<?php

/**

 * Zend Framework

 *

 * LICENSE

 *

 * This source file is subject to the new BSD license that is bundled

 * with this package in the file LICENSE.txt.

 * It is also available through the world-wide-web at this URL:

 * http://framework.zend.com/license/new-bsd

 * If you did not receive a copy of the license and are unable to

 * obtain it through the world-wide-web, please send an email

 * to license@zend.com so we can send you a copy immediately.

 *

 * @category   Zend

 * @package    Zend_Memory

 * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 * @version    $Id: Value.php 20096 2010-01-06 02:05:09Z bkarwin $

 */

/**

 * String value object

 *

 * It's an OO string wrapper.

 * Used to intercept string updates.

 *

 * @category   Zend

 * @package    Zend_Memory

 * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 * @todo       also implement Countable for PHP 5.1 but not yet to stay 5.0 compatible

 */

class Zend_Memory_Value implements ArrayAccess {

    /**

     * Value

     *

     * @var string

     */

    private $_value;

    /**

     * Container

     *

     * @var Zend_Memory_Container_Interface

     */

    private $_container;

    /**

     * Boolean flag which signals to trace value modifications

     *

     * @var boolean

     */

    private $_trace;

    /**

     * Object constructor

     *

     * @param string $value

     * @param Zend_Memory_Container_Movable $container

     */

    public function __construct($value, Zend_Memory_Container_Movable $container)

    {

        $this->_container = $container;

        $this->_value = (string)$value;

        /**

         * Object is marked as just modified by memory manager

         * So we don't need to trace followed object modifications and

         * object is processed (and marked as traced) when another

         * memory object is modified.

         *

         * It reduces overall numberr of calls necessary to modification trace

         */

        $this->_trace = false;

    }

    /**

     * ArrayAccess interface method

     * returns true if string offset exists

     *

     * @param integer $offset

     * @return boolean

     */

    public function offsetExists($offset)

    {

        return $offset >= 0  &&  $offset < strlen($this->_value);

    }

    /**

     * ArrayAccess interface method

     * Get character at $offset position

     *

     * @param integer $offset

     * @return string

     */

    public function offsetGet($offset)

    {

        return $this->_value[$offset];

    }

    /**

     * ArrayAccess interface method

     * Set character at $offset position

     *

     * @param integer $offset

     * @param string $char

     */

    public function offsetSet($offset, $char)

    {

        $this->_value[$offset] = $char;

        if ($this->_trace) {

            $this->_trace = false;

            $this->_container->processUpdate();

        }

    }

    /**

     * ArrayAccess interface method

     * Unset character at $offset position

     *

     * @param integer $offset

     */

    public function offsetUnset($offset)

    {

        unset($this->_value[$offset]);

        if ($this->_trace) {

            $this->_trace = false;

            $this->_container->processUpdate();

        }

    }

    /**

     * To string conversion

     *

     * @return string

     */

    public function __toString()

    {

        return $this->_value;

    }

    /**

     * Get string value reference

     *

     * _Must_ be used for value access before PHP v 5.2

     * or _may_ be used for performance considerations

     *

     * @internal

     * @return string

     */

    public function &getRef()

    {

        return $this->_value;

    }

    /**

     * Start modifications trace

     *

     * _Must_ be used for value access before PHP v 5.2

     * or _may_ be used for performance considerations

     *

     * @internal

     */

    public function startTrace()

    {

        $this->_trace = true;

    }

}