Merged devel-framework branch (r5746:5779) back into trunk

1 files changed, 745 insertions, 0 deletions

diff --git a/program/include/rcube_charset.php b/program/include/rcube_charset.php
new file mode 100644
index 000000000..29de426d8
--- /dev/null
+++ b/program/include/rcube_charset.php
@@ -0,0 +1,745 @@
+<?php
+
+/*
+ +-----------------------------------------------------------------------+
+ | program/include/rcube_charset.php                                     |
+ |                                                                       |
+ | This file is part of the Roundcube Webmail client                     |
+ | Copyright (C) 2005-2012, The Roundcube Dev Team                       |
+ | Copyright (C) 2011-2012, Kolab Systems AG                             |
+ | Copyright (C) 2000 Edmund Grimley Evans <edmundo@rano.org>            |
+ | Licensed under the GNU GPL                                            |
+ |                                                                       |
+ | PURPOSE:                                                              |
+ |   Provide charset conversion functionality                            |
+ |                                                                       |
+ +-----------------------------------------------------------------------+
+ | Author: Thomas Bruederli <roundcube@gmail.com>                        |
+ | Author: Aleksander Machniak <alec@alec.pl>                            |
+ +-----------------------------------------------------------------------+
+
+ $Id$
+
+*/
+
+/**
+ * Character sets conversion functionality
+ *
+ * @package Core
+ * @author Thomas Bruederli <roundcube@gmail.com>
+ * @author Aleksander Machniak <alec@alec.pl>
+ * @author Edmund Grimley Evans <edmundo@rano.org>
+ */
+class rcube_charset
+{
+    // Aliases: some of them from HTML5 spec.
+    static public $aliases = array(
+        'USASCII'       => 'WINDOWS-1252',
+        'ANSIX31101983' => 'WINDOWS-1252',
+        'ANSIX341968'   => 'WINDOWS-1252',
+        'UNKNOWN8BIT'   => 'ISO-8859-15',
+        'UNKNOWN'       => 'ISO-8859-15',
+        'USERDEFINED'   => 'ISO-8859-15',
+        'KSC56011987'   => 'EUC-KR',
+        'GB2312' 	    => 'GBK',
+        'GB231280'	    => 'GBK',
+        'UNICODE'	    => 'UTF-8',
+        'UTF7IMAP'	    => 'UTF7-IMAP',
+        'TIS620'	    => 'WINDOWS-874',
+        'ISO88599'	    => 'WINDOWS-1254',
+        'ISO885911'	    => 'WINDOWS-874',
+        'MACROMAN'	    => 'MACINTOSH',
+        '77'            => 'MAC',
+        '128'           => 'SHIFT-JIS',
+        '129'           => 'CP949',
+        '130'           => 'CP1361',
+        '134'           => 'GBK',
+        '136'           => 'BIG5',
+        '161'           => 'WINDOWS-1253',
+        '162'           => 'WINDOWS-1254',
+        '163'           => 'WINDOWS-1258',
+        '177'           => 'WINDOWS-1255',
+        '178'           => 'WINDOWS-1256',
+        '186'           => 'WINDOWS-1257',
+        '204'           => 'WINDOWS-1251',
+        '222'           => 'WINDOWS-874',
+        '238'           => 'WINDOWS-1250',
+        'MS950'         => 'CP950',
+        'WINDOWS949'    => 'UHC',
+    );
+
+
+    /**
+     * Catch an error and throw an exception.
+     *
+     * @param  int    Level of the error
+     * @param  string Error message
+     */
+    public function error_handler($errno, $errstr)
+    {
+        throw new ErrorException($errstr, 0, $errno);
+    }
+
+
+    /**
+     * Parse and validate charset name string (see #1485758).
