PHP：使用过滤器删除XML中的无效utf-8字符

I have a large file, so I have created a filter for removing invalid utf-8 characters from XML.

class ValidUTF8XMLFilter extends php_user_filter {

    protected static $pattern = '/([\x09\x0A\x0D\x20-\x7E]|[\xC2-\xDF][\x80-\xBF]|\xE0[\xA0-\xBF][\x80-\xBF]|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}|\xED[\x80-\x9F][\x80-\xBF]|\xF0[\x90-\xBF][\x80-\xBF]{2}|[\xF1-\xF3][\x80-\xBF]{3}|\xF4[\x80-\x8F][\x80-\xBF]{2})|./x';

    function filter($in, $out, &$consumed, $closing)
    {
        while ($bucket = stream_bucket_make_writeable($in)) {
            $bucket->data = preg_replace(self::$pattern, '$1', $bucket->data);
            $consumed += $bucket->datalen;
            stream_bucket_append($out, $bucket);
        }
        return PSFS_PASS_ON;
    }
}

This filter will remove also utf-8 characters not only invalid in xml, but also in utf-8. The regex is taken from Multilingual form encoding. The class was taken from this answer: How to skip invalid characters in XML file using PHP and rewritten. The pattern in that answer won't work for invalid utf-8 characters, eg. 0x1D.

Will this filter work, in situation, where invalid bytes starts at the end of buffer and ends in beginning of next filtering? Is this situation possible?