UtfNormal.php

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<?php
# Copyright (C) 2004 Brion Vibber <brion@pobox.com>
# http://www.mediawiki.org/
# 
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or 
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
# http://www.gnu.org/copyleft/gpl.html

require_once 'UtfNormalUtil.php';

global $utfCombiningClass, $utfCanonicalComp, $utfCanonicalDecomp;
$utfCombiningClass = NULL;
$utfCanonicalComp = NULL;
$utfCanonicalDecomp = NULL;

# Load compatibility decompositions on demand if they are needed.
global $utfCompatibilityDecomp;
$utfCompatibilityDecomp = NULL;

define( 'UNICODE_HANGUL_FIRST', 0xac00 );
define( 'UNICODE_HANGUL_LAST',  0xd7a3 );

define( 'UNICODE_HANGUL_LBASE', 0x1100 );
define( 'UNICODE_HANGUL_VBASE', 0x1161 );
define( 'UNICODE_HANGUL_TBASE', 0x11a7 );

define( 'UNICODE_HANGUL_LCOUNT', 19 );
define( 'UNICODE_HANGUL_VCOUNT', 21 );
define( 'UNICODE_HANGUL_TCOUNT', 28 );
define( 'UNICODE_HANGUL_NCOUNT', UNICODE_HANGUL_VCOUNT * UNICODE_HANGUL_TCOUNT );

define( 'UNICODE_HANGUL_LEND', UNICODE_HANGUL_LBASE + UNICODE_HANGUL_LCOUNT - 1 );
define( 'UNICODE_HANGUL_VEND', UNICODE_HANGUL_VBASE + UNICODE_HANGUL_VCOUNT - 1 );
define( 'UNICODE_HANGUL_TEND', UNICODE_HANGUL_TBASE + UNICODE_HANGUL_TCOUNT - 1 );

define( 'UNICODE_SURROGATE_FIRST', 0xd800 );
define( 'UNICODE_SURROGATE_LAST', 0xdfff );
define( 'UNICODE_MAX', 0x10ffff );
define( 'UNICODE_REPLACEMENT', 0xfffd );


define( 'UTF8_HANGUL_FIRST', codepointToUtf8( UNICODE_HANGUL_FIRST ) );
define( 'UTF8_HANGUL_LAST', codepointToUtf8( UNICODE_HANGUL_LAST ) );

define( 'UTF8_HANGUL_LBASE', codepointToUtf8( UNICODE_HANGUL_LBASE ) );
define( 'UTF8_HANGUL_VBASE', codepointToUtf8( UNICODE_HANGUL_VBASE ) );
define( 'UTF8_HANGUL_TBASE', codepointToUtf8( UNICODE_HANGUL_TBASE ) );

define( 'UTF8_HANGUL_LEND', codepointToUtf8( UNICODE_HANGUL_LEND ) );
define( 'UTF8_HANGUL_VEND', codepointToUtf8( UNICODE_HANGUL_VEND ) );
define( 'UTF8_HANGUL_TEND', codepointToUtf8( UNICODE_HANGUL_TEND ) );

define( 'UTF8_SURROGATE_FIRST', codepointToUtf8( UNICODE_SURROGATE_FIRST ) );
define( 'UTF8_SURROGATE_LAST', codepointToUtf8( UNICODE_SURROGATE_LAST ) );
define( 'UTF8_MAX', codepointToUtf8( UNICODE_MAX ) );
define( 'UTF8_REPLACEMENT', codepointToUtf8( UNICODE_REPLACEMENT ) );
#define( 'UTF8_REPLACEMENT', '!' );

define( 'UTF8_OVERLONG_A', "\xc1\xbf" );
define( 'UTF8_OVERLONG_B', "\xe0\x9f\xbf" );
define( 'UTF8_OVERLONG_C', "\xf0\x8f\xbf\xbf" );

# These two ranges are illegal
define( 'UTF8_FDD0', codepointToUtf8( 0xfdd0 ) );
define( 'UTF8_FDEF', codepointToUtf8( 0xfdef ) );
define( 'UTF8_FFFE', codepointToUtf8( 0xfffe ) );
define( 'UTF8_FFFF', codepointToUtf8( 0xffff ) );

define( 'UTF8_HEAD', false );
define( 'UTF8_TAIL', true );


define( 'UNORM_NONE', 1 );
define( 'UNORM_NFD',  2 );
define( 'UNORM_NFKD', 3 );
define( 'UNORM_NFC',  4 );
define( 'UNORM_DEFAULT', UNORM_NFC );
define( 'UNORM_NFKC', 5 );
define( 'UNORM_FCD',  6 );

