Source for file MDB2.php

<?php
require_once('Driver.php');
require_once('MDB2.php');
 
/**
 * A driver that use MDB2 as data store
 */
class AJAX_Locking_Driver_MDB2 extends AJAX_Locking_Driver
{
    /**
     * Instance of a MDB2 connection
     *
     * @var MBD2 connection
     */
    var $mdb2;
 
    /**
     * Default table and columns names
     *
     * @var array 
     */
    var $names = array(
       'table' => 'ajax_locks',
       'columns' => array(
           'type' => 'type',
           'id' => 'id',
           'user' => '[user]',
           'time' => '[time]'
       )
    );
 
    /**
     * Constructor
     *
     * @param mixed $dsn DSN for MDB2 connection
     * @param array $names names of table and its columns where store data
     * @param int $timeout session timeout
     * @return AJAX_Locking_Driver 
     */
    function AJAX_Locking_Driver_MDB2($dsn = false, $names = false, $timeout = false)
    {
        parent::AJAX_Locking_Driver($timeout);
 
        $this->mdb2 =& MDB2::factory($dsn);
        if (PEAR::isError($this->mdb2)) {
            die($this->mdb2->getMessage());
        }
 
        // eventually override default names of table and columns
        if ($names && is_array($names)) {
            $names['columns'] = array_merge($this->names['columns'], $names['columns']);
            $this->names = array_merge($this->names, $names);
        }
    }
 
    /**
     * Locks an object
     *
     * @param mixed $user    id of the user who wants to lock
     * @param string $type    type/classname of the object
     * @param mixed $id        id of the object
     * @return boolean true if the unlock was successfull, false otherwise
     */
    function lock($user, $type, $id)
    {
        $result = false;
        $this->mdb2->beginTransaction();
 
        $sql = $this->_getStatusSQL($type, $id);
        $rs = $this->mdb2->query($sql);
        if (PEAR::isError($rs)) {
            die($rs->getMessage());
        }
        $row = $rs->fetchRow();
        if (!$row) {
            // object is unlocked: lock it
            $sql = $this->_getLockSQL($user, $type, $id);
            $affected =& $this->mdb2->exec($sql);
            if (PEAR::isError($affected)) {
               die($affected->getMessage());
            }
            $result = true;
        } else {
            // object is locked: check if lock expired
            $time = $row[3];
            if (time() - $time > $this->timeout) {
                // lock expired: remove it and lock
                $sql = $this->_getUnlockSQL($type, $id);
                $this->mdb2->exec($sql);
                $sql = $this->_getLockSQL($user, $type, $id);
                $this->mdb2->exec($sql);
                $result = true;
            } else {
                // object properly locked by (another?) user
                $result = ($owner == $user);
            }
        }
 
        $this->mdb2->commit();
 
        return $result;
    }
 
    /**
     * Unlocks an object
     *
     * @param mixed $user    id of the user who wants to unlock
     * @param string $type    type/classname of the object
     * @param mixed $id        id of the object
     * @return boolean true if the unlock was successfull, false otherwise
     */
    function unlock($user, $type, $id)
    {
        $result = false;
        $this->mdb2->beginTransaction();
 
        $sql = $this->_getStatusSQL($type, $id);
        $rs = $this->mdb2->query($sql);
        if (PEAR::isError($rs)) {
            die($rs->getMessage());
        }
        $row = $rs->fetchRow();
        if (!$row) {
            // object was not locked
            $result = false;
        } else {
            // check if user is owner of the lock
            $owner = $row[2];
            if ($user == $owner) {
                // unlock it
                $sql = $this->_getUnlockSQL($type, $id);
                $this->mdb2->exec($sql);
                $result = true;
            } else {
                // user cannot unlock it
                $result = false;
            }
        }
 
