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   1  <?php
   2  
   3  /**
   4   * A UTF-8 specific character encoder that handles cleaning and transforming.
   5   * @note All functions in this class should be static.
   6   */
   7  class HTMLPurifier_Encoder
   8  {
   9  
  10      /**
  11       * Constructor throws fatal error if you attempt to instantiate class
  12       */
  13      private function __construct()
  14      {
  15          trigger_error('Cannot instantiate encoder, call methods statically', E_USER_ERROR);
  16      }
  17  
  18      /**
  19       * Error-handler that mutes errors, alternative to shut-up operator.
  20       */
  21      public static function muteErrorHandler()
  22      {
  23      }
  24  
  25      /**
  26       * iconv wrapper which mutes errors, but doesn't work around bugs.
  27       * @param string $in Input encoding
  28       * @param string $out Output encoding
  29       * @param string $text The text to convert
  30       * @return string
  31       */
  32      public static function unsafeIconv($in, $out, $text)
  33      {
  34          set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
  35          $r = iconv($in, $out, $text);
  36          restore_error_handler();
  37          return $r;
  38      }
  39  
  40      /**
  41       * iconv wrapper which mutes errors and works around bugs.
  42       * @param string $in Input encoding
  43       * @param string $out Output encoding
  44       * @param string $text The text to convert
  45       * @param int $max_chunk_size
  46       * @return string
  47       */
  48      public static function iconv($in, $out, $text, $max_chunk_size = 8000)
  49      {
  50          $code = self::testIconvTruncateBug();
  51          if ($code == self::ICONV_OK) {
  52              return self::unsafeIconv($in, $out, $text);
  53          } elseif ($code == self::ICONV_TRUNCATES) {
  54              // we can only work around this if the input character set
  55              // is utf-8
  56              if ($in == 'utf-8') {
  57                  if ($max_chunk_size < 4) {
  58                      trigger_error('max_chunk_size is too small', E_USER_WARNING);
  59                      return false;
  60                  }
  61                  // split into 8000 byte chunks, but be careful to handle
  62                  // multibyte boundaries properly
  63                  if (($c = strlen($text)) <= $max_chunk_size) {
  64                      return self::unsafeIconv($in, $out, $text);
  65                  }
  66                  $r = '';
  67                  $i = 0;
  68                  while (true) {
  69                      if ($i + $max_chunk_size >= $c) {
  70                          $r .= self::unsafeIconv($in, $out, substr($text, $i));
  71                          break;
  72                      }
  73                      // wibble the boundary
  74                      if (0x80 != (0xC0 & ord($text[$i + $max_chunk_size]))) {
  75                          $chunk_size = $max_chunk_size;
  76                      } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 1]))) {
  77                          $chunk_size = $max_chunk_size - 1;
  78                      } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 2]))) {
  79                          $chunk_size = $max_chunk_size - 2;
  80                      } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 3]))) {
  81                          $chunk_size = $max_chunk_size - 3;
  82                      } else {
  83                          return false; // rather confusing UTF-8...
  84                      }
  85                      $chunk = substr($text, $i, $chunk_size); // substr doesn't mind overlong lengths
  86                      $r .= self::unsafeIconv($in, $out, $chunk);
  87                      $i += $chunk_size;
  88                  }
  89                  return $r;
  90              } else {
  91                  return false;
  92              }
  93          } else {
  94              return false;
  95          }
  96      }
  97  
  98      /**
  99       * Cleans a UTF-8 string for well-formedness and SGML validity
 100       *
 101       * It will parse according to UTF-8 and return a valid UTF8 string, with
 102       * non-SGML codepoints excluded.
 103       *
 104       * @param string $str The string to clean
 105       * @param bool $force_php
 106       * @return string
 107       *
 108       * @note Just for reference, the non-SGML code points are 0 to 31 and
 109       *       127 to 159, inclusive.  However, we allow code points 9, 10
 110       *       and 13, which are the tab, line feed and carriage return
 111       *       respectively. 128 and above the code points map to multibyte
 112       *       UTF-8 representations.
 113       *
 114       * @note Fallback code adapted from utf8ToUnicode by Henri Sivonen and
 115       *       hsivonen@iki.fi at <http://iki.fi/hsivonen/php-utf8/> under the
 116       *       LGPL license.  Notes on what changed are inside, but in general,
 117       *       the original code transformed UTF-8 text into an array of integer
 118       *       Unicode codepoints. Understandably, transforming that back to
 119       *       a string would be somewhat expensive, so the function was modded to
 120       *       directly operate on the string.  However, this discourages code
 121       *       reuse, and the logic enumerated here would be useful for any
 122       *       function that needs to be able to understand UTF-8 characters.
