def startTrustSchemaUpdate(self, appPrefix, onUpdateSuccess = None, onUpdateFailed = None):
        """
        Starts trust schema update for under an application prefix: initial 
        interest asks for the rightMostChild, and later interests are sent 
        with previous version excluded. Each verified trust schema will trigger
        onUpdateSuccess and update the ConfigPolicyManager for the keyChain
        in this instance, and unverified ones will trigger onUpdateFailed.

        The keyChain and trust anchor should be set up using setupDefaultIdentityAndRoot
        before calling this method. 

        :param appPrefix: the prefix to ask trust schema for. (interest name: /<prefix>/_schema)
        :type appPrefix: Name
        :param onUpdateSuccess: (optional) onUpdateSuccess(trustSchemaStr, isInitial) is 
          called when update succeeds
        :type onUpdateSuccess: function object
        :param onUpdateFailed: (optional) onUpdateFailed(msg) is called when update fails
        :type onUpdateFailed: function object
        """
        namespace = appPrefix.toUri()
        if namespace in self._trustSchemas:
            if self._trustSchemas[namespace]["following"] == True:
                print "Already following trust schema under this namespace!"
                return
            self._trustSchemas[namespace]["following"] = True
        else:
            self._trustSchemas[namespace] = {"following": True, "version": 0, "is-initial": True}

        initialInterest = Interest(Name(namespace).append("_schema"))
        initialInterest.setChildSelector(1)
        self._face.expressInterest(initialInterest, 
          lambda interest, data: self.onTrustSchemaData(interest, data, onUpdateSuccess, onUpdateFailed), 
          lambda interest: self.onTrustSchemaTimeout(interest, onUpdateSuccess, onUpdateFailed))
        return

    def startPublishingAggregation(self, params, childrenList, dataType, aggregationType):
        if __debug__:
            print('Start publishing for ' + dataType + '-' + aggregationType)
        
        # aggregation calculating and publishing mechanism
        publishingPrefix = Name(self._identityName).append(DATA_COMPONENT).append(dataType).append(AGGREGATION_COMPONENT).append(aggregationType)
        self._dataQueue[dataType + aggregationType] = DataQueue(params, childrenList, publishingPrefix)

        if len(childrenList.keys()) == 0:
            # TODO: make start_time optional for leaf nodes
            self._loop.call_later(int(params['producer_interval']), self.calculateAggregation, dataType, aggregationType, childrenList, int(params['start_time']), int(params['producer_interval']), publishingPrefix, True)
        else:
            # express interest for children who produce the same data and aggregation type
            for childName in childrenList.keys():
                name = Name(self._identityName).append(childName).append(DATA_COMPONENT).append(dataType).append(AGGREGATION_COMPONENT).append(aggregationType)
                interest = Interest(name)
                # if start_time is specified, we ask for data starting at start_time; 
                # if not, we ask for the right most child and go from there
                if ('start_time' in childrenList[childName]):
                    endTime = int(childrenList[childName]['start_time']) + int(childrenList[childName]['producer_interval'])
                    interest.getName().append(str(childrenList[childName]['start_time'])).append(str(endTime))
                else:
                    # TODO: For now we are playing with historical data, for each run we don't want to miss any data, thus we start with leftMost
                    interest.setChildSelector(0)
                    interest.setMustBeFresh(True)
                interest.setInterestLifetimeMilliseconds(DEFAULT_INTEREST_LIFETIME)
                if __debug__:
                    print('  Issue interest: ' + interest.getName().toUri())
                self._face.expressInterest(interest, self.onData, self.onTimeout)

        return

    def _onData(self, interest, data):
        """
        Process the incoming Chat data.
        """
        # TODO: Check if this works in Python 3.
        content = chatbuf_pb2.ChatMessage()
        content.ParseFromString(data.getContent().toRawStr())

        if self.getNowMilliseconds() - content.timestamp * 1000.0 < 120000.0:
            # Use getattr because "from" is a reserved keyword.
            name = getattr(content, "from")
            prefix = data.getName().getPrefix(-2).toUri()
            sessionNo = int(data.getName().get(-2).toEscapedString())
            sequenceNo = int(data.getName().get(-1).toEscapedString())
            nameAndSession = name + str(sessionNo)

            l = 0
            # Update roster.
            while l < len(self._roster):
                entry = self._roster[l]
                tempName = entry[0:len(entry) - 10]
                tempSessionNo = int(entry[len(entry) - 10:])
                if (name != tempName and
                    content.type != chatbuf_pb2.ChatMessage.LEAVE):
                    l += 1
                else:
                    if name == tempName and sessionNo > tempSessionNo:
                        self._roster[l] = nameAndSession
                    break

            if l == len(self._roster):
                self._roster.append(nameAndSession)
                print(name + ": Join")

