Source for file SharedMemory.php

<?php
require_once('Driver.php');
require_once('System/SharedMemory.php');
 
/**
 * A driver that use System_SharedMemory as data store
 */
class AJAX_Locking_Driver_SharedMemory extends AJAX_Locking_Driver
{
    var $shared;
 
    /**
     * Constructor
     *
     * @return AJAX_Locking_Driver 
     */
    function AJAX_Locking_Driver_SharedMemory($type = false, $options = false, $timeout = false)
    {
        parent::AJAX_Locking_Driver($timeout);
 
        $this->shared = &System_SharedMemory::factory($type, $options);
    }
 
    /**
     * 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)
    {
        $key = $this->_getKey($type, $id);
        $value = $this->shared->get($key);
        if (empty($value)) {
            // object is unlocked: lock it
            $value = $this->_getValue($user, $type, $id);
            $this->shared->set($key, $value);
            return true;
        } else {
            // object is locked: check if lock expired
            list($owner, $type, $id, $time) = $this->_parseValue($value);
            if (time() - $time > $this->timeout) {
                // lock expired: remove it and lock
                // $this->shared->rm($key);
                $this->shared->set($key, $value);
                return true;
            } else {
                // object properly locked by (another?) user
                return ($owner == $user);
            }
        }
 
    }
 
    /**
     * 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)
    {
        $key = $this->_getKey($type, $id);
        $value = $this->shared->get($key);
        if (empty($value)) {
            // object was not locked
            return false;
        } else {
            // check if user is owner of the lock
            list($owner, $type, $id, $time) = $this->_parseValue($value);
            if ($user == $owner) {
                // unlock it
                $this->shared->rm($key);
                return true;
            } else {
                // user cannot unlock it
                return false;
            }
        }
    }
 
    /**
     * 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)
    {
        $key = $this->_getKey($type, $id);
        $value = $this->shared->get($key);
        if (empty($value)) {
            // object is unlocked
            return AJAX_LOCKING_UNLOCKED . '~' . 'noboby';
        } else {
            // object is locked:
            // 1. check if current user is owner of the lock
            // 2. check if lock expired
            list($owner, $type, $id, $time) = $this->_parseValue($value);
            $timeout = (time() - $time > $this->timeout);
            if ($owner == $user) {
                if ($timeout) {
                    // lock expired: remove it and inform it's ower
                    $this->shared->rm($key);
                    return AJAX_LOCKING_TIMEOUT . '~' . $owner;
                } else {
                    return AJAX_LOCKING_OWNED . '~' . $owner;
                }
            } else {
                if ($timeout) {
                    // lock expired: remove it
                    $this->shared->rm($key);
                    return AJAX_LOCKING_UNLOCKED . '~' . 'nobody';
                } else {
                    return AJAX_LOCKING_LOCKED . '~' . $owner;
                }
            }
        }
    }
}
?>