 123       *       As of right now, only smart lossless character encoding converters
 124       *       would need that, and I'm probably not going to implement them.
 125       *       Once again, PHP 6 should solve all our problems.
 126       */
 127      public static function cleanUTF8($str, $force_php = false)
 128      {
 129          // UTF-8 validity is checked since PHP 4.3.5
 130          // This is an optimization: if the string is already valid UTF-8, no
 131          // need to do PHP stuff. 99% of the time, this will be the case.
 132          // The regexp matches the XML char production, as well as well as excluding
 133          // non-SGML codepoints U+007F to U+009F
 134          if (preg_match(
 135              '/^[\x{9}\x{A}\x{D}\x{20}-\x{7E}\x{A0}-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]*$/Du',
 136              $str
 137          )) {
 138              return $str;
 139          }
 140  
 141          $mState = 0; // cached expected number of octets after the current octet
 142                       // until the beginning of the next UTF8 character sequence
 143          $mUcs4  = 0; // cached Unicode character
 144          $mBytes = 1; // cached expected number of octets in the current sequence
 145  
 146          // original code involved an $out that was an array of Unicode
 147          // codepoints.  Instead of having to convert back into UTF-8, we've
 148          // decided to directly append valid UTF-8 characters onto a string
 149          // $out once they're done.  $char accumulates raw bytes, while $mUcs4
 150          // turns into the Unicode code point, so there's some redundancy.
 151  
 152          $out = '';
 153          $char = '';
 154  
 155          $len = strlen($str);
 156          for ($i = 0; $i < $len; $i++) {
 157              $in = ord($str{$i});
 158              $char .= $str[$i]; // append byte to char
 159              if (0 == $mState) {
 160                  // When mState is zero we expect either a US-ASCII character
 161                  // or a multi-octet sequence.
 162                  if (0 == (0x80 & ($in))) {
 163                      // US-ASCII, pass straight through.
 164                      if (($in <= 31 || $in == 127) &&
 165                          !($in == 9 || $in == 13 || $in == 10) // save \r\t\n
 166                      ) {
 167                          // control characters, remove
 168                      } else {
 169                          $out .= $char;
 170                      }
 171                      // reset
 172                      $char = '';
 173                      $mBytes = 1;
 174                  } elseif (0xC0 == (0xE0 & ($in))) {
 175                      // First octet of 2 octet sequence
 176                      $mUcs4 = ($in);
 177                      $mUcs4 = ($mUcs4 & 0x1F) << 6;
 178                      $mState = 1;
 179                      $mBytes = 2;
 180                  } elseif (0xE0 == (0xF0 & ($in))) {
 181                      // First octet of 3 octet sequence
 182                      $mUcs4 = ($in);
 183                      $mUcs4 = ($mUcs4 & 0x0F) << 12;
 184                      $mState = 2;
 185                      $mBytes = 3;
 186                  } elseif (0xF0 == (0xF8 & ($in))) {
 187                      // First octet of 4 octet sequence
 188                      $mUcs4 = ($in);
 189                      $mUcs4 = ($mUcs4 & 0x07) << 18;
 190                      $mState = 3;
 191                      $mBytes = 4;
 192                  } elseif (0xF8 == (0xFC & ($in))) {
 193                      // First octet of 5 octet sequence.
 194                      //
 195                      // This is illegal because the encoded codepoint must be
 196                      // either:
 197                      // (a) not the shortest form or
 198                      // (b) outside the Unicode range of 0-0x10FFFF.
 199                      // Rather than trying to resynchronize, we will carry on
 200                      // until the end of the sequence and let the later error
 201                      // handling code catch it.
 202                      $mUcs4 = ($in);
 203                      $mUcs4 = ($mUcs4 & 0x03) << 24;
 204                      $mState = 4;
 205                      $mBytes = 5;
 206                  } elseif (0xFC == (0xFE & ($in))) {
 207                      // First octet of 6 octet sequence, see comments for 5
 208                      // octet sequence.