            # Set the alive timeout using the Interest timeout mechanism.
            # TODO: Are we sure using a "/local/timeout" interest is the best
            # future call approach?
            timeout = Interest(Name("/local/timeout"))
            timeout.setInterestLifetimeMilliseconds(120000)
            self._face.expressInterest(
              timeout, self._dummyOnData,
              self._makeAlive(sequenceNo, name, sessionNo, prefix))

            # isRecoverySyncState_ was set by sendInterest.
            # TODO: If isRecoverySyncState_ changed, this assumes that we won't get
            #     data from an interest sent before it changed.
            # Use getattr because "from" is a reserved keyword.
            if (content.type == chatbuf_pb2.ChatMessage.CHAT and
                 not self._isRecoverySyncState and
                 getattr(content, "from") != self._screenName):
                print(getattr(content, "from") + ": " + content.data)
            elif content.type == chatbuf_pb2.ChatMessage.LEAVE:
                # leave message
                try:
                    n = self._roster.index(nameAndSession)
                    if name != self._screenName:
                        self._roster.pop(n)
                        print(name + ": Leave")
                except ValueError:
                    pass

    def test_find_by_interest(self):
        self.anchorContainer.insert("group1", self.certificatePath1, 400.0)
        interest = Interest(self.identity1.getName())
        self.assertTrue(self.anchorContainer.find(interest) != None)
        interest1 = Interest(self.identity1.getName().getPrefix(-1))
        self.assertTrue(self.anchorContainer.find(interest1) != None)
        interest2 = Interest(Name(self.identity1.getName()).appendVersion(1))
        self.assertTrue(self.anchorContainer.find(interest2) == None)

        certificate3 = self.fixture.addCertificate(
          self.identity1.getDefaultKey(), "3")
        certificate4 = self.fixture.addCertificate(
          self.identity1.getDefaultKey(), "4")
        certificate5 = self.fixture.addCertificate(
          self.identity1.getDefaultKey(), "5")

        certificate3Copy = CertificateV2(certificate3)
        self.anchorContainer.insert("group2", certificate3Copy)
        self.anchorContainer.insert("group3", certificate4)
        self.anchorContainer.insert("group4", certificate5)

        interest3 = Interest(certificate3.getKeyName())
        foundCertificate = self.anchorContainer.find(interest3)
        self.assertTrue(foundCertificate != None)
        self.assertTrue(interest3.getName().isPrefixOf(foundCertificate.getName()))
        self.assertTrue(certificate3.getName().equals(foundCertificate.getName()))

        interest3.getExclude().appendComponent(
          certificate3.getName().get(CertificateV2.ISSUER_ID_OFFSET))
        foundCertificate = self.anchorContainer.find(interest3)
        self.assertTrue(foundCertificate != None)
        self.assertTrue(interest3.getName().isPrefixOf(foundCertificate.getName()))
        self.assertTrue(not foundCertificate.getName().equals(certificate3.getName()))

    def consume(self, prefix, onVerified, onVerifyFailed, onTimeout):
        """
        Consume data continuously under a given prefix, each time sending interest with
        the last timestamp excluded

