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XmppTask Class

A specialization of the Task class that acts as a base class for asynchronous XMPP tasks. Classes derived from XmppTask can act as stanza senders, stanza listeners, or both. They can also perform additional processing, such as listening for presence stanzas, translating them, and sending translated notifications out to registered listeners.

When an incoming stanza arrives from the network, the parent object (XmppClient) sends the stanza to each child object to see whether it can handle this stanza by calling its HandleStanza method. If the object can handle the stanza, it returns true, and XmppClient discards the stanza; otherwise, XmppClient tries the next child in its list. Child objects are queried in order of their priority. Priority is determined by a buzz::XmppEngine::HandlerLevel enumeration, where a lower number indicates a higher priority. An XmppTask object's priority is declared in its constructor.

See Sending and Receiving Stanzas for more information about using XmppTask objects.

If extending XmppTask, you must implement the following methods:

  • HandleStanza   This is called before ProcessStart with a stanza to see whether the object can handle the stanza. If the object determines that it can handle the stanza, it should call QueueStanza and pass in the stanza, and the task manager will then call ProcessStart.
  • ProcessStart   Called by the task manager asynchronously after HandleStanza has returned true. To get the stanza queued in HandleStanza, call NextStanza.

Additionally, you might override the following methods:

  • Stop
  • OnDisconnect   Perform any special events in the event that the connection is broken.
  • ProcessResponse   If your subclass should be called more than once (for instance, Receiver continues to send stanzas to SessionClient throughout the lifetime of the application) it should implement this class and return an appropriate state value.
  • Any other virtual methods in XmppTask or Task.

See Task to learn more about the base task class.


class XmppTask : public Task, 
                 public XmppStanzaHandler, 
                 public sigslot::has_slots<>


Name Description
XmppClient* GetClient() Returns a handle to the XmppClient managing object.
bool HandleStanza(const XmlElement *stanza) Called by the parent to see whether this object can handle a new incoming stanza. Return true if you can, false if you cannot. If you return true, XmppClient will not send the stanza to any other handlers.
bool MatchRequestIq(const XmlElement *stanza, const std::string &type, const QName &qn) Verifies the name, type, and presence of an element.
bool MatchResponseIq(const XmlElement *stanza, const Jid &to, const std::string &task_id) Determines whether an incoming stanza is a reply for a previously sent stanza by matching the to, from, and ID fields.
bool MatchResponseIqFromArbitrary(const XmlElement *stanza, const Jid &to, const std::string &task_id) Determines whether an incoming stanza matches a previously sent stanza by ID only.
XmlElement* NextStanza() Retrieves the next stanza added to the queue by QueueStanza.
void OnDisconnect() Called by XmppClient when the connection is disconnected. Causes an error to bubble up.
int ProcessReponse() You should not need to call this. Called by the task manager on subsequent calls to the object after the initial step. Should return a Task::State value indicating the state of the task after attempting to process data.
void QueueStanza(const XmlElement *stanza) Sends the stanza to an internal queue to be handled asynchronously. Call this from HandleStanza if the object determines that it can handle this stanza.
XmppReturnStatus SendStanza(const XmlElement *stanza) Called by an external class to send a stanza out over the network.
XmppReturnStatus SendStanzaError(const XmlElement *element_original, XmppStanzaError code, const std::string &text) Called by an external class to send out an error code in response to an erroneous stanza.
void set_task_id(std::string id) Called internally to set the ID to that of the next stanza queued by XmppClient.
void Stop() Internal method to loop through all queried stanzas.
void StopImpl() Internal method to loop through all queued stanzas.
std::string task_id() Called internally to retrieve the ID to that of the next stanza queued by XmppClient.
XmppTask( Task *parent, XmppEngine::HandlerLevel level=XmppEngine::HL_NONE)

Constructor with the following parameters:

parent   The parent object, typically XmppClient.

level   The priority level of this object, where objects with a lower enumeration value have a higher priority and are given an earlier opportunity to handle the stanza.

~XmppTask Destructor.



Attributes: public

Declaration file: libjingle-0.3.0/talk/xmpp/xmpptask.h