 209                      $mUcs4 = ($in);
 210                      $mUcs4 = ($mUcs4 & 1) << 30;
 211                      $mState = 5;
 212                      $mBytes = 6;
 213                  } else {
 214                      // Current octet is neither in the US-ASCII range nor a
 215                      // legal first octet of a multi-octet sequence.
 216                      $mState = 0;
 217                      $mUcs4  = 0;
 218                      $mBytes = 1;
 219                      $char = '';
 220                  }
 221              } else {
 222                  // When mState is non-zero, we expect a continuation of the
 223                  // multi-octet sequence
 224                  if (0x80 == (0xC0 & ($in))) {
 225                      // Legal continuation.
 226                      $shift = ($mState - 1) * 6;
 227                      $tmp = $in;
 228                      $tmp = ($tmp & 0x0000003F) << $shift;
 229                      $mUcs4 |= $tmp;
 230  
 231                      if (0 == --$mState) {
 232                          // End of the multi-octet sequence. mUcs4 now contains
 233                          // the final Unicode codepoint to be output
 234  
 235                          // Check for illegal sequences and codepoints.
 236  
 237                          // From Unicode 3.1, non-shortest form is illegal
 238                          if (((2 == $mBytes) && ($mUcs4 < 0x0080)) ||
 239                              ((3 == $mBytes) && ($mUcs4 < 0x0800)) ||
 240                              ((4 == $mBytes) && ($mUcs4 < 0x10000)) ||
 241                              (4 < $mBytes) ||
 242                              // From Unicode 3.2, surrogate characters = illegal
 243                              (($mUcs4 & 0xFFFFF800) == 0xD800) ||
 244                              // Codepoints outside the Unicode range are illegal
 245                              ($mUcs4 > 0x10FFFF)
 246                          ) {
 247  
 248                          } elseif (0xFEFF != $mUcs4 && // omit BOM
 249                              // check for valid Char unicode codepoints
 250                              (
 251                                  0x9 == $mUcs4 ||
 252                                  0xA == $mUcs4 ||
 253                                  0xD == $mUcs4 ||
 254                                  (0x20 <= $mUcs4 && 0x7E >= $mUcs4) ||
 255                                  // 7F-9F is not strictly prohibited by XML,
 256                                  // but it is non-SGML, and thus we don't allow it
 257                                  (0xA0 <= $mUcs4 && 0xD7FF >= $mUcs4) ||
 258                                  (0x10000 <= $mUcs4 && 0x10FFFF >= $mUcs4)
 259                              )
 260                          ) {
 261                              $out .= $char;
 262                          }
 263                          // initialize UTF8 cache (reset)
 264                          $mState = 0;
 265                          $mUcs4  = 0;
 266                          $mBytes = 1;
 267                          $char = '';
 268                      }
 269                  } else {
 270                      // ((0xC0 & (*in) != 0x80) && (mState != 0))
 271                      // Incomplete multi-octet sequence.
 272                      // used to result in complete fail, but we'll reset
 273                      $mState = 0;
 274                      $mUcs4  = 0;
 275                      $mBytes = 1;
 276                      $char ='';
 277                  }
 278              }
 279          }
 280          return $out;
 281      }
 282  
 283      /**
 284       * Translates a Unicode codepoint into its corresponding UTF-8 character.
 285       * @note Based on Feyd's function at
 286       *       <http://forums.devnetwork.net/viewtopic.php?p=191404#191404>,
 287       *       which is in public domain.
 288       * @note While we're going to do code point parsing anyway, a good
 289       *       optimization would be to refuse to translate code points that
 290       *       are non-SGML characters.  However, this could lead to duplication.
 291       * @note This is very similar to the unichr function in
 292       *       maintenance/generate-entity-file.php (although this is superior,
 293       *       due to its sanity checks).
