includes/normal/UtfNormal.php

   1 <?php
   2 # Copyright (C) 2004 Brion Vibber <brion@pobox.com>
   3 # http://www.mediawiki.org/
   4 #
   5 # This program is free software; you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License as published by
   7 # the Free Software Foundation; either version 2 of the License, or
   8 # (at your option) any later version.
   9 #
  10 # This program is distributed in the hope that it will be useful,
  11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13 # GNU General Public License for more details.
  14 #
  15 # You should have received a copy of the GNU General Public License along
  16 # with this program; if not, write to the Free Software Foundation, Inc.,
  17 # 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  18 # http://www.gnu.org/copyleft/gpl.html
  19
  20 /**
  21  * Unicode normalization routines for working with UTF-8 strings.
  22  * Currently assumes that input strings are valid UTF-8!
  23  *
  24  * Not as fast as I'd like, but should be usable for most purposes.
  25  * UtfNormal::toNFC() will bail early if given ASCII text or text
  26  * it can quickly deterimine is already normalized.
  27  *
  28  * All functions can be called static.
  29  *
  30  * See description of forms at http://www.unicode.org/reports/tr15/
  31  *
  32  * @package UtfNormal
  33  */
  34
  35 /** */
  36 require_once 'UtfNormalUtil.php';
  37
  38 global $utfCombiningClass, $utfCanonicalComp, $utfCanonicalDecomp;
  39 $utfCombiningClass = NULL;
  40 $utfCanonicalComp = NULL;
  41 $utfCanonicalDecomp = NULL;
  42
  43 # Load compatibility decompositions on demand if they are needed.
  44 global $utfCompatibilityDecomp;
  45 $utfCompatibilityDecomp = NULL;
  46
  47 define( 'UNICODE_HANGUL_FIRST', 0xac00 );
  48 define( 'UNICODE_HANGUL_LAST',  0xd7a3 );
  49
  50 define( 'UNICODE_HANGUL_LBASE', 0x1100 );
  51 define( 'UNICODE_HANGUL_VBASE', 0x1161 );
  52 define( 'UNICODE_HANGUL_TBASE', 0x11a7 );
  53
  54 define( 'UNICODE_HANGUL_LCOUNT', 19 );
  55 define( 'UNICODE_HANGUL_VCOUNT', 21 );
  56 define( 'UNICODE_HANGUL_TCOUNT', 28 );
  57 define( 'UNICODE_HANGUL_NCOUNT', UNICODE_HANGUL_VCOUNT * UNICODE_HANGUL_TCOUNT );
  58
  59 define( 'UNICODE_HANGUL_LEND', UNICODE_HANGUL_LBASE + UNICODE_HANGUL_LCOUNT - 1 );
  60 define( 'UNICODE_HANGUL_VEND', UNICODE_HANGUL_VBASE + UNICODE_HANGUL_VCOUNT - 1 );
  61 define( 'UNICODE_HANGUL_TEND', UNICODE_HANGUL_TBASE + UNICODE_HANGUL_TCOUNT - 1 );
  62
  63 define( 'UNICODE_SURROGATE_FIRST', 0xd800 );
  64 define( 'UNICODE_SURROGATE_LAST', 0xdfff );
  65 define( 'UNICODE_MAX', 0x10ffff );
  66 define( 'UNICODE_REPLACEMENT', 0xfffd );
  67
  68
  69 define( 'UTF8_HANGUL_FIRST', codepointToUtf8( UNICODE_HANGUL_FIRST ) );
  70 define( 'UTF8_HANGUL_LAST', codepointToUtf8( UNICODE_HANGUL_LAST ) );
  71
  72 define( 'UTF8_HANGUL_LBASE', codepointToUtf8( UNICODE_HANGUL_LBASE ) );
  73 define( 'UTF8_HANGUL_VBASE', codepointToUtf8( UNICODE_HANGUL_VBASE ) );
  74 define( 'UTF8_HANGUL_TBASE', codepointToUtf8( UNICODE_HANGUL_TBASE ) );
  75
  76 define( 'UTF8_HANGUL_LEND', codepointToUtf8( UNICODE_HANGUL_LEND ) );
  77 define( 'UTF8_HANGUL_VEND', codepointToUtf8( UNICODE_HANGUL_VEND ) );
  78 define( 'UTF8_HANGUL_TEND', codepointToUtf8( UNICODE_HANGUL_TEND ) );
  79
  80 define( 'UTF8_SURROGATE_FIRST', codepointToUtf8( UNICODE_SURROGATE_FIRST ) );
  81 define( 'UTF8_SURROGATE_LAST', codepointToUtf8( UNICODE_SURROGATE_LAST ) );