        $this->mdb2->commit();
        return $result;
    }
 
    /**
     * Returns the status of the object (lock or unlocked)
     *
     * @param mixed $user    id of the user who wants to know the object's status
     * @param string $type    type/classname of the object
     * @param mixed $id        id of the object
     * @return string the status and the owner of the object
     */
    function status($user, $type, $id)
    {
        $result = "~";
        $this->mdb2->beginTransaction();
 
        $sql = $this->_getStatusSQL($type, $id);
        $rs = $this->mdb2->query($sql);
        if (PEAR::isError($rs)) {
            die($rs->getMessage());
        }
        $row = $rs->fetchRow();
        if (!$row) {
            // object is unlocked
            $result =  AJAX_LOCKING_UNLOCKED . '~' . 'noboby';
        } else {
            // object is locked:
            // 1. check if current user is owner of the lock
            // 2. check if lock expired
            $owner = $row[2]; $time = $row[3];
            $timeout = (time() - $time > $this->timeout);
            if ($owner == $user) {
                if ($timeout) {
                    // lock expired: remove it and inform it's ower
                    $sql = $this->_getUnlockSQL($type, $id);
                    $this->mdb2->exec($sql);
                    $result = AJAX_LOCKING_TIMEOUT . '~' . $owner;
                } else {
                    $result = AJAX_LOCKING_OWNED . '~' . $owner;
                }
            } else {
                if ($timeout) {
                    // lock expired: remove it
                    $sql = $this->_getUnlockSQL($type, $id);
                    $this->mdb2->exec($sql);
                    $result = AJAX_LOCKING_UNLOCKED . '~' . 'nobody';
                } else {
                    $result = AJAX_LOCKING_LOCKED . '~' . $owner;
                }
            }
        }
 
        $this->mdb2->commit();
        return $result;
    }
 
    /**
     * Returns the list of all active locks for administration purpose
     *
     * @return array of locks (owner, type, id), false if not implemented
     */
    function getLocks()
    {
        $locks = array();
 
        $sql = $this->_getListSQL($type, $id);
        $rs = $this->mdb2->query($sql);
        if (PEAR::isError($rs)) {
            die($rs->getMessage());
        }
        while (($row = $rs->fetchRow())) {
            list($owner, $type, $id, $time) = $row;
            $timeout = (time() - $time > $this->timeout);
            if (!$timeout) {
                $locks[] = array(
                    'owner' => $owner,
                    'type' => $type,
                    'id' => $id
                );
            }
        }
 
        return $locks;
    }
 
    /**
     * Administrately delete lock
     *
     * @param string $type 
     * @param mixed $id 
     *
     * @return true if the lock is deleted successfully, false otherwise
     */
    function delete($type, $id)
    {
        $sql = $this->_getUnlockSQL($type, $id);
        return $this->mdb2->exec($sql);
    }
 
 
    function _getStatusSQL($type, $id)
    {
        $sql = sprintf("select * from %s where %s = %s and %s = %s",
           $this->names['table'],
           $this->names['columns']['type'], $this->mdb2->quote($type),
           $this->names['columns']['id'], $this->mdb2->quote($id));
        return $sql;
    }
 
    function _getLockSQL($user, $type, $id)
    {
        $timestamp = time();
        $sql = sprintf("insert into %s (%s, %s, %s, %s) values(%s, %s, %s, %s)",
           $this->names['table'],
           $this->names['columns']['type'], $this->names['columns']['id'], $this->names['columns']['user'], $this->names['columns']['time'],
           $this->mdb2->quote($type),
           $this->mdb2->quote($id),
           $this->mdb2->quote($user),
           $timestamp);
        return $sql;
    }
 
    function _getUnlockSQL($type, $id)
    {
        $sql = sprintf("delete from %s where %s = %s and %s = %s",
           $this->names['table'],
           $this->names['columns']['type'], $this->mdb2->quote($type),
           $this->names['columns']['id'], $this->mdb2->quote($id));
        return $sql;
    }
 
    function _getListSQL($type, $id)
    {
        $sql = sprintf("select * from %s",
           $this->names['table']);
        return $sql;
    }
 
}
?>