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Chapter 4. YAZ C++ API

The YAZ C++ API is an client - and server API that exposes all YAZ features. The API doesn't hide YAZ C data structures, but provides a set of useful high-level objects for creating clients - and servers.

The following sections include a short description of the interfaces and implementations (concrete classes).

In order to understand the structure, you should look at the example client yaz-my-client.cpp and the example server yaz-my-server.cpp. If that is too easy, you can always turn to the implementation of the proxy itself and send us a patch if you implement a new useful feature.

Note: The documentation here is very limited. We plan to enhance it - provided there is interest for it.



This interface is capable of observing sockets. When a socket even occurs it invokes an object implementing the IYazSocketObserver interface.

     #include <yaz++/socket-observer.h>
     class my_socketobservable : public IYazSocketObservable {
        // Add an observer interested in socket fd
        virtual void addObserver(int fd, IYazSocketObserver *observer) = 0;
        // Delete an observer
        virtual void deleteObserver(IYazSocketObserver *observer) = 0;
        // Delete all observers
        virtual void deleteObservers() = 0;
        // Specify the events that the observer is interested in.
        virtual void maskObserver(IYazSocketObserver *observer,
                                  int mask) = 0;
        // Specify timeout
        virtual void timeoutObserver(IYazSocketObserver *observer,
                                     unsigned timeout)=0;


This interface is interested in socket events supporting the IYazSocketObservable interface.

     #include <yaz++/socket-observer.h>

     class my_socketobserver : public IYazSocketObserver {
          // Notify the observer that something happened to socket
          virtual void socketNotify(int event) = 0;


This interface is is responsible for sending - and receiving PDUs over the network (YAZ COMSTACK). When events occur, an instance implementing IYaz_PDU_Observer is notified.

     #include <yaz++/pdu-observer.h>

     class my_pduobservable : public IYaz_PDU_Observable {
         // Send encoded PDU buffer of specified length
         virtual int send_PDU(const char *buf, int len) = 0;
         // Connect with server specified by addr.
         virtual void connect(IYaz_PDU_Observer *observer,
                     const char *addr) = 0;
         // Listen on address addr.
         virtual void listen(IYaz_PDU_Observer *observer, const char *addr)=0;
         // Close connection
         virtual void close() = 0;
         // Make clone of this object using this interface
         virtual IYaz_PDU_Observable *clone() = 0;
         // Destroy completely
         virtual void destroy() = 0;
         // Set Idle Time
         virtual void idleTime (int timeout) = 0;


This interface is interested in PDUs and using an object implementing IYaz_PDU_Observable.

     #include <yaz++/pdu-observer.h>

     class my_pduobserver : public IYaz_PDU_Observer {
         // A PDU has been received
         virtual void recv_PDU(const char *buf, int len) = 0;
         // Called when Iyaz_PDU_Observable::connect was successful.
         virtual void connectNotify() = 0;
         // Called whenever the connection was closed
         virtual void failNotify() = 0;
         // Called whenever there is a timeout
         virtual void timeoutNotify() = 0;
         // Make clone of observer using IYaz_PDU_Observable interface
         virtual IYaz_PDU_Observer *sessionNotify(
         IYaz_PDU_Observable *the_PDU_Observable, int fd) = 0;


Abstract query.

     #include <yaz++/query.h>
     class my_query : public Yaz_Query {
         // Print query in buffer described by str and len
         virtual void print (char *str, int len) = 0;