  82 define( 'UTF8_MAX', codepointToUtf8( UNICODE_MAX ) );
  83 define( 'UTF8_REPLACEMENT', codepointToUtf8( UNICODE_REPLACEMENT ) );
  84 #define( 'UTF8_REPLACEMENT', '!' );
  85
  86 define( 'UTF8_OVERLONG_A', "\xc1\xbf" );
  87 define( 'UTF8_OVERLONG_B', "\xe0\x9f\xbf" );
  88 define( 'UTF8_OVERLONG_C', "\xf0\x8f\xbf\xbf" );
  89
  90 # These two ranges are illegal
  91 define( 'UTF8_FDD0', codepointToUtf8( 0xfdd0 ) );
  92 define( 'UTF8_FDEF', codepointToUtf8( 0xfdef ) );
  93 define( 'UTF8_FFFE', codepointToUtf8( 0xfffe ) );
  94 define( 'UTF8_FFFF', codepointToUtf8( 0xffff ) );
  95
  96 define( 'UTF8_HEAD', false );
  97 define( 'UTF8_TAIL', true );
  98
  99
 100 /**
 101  * For using the ICU wrapper
 102  */
 103 define( 'UNORM_NONE', 1 );
 104 define( 'UNORM_NFD',  2 );
 105 define( 'UNORM_NFKD', 3 );
 106 define( 'UNORM_NFC',  4 );
 107 define( 'UNORM_DEFAULT', UNORM_NFC );
 108 define( 'UNORM_NFKC', 5 );
 109 define( 'UNORM_FCD',  6 );
 110
 111 define( 'NORMALIZE_ICU', function_exists( 'utf8_normalize' ) );
 112
 113 /**
 114  *
 115  * @package MediaWiki
 116  */
 117 class UtfNormal {
 118         /**
 119          * The ultimate convenience function! Clean up invalid UTF-8 sequences,
 120          * and convert to normal form C, canonical composition.
 121          *
 122          * Fast return for pure ASCII strings; some lesser optimizations for
 123          * strings containing only known-good characters. Not as fast as toNFC().
 124          *
 125          * @param string $string a UTF-8 string
 126          * @return string a clean, shiny, normalized UTF-8 string
 127          */
 128         function cleanUp( $string ) {
 129                 if( UtfNormal::quickIsNFCVerify( $string ) )
 130                         return $string;
 131                 else
 132                         return UtfNormal::NFC( $string );
 133         }
 134
 135         /**
 136          * Convert a UTF-8 string to normal form C, canonical composition.
 137          * Fast return for pure ASCII strings; some lesser optimizations for
 138          * strings containing only known-good characters.
 139          *
 140          * @param string $string a valid UTF-8 string. Input is not validated.
 141          * @return string a UTF-8 string in normal form C
 142          */
 143         function toNFC( $string ) {
 144                 if( NORMALIZE_ICU )
 145                         return utf8_normalize( $string, UNORM_NFC );
 146                 elseif( UtfNormal::quickIsNFC( $string ) )
 147                         return $string;
 148                 else
 149                         return UtfNormal::NFC( $string );
 150         }
 151
 152         /**
 153          * Convert a UTF-8 string to normal form D, canonical decomposition.
 154          * Fast return for pure ASCII strings.
 155          *
 156          * @param string $string a valid UTF-8 string. Input is not validated.
 157          * @return string a UTF-8 string in normal form D
 158          */
 159         function toNFD( $string ) {
 160                 if( NORMALIZE_ICU )
 161                         return utf8_normalize( $string, UNORM_NFD );
 162                 elseif( preg_match( '/[\x80-\xff]/', $string ) )
 163                         return UtfNormal::NFD( $string );
 164                 else
 165                         return $string;
 166         }
 167
 168         /**
 169          * Convert a UTF-8 string to normal form KC, compatibility composition.
