# Source: connector.h |
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    /*
       This file is part of the KDB libraries
       Copyright (c) 2000 Praduroux Alessandro <pradu@thekompany.com>

       This library is free software; you can redistribute it and/or
       modify it under the terms of the GNU Library General Public
       License as published by the Free Software Foundation; either
       version 2 of the License, or (at your option) any later version.

       This library is distributed in the hope that it will be useful,
       but WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
       Library General Public License for more details.

       You should have received a copy of the GNU Library General Public License
       along with this library; see the file COPYING.LIB.  If not, write to
       the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
       Boston, MA 02111-1307, USA.
    */

    #ifndef KDB_CONNECTOR_H
    #define KDB_CONNECTOR_H "$Id: connector.h,v 1.6 2001/02/01 03:15:49 garbanzo Exp $"

    #include <qstring.h>
    #include <qstringlist.h>

    #include <kdb/exception.h>
    #include <kdb/object.h>
    #include <kdb/kdb.h>

    namespace KDB {

    class Exception;
    class Handler;
    class Table;
    class Field;
    class Query;

    /**
     * @short base interaction class for plugins.
     *
     * This is the base class for the interaction between kdbcore and
     * the various plugins. It should be subclassed by plugins, but should
     * not be used by the client programs
     *
     *
     * @author Alessandro Praduroux <pradu@thekompany.com>
     * @version kdbcore 0.0.2
     */

    class Connector :
    	public Object {

     public:
        Connector();
        Connector(const Connector& c);
        virtual ~Connector();

        // virtual methods: must be overridden in the subclass

        /**
         * closes the connection to the database backend
         */
        virtual void close();

        /**
         * opens the connection to the database backend
         */
        virtual bool connect() = 0;

        /**
         * returns the list of the available databases
         * for the current open connection
         */
        virtual QStringList databases() = 0;

        /**
         * returns the list of the available tables
         * for the current open database
         */
        virtual QStringList tables() = 0;

        /**
         * returns the list of the fields for the given table
         * for the current open database. The rows must contain:
         *
         * @li field name
         * @li datatype, native form
         * @li size, where applicable
         * @li precision, where applicable
         * @li Null constraint (Y/N)
         * @li Default value
         * @li referential constraint
         * @li comment
         *
         * the only mandatory fields are field name, datatype and size. All
         * other values can be present if the DBMS is able to give them
         */
        virtual RowList fields(const QString & tableName) = 0;

        /**
         * executes an SQL statement. The return value is the number of
         * rows affected by the statement
         */
        virtual KDB_ULONG execute(const QString &sql) = 0;

        /**
         * creates an empty database
         */
        virtual bool createDatabase(const QString & name) = 0;

        /**
         * drops a database with all its content
         */
        virtual bool dropDatabase(const QString & name) = 0;

        /**
         * creates a table with the characteristic of the given one
         */
        virtual bool createTable(const Table & tab) = 0;

        /**
         * remove a table in the currend database deleting all its content
         */
        virtual bool dropTable(const QString & name) = 0;

        /**
         * append a file to a table. the underlying DBMS must issue an alter here
         */
        virtual bool appendField(const QString &table, Field *f) = 0;

        /**
         * remove a field from a table. the underlying DBMS must issue an alter here
         */
        virtual bool removeField(const QString &table, const QString &field) = 0;

        /**
         * change the definition of a field of the given table. the underlying DBMS
         * must issue an alter here
         */
        virtual bool changeField(const QString &table, Field *f) = 0;

        /**
         * clones the current object. If the object holds an open connection,
         * the resulting connector must be open too.
         */
        virtual Connector * clone() = 0;

        /**
         * set the operational database for the current connector. From this
         * point all the methods will affect the selected database
         */
        virtual bool setCurrentDatabase(const QString &name) = 0;

        /**
         * returns the corresponding KDB datatype for the given native one
         */
        virtual DataType nativeToKDB(const QString &type) = 0;

        /**
         *  returns the corresponding native datatype for the given KDB one
         */
        virtual QString KDBToNative(DataType type) = 0;

        /**
         * executes a select to the backend and returns an handler to the
         * result
         */
        virtual Handler *query(const QString &SQL) = 0;

        /**
         * Create a query object. Plugins can override some functions of the class Query to take
         * advantage of some specific optimizations. This is entirely optional, default implementations
         * with a meaningful behaviour are provided in the kdedb core library
         */
        virtual Query *createQueryObject(QObject *parent = 0L,
                                         const char *name = 0L,
                                         const QString &sql = QString::null);

        /**
         * start a transaction for the current connection
         * an error is raised if the underlying DBMS does not support
         * transactions
         */
        virtual void beginTransaction() = 0;

        /**
         * end the current transaction and save all the changes to the
         * database.
         * an error is raised if the underlying DBMS does not support
         * transactions or if there isn't any transaction started
         */
        virtual void commit() = 0;

        /**
         * end the current transaction and drop all changes made up to now.
         * an error is raised if the underlying DBMS does not support
         * transactions or if there isn't any transaction started
         */
        virtual void rollback() = 0;

        // nonvirtual methods
        /// @internal
        void setHost(const QString & host);
        /// @internal
        void setPort(int port);
        /// @internal
        void setUser(const QString & user);
        /// @internal
        void setPassword(const QString & pwd);

        /// @internal
        QString host() const;
        /// @internal
        int port() const;
        /// @internal
        QString user() const;
        /// @internal
        QString password() const;
        /// @internal
        bool isConnected() const;

     protected:

        /**
         * must be called by subclasses when a connection to the backend
         * is established
         */
        void setConnected(bool conn);

     private:

        QString _host;
        int _port;
        QString _user;
        QString _pwd;

        bool _connected;

    };

    };
    #endif

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