+     * Sometimes charset string is malformed, there are also charset aliases 
+     * but we need strict names for charset conversion (specially utf8 class)
+     *
+     * @param  string Input charset name
+     *
+     * @return string The validated charset name
+     */
+    public static function parse($input)
+    {
+        static $charsets = array();
+        $charset = strtoupper($input);
+
+        if (isset($charsets[$input])) {
+            return $charsets[$input];
+        }
+
+        $charset = preg_replace(array(
+            '/^[^0-9A-Z]+/',    // e.g. _ISO-8859-JP$SIO
+            '/\$.*$/',          // e.g. _ISO-8859-JP$SIO
+            '/UNICODE-1-1-*/',  // RFC1641/1642
+            '/^X-/',            // X- prefix (e.g. X-ROMAN8 => ROMAN8)
+        ), '', $charset);
+
+        if ($charset == 'BINARY') {
+            return $charsets[$input] = null;
+        }
+
+        // allow A-Z and 0-9 only
+        $str = preg_replace('/[^A-Z0-9]/', '', $charset);
+
+        if (isset(self::$aliases[$str])) {
+            $result = self::$aliases[$str];
+        }
+        // UTF
+        else if (preg_match('/U[A-Z][A-Z](7|8|16|32)(BE|LE)*/', $str, $m)) {
+            $result = 'UTF-' . $m[1] . $m[2];
+        }
+        // ISO-8859
+        else if (preg_match('/ISO8859([0-9]{0,2})/', $str, $m)) {
+            $iso = 'ISO-8859-' . ($m[1] ? $m[1] : 1);
+            // some clients sends windows-1252 text as latin1,
+            // it is safe to use windows-1252 for all latin1
+            $result = $iso == 'ISO-8859-1' ? 'WINDOWS-1252' : $iso;
+        }
+        // handle broken charset names e.g. WINDOWS-1250HTTP-EQUIVCONTENT-TYPE
+        else if (preg_match('/(WIN|WINDOWS)([0-9]+)/', $str, $m)) {
+            $result = 'WINDOWS-' . $m[2];
+        }
+        // LATIN
+        else if (preg_match('/LATIN(.*)/', $str, $m)) {
+            $aliases = array('2' => 2, '3' => 3, '4' => 4, '5' => 9, '6' => 10,
+                '7' => 13, '8' => 14, '9' => 15, '10' => 16,
+                'ARABIC' => 6, 'CYRILLIC' => 5, 'GREEK' => 7, 'GREEK1' => 7, 'HEBREW' => 8
+            );
+
+            // some clients sends windows-1252 text as latin1,
+            // it is safe to use windows-1252 for all latin1
+            if ($m[1] == 1) {
+                $result = 'WINDOWS-1252';
+            }
+            // if iconv is not supported we need ISO labels, it's also safe for iconv
+            else if (!empty($aliases[$m[1]])) {
+                $result = 'ISO-8859-'.$aliases[$m[1]];
+            }
+            // iconv requires convertion of e.g. LATIN-1 to LATIN1
+            else {
+                $result = $str;
+            }
+        }
+        else {
+            $result = $charset;
+        }
+
+        $charsets[$input] = $result;
+
+        return $result;
+    }
+
+
+    /**
+     * Convert a string from one charset to another.
+     * Uses mbstring and iconv functions if possible
+     *
+     * @param  string Input string
+     * @param  string Suspected charset of the input string
+     * @param  string Target charset to convert to; defaults to RCMAIL_CHARSET
+     *
+     * @return string Converted string
+     */
+    public static function convert($str, $from, $to = null)
+    {
+        static $iconv_options   = null;
+        static $mbstring_loaded = null;
+        static $mbstring_list   = null;
+        static $conv            = null;
+
+        $to   = empty($to) ? strtoupper(RCMAIL_CHARSET) : self::parse($to);
+        $from = self::parse($from);
+
+        if ($from == $to || empty($str) || empty($from)) {
+            return $str;
+        }
+
+        // convert charset using iconv module
+        if (function_exists('iconv') && $from != 'UTF7-IMAP' && $to != 'UTF7-IMAP') {