 294       */
 295  
 296      // +----------+----------+----------+----------+
 297      // | 33222222 | 22221111 | 111111   |          |
 298      // | 10987654 | 32109876 | 54321098 | 76543210 | bit
 299      // +----------+----------+----------+----------+
 300      // |          |          |          | 0xxxxxxx | 1 byte 0x00000000..0x0000007F
 301      // |          |          | 110yyyyy | 10xxxxxx | 2 byte 0x00000080..0x000007FF
 302      // |          | 1110zzzz | 10yyyyyy | 10xxxxxx | 3 byte 0x00000800..0x0000FFFF
 303      // | 11110www | 10wwzzzz | 10yyyyyy | 10xxxxxx | 4 byte 0x00010000..0x0010FFFF
 304      // +----------+----------+----------+----------+
 305      // | 00000000 | 00011111 | 11111111 | 11111111 | Theoretical upper limit of legal scalars: 2097151 (0x001FFFFF)
 306      // | 00000000 | 00010000 | 11111111 | 11111111 | Defined upper limit of legal scalar codes
 307      // +----------+----------+----------+----------+
 308  
 309      public static function unichr($code)
 310      {
 311          if ($code > 1114111 or $code < 0 or
 312            ($code >= 55296 and $code <= 57343) ) {
 313              // bits are set outside the "valid" range as defined
 314              // by UNICODE 4.1.0
 315              return '';
 316          }
 317  
 318          $x = $y = $z = $w = 0;
 319          if ($code < 128) {
 320              // regular ASCII character
 321              $x = $code;
 322          } else {
 323              // set up bits for UTF-8
 324              $x = ($code & 63) | 128;
 325              if ($code < 2048) {
 326                  $y = (($code & 2047) >> 6) | 192;
 327              } else {
 328                  $y = (($code & 4032) >> 6) | 128;
 329                  if ($code < 65536) {
 330                      $z = (($code >> 12) & 15) | 224;
 331                  } else {
 332                      $z = (($code >> 12) & 63) | 128;
 333                      $w = (($code >> 18) & 7)  | 240;
 334                  }
 335              }
 336          }
 337          // set up the actual character
 338          $ret = '';
 339          if ($w) {
 340              $ret .= chr($w);
 341          }
 342          if ($z) {
 343              $ret .= chr($z);
 344          }
 345          if ($y) {
 346              $ret .= chr($y);
 347          }
 348          $ret .= chr($x);
 349  
 350          return $ret;
 351      }
 352  
 353      /**
 354       * @return bool
 355       */
 356      public static function iconvAvailable()
 357      {
 358          static $iconv = null;
 359          if ($iconv === null) {
 360              $iconv = function_exists('iconv') && self::testIconvTruncateBug() != self::ICONV_UNUSABLE;
 361          }
 362          return $iconv;
 363      }
 364  
 365      /**
 366       * Convert a string to UTF-8 based on configuration.
 367       * @param string $str The string to convert
 368       * @param HTMLPurifier_Config $config
 369       * @param HTMLPurifier_Context $context
 370       * @return string
 371       */
 372      public static function convertToUTF8($str, $config, $context)
 373      {
 374          $encoding = $config->get('Core.Encoding');
 375          if ($encoding === 'utf-8') {
 376              return $str;
 377          }
 378          static $iconv = null;
 379          if ($iconv === null) {
 380              $iconv = self::iconvAvailable();
 381          }
 382          if ($iconv && !$config->get('Test.ForceNoIconv')) {
 383              // unaffected by bugs, since UTF-8 support all characters
 384              $str = self::unsafeIconv($encoding, 'utf-8//IGNORE', $str);
 385              if ($str === false) {
 386                  // $encoding is not a valid encoding
 387                  trigger_error('Invalid encoding ' . $encoding, E_USER_ERROR);
 388                  return '';
 389              }
 390              // If the string is bjorked by Shift_JIS or a similar encoding
 391              // that doesn't support all of ASCII, convert the naughty
 392              // characters to their true byte-wise ASCII/UTF-8 equivalents.
 393              $str = strtr($str, self::testEncodingSupportsASCII($encoding));
 394              return $str;
 395          } elseif ($encoding === 'iso-8859-1') {
 396              $str = utf8_encode($str);
 397              return $str;
 398          }
 399          $bug = HTMLPurifier_Encoder::testIconvTruncateBug();
 400          if ($bug == self::ICONV_OK) {
 401              trigger_error('Encoding not supported, please install iconv', E_USER_ERROR);
 402          } else {
 403              trigger_error(
 404                  'You have a buggy version of iconv, see https://bugs.php.net/bug.php?id=48147 ' .
 405                  'and http://sourceware.org/bugzilla/show_bug.cgi?id=13541',
 406                  E_USER_ERROR
 407              );
 408          }
 409      }
 410  
 411      /**
 412       * Converts a string from UTF-8 based on configuration.
 413       * @param string $str The string to convert
 414       * @param HTMLPurifier_Config $config
 415       * @param HTMLPurifier_Context $context
 416       * @return string
 417       * @note Currently, this is a lossy conversion, with unexpressable
 418       *       characters being omitted.