 170          * This may cause irreversible information loss, use judiciously.
 171          * Fast return for pure ASCII strings.
 172          *
 173          * @param string $string a valid UTF-8 string. Input is not validated.
 174          * @return string a UTF-8 string in normal form KC
 175          */
 176         function toNFKC( $string ) {
 177                 if( NORMALIZE_ICU )
 178                         return utf8_normalize( $string, UNORM_NFKC );
 179                 elseif( preg_match( '/[\x80-\xff]/', $string ) )
 180                         return UtfNormal::NFKC( $string );
 181                 else
 182                         return $string;
 183         }
 184
 185         /**
 186          * Convert a UTF-8 string to normal form KD, compatibility decomposition.
 187          * This may cause irreversible information loss, use judiciously.
 188          * Fast return for pure ASCII strings.
 189          *
 190          * @param string $string a valid UTF-8 string. Input is not validated.
 191          * @return string a UTF-8 string in normal form KD
 192          */
 193         function toNFKD( $string ) {
 194                 if( NORMALIZE_ICU )
 195                         return utf8_normalize( $string, UNORM_NFKD );
 196                 elseif( preg_match( '/[\x80-\xff]/', $string ) )
 197                         return UtfNormal::NFKD( $string );
 198                 else
 199                         return $string;
 200         }
 201
 202         /**
 203          * Load the basic composition data if necessary
 204          * @access private
 205          */
 206         function loadData() {
 207                 global $utfCombiningClass, $utfCanonicalComp, $utfCanonicalDecomp;
 208                 if( !isset( $utfCombiningClass ) ) {
 209                         require_once( 'UtfNormalData.inc' );
 210                 }
 211         }
 212
 213         /**
 214          * Returns true if the string is _definitely_ in NFC.
 215          * Returns false if not or uncertain.
 216          * @param string $string a valid UTF-8 string. Input is not validated.
 217          * @return bool
 218          */
 219         function quickIsNFC( $string ) {
 220                 # ASCII is always valid NFC!
 221                 # If it's pure ASCII, let it through.
 222                 if( !preg_match( '/[\x80-\xff]/', $string ) ) return true;
 223
 224                 UtfNormal::loadData();
 225                 global $utfCheckNFC, $utfCombiningClass;
 226                 $len = strlen( $string );
 227                 for( $i = 0; $i < $len; $i++ ) {
 228                         $c = $string{$i};
 229                         $n = ord( $c );
 230                         if( $n < 0x80 ) {
 231                                 continue;
 232                         } elseif( $n >= 0xf0 ) {
 233                                 $c = substr( $string, $i, 4 );
 234                                 $i += 3;
 235                         } elseif( $n >= 0xe0 ) {
 236                                 $c = substr( $string, $i, 3 );
 237                                 $i += 2;
 238                         } elseif( $n >= 0xc0 ) {
 239                                 $c = substr( $string, $i, 2 );
 240                                 $i++;
 241                         }
 242                         if( isset( $utfCheckNFC[$c] ) ) {
 243                                 # If it's NO or MAYBE, bail and do the slow check.
 244                                 return false;
 245                         }
 246                         if( isset( $utfCombiningClass[$c] ) ) {
 247                                 # Combining character? We might have to do sorting, at least.
 248                                 return false;
 249                         }
 250                 }
 251                 return true;
 252         }
 253
 254         /**
 255          * Returns true if the string is _definitely_ in NFC.
 256          * Returns false if not or uncertain.
 257          * @param string $string a UTF-8 string, altered on output to be valid UTF-8 safe for XML.
 258          * @return bool
 259          */
 260         function quickIsNFCVerify( &$string ) {
 261                 # ASCII is always valid NFC!