+            if ($iconv_options === null) {
+                // ignore characters not available in output charset
+                $iconv_options = '//IGNORE';
+                if (iconv('', $iconv_options, '') === false) {
+                    // iconv implementation does not support options
+                    $iconv_options = '';
+                }
+            }
+
+            // throw an exception if iconv reports an illegal character in input
+            // it means that input string has been truncated
+            set_error_handler(array('rcube_charset', 'error_handler'), E_NOTICE);
+            try {
+                $_iconv = iconv($from, $to . $iconv_options, $str);
+            } catch (ErrorException $e) {
+                $_iconv = false;
+            }
+            restore_error_handler();
+
+            if ($_iconv !== false) {
+                return $_iconv;
+            }
+        }
+
+        if ($mbstring_loaded === null) {
+            $mbstring_loaded = extension_loaded('mbstring');
+        }
+
+        // convert charset using mbstring module
+        if ($mbstring_loaded) {
+            $aliases['WINDOWS-1257'] = 'ISO-8859-13';
+
+            if ($mbstring_list === null) {
+                $mbstring_list = mb_list_encodings();
+                $mbstring_list = array_map('strtoupper', $mbstring_list);
+            }
+
+            $mb_from = $aliases[$from] ? $aliases[$from] : $from;
+            $mb_to   = $aliases[$to] ? $aliases[$to] : $to;
+
+            // return if encoding found, string matches encoding and convert succeeded
+            if (in_array($mb_from, $mbstring_list) && in_array($mb_to, $mbstring_list)) {
+                if (mb_check_encoding($str, $mb_from) && ($out = mb_convert_encoding($str, $mb_to, $mb_from))) {
+                    return $out;
+                }
+            }
+        }
+
+        // convert charset using bundled classes/functions
+        if ($to == 'UTF-8') {
+            if ($from == 'UTF7-IMAP') {
+                if ($_str = self::utf7imap_to_utf8($str)) {
+                    return $_str;
+                }
+            }
+            else if ($from == 'UTF-7') {
+                if ($_str = self::utf7_to_utf8($str)) {
+                    return $_str;
+                }
+            }
+            else if ($from == 'ISO-8859-1' && function_exists('utf8_encode')) {
+                return utf8_encode($str);
+            }
+            else if (class_exists('utf8')) {
+                if (!$conv) {
+                    $conv = new utf8($from);
+                }
+                else {
+                    $conv->loadCharset($from);
+                }
+
+                if ($_str = $conv->strToUtf8($str)) {
+                    return $_str;
+                }
+            }
+        }
+
+        // encode string for output
+        if ($from == 'UTF-8') {
+            // @TODO: we need a function for UTF-7 (RFC2152) conversion
+            if ($to == 'UTF7-IMAP' || $to == 'UTF-7') {
+                if ($_str = utf8_to_utf7imap($str)) {
+                    return $_str;
+                }
+            }
+            else if ($to == 'ISO-8859-1' && function_exists('utf8_decode')) {
+                return utf8_decode($str);
+            }
+            else if (class_exists('utf8')) {
+                if (!$conv) {
+                    $conv = new utf8($to);
+                }
+                else {
+                    $conv->loadCharset($from);
+                }
+
+                if ($_str = $conv->strToUtf8($str)) {
+                    return $_str;
+                }
+            }
+        }
+
+        // return original string
+        return $str;
+    }
+
+
+    /**
+     * Converts string from standard UTF-7 (RFC 2152) to UTF-8.