define( 'NORMALIZE_ICU', function_exists( 'utf8_normalize' ) );

class UtfNormal {
        function cleanUp( $string ) {
                if( NORMALIZE_ICU ) {
                        # We exclude a few chars that ICU would not.
                        $string = preg_replace(
                                '/[\x00-\x08\x0b\x0c\x0e-\x1f]/',
                                UTF8_REPLACEMENT,
                                $string );
                        $string = str_replace( UTF8_FFFE, UTF8_REPLACEMENT, $string );
                        $string = str_replace( UTF8_FFFF, UTF8_REPLACEMENT, $string );
                        
                        # UnicodeString constructor fails if the string ends with a
                        # head byte. Add a junk char at the end, we'll strip it off.
                        return rtrim( utf8_normalize( $string . "\x01", UNORM_NFC ), "\x01" );
                } elseif( UtfNormal::quickIsNFCVerify( $string ) ) {
                        # Side effect -- $string has had UTF-8 errors cleaned up.
                        return $string;
                } else {
                        return UtfNormal::NFC( $string );
                }
        }

        function toNFC( $string ) {
                if( NORMALIZE_ICU )
                        return utf8_normalize( $string, UNORM_NFC );
                elseif( UtfNormal::quickIsNFC( $string ) )
                        return $string;
                else
                        return UtfNormal::NFC( $string );
        }
        
        function toNFD( $string ) {
                if( NORMALIZE_ICU )
                        return utf8_normalize( $string, UNORM_NFD );
                elseif( preg_match( '/[\x80-\xff]/', $string ) )
                        return UtfNormal::NFD( $string );
                else
                        return $string;
        }
        
        function toNFKC( $string ) {
                if( NORMALIZE_ICU )
                        return utf8_normalize( $string, UNORM_NFKC );
                elseif( preg_match( '/[\x80-\xff]/', $string ) )
                        return UtfNormal::NFKC( $string );
                else
                        return $string;
        }
        
        function toNFKD( $string ) {
                if( NORMALIZE_ICU )
                        return utf8_normalize( $string, UNORM_NFKD );
                elseif( preg_match( '/[\x80-\xff]/', $string ) )
                        return UtfNormal::NFKD( $string );
                else
                        return $string;
        }
        
        function loadData() {
                global $utfCombiningClass, $utfCanonicalComp, $utfCanonicalDecomp;
                if( !isset( $utfCombiningClass ) ) {
                        require_once( 'UtfNormalData.inc' );
                }
        }
        
        function quickIsNFC( $string ) {
                # ASCII is always valid NFC!
                # If it's pure ASCII, let it through.
                if( !preg_match( '/[\x80-\xff]/', $string ) ) return true;
                
                UtfNormal::loadData();
                global $utfCheckNFC, $utfCombiningClass;
                $len = strlen( $string );
                for( $i = 0; $i < $len; $i++ ) {
                        $c = $string{$i};
                        $n = ord( $c );
                        if( $n < 0x80 ) {
                                continue;
                        } elseif( $n >= 0xf0 ) {
                                $c = substr( $string, $i, 4 );
                                $i += 3;
                        } elseif( $n >= 0xe0 ) {
                                $c = substr( $string, $i, 3 );
                                $i += 2;
                        } elseif( $n >= 0xc0 ) {
                                $c = substr( $string, $i, 2 );
                                $i++;
                        }
                        if( isset( $utfCheckNFC[$c] ) ) {
                                # If it's NO or MAYBE, bail and do the slow check.
                                return false;
                        }
                        if( isset( $utfCombiningClass[$c] ) ) {
                                # Combining character? We might have to do sorting, at least.
                                return false;
                        }
                }
                return true;
        }

        function quickIsNFCVerify( &$string ) {
                # Screen out some characters that eg won't be allowed in XML
                $string = preg_replace( '/[\x00-\x08\x0b\x0c\x0e-\x1f]/', UTF8_REPLACEMENT, $string );
                
                # ASCII is always valid NFC!
                # If we're only ever given plain ASCII, we can avoid the overhead
                # of initializing the decomposition tables by skipping out early.
                if( !preg_match( '/[\x80-\xff]/', $string ) ) return true;
                
                static $checkit = null, $tailBytes = null, $utfCheckOrCombining = null;
                if( !isset( $checkit ) ) {
                        # Load/build some scary lookup tables...
                        UtfNormal::loadData();
                        global $utfCheckNFC, $utfCombiningClass;
                        