 419       */
 420      public static function convertFromUTF8($str, $config, $context)
 421      {
 422          $encoding = $config->get('Core.Encoding');
 423          if ($escape = $config->get('Core.EscapeNonASCIICharacters')) {
 424              $str = self::convertToASCIIDumbLossless($str);
 425          }
 426          if ($encoding === 'utf-8') {
 427              return $str;
 428          }
 429          static $iconv = null;
 430          if ($iconv === null) {
 431              $iconv = self::iconvAvailable();
 432          }
 433          if ($iconv && !$config->get('Test.ForceNoIconv')) {
 434              // Undo our previous fix in convertToUTF8, otherwise iconv will barf
 435              $ascii_fix = self::testEncodingSupportsASCII($encoding);
 436              if (!$escape && !empty($ascii_fix)) {
 437                  $clear_fix = array();
 438                  foreach ($ascii_fix as $utf8 => $native) {
 439                      $clear_fix[$utf8] = '';
 440                  }
 441                  $str = strtr($str, $clear_fix);
 442              }
 443              $str = strtr($str, array_flip($ascii_fix));
 444              // Normal stuff
 445              $str = self::iconv('utf-8', $encoding . '//IGNORE', $str);
 446              return $str;
 447          } elseif ($encoding === 'iso-8859-1') {
 448              $str = utf8_decode($str);
 449              return $str;
 450          }
 451          trigger_error('Encoding not supported', E_USER_ERROR);
 452          // You might be tempted to assume that the ASCII representation
 453          // might be OK, however, this is *not* universally true over all
 454          // encodings.  So we take the conservative route here, rather
 455          // than forcibly turn on %Core.EscapeNonASCIICharacters
 456      }
 457  
 458      /**
 459       * Lossless (character-wise) conversion of HTML to ASCII
 460       * @param string $str UTF-8 string to be converted to ASCII
 461       * @return string ASCII encoded string with non-ASCII character entity-ized
 462       * @warning Adapted from MediaWiki, claiming fair use: this is a common
 463       *       algorithm. If you disagree with this license fudgery,
 464       *       implement it yourself.
 465       * @note Uses decimal numeric entities since they are best supported.
 466       * @note This is a DUMB function: it has no concept of keeping
 467       *       character entities that the projected character encoding
 468       *       can allow. We could possibly implement a smart version
 469       *       but that would require it to also know which Unicode
 470       *       codepoints the charset supported (not an easy task).
 471       * @note Sort of with cleanUTF8() but it assumes that $str is
 472       *       well-formed UTF-8
 473       */
 474      public static function convertToASCIIDumbLossless($str)
 475      {
 476          $bytesleft = 0;
 477          $result = '';
 478          $working = 0;
 479          $len = strlen($str);
 480          for ($i = 0; $i < $len; $i++) {
 481              $bytevalue = ord($str[$i]);
 482              if ($bytevalue <= 0x7F) { //0xxx xxxx
 483                  $result .= chr($bytevalue);
 484                  $bytesleft = 0;
 485              } elseif ($bytevalue <= 0xBF) { //10xx xxxx
 486                  $working = $working << 6;
 487                  $working += ($bytevalue & 0x3F);
 488                  $bytesleft--;
 489                  if ($bytesleft <= 0) {
 490                      $result .= "&#" . $working . ";";
 491                  }
 492              } elseif ($bytevalue <= 0xDF) { //110x xxxx
 493                  $working = $bytevalue & 0x1F;
 494                  $bytesleft = 1;
 495              } elseif ($bytevalue <= 0xEF) { //1110 xxxx
 496                  $working = $bytevalue & 0x0F;
 497                  $bytesleft = 2;
 498              } else { //1111 0xxx
 499                  $working = $bytevalue & 0x07;
 500                  $bytesleft = 3;
 501              }
 502          }
 503          return $result;
 504      }
 505  
 506      /** No bugs detected in iconv. */
 507      const ICONV_OK = 0;
 508  
 509      /** Iconv truncates output if converting from UTF-8 to another
 510       *  character set with //IGNORE, and a non-encodable character is found */
 511      const ICONV_TRUNCATES = 1;
 512  
 513      /** Iconv does not support //IGNORE, making it unusable for
 514       *  transcoding purposes */
 515      const ICONV_UNUSABLE = 2;
 516  
 517      /**
 518       * glibc iconv has a known bug where it doesn't handle the magic
 519       * //IGNORE stanza correctly.  In particular, rather than ignore
 520       * characters, it will return an EILSEQ after consuming some number
 521       * of characters, and expect you to restart iconv as if it were
 522       * an E2BIG.  Old versions of PHP did not respect the errno, and
 523       * returned the fragment, so as a result you would see iconv
 524       * mysteriously truncating output. We can work around this by
 525       * manually chopping our input into segments of about 8000
 526       * characters, as long as PHP ignores the error code.  If PHP starts
 527       * paying attention to the error code, iconv becomes unusable.