+     *
+     * @param  string  Input string (UTF-7)
+     *
+     * @return string  Converted string (UTF-8)
+     */
+    public static function utf7_to_utf8($str)
+    {
+        $Index_64 = array(
+            0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
+            0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
+            0,0,0,0, 0,0,0,0, 0,0,0,1, 0,0,0,0,
+            1,1,1,1, 1,1,1,1, 1,1,0,0, 0,0,0,0,
+            0,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1,
+            1,1,1,1, 1,1,1,1, 1,1,1,0, 0,0,0,0,
+            0,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1,
+            1,1,1,1, 1,1,1,1, 1,1,1,0, 0,0,0,0,
+        );
+
+        $u7len = strlen($str);
+        $str   = strval($str);
+        $res   = '';
+
+        for ($i=0; $u7len > 0; $i++, $u7len--) {
+            $u7 = $str[$i];
+            if ($u7 == '+') {
+                $i++;
+                $u7len--;
+                $ch = '';
+
+                for (; $u7len > 0; $i++, $u7len--) {
+                    $u7 = $str[$i];
+
+                    if (!$Index_64[ord($u7)]) {
+                        break;
+                    }
+
+	                $ch .= $u7;
+                }
+
+                if ($ch == '') {
+                    if ($u7 == '-') {
+                        $res .= '+';
+                    }
+
+                    continue;
+                }
+
+                $res .= self::utf16_to_utf8(base64_decode($ch));
+            }
+            else {
+                $res .= $u7;
+            }
+        }
+
+        return $res;
+    }
+
+
+    /**
+     * Converts string from UTF-16 to UTF-8 (helper for utf-7 to utf-8 conversion)
+     *
+     * @param  string  Input string
+     *
+     * @return string  The converted string
+     */
+    public static function utf16_to_utf8($str)
+    {
+        $len = strlen($str);
+        $dec = '';
+
+        for ($i = 0; $i < $len; $i += 2) {
+            $c = ord($str[$i]) << 8 | ord($str[$i + 1]);
+            if ($c >= 0x0001 && $c <= 0x007F) {
+                $dec .= chr($c);
+            }
+            else if ($c > 0x07FF) {
+                $dec .= chr(0xE0 | (($c >> 12) & 0x0F));
+                $dec .= chr(0x80 | (($c >>  6) & 0x3F));
+                $dec .= chr(0x80 | (($c >>  0) & 0x3F));
+            }
+            else {
+                $dec .= chr(0xC0 | (($c >>  6) & 0x1F));
+                $dec .= chr(0x80 | (($c >>  0) & 0x3F));
+            }
+        }
+
+        return $dec;
+    }
+
+
+    /**
+     * Convert the data ($str) from RFC 2060's UTF-7 to UTF-8.
+     * If input data is invalid, return the original input string.
+     * RFC 2060 obviously intends the encoding to be unique (see
+     * point 5 in section 5.1.3), so we reject any non-canonical
+     * form, such as &ACY- (instead of &-) or &AMA-&AMA- (instead
+     * of &AMAAwA-).
+     *
+     * Translated from C to PHP by Thomas Bruederli <roundcube@gmail.com>
+     *
+     * @param string $str Input string (UTF7-IMAP)
+     *
+     * @return string Output string (UTF-8)
+     */
+    public static function utf7imap_to_utf8($str)
+    {
+        $Index_64 = array(
+            -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
+            -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
+            -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, 63,-1,-1,-1,
+            52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-1,-1,-1,
+            -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
+            15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
+            -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
+            41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
+        );
+
+        $u7len = strlen($str);
+        $str   = strval($str);
+        $p     = '';
+        $err   = '';
+
+        for ($i=0; $u7len > 0; $i++, $u7len--) {
+            $u7 = $str[$i];
+            if ($u7 == '&') {
+                $i++;
+                $u7len--;
+                $u7 = $str[$i];
+
+                if ($u7len && $u7 == '-') {
+                    $p .= '&';
+                    continue;
+                }
+
+                $ch = 0;
+                $k = 10;
+                for (; $u7len > 0; $i++, $u7len--) {
+                    $u7 = $str[$i];
+
+                    if ((ord($u7) & 0x80) || ($b = $Index_64[ord($u7)]) == -1) {
+                        break;
+                    }
+
+                    if ($k > 0) {
+                        $ch |= $b << $k;
+                        $k -= 6;
+                    }
+                    else {
+                        $ch |= $b >> (-$k);
+                        if ($ch < 0x80) {
+                            // Printable US-ASCII
+                            if (0x20 <= $ch && $ch < 0x7f) {
+                                return $err;
+                            }
+                            $p .= chr($ch);
+                        }
+                        else if ($ch < 0x800) {
+                            $p .= chr(0xc0 | ($ch >> 6));
+                            $p .= chr(0x80 | ($ch & 0x3f));
+                        }
+                        else {
+                            $p .= chr(0xe0 | ($ch >> 12));
+                            $p .= chr(0x80 | (($ch >> 6) & 0x3f));
+                            $p .= chr(0x80 | ($ch & 0x3f));
+                        }
+
+                        $ch = ($b << (16 + $k)) & 0xffff;
+                        $k += 10;
+                    }
+                }
+
+                // Non-zero or too many extra bits
+                if ($ch || $k < 6) {
+                    return $err;
+                }
+
+                // BASE64 not properly terminated
+                if (!$u7len || $u7 != '-') {
+                    return $err;
+                }
+
+                // Adjacent BASE64 sections
+                if ($u7len > 2 && $str[$i+1] == '&' && $str[$i+2] != '-') {
+                    return $err;
+                }
+            }
+            // Not printable US-ASCII
+            else if (ord($u7) < 0x20 || ord($u7) >= 0x7f) {
+                return $err;
+            }
+            else {
+                $p .= $u7;
+            }
+        }
+
+        return $p;
+    }
+
+
+    /**
+     * Convert the data ($str) from UTF-8 to RFC 2060's UTF-7.