                        $utfCheckOrCombining = array_merge( $utfCheckNFC, $utfCombiningClass );

                        # Head bytes for sequences which we should do further validity checks
                        $checkit = array_flip( array_map( 'chr',
                                        array( 0xc0, 0xc1, 0xe0, 0xed, 0xef,
                                                   0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
                                                   0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff ) ) );
                        
                        # Each UTF-8 head byte is followed by a certain
                        # number of tail bytes.
                        $tailBytes = array();
                        for( $n = 0; $n < 256; $n++ ) {
                                if( $n < 0xc0 ) {
                                        $remaining = 0;
                                } elseif( $n < 0xe0 ) {
                                        $remaining = 1;
                                } elseif( $n < 0xf0 ) {
                                        $remaining = 2;
                                } elseif( $n < 0xf8 ) {
                                        $remaining = 3;
                                } elseif( $n < 0xfc ) {
                                        $remaining = 4;
                                } elseif( $n < 0xfe ) {
                                        $remaining = 5;
                                } else {
                                        $remaining = 0;
                                }
                                $tailBytes[chr($n)] = $remaining;
                        }
                }
                
                # Chop the text into pure-ASCII and non-ASCII areas;
                # large ASCII parts can be handled much more quickly.
                # Don't chop up Unicode areas for punctuation, though,
                # that wastes energy.
                preg_match_all(
                        '/([\x00-\x7f]+|[\x80-\xff][\x00-\x40\x5b-\x5f\x7b-\xff]*)/',
                        $string, $matches );
                
                $looksNormal = true;
                $base = 0;
                $replace = array();
                foreach( $matches[1] as $str ) {
                        $chunk = strlen( $str );
                        
                        if( $str{0} < "\x80" ) {
                                # ASCII chunk: guaranteed to be valid UTF-8
                                # and in normal form C, so skip over it.
                                $base += $chunk;
                                continue;
                        }
                        
                        # We'll have to examine the chunk byte by byte to ensure
                        # that it consists of valid UTF-8 sequences, and to see
                        # if any of them might not be normalized.
                        #
                        # Since PHP is not the fastest language on earth, some of
                        # this code is a little ugly with inner loop optimizations.
                        
                        $head = '';
                        $len = $chunk + 1; # Counting down is faster. I'm *so* sorry.
                        
                        for( $i = -1; --$len; ) {
                                if( $remaining = $tailBytes[$c = $str{++$i}] ) {
                                        # UTF-8 head byte!
                                        $sequence = $head = $c;
                                        do {
                                                # Look for the defined number of tail bytes...
                                                if( --$len && ( $c = $str{++$i} ) >= "\x80" && $c < "\xc0" ) {
                                                        # Legal tail bytes are nice.
                                                        $sequence .= $c;
                                                } else {
                                                        if( 0 == $len ) {
                                                                # Premature end of string!
                                                                # Drop a replacement character into output to
                                                                # represent the invalid UTF-8 sequence.
                                                                $replace[] = array( UTF8_REPLACEMENT,
                                                                                                        $base + $i + 1 - strlen( $sequence ),
                                                                                                        strlen( $sequence ) );
                                                                break 2;
                                                        } else {
                                                                # Illegal tail byte; abandon the sequence.
                                                                $replace[] = array( UTF8_REPLACEMENT,
                                                                                                        $base + $i - strlen( $sequence ),
                                                                                                        strlen( $sequence ) );
                                                                # Back up and reprocess this byte; it may itself
                                                                # be a legal ASCII or UTF-8 sequence head.
                                                                --$i;
                                                                ++$len;
                                                                continue 2;
                                                        }
                                                }
                                        } while( --$remaining );

                                        if( isset( $checkit[$head] ) ) {
                                                # Do some more detailed validity checks, for
                                                # invalid characters and illegal sequences.
                                                if( $head == "\xed" ) {
                                                        # 0xed is relatively frequent in Korean, which
                                                        # abuts the surrogate area, so we're doing
                                                        # this check separately to speed things up.
                                                        