        :param name: prefix to consume data under
        :type name: Name
        :param onData: onData(data) gets called after received data's onVerifyFailed
        :type onData: function object
        :param onVerifyFailed: onVerifyFailed(data) gets called if received data 
          cannot be verified
        :type onVerifyFailed: function object
        :param onTimeout: onTimeout(interest) gets called if a consumer interest times out
        :type onTimeout: function object
        """
        name = Name(prefix)
        interest = Interest(name)
        interest.setInterestLifetimeMilliseconds(self._defaultInterestLifetime)

        if self._currentTimestamp:
            exclude = Exclude()
            exclude.appendAny()
            exclude.appendComponent(Name.Component.fromVersion(self._currentTimestamp))
            interest.setExclude(exclude)

        self._face.expressInterest(interest, 
          lambda i, d : self.onData(i, d, onVerified, onVerifyFailed, onTimeout), 
          lambda i: self.beforeReplyTimeout(i, onVerified, onVerifyFailed, onTimeout))
        return

def main():
    # Silence the warning from Interest wire encode.
    Interest.setDefaultCanBePrefix(True)

    loop = asyncio.get_event_loop()
    face = ThreadsafeFace(loop, "memoria.ndn.ucla.edu")

    # Counter will stop the ioService after callbacks for all expressInterest.
    counter = Counter(loop, 3)

    # Try to fetch anything.
    name1 = Name("/")
    dump("Express name ", name1.toUri())
    # These call to exressIinterest is thread safe because face is a ThreadsafeFace.
    face.expressInterest(name1, counter.onData, counter.onTimeout)

    # Try to fetch using a known name.
    name2 = Name("/ndn/edu/ucla/remap/demo/ndn-js-test/hello.txt/%FDU%8D%9DM")
    dump("Express name ", name2.toUri())
    face.expressInterest(name2, counter.onData, counter.onTimeout)

    # Expect this to time out.
    name3 = Name("/test/timeout")
    dump("Express name ", name3.toUri())
    face.expressInterest(name3, counter.onData, counter.onTimeout)

    # Run until the Counter calls stop().
    loop.run_forever()
    face.shutdown()

        def helper(identityName, signerName):
            try:
                self._defaultIdentity = identityName
                self._defaultCertificateName = self._identityManager.getDefaultCertificateNameForIdentity(self._defaultIdentity)
                self._defaultKeyName = self._identityManager.getDefaultKeyNameForIdentity(identityName)
            except SecurityException:
                msg = "Identity " + identityName.toUri() + " in configuration does not exist. Please configure the device with this identity first."
                if onSetupFailed:
                    onSetupFailed(msg)
                return

            if not self._defaultCertificateName:
                msg = "Unable to get default certificate name for identity " + identityName.toUri() + ". Please configure the device with this identity first."
                if onSetupFailed:
                    onSetupFailed(msg)
                return

            if not self._defaultKeyName:
                msg = "Unable to get default key name for identity " + identityName.toUri() + ". Please configure the device with this identity first."
                if onSetupFailed:
                    onSetupFailed(msg)
                return
            
            # Note we'll not be able to issue face commands before this point
            self._face.setCommandSigningInfo(self._keyChain, self._defaultCertificateName)
            # Serve our own certificate
            self._certificateContentCache.registerPrefix(Name(self._defaultCertificateName).getPrefix(-1), self.onRegisterFailed)
            self._certificateContentCache.add(self._keyChain.getCertificate(self._defaultCertificateName))

            actualSignerName = self._keyChain.getCertificate(self._defaultCertificateName).getSignature().getKeyLocator().getKeyName()    
            if not signerName:
                print "Deriving from " + actualSignerName.toUri() + " for controller name"
            else:
                if signerName and actualSignerName.toUri() != signerName.toUri():
                    msg = "Configuration signer names mismatch: expected " + signerName.toUri() + "; got " + actualSignerName.toUri()
                    print msg
                    if onSetupFailed:
                        onSetupFailed(msg)

            self._controllerName = self.getIdentityNameFromCertName(actualSignerName)
            print "Controller name: " + self._controllerName.toUri()

            try:
                self._controllerCertificate = self._keyChain.getCertificate(self._identityManager.getDefaultCertificateNameForIdentity(self._controllerName))
                