+     * Unicode characters above U+FFFF are replaced by U+FFFE.
+     * If input data is invalid, return an empty string.
+     *
+     * Translated from C to PHP by Thomas Bruederli <roundcube@gmail.com>
+     *
+     * @param string $str Input string (UTF-8)
+     *
+     * @return string Output string (UTF7-IMAP)
+     */
+    public static function utf8_to_utf7imap($str)
+    {
+        $B64Chars = array(
+            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
+            'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
+            'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
+            't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
+            '8', '9', '+', ','
+        );
+
+        $u8len  = strlen($str);
+        $base64 = 0;
+        $i      = 0;
+        $p      = '';
+        $err    = '';
+
+        while ($u8len) {
+            $u8 = $str[$i];
+            $c  = ord($u8);
+
+            if ($c < 0x80) {
+                $ch = $c;
+                $n  = 0;
+            }
+            else if ($c < 0xc2) {
+                return $err;
+            }
+            else if ($c < 0xe0) {
+                $ch = $c & 0x1f;
+                $n  = 1;
+            }
+            else if ($c < 0xf0) {
+                $ch = $c & 0x0f;
+                $n  = 2;
+            }
+            else if ($c < 0xf8) {
+                $ch = $c & 0x07;
+                $n  = 3;
+            }
+            else if ($c < 0xfc) {
+                $ch = $c & 0x03;
+                $n  = 4;
+            }
+            else if ($c < 0xfe) {
+                $ch = $c & 0x01;
+                $n  = 5;
+            }
+            else {
+                return $err;
+            }
+
+            $i++;
+            $u8len--;
+
+            if ($n > $u8len) {
+                return $err;
+            }
+
+            for ($j=0; $j < $n; $j++) {
+                $o = ord($str[$i+$j]);
+                if (($o & 0xc0) != 0x80) {
+                    return $err;
+                }
+                $ch = ($ch << 6) | ($o & 0x3f);
+            }
+
+            if ($n > 1 && !($ch >> ($n * 5 + 1))) {
+                return $err;
+            }
+
+            $i += $n;
+            $u8len -= $n;
+
+            if ($ch < 0x20 || $ch >= 0x7f) {
+                if (!$base64) {
+                    $p .= '&';
+                    $base64 = 1;
+                    $b = 0;
+                    $k = 10;
+                }
+                if ($ch & ~0xffff) {
+                    $ch = 0xfffe;
+                }
+
+                $p .= $B64Chars[($b | $ch >> $k)];
+                $k -= 6;
+                for (; $k >= 0; $k -= 6) {
+                    $p .= $B64Chars[(($ch >> $k) & 0x3f)];
+                }
+
+                $b = ($ch << (-$k)) & 0x3f;
+                $k += 16;
+            }
+            else {
+                if ($base64) {
+                    if ($k > 10) {
+                        $p .= $B64Chars[$b];
+                    }
+                    $p .= '-';
+                    $base64 = 0;
+                }
+
+                $p .= chr($ch);
+                if (chr($ch) == '&') {
+                    $p .= '-';
+                }
+            }
+        }
+
+        if ($base64) {
+            if ($k > 10) {
+                $p .= $B64Chars[$b];
+            }
+            $p .= '-';
+        }
+
+        return $p;
+    }
+
+
+    /**
+     * A method to guess character set of a string.
+     *
+     * @param string $string    String.
+     * @param string $failover 	Default result for failover.