 528       *
 529       * @return int Error code indicating severity of bug.
 530       */
 531      public static function testIconvTruncateBug()
 532      {
 533          static $code = null;
 534          if ($code === null) {
 535              // better not use iconv, otherwise infinite loop!
 536              $r = self::unsafeIconv('utf-8', 'ascii//IGNORE', "\xCE\xB1" . str_repeat('a', 9000));
 537              if ($r === false) {
 538                  $code = self::ICONV_UNUSABLE;
 539              } elseif (($c = strlen($r)) < 9000) {
 540                  $code = self::ICONV_TRUNCATES;
 541              } elseif ($c > 9000) {
 542                  trigger_error(
 543                      'Your copy of iconv is extremely buggy. Please notify HTML Purifier maintainers: ' .
 544                      'include your iconv version as per phpversion()',
 545                      E_USER_ERROR
 546                  );
 547              } else {
 548                  $code = self::ICONV_OK;
 549              }
 550          }
 551          return $code;
 552      }
 553  
 554      /**
 555       * This expensive function tests whether or not a given character
 556       * encoding supports ASCII. 7/8-bit encodings like Shift_JIS will
 557       * fail this test, and require special processing. Variable width
 558       * encodings shouldn't ever fail.
 559       *
 560       * @param string $encoding Encoding name to test, as per iconv format
 561       * @param bool $bypass Whether or not to bypass the precompiled arrays.
 562       * @return Array of UTF-8 characters to their corresponding ASCII,
 563       *      which can be used to "undo" any overzealous iconv action.
 564       */
 565      public static function testEncodingSupportsASCII($encoding, $bypass = false)
 566      {
 567          // All calls to iconv here are unsafe, proof by case analysis:
 568          // If ICONV_OK, no difference.
 569          // If ICONV_TRUNCATE, all calls involve one character inputs,
 570          // so bug is not triggered.
 571          // If ICONV_UNUSABLE, this call is irrelevant
 572          static $encodings = array();
 573          if (!$bypass) {
 574              if (isset($encodings[$encoding])) {
 575                  return $encodings[$encoding];
 576              }
 577              $lenc = strtolower($encoding);
 578              switch ($lenc) {
 579                  case 'shift_jis':
 580                      return array("\xC2\xA5" => '\\', "\xE2\x80\xBE" => '~');
 581                  case 'johab':
 582                      return array("\xE2\x82\xA9" => '\\');
 583              }
 584              if (strpos($lenc, 'iso-8859-') === 0) {
 585                  return array();
 586              }
 587          }
 588          $ret = array();
 589          if (self::unsafeIconv('UTF-8', $encoding, 'a') === false) {
 590              return false;
 591          }
 592          for ($i = 0x20; $i <= 0x7E; $i++) { // all printable ASCII chars
 593              $c = chr($i); // UTF-8 char
 594              $r = self::unsafeIconv('UTF-8', "$encoding//IGNORE", $c); // initial conversion
 595              if ($r === '' ||
 596                  // This line is needed for iconv implementations that do not
 597                  // omit characters that do not exist in the target character set
 598                  ($r === $c && self::unsafeIconv($encoding, 'UTF-8//IGNORE', $r) !== $c)
 599              ) {
 600                  // Reverse engineer: what's the UTF-8 equiv of this byte
 601                  // sequence? This assumes that there's no variable width
 602                  // encoding that doesn't support ASCII.
 603                  $ret[self::unsafeIconv($encoding, 'UTF-8//IGNORE', $c)] = $c;
 604              }
 605          }
 606          $encodings[$encoding] = $ret;
 607          return $ret;
 608      }
 609  }
 610  
 611  // vim: et sw=4 sts=4