                # TODO: this does not seem a good approach, implementation-wise and security implication
                self._policyManager._certificateCache.insertCertificate(self._controllerCertificate)
                if onSetupComplete:
                    onSetupComplete(Name(self._defaultCertificateName), self._keyChain)
            except SecurityException as e:
                print "don't have controller certificate " + actualSignerName.toUri() + " yet"
                controllerCertInterest = Interest(Name(actualSignerName))
                controllerCertInterest.setInterestLifetimeMilliseconds(4000)
                
                controllerCertRetries = 3

                self._face.expressInterest(controllerCertInterest, 
                  lambda interest, data: self.onControllerCertData(interest, data, onSetupComplete, onSetupFailed), 
                  lambda interest: self.onControllerCertTimeout(interest, onSetupComplete, onSetupFailed, controllerCertRetries))
            return

    def _scanForUnconfiguredDevices(self):
        # unconfigured devices should register '/localhop/configure'
        # we keep asking for unconfigured devices until we stop getting replies

        foundDevices = []

        self.ui.alert("Scanning for unconfigured devices...", False)

        def onDeviceTimeout(interest):
            # assume we're done - everyone is excluded
            self.unconfiguredDevices = foundDevices
            self.loop.call_soon(self._showConfigurationList)

        def onDeviceResponse(interest, data):
            updatedInterest = Interest(interest)
            deviceSerial = str(data.getContent())
            if len(deviceSerial) > 0:
                foundDevices.append(deviceSerial)
                updatedInterest.getExclude().appendComponent(Name.Component(deviceSerial))
            # else ignore the malformed response
            self.face.expressInterest(updatedInterest, onDeviceResponse, onDeviceTimeout)

        interest = Interest(Name("/localhop/configure"))
        interest.setInterestLifetimeMilliseconds(2000)
        self.face.expressInterest(interest, onDeviceResponse, onDeviceTimeout)

class TestInterestDump(ut.TestCase):
    def setUp(self):
        self.referenceInterest = Interest()
        self.referenceInterest.wireDecode(codedInterest)

    def test_dump(self):
        # see if the dump format is the same as we expect
        decodedDump = dumpInterest(self.referenceInterest)
        self.assertEqual(initialDump, decodedDump, 'Initial dump does not have expected format')

    def test_redecode(self):
        # check that we encode and decode correctly
        encoding = self.referenceInterest.wireEncode()
        reDecodedInterest = Interest()
        reDecodedInterest.wireDecode(encoding)
        redecodedDump = dumpInterest(reDecodedInterest)
        self.assertEqual(initialDump, redecodedDump, 'Re-decoded interest does not match original')

    def test_create_fresh(self):
        freshInterest = createFreshInterest()
        freshDump = dumpInterest(freshInterest)
        self.assertTrue(interestDumpsEqual(initialDump, freshDump), 'Fresh interest does not match original')

        reDecodedFreshInterest = Interest()
        reDecodedFreshInterest.wireDecode(freshInterest.wireEncode())
        reDecodedFreshDump = dumpInterest(reDecodedFreshInterest)

        self.assertTrue(interestDumpsEqual(freshDump, reDecodedFreshDump), 'Redecoded fresh interest does not match original')

    def requestCertificate(self, keyIdentity):
        """
        We compose a command interest with our public key info so the controller
        can sign us a certificate that can be used with other nodes in the network.
        Name format : /home/<device-category>/KEY/<device-id>/<key-id>/<publickey>/ID-CERT/<version-number>
        """
        certificateRequestName = self._keyChain.getDefaultIdentity()
        deviceIdComponent = certificateRequestName.get(-1)
        keyIdComponent = keyIdentity.get(-1)

        certificateRequestName = certificateRequestName
        certificateRequestName.append("KEY")
        #certificateRequestName.append(deviceIdComponent)
        certificateRequestName.append(keyIdComponent)

        key = self._identityManager.getPublicKey(keyIdentity)
        keyInfo = {}
        keyInfo["keyType"] = key.getKeyType()
        keyInfo["keyDer"] = key.getKeyDer().toRawStr()

        certificateRequestName.append(json.dumps(keyInfo, encoding="latin-1"))

        certificateRequestName.append("ID-CERT")

        certificateRequest = Interest(certificateRequestName)
        certificateRequest.setInterestLifetimeMilliseconds(5000)
        self._hmacHelper.signInterest(certificateRequest)
        
        dump("Sending certificate request : ",certificateRequestName)

        self.face.expressInterest(certificateRequest, self.onCertificateData, self.onTimeout)

def main():
    # Silence the warning from Interest wire encode.
    Interest.setDefaultCanBePrefix(True)