 262                 if( !preg_match( '/[\x80-\xff]/', $string ) ) return true;
 263
 264                 UtfNormal::loadData();
 265                 global $utfCheckNFC, $utfCombiningClass;
 266                 $len = strlen( $string );
 267                 $out = '';
 268                 $state = UTF8_HEAD;
 269                 $looksNormal = true;
 270
 271                 $rep = false;
 272                 $head = 0;
 273                 for( $i = 0; $i < $len; $i++ ) {
 274                         $c = $string{$i};
 275                         $n = ord( $c );
 276                         if( $state == UTF8_TAIL ) {
 277                                 if( $n >= 0x80 && $n < 0xc0 ) {
 278                                         $sequence .= $c;
 279                                         if( --$remaining == 0 ) {
 280                                                 if( $head < 0xc2 || $head == 0xed || $head == 0xe0 || $head > 0xee ) {
 281                                                         if( ( $sequence >= UTF8_SURROGATE_FIRST
 282                                                                         && $sequence <= UTF8_SURROGATE_LAST)
 283                                                                 || ($head == 0xc0 && $sequence <= UTF8_OVERLONG_A)
 284                                                                 || ($head == 0xc1 && $sequence <= UTF8_OVERLONG_A)
 285                                                                 || ($head == 0xe0 && $sequence <= UTF8_OVERLONG_B)
 286                                                                 || ($head == 0xef &&
 287                                                                         ($sequence >= UTF8_FDD0 && $sequence <= UTF8_FDEF)
 288                                                                         || ($sequence == UTF8_FFFE)
 289                                                                         || ($sequence == UTF8_FFFF) )
 290                                                                 || ($head == 0xf0 && $sequence <= UTF8_OVERLONG_C)
 291                                                                 || ($sequence > UTF8_MAX) ) {
 292                                                                 $out .= UTF8_REPLACEMENT;
 293                                                                 $state = UTF8_HEAD;
 294                                                                 continue;
 295                                                         }
 296                                                 }
 297                                                 if( isset( $utfCheckNFC[$sequence] ) ||
 298                                                         isset( $utfCombiningClass[$sequence] ) ) {
 299                                                         # If it's NO or MAYBE, we'll have to do the slow check.
 300                                                         $looksNormal = false;
 301                                                 }
 302                                                 $out .= $sequence;
 303                                                 $state = UTF8_HEAD;
 304                                                 $head = 0;
 305                                         }
 306                                         continue;
 307                                 }
 308                                 # Not a valid tail byte! DIscard the char we've been building.
 309                                 #printf ("Invalid '%x' in tail with %d remaining bytes\n", $n, $remaining );
 310                                 $state = UTF8_HEAD;
 311                                 $out .= UTF8_REPLACEMENT;
 312                         }
 313                         if( $n < 0x20 ) {
 314                                 if( $n < 0x09 ) {
 315                                         $out .= UTF8_REPLACEMENT;
 316                                 } elseif( $n == 0x0a ) {
 317                                         $out .= $c;
 318                                 } elseif( $n < 0x0d ) {
 319                                         $out .= UTF8_REPLACEMENT;
 320                                 } elseif( $n == 0x0d ) {
 321                                         # Strip \r silently
 322                                 } else {
 323                                         $out .= UTF8_REPLACEMENT;
 324                                 }
 325                         } elseif( $n < 0x80 ) {
 326                                 # Friendly ASCII chars.
 327                                 $out .= $c;
 328                         } elseif( $n < 0xc0 ) {
 329                                 # illegal tail bytes or head byte of overlong sequence
 330                                 if( $head == 0 ) $out .= UTF8_REPLACEMENT;
 331                         } elseif( $n < 0xe0 ) {
 332                                 $state = UTF8_TAIL;
 333                                 $remaining = 1;
 334                                 $sequence = $c;
 335                                 $head = $n;
 336                         } elseif( $n < 0xf0 ) {
 337                                 $state = UTF8_TAIL;
 338                                 $remaining = 2;
 339                                 $sequence = $c;
 340                                 $head = $n;
 341                         } elseif( $n < 0xf8 ) {
 342                                 $state = UTF8_TAIL;
 343                                 $remaining = 3;
 344                                 $sequence = $c;
 345                                 $head = $n;
 346                         } elseif( $n < 0xfc ) {
 347                                 $state = UTF8_TAIL;
 348                                 $remaining = 4;
 349                                 $sequence = $c;
 350                                 $head = $n;
 351                         } elseif( $n < 0xfe ) {
 352                                 $state = UTF8_TAIL;
 353                                 $remaining = 5;
 354                                 $sequence = $c;
 355                                 $head = $n;
 356                         } else {
 357                                 $out .= UTF8_REPLACEMENT;
 358                         }
 359                 }
 360                 if( $state == UTF8_TAIL ) {
 361                         $out .= UTF8_REPLACEMENT;
 362                 }
 363                 $string = $out;
 364                 return $looksNormal;
 365         }
 366
 367         # These take a string and run the normalization on them, without
 368         # checking for validity or any optimization etc. Input must be
 369         # VALID UTF-8!
