind))
                    connection.account_kind = 0;
                else
                    connection.account_kind = -1;
                String status = node.getAttributeValue("status");
                if("expired".equals(status))
                {
                    LoginFailureException failex = new LoginFailureException(1);
                    failex.expire_date = connection.expire_date;
                    throw failex;
                }
                if("active".equals(status))
                {
                    if(expiration == null)
                        throw new IOException("active account with no expiration");
                } else
                {
                    connection.account_kind = -1;
                }
            }

            public WhatsApp(TreeNodeReader r, TreeNodeWriter w, MessageDigest d)
            {
                super(d, r, w);
            }
        }