    # The default Face will connect using a Unix socket, or to "localhost".
    face = Face()

    counter = Counter()

    if sys.version_info[0] <= 2:
        word = raw_input("Enter a word to echo: ")
    else:
        word = input("Enter a word to echo: ")

    name = Name("/testecho")
    name.append(word)
    dump("Express name ", name.toUri())
    face.expressInterest(name, counter.onData, counter.onTimeout)

    while counter._callbackCount < 1:
        face.processEvents()
        # We need to sleep for a few milliseconds so we don't use 100% of the CPU.
        time.sleep(0.01)

    face.shutdown()

    def _updateCapabilities(self):
        """
        Send the controller a list of our commands.
        """ 
        fullCommandName = Name(self._policyManager.getTrustRootIdentity()
                ).append('updateCapabilities')
        capabilitiesMessage = UpdateCapabilitiesCommandMessage()

        for command in self._commands:
            commandName = Name(self.prefix).append(Name(command.suffix))
            capability = capabilitiesMessage.capabilities.add()
            for i in range(commandName.size()):
                capability.commandPrefix.components.append(
                        str(commandName.get(i).getValue()))

            for kw in command.keywords:
                capability.keywords.append(kw)

            capability.needsSignature = command.isSigned

        encodedCapabilities = ProtobufTlv.encode(capabilitiesMessage)
        fullCommandName.append(encodedCapabilities)
        interest = Interest(fullCommandName)
        interest.setInterestLifetimeMilliseconds(5000)
        self.face.makeCommandInterest(interest)
        signature = self._policyManager._extractSignature(interest)

        self.log.info("Sending capabilities to controller")
        self.face.expressInterest(interest, self._onCapabilitiesAck, self._onCapabilitiesTimeout)

        # update twice a minute
        self.loop.call_later(30, self._updateCapabilities)

    def expressInterest(self, interestTemplate = None):
        """
        Call expressInterest on this (or a parent's) Face where the interest
        name is the name of this Namespace node. When the Data packet is
        received this calls setData, so you should use a callback with
        addOnContentSet. This uses ExponentialReExpress to re-express a timed-out
        interest with longer lifetimes.
        TODO: How to alert the application on a final interest timeout?
        TODO: Replace this by a mechanism for requesting a Data object which is
        more general than a Face network operation.
        :raises RuntimeError: If a Face object has not been set for this or a
          parent Namespace node.

        :param Interest interestTemplate: (optional) The interest template for
          expressInterest. If omitted, just use a default interest lifetime.
        """
        face = self._getFace()
        if face == None:
            raise ValueError("A Face object has not been set for this or a parent.")

        def onData(interest, data):
            self[data.name].setData(data)

        if interestTemplate == None:
            interestTemplate = Interest()
            interestTemplate.setInterestLifetimeMilliseconds(4000)
        face.expressInterest(
          self._name, interestTemplate, onData,
          ExponentialReExpress.makeOnTimeout(face, onData, None))

    def _sendCertificateRequest(self, keyIdentity):
        """
        We compose a command interest with our public key info so the controller
        can sign us a certificate that can be used with other nodes in the network.
        """

        try:
            defaultKey = self._identityStorage.getDefaultKeyNameForIdentity(keyIdentity)
        except SecurityException:
            defaultKey = self._identityManager.generateRSAKeyPairAsDefault(keyIdentity)
        
        self.log.debug("Key name: " + defaultKey.toUri())

        message = CertificateRequestMessage()
        publicKey = self._identityManager.getPublicKey(defaultKey)

        message.command.keyType = publicKey.getKeyType()
        message.command.keyBits = publicKey.getKeyDer().toRawStr()

        for component in range(defaultKey.size()):
            message.command.keyName.components.append(defaultKey.get(component).toEscapedString())

        paramComponent = ProtobufTlv.encode(message)

        interestName = Name(self._policyManager.getTrustRootIdentity()).append("certificateRequest").append(paramComponent)
        interest = Interest(interestName)
        interest.setInterestLifetimeMilliseconds(10000) # takes a tick to verify and sign
        self._hmacHandler.signInterest(interest, keyName=self.prefix)

        self.log.info("Sending certificate request to controller")
        self.log.debug("Certificate request: "+interest.getName().toUri())
        self.face.expressInterest(interest, self._onCertificateReceived, self._onCertificateTimeout)

def main():
    # The default Face connects to the local NFD.
    face = Face()

    interest = Interest(Name("/localhost/nfd/faces/list"))
    interest.setInterestLifetimeMilliseconds(4000)
    dump("Express interest", interest.getName().toUri())

    enabled = [True]

    def onComplete(content):
        enabled[0] = False
        printFaceStatuses(content)

    def onError(errorCode, message):
        enabled[0] = False
        dump(message)