                                                        if( $sequence >= UTF8_SURROGATE_FIRST ) {
                                                                # Surrogates are legal only in UTF-16 code.
                                                                # They are totally forbidden here in UTF-8
                                                                # utopia.
                                                                $replace[] = array( UTF8_REPLACEMENT,
                                                                             $base + $i + 1 - strlen( $sequence ),
                                                                             strlen( $sequence ) );
                                                                $head = '';
                                                                continue;
                                                        }
                                                } else {
                                                        # Slower, but rarer checks...
                                                        $n = ord( $head );
                                                        if(
                                                                # "Overlong sequences" are those that are syntactically
                                                                # correct but use more UTF-8 bytes than are necessary to
                                                                # encode a character. Naïve string comparisons can be
                                                                # tricked into failing to see a match for an ASCII
                                                                # character, for instance, which can be a security hole
                                                                # if blacklist checks are being used.
                                                               ($n  < 0xc2 && $sequence <= UTF8_OVERLONG_A)
                                                                || ($n == 0xe0 && $sequence <= UTF8_OVERLONG_B)
                                                                || ($n == 0xf0 && $sequence <= UTF8_OVERLONG_C)
                                                                
                                                                # U+FFFE and U+FFFF are explicitly forbidden in Unicode.
                                                                || ($n == 0xef && 
                                                                           ($sequence == UTF8_FFFE)
                                                                        || ($sequence == UTF8_FFFF) )
                                                                
                                                                # Unicode has been limited to 21 bits; longer
                                                                # sequences are not allowed.
                                                                || ($n >= 0xf0 && $sequence > UTF8_MAX) ) {
                                                                
                                                                $replace[] = array( UTF8_REPLACEMENT,
                                                                                    $base + $i + 1 - strlen( $sequence ), 
                                                                                    strlen( $sequence ) );
                                                                $head = '';
                                                                continue;
                                                        }
                                                }
                                        }
                                        
                                        if( isset( $utfCheckOrCombining[$sequence] ) ) {
                                                # If it's NO or MAYBE, we'll have to rip
                                                # the string apart and put it back together.
                                                # That's going to be mighty slow.
                                                $looksNormal = false;
                                        }
                                        
                                        # The sequence is legal!
                                        $head = '';
                                } elseif( $c < "\x80" ) {
                                        # ASCII byte.
                                        $head = '';
                                } elseif( $c < "\xc0" ) {
                                        # Illegal tail bytes
                                        if( $head == '' ) {
                                                # Out of the blue!
                                                $replace[] = array( UTF8_REPLACEMENT, $base + $i, 1 );
                                        } else {
                                                # Don't add if we're continuing a broken sequence;
                                                # we already put a replacement character when we looked
                                                # at the broken sequence.
                                                $replace[] = array( '', $base + $i, 1 );
                                        }
                                } else {
                                        # Miscellaneous freaks.
                                        $replace[] = array( UTF8_REPLACEMENT, $base + $i, 1 );
                                        $head = '';
                                }
                        }
                        $base += $chunk;
                }
                if( count( $replace ) ) {
                        # There were illegal UTF-8 sequences we need to fix up.
                        $out = '';
                        $last = 0;
                        foreach( $replace as $rep ) {
                                list( $replacement, $start, $length ) = $rep;
                                if( $last < $start ) {
                                        $out .= substr( $string, $last, $start - $last );
                                }
                                $out .= $replacement;
                                $last = $start + $length;
                        }
                        if( $last < strlen( $string ) ) {
                                $out .= substr( $string, $last );
                        }
                        $string = $out;
                }
                return $looksNormal;
        }
        
        # These take a string and run the normalization on them, without
        # checking for validity or any optimization etc. Input must be
        # VALID UTF-8!

        function NFC( $string ) {
                return UtfNormal::fastCompose( UtfNormal::NFD( $string ) );
        }
        
        function NFD( $string ) {
                UtfNormal::loadData();
                global $utfCanonicalDecomp;
                return UtfNormal::fastCombiningSort(
                        UtfNormal::fastDecompose( $string, $utfCanonicalDecomp ) );
        }
        
        function NFKC( $string ) {
                return UtfNormal::fastCompose( UtfNormal::NFKD( $string ) );
        }
        
        function NFKD( $string ) {
                global $utfCompatibilityDecomp;
                if( !isset( $utfCompatibilityDecomp ) ) {
                        require_once( 'UtfNormalDataK.inc' );
                }
                return UtfNormal::fastCombiningSort(
                        UtfNormal::fastDecompose( $string, $utfCompatibilityDecomp ) );
        }
        
