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/* Copyright 2002-2010, OpenNebula Project Leads (OpenNebula.org)             */
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/* Licensed under the Apache License, Version 2.0 (the "License"); you may    */
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/* a copy of the License at                                                   */
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/* http://www.apache.org/licenses/LICENSE-2.0                                 */
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/* Unless required by applicable law or agreed to in writing, software        */
/* distributed under the License is distributed on an "AS IS" BASIS,          */
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/* -------------------------------------------------------------------------- */

#ifndef OBJECT_SQL_H_
#define OBJECT_SQL_H_

#include "SqlDB.h"

using namespace std;

class SqlDB;

/**
 * ObjectSQL class. Provides a SQL backend interface, it should be implemented
 * by persistent objects.
 */
class ObjectSQL
{
public:

    ObjectSQL(){};

    virtual ~ObjectSQL(){};

    /**
     *  Datatype for call back pointers
     */
    typedef int (ObjectSQL::*CallBackPtr)(void *, int, char ** ,char **);

    /**
     *  Set the callback function and custom arguments to be executed by the
     *  next SQL command
     *    @param ptr to the callback function
     *    @param arg custom arguments for the callback function
     */
    void set_callback(CallBackPtr ptr, void * arg)
    {
        callback.cb  = ptr;
        callback.arg = arg;
    };

    /**
     *  Test if the CallBack is set for the object.
     *    @return true if the callback is set
     */
    bool isCallBackSet()
    {
        return (callback.cb != 0);
    };

    /**
     *  Set the callback function and custom arguments to be executed by the
     *  next SQL command
     *    @param ptr to the callback function
     *    @param arg custom arguments for the callback function
     */
    int do_callback(int num, char **values, char **names)
    {
        return (this->*(callback.cb))(callback.arg, num, values, names);
    };

protected:
    /**
     *  Reads the ObjectSQL (identified with its OID) from the database.
     *    @param db pointer to the db
     *    @return 0 on success
     */
    virtual int select(
        SqlDB * db) = 0;

    /**
     *  Writes the ObjectSQL in the database.
     *    @param db pointer to the db
     *    @return 0 on success
     */
    virtual int insert(
        SqlDB * db) = 0;

    /**
     *  Updates the ObjectSQL in the database.
     *    @param db pointer to the db
     *    @return 0 on success
     */
    virtual int update(
        SqlDB * db) = 0;

    /**
     *  Removes the ObjectSQL from the database.
     *    @param db pointer to the db
     *    @return 0 on success
     */
    virtual int drop(
        SqlDB * db) = 0;

private:
    /**
     *  A Callback defined by the function to be executed, a generic argument
     *  and the columns returned by the query
     */
    struct CallBackRegister
    {
        CallBackPtr cb;
        void *      arg;
    };

    /**
     *  SQL callback to be executed for each row result of an SQL statement
     */
    CallBackRegister callback;
};

#endif /*OBJECT_SQL_H_*/