SMF 2.0.12 safe_unserialize

/**
 * Safe unserialize() replacement
 * - accepts a strict subset of PHP's native serialized representation
 * - does not unserialize objects
 *
 * @param string $str
 * @return mixed
 * @throw Exception if $str is malformed or contains unsupported types (e.g., resources, objects)
 */
function _safe_unserialize($str)
{
    // Input  is not a string.
    if(empty($str) || !is_string($str))
        return false;

    $stack = array();
    $expected = array();

    /*
     * states:
     *   0 - initial state, expecting a single value or array
     *   1 - terminal state
     *   2 - in array, expecting end of array or a key
     *   3 - in array, expecting value or another array
     */
    $state = 0;
    while($state != 1)
    {
        $type = isset($str[0]) ? $str[0] : '';
        if($type == '}')
            $str = substr($str, 1);

        else if($type == 'N' && $str[1] == ';')
        {
            $value = null;
            $str = substr($str, 2);
        }
        else if($type == 'b' && preg_match('/^b:([01]);/', $str, $matches))
        {
            $value = $matches[1] == '1' ? true : false;
            $str = substr($str, 4);
        }
        else if($type == 'i' && preg_match('/^i:(-?[0-9]+);(.*)/s', $str, $matches))
        {
            $value = (int)$matches[1];
            $str = $matches[2];
        }
        else if($type == 'd' && preg_match('/^d:(-?[0-9]+\.?[0-9]*(E[+-][0-9]+)?);(.*)/s', $str, $matches))
        {
            $value = (float)$matches[1];
            $str = $matches[3];
        }
        else if($type == 's' && preg_match('/^s:([0-9]+):"(.*)/s', $str, $matches) && substr($matches[2], (int)$matches[1], 2) == '";')
        {
            $value = substr($matches[2], 0, (int)$matches[1]);
            $str = substr($matches[2], (int)$matches[1] + 2);
        }
        else if($type == 'a' && preg_match('/^a:([0-9]+):{(.*)/s', $str, $matches))
        {
            $expectedLength = (int)$matches[1];
            $str = $matches[2];
        }

        // Object or unknown/malformed type.
        else
            return false;

        switch($state)
        {
            case 3: // In array, expecting value or another array.
                if($type == 'a')
                {
                    $stack[] = &$list;
                    $list[$key] = array();
                    $list = &$list[$key];
                    $expected[] = $expectedLength;
                    $state = 2;
                    break;
                }
                if($type != '}')
                {
                    $list[$key] = $value;
                    $state = 2;
                    break;
                }

                // Missing array value.
                return false;

            case 2: // in array, expecting end of array or a key
                if($type == '}')
                {
                    // Array size is less than expected.
                    if(count($list) < end($expected))
                        return false;

                    unset($list);
                    $list = &$stack[count($stack)-1];
                    array_pop($stack);

                    // Go to terminal state if we're at the end of the root array.
                    array_pop($expected);

                    if(count($expected) == 0)
                        $state = 1;

                    break;
                }

                if($type == 'i' || $type == 's')
                {
                    // Array size exceeds expected length.
                    if(count($list) >= end($expected))
                        return false;

                    $key = $value;
                    $state = 3;
                    break;
                }

                // Illegal array index type.
                return false;

            // Expecting array or value.
            case 0:
                if($type == 'a')
                {
                    $data = array();
                    $list = &$data;
                    $expected[] = $expectedLength;
                    $state = 2;
                    break;
                }

                if($type != '}')
                {
                    $data = $value;
                    $state = 1;
                    break;
                }

                // Not in array.
                return false;
        }
    }

    // Trailing data in input.
    if(!empty($str))
        return false;

    return $data;
}

/**
 * Wrapper for _safe_unserialize() that handles exceptions and multibyte encoding issue
 *
 * @param string $str
 * @return mixed
 */
function safe_unserialize($str)
{
    // Make sure we use the byte count for strings even when strlen() is overloaded by mb_strlen()
    if (function_exists('mb_internal_encoding') &&
        (((int) ini_get('mbstring.func_overload')) & 0x02))
    {
        $mbIntEnc = mb_internal_encoding();
        mb_internal_encoding('ASCII');
    }

    $out = _safe_unserialize($str);

    if (isset($mbIntEnc))
        mb_internal_encoding($mbIntEnc);

    return $out;
}