 370         /**
 371          * @param string $string
 372          * @return string
 373          * @access private
 374          */
 375         function NFC( $string ) {
 376                 return UtfNormal::fastCompose( UtfNormal::NFD( $string ) );
 377         }
 378
 379         /**
 380          * @param string $string
 381          * @return string
 382          * @access private
 383          */
 384         function NFD( $string ) {
 385                 UtfNormal::loadData();
 386                 global $utfCanonicalDecomp;
 387                 return UtfNormal::fastCombiningSort(
 388                         UtfNormal::fastDecompose( $string, $utfCanonicalDecomp ) );
 389         }
 390
 391         /**
 392          * @param string $string
 393          * @return string
 394          * @access private
 395          */
 396         function NFKC( $string ) {
 397                 return UtfNormal::fastCompose( UtfNormal::NFKD( $string ) );
 398         }
 399
 400         /**
 401          * @param string $string
 402          * @return string
 403          * @access private
 404          */
 405         function NFKD( $string ) {
 406                 global $utfCompatibilityDecomp;
 407                 if( !isset( $utfCompatibilityDecomp ) ) {
 408                         require_once( 'UtfNormalDataK.inc' );
 409                 }
 410                 return UtfNormal::fastCombiningSort(
 411                         UtfNormal::fastDecompose( $string, $utfCompatibilityDecomp ) );
 412         }
 413
 414
 415         /**
 416          * Perform decomposition of a UTF-8 string into either D or KD form
 417          * (depending on which decomposition map is passed to us).
 418          * Input is assumed to be *valid* UTF-8. Invalid code will break.
 419          * @access private
 420          * @param string &$string Valid UTF-8 string
 421          * @param array &$map hash of expanded decomposition map
 422          * @return string a UTF-8 string decomposed, not yet normalized (needs sorting)
 423          */
 424         function fastDecompose( &$string, &$map ) {
 425                 UtfNormal::loadData();
 426                 $len = strlen( $string );
 427                 $out = '';
 428                 for( $i = 0; $i < $len; $i++ ) {
 429                         $c = $string{$i};
 430                         $n = ord( $c );
 431                         if( $n < 0x80 ) {
 432                                 # ASCII chars never decompose
 433                                 # THEY ARE IMMORTAL
 434                                 $out .= $c;
 435                                 continue;
 436                         } elseif( $n >= 0xf0 ) {
 437                                 $c = substr( $string, $i, 4 );
 438                                 $i += 3;
 439                         } elseif( $n >= 0xe0 ) {
 440                                 $c = substr( $string, $i, 3 );
 441                                 $i += 2;
 442                         } elseif( $n >= 0xc0 ) {
 443                                 $c = substr( $string, $i, 2 );
 444                                 $i++;
 445                         }
 446                         if( isset( $map[$c] ) ) {
 447                                 $out .= $map[$c];
 448                         } else {
 449                                 if( $c >= UTF8_HANGUL_FIRST && $c <= UTF8_HANGUL_LAST ) {
 450                                         $out .= UtfNormal::decomposeHangul( $c );
 451                                 } else {
 452                                         $out .= $c;
 453                                 }
 454                         }
 455                 }
 456                 return $out;
 457         }
 458
 459         /**
 460          * Decompose a Hangul syllable character into its constituent jamo.