    SegmentFetcher.fetch(
        face, interest, SegmentFetcher.DontVerifySegment, onComplete, onError)

    # Loop calling processEvents until a callback sets enabled[0] = False.
    while enabled[0]:
        face.processEvents()

        # We need to sleep for a few milliseconds so we don't use 100% of the CPU.
        time.sleep(0.01)

 def test_redecode(self):
     # check that we encode and decode correctly
     encoding = self.referenceInterest.wireEncode()
     reDecodedInterest = Interest()
     reDecodedInterest.wireDecode(encoding)
     redecodedDump = dumpInterest(reDecodedInterest)
     self.assertEqual(initialDump, redecodedDump, 'Re-decoded interest does not match original')

    def consume(self, prefix, onVerified, onVerifyFailed, onTimeout):
        """
        Consume data continuously under a given prefix, maintaining pipelineSize number of
        interest in the pipeline

        :param name: prefix to consume data under
        :type name: Name
        :param onData: onData(data) gets called after received data's onVerifyFailed
        :type onData: function object
        :param onVerifyFailed: onVerifyFailed(data) gets called if received data 
          cannot be verified
        :type onVerifyFailed: function object
        :param onTimeout: onTimeout(interest) gets called if a consumer interest times out
        :type onTimeout: function object
        """
        num = self._emptySlot
        for i in range(0, num):
            name = Name(prefix).append(str(self._currentSeqNumber))
            interest = Interest(name)
            # interest configuration / template?
            interest.setInterestLifetimeMilliseconds(self._defaultInterestLifetime)
            self._face.expressInterest(interest, 
              lambda i, d : self.onData(i, d, onVerified, onVerifyFailed, onTimeout), 
              lambda i: self.beforeReplyTimeout(i, onVerified, onVerifyFailed, onTimeout))
            self._currentSeqNumber += 1
            self._emptySlot -= 1
        return

def main():
    # The default Face will connect using a Unix socket, or to "localhost".
    face = Face()
    keyChain = KeyChain()
    face.setCommandSigningInfo(keyChain, keyChain.getDefaultCertificateName())

    dataPrefix = "/home/test1/data"
    repoDataPrefix = "/home/test1/data"
    # Set up repo-ng, register prefix for repo-ng's fetch prefix
    # Per configuration file in /usr/local/etc/ndn/repo-ng.conf
    # memCache is not used for now; repo is hoping that the piece of data in question is still being held at nfd
    #memCache = MemoryContentCache(face, 100000)
    #memCache.registerPrefix(Name(repoDataPrefix), onRegisterFailed, onDataNotFound)

    counter = Counter(face, repoDataPrefix)

    interest = Interest(Name(dataPrefix))
    interest.setChildSelector(1)
    interest.setInterestLifetimeMilliseconds(defaultInterestLifetime)
    face.expressInterest(interest, counter.onData, counter.onTimeout)
    
    while True:
        face.processEvents()
        # We need to sleep for a few milliseconds so we don't use 100% of the CPU.
        time.sleep(1)
    face.shutdown()

 def onHeartbeatTimeout(self, interest):
     if self.incrementTimeoutCnt(interest.getName().toUri()):
         print "Remove: " + interest.getName().toUri() + " because of consecutive timeout cnt exceeded"
     else:
         newInterest = Interest(interest.getName())
         newInterest.setInterestLifetimeMilliseconds(4000)
         self._face.expressInterest(newInterest, self.onHeartbeatData, self.onHeartbeatTimeout)

 def test_set_removes_nonce(self):
     # Ensure that changing a value on an interest clears the nonce.
     self.assertFalse(self.referenceInterest.getNonce().isNull())
     interest = Interest(self.referenceInterest)
     # Change a child object.
     interest.getExclude().clear()
     self.assertTrue(interest.getNonce().isNull(), 'Interest should not have a nonce after changing fields')