+     *
+     * @return string Charset name
+     */
+    public static function detect($string, $failover='')
+    {
+        if (!function_exists('mb_detect_encoding')) {
+            return $failover;
+        }
+
+        // FIXME: the order is important, because sometimes 
+        // iso string is detected as euc-jp and etc.
+        $enc = array(
+            'UTF-8', 'SJIS', 'BIG5', 'GB2312',
+            'ISO-8859-1', 'ISO-8859-2', 'ISO-8859-3', 'ISO-8859-4',
+            'ISO-8859-5', 'ISO-8859-6', 'ISO-8859-7', 'ISO-8859-8', 'ISO-8859-9',
+            'ISO-8859-10', 'ISO-8859-13', 'ISO-8859-14', 'ISO-8859-15', 'ISO-8859-16',
+            'WINDOWS-1252', 'WINDOWS-1251', 'EUC-JP', 'EUC-TW', 'KOI8-R', 
+            'ISO-2022-KR', 'ISO-2022-JP'
+        );
+
+        $result = mb_detect_encoding($string, join(',', $enc));
+
+        return $result ? $result : $failover;
+    }
+
+
+    /**
+     * Removes non-unicode characters from input.
+     *
+     * @param mixed $input String or array.
+     *
+     * @return mixed String or array
+     */
+    public static function clean($input)
+    {
+        // handle input of type array
+        if (is_array($input)) {
+            foreach ($input as $idx => $val) {
+                $input[$idx] = self::clean($val);
+            }
+            return $input;
+        }
+
+        if (!is_string($input) || $input == '') {
+            return $input;
+        }
+
+        // iconv/mbstring are much faster (especially with long strings)
+        if (function_exists('mb_convert_encoding')) {
+            if (($res = mb_convert_encoding($input, 'UTF-8', 'UTF-8')) !== false) {
+                return $res;
+            }
+        }
+
+        if (function_exists('iconv')) {
+            if (($res = @iconv('UTF-8', 'UTF-8//IGNORE', $input)) !== false) {
+                return $res;
+            }
+        }
+
+        $seq    = '';
+        $out    = '';
+        $regexp = '/^('.
+//          '[\x00-\x7F]'.                                  // UTF8-1
+            '|[\xC2-\xDF][\x80-\xBF]'.                      // UTF8-2
+            '|\xE0[\xA0-\xBF][\x80-\xBF]'.                  // UTF8-3
+            '|[\xE1-\xEC][\x80-\xBF][\x80-\xBF]'.           // UTF8-3
+            '|\xED[\x80-\x9F][\x80-\xBF]'.                  // UTF8-3
+            '|[\xEE-\xEF][\x80-\xBF][\x80-\xBF]'.           // UTF8-3
+            '|\xF0[\x90-\xBF][\x80-\xBF][\x80-\xBF]'.       // UTF8-4
+            '|[\xF1-\xF3][\x80-\xBF][\x80-\xBF][\x80-\xBF]'.// UTF8-4
+            '|\xF4[\x80-\x8F][\x80-\xBF][\x80-\xBF]'.       // UTF8-4
+            ')$/';
+
+        for ($i = 0, $len = strlen($input); $i < $len; $i++) {
+            $chr = $input[$i];
+            $ord = ord($chr);
+
+            // 1-byte character
+            if ($ord <= 0x7F) {
+                if ($seq) {
+                    $out .= preg_match($regexp, $seq) ? $seq : '';
+                }
+                $seq = '';
+                $out .= $chr;
+            // first (or second) byte of multibyte sequence
+            }
+            else if ($ord >= 0xC0) {
+                if (strlen($seq) > 1) {
+	                $out .= preg_match($regexp, $seq) ? $seq : '';
+                    $seq = '';
+                }
+                else if ($seq && ord($seq) < 0xC0) {
+                    $seq = '';
+                }
+                $seq .= $chr;
+            // next byte of multibyte sequence
+            }
+            else if ($seq) {
+                $seq .= $chr;
+            }
+        }
+
+        if ($seq) {
+            $out .= preg_match($regexp, $seq) ? $seq : '';
+        }
+
+        return $out;
+    }
+
+}