 461          * @access private
 462          * @param int $c Unicode code point of the character
 463          * @return string a UTF-8 string containing a sequence of jamo
 464          */
 465         function decomposeHangul( $c ) {
 466                 $codepoint = utf8ToCodepoint( $c );
 467                 $index = $codepoint - UNICODE_HANGUL_FIRST;
 468                 $l = IntVal( $index / UNICODE_HANGUL_NCOUNT );
 469                 $v = IntVal( ($index % UNICODE_HANGUL_NCOUNT) / UNICODE_HANGUL_TCOUNT);
 470                 $t = $index % UNICODE_HANGUL_TCOUNT;
 471                 $out = codepointToUtf8( $l + UNICODE_HANGUL_LBASE );
 472                 $out .= codepointToUtf8( $v + UNICODE_HANGUL_VBASE );
 473                 if( $t ) $out .= codepointToUtf8( $t + UNICODE_HANGUL_TBASE );
 474                 return $out;
 475         }
 476
 477         /**
 478          * Sorts combining characters into canonical order. This is the
 479          * final step in creating decomposed normal forms D and KD.
 480          * @access private
 481          * @param string $string a valid, decomposed UTF-8 string. Input is not validated.
 482          * @return string a UTF-8 string with combining characters sorted in canonical order
 483          */
 484         function fastCombiningSort( $string ) {
 485                 UtfNormal::loadData();
 486                 global $utfCombiningClass;
 487                 $replacedCount = 1;
 488                 while( $replacedCount > 0 ) {
 489                         $replacedCount = 0;
 490                         $len = strlen( $string );
 491                         $out = '';
 492                         $lastClass = -1;
 493                         $lastChar = '';
 494                         for( $i = 0; $i < $len; $i++ ) {
 495                                 $c = $string{$i};
 496                                 $n = ord( $c );
 497                                 if( $n < 0x80 ) {
 498                                         # No combining characters in ASCII.
 499                                         $out .= $lastChar;
 500                                         $lastChar = $c;
 501                                         $lastClass = 0;
 502                                         continue;
 503                                 } elseif( $n >= 0xf0 ) {
 504                                         $c = substr( $string, $i, 4 );
 505                                         $i += 3;
 506                                 } elseif( $n >= 0xe0 ) {
 507                                         $c = substr( $string, $i, 3 );
 508                                         $i += 2;
 509                                 } elseif( $n >= 0xc0 ) {
 510                                         $c = substr( $string, $i, 2 );
 511                                         $i++;
 512                                 }
 513                                 $class = 0;
 514                                 if( $lastClass == -1 ) {
 515                                         # First one
 516                                         $lastChar = $c;
 517                                         $class = isset( $utfCombiningClass[$c] ) ? $utfCombiningClass[$c] : 0;
 518                                         $lastClass = $class;
 519                                         continue;
 520                                 }
 521                                 if( isset( $utfCombiningClass[$c] ) ) {
 522                                         $class = $utfCombiningClass[$c];
 523                                         if( $lastClass > $class ) {
 524                                                 # Swap -- put this one on the stack
 525                                                 $out .= $c;
 526                                                 $replacedCount++;
 527                                                 continue;
 528                                         }
 529                                 }
 530                                 $out .= $lastChar;
 531                                 $lastChar = $c;
 532                                 $lastClass = $class;
 533                         }
 534                         $out .= $lastChar;
 535                         $string = $out;
 536                 }
 537                 return $string;
 538         }
 539
 540         /**
 541          * Produces canonically composed sequences, i.e. normal form C or KC.
 542          *
 543          * @access private
 544          * @param string $string a valid UTF-8 string in sorted normal form D or KD. Input is not validated.
 545          * @return string a UTF-8 string with canonical precomposed characters used where possible
 546          */
 547         function fastCompose( $string ) {
 548                 UtfNormal::loadData();
 549                 global $utfCanonicalComp, $utfCombiningClass;
 550                 $len = strlen( $string );
 551                 $out = '';
 552                 $lastClass = -1;
 553                 $startChar = '';
 554                 $combining = '';
 555                 $x1 = ord(substr(UTF8_HANGUL_VBASE,0,1));
 556                 $x2 = ord(substr(UTF8_HANGUL_TEND,0,1));
 557                 for( $i = 0; $i < $len; $i++ ) {
 558                         $c = $string{$i};
 559                         $n = ord( $c );
 560                         if( $n < 0x80 ) {
 561                                 # No combining characters here...
 562                                 $out .= $startChar;
 563                                 $out .= $combining;
 564                                 $startChar = $c;
 565                                 $combining = '';
 566                                 $lastClass = 0;
 567                                 continue;
 568                         } elseif( $n >= 0xf0 ) {
 569                                 $c = substr( $string, $i, 4 );
 570                                 $i += 3;
 571                         } elseif( $n >= 0xe0 ) {
 572                                 $c = substr( $string, $i, 3 );
 573                                 $i += 2;
 574                         } elseif( $n >= 0xc0 ) {
 575                                 $c = substr( $string, $i, 2 );
 576                                 $i++;
 577                         }
 578                         $pair = $startChar . $c;
 579                         if( $n > 0x80 ) {
 580                                 if( isset( $utfCombiningClass[$c] ) ) {
 581                                         # A combining char; see what we can do with it
 582                                         $class = $utfCombiningClass[$c];
 583                                         if( !empty( $startChar ) &&
 584                                                 $lastClass < $class &&
 585                                                 $class > 0 &&
 586                                                 isset( $utfCanonicalComp[$pair] ) ) {
 587                                                 $startChar = $utfCanonicalComp[$pair];
 588                                                 $class = 0;
 589                                         } else {
 590                                                 $combining .= $c;
 591                                         }
 592                                         $lastClass = $class;
 593                                         continue;
 594                                 }
 595                         }
 596                         # New start char
 597                         if( $lastClass == 0 ) {
 598                                 if( isset( $utfCanonicalComp[$pair] ) ) {
 599                                         $startChar = $utfCanonicalComp[$pair];
 600                                         continue;
 601                                 }
 602                                 if( $n >= $x1 && $n <= $x2 ) {
 603                                         # WARNING: Hangul code is painfully slow.
 604                                         if( $c >= UTF8_HANGUL_VBASE &&
 605                                                 $c <= UTF8_HANGUL_VEND &&
 606                                                 $startChar >= UTF8_HANGUL_LBASE &&
 607                                                 $startChar <= UTF8_HANGUL_LEND ) {
 608                                                 #
 609                                                 $lIndex = utf8ToCodepoint( $startChar ) - UNICODE_HANGUL_LBASE;
 610                                                 $vIndex = utf8ToCodepoint( $c ) - UNICODE_HANGUL_VBASE;
 611                                                 $hangulPoint = UNICODE_HANGUL_FIRST +
 612                                                         UNICODE_HANGUL_TCOUNT *
 613                                                         (UNICODE_HANGUL_VCOUNT * $lIndex + $vIndex);
 614                                                 $startChar = codepointToUtf8( $hangulPoint );
 615                                                 continue;
 616                                         } elseif( $c >= UTF8_HANGUL_TBASE &&
 617                                                           $c <= UTF8_HANGUL_TEND &&
 618                                                           $startChar >= UTF8_HANGUL_FIRST &&
 619                                                           $startChar <= UTF8_HANGUL_LAST ) {
 620                                                 $tIndex = utf8ToCodepoint( $c ) - UNICODE_HANGUL_TBASE;
 621                                                 $hangulPoint = utf8ToCodepoint( $startChar ) + $tIndex;
 622                                                 $startChar = codepointToUtf8( $hangulPoint );
 623                                                 continue;
 624                                         }
 625                                 }
 626                         }
 627                         $out .= $startChar;
 628                         $out .= $combining;
 629                         $startChar = $c;
 630                         $combining = '';
 631                         $lastClass = 0;
 632                 }
 633                 $out .= $startChar . $combining;
 634                 return $out;
 635         }
 636
 637         /**
 638          * This is just used for the benchmark, comparing how long it takes to
 639          * interate through a string without really doing anything of substance.
 640          * @param string $string
 641          * @return string
 642          */
 643         function placebo( $string ) {
 644                 $len = strlen( $string );
 645                 $out = '';
 646                 for( $i = 0; $i < $len; $i++ ) {
 647                         $out .= $string{$i};
 648                 }
 649                 return $out;
 650         }
 651 }
 652
 653 ?>