        
        function fastDecompose( $string, &$map ) {
                UtfNormal::loadData();
                $len = strlen( $string );
                $out = '';
                for( $i = 0; $i < $len; $i++ ) {
                        $c = $string{$i};
                        $n = ord( $c );
                        if( $n < 0x80 ) {
                                # ASCII chars never decompose
                                # THEY ARE IMMORTAL
                                $out .= $c;
                                continue;
                        } elseif( $n >= 0xf0 ) {
                                $c = substr( $string, $i, 4 );
                                $i += 3;
                        } elseif( $n >= 0xe0 ) {
                                $c = substr( $string, $i, 3 );
                                $i += 2;
                        } elseif( $n >= 0xc0 ) {
                                $c = substr( $string, $i, 2 );
                                $i++;
                        }
                        if( isset( $map[$c] ) ) {
                                $out .= $map[$c];
                                continue;
                        } else {
                                if( $c >= UTF8_HANGUL_FIRST && $c <= UTF8_HANGUL_LAST ) {
                                        # Decompose a hangul syllable into jamo;
                                        # hardcoded for three-byte UTF-8 sequence.
                                        # A lookup table would be slightly faster,
                                        # but adds a lot of memory & disk needs.
                                        #
                                        $index = ( (ord( $c{0} ) & 0x0f) << 12
                                                 | (ord( $c{1} ) & 0x3f) <<  6
                                                 | (ord( $c{2} ) & 0x3f) )
                                               - UNICODE_HANGUL_FIRST;
                                        $l = IntVal( $index / UNICODE_HANGUL_NCOUNT );
                                        $v = IntVal( ($index % UNICODE_HANGUL_NCOUNT) / UNICODE_HANGUL_TCOUNT);
                                        $t = $index % UNICODE_HANGUL_TCOUNT;
                                        $out .= "\xe1\x84" . chr( 0x80 + $l ) . "\xe1\x85" . chr( 0xa1 + $v );
                                        if( $t >= 25 ) {
                                                $out .= "\xe1\x87" . chr( 0x80 + $t - 25 );
                                        } elseif( $t ) {
                                                $out .= "\xe1\x86" . chr( 0xa7 + $t );
                                        }
                                        continue;
                                }
                        }
                        $out .= $c;
                }
                return $out;
        }

        function fastCombiningSort( $string ) {
                UtfNormal::loadData();
                global $utfCombiningClass;
                $len = strlen( $string );
                $out = '';
                $combiners = array();
                $lastClass = -1;
                for( $i = 0; $i < $len; $i++ ) {
                        $c = $string{$i};
                        $n = ord( $c );
                        if( $n >= 0x80 ) {
                                if( $n >= 0xf0 ) {
                                        $c = substr( $string, $i, 4 );
                                        $i += 3;
                                } elseif( $n >= 0xe0 ) {
                                        $c = substr( $string, $i, 3 );
                                        $i += 2;
                                } elseif( $n >= 0xc0 ) {
                                        $c = substr( $string, $i, 2 );
                                        $i++;
                                }
                                if( isset( $utfCombiningClass[$c] ) ) {
                                        $lastClass = $utfCombiningClass[$c];
                                        @$combiners[$lastClass] .= $c;
                                        continue;
                                }
                        }
                        if( $lastClass ) {
                                ksort( $combiners );
                                $out .= implode( '', $combiners );
                                $combiners = array();
                        }
                        $out .= $c;
                        $lastClass = 0;
                }
                if( $lastClass ) {
                        ksort( $combiners );
                        $out .= implode( '', $combiners );
                }
                return $out;
        }

        function fastCompose( $string ) {
                UtfNormal::loadData();
                global $utfCanonicalComp, $utfCombiningClass;
                $len = strlen( $string );
                $out = '';
                $lastClass = -1;
                $lastHangul = 0;
                $startChar = '';
                $combining = '';
                $x1 = ord(substr(UTF8_HANGUL_VBASE,0,1));
                $x2 = ord(substr(UTF8_HANGUL_TEND,0,1));
                for( $i = 0; $i < $len; $i++ ) {
                        $c = $string{$i};
                        $n = ord( $c );
                        if( $n < 0x80 ) {
                                # No combining characters here...
                                $out .= $startChar;
                                $out .= $combining;
                                $startChar = $c;
                                $combining = '';
                                $lastClass = 0;
                                continue;
                        } elseif( $n >= 0xf0 ) {
                                $c = substr( $string, $i, 4 );
                                $i += 3;
                        } elseif( $n >= 0xe0 ) {
                                $c = substr( $string, $i, 3 );
                                $i += 2;
                        } elseif( $n >= 0xc0 ) {
                                $c = substr( $string, $i, 2 );
                                $i++;
                        }
                        $pair = $startChar . $c;
                        if( $n > 0x80 ) {
                                if( isset( $utfCombiningClass[$c] ) ) {
                                        # A combining char; see what we can do with it
                                        $class = $utfCombiningClass[$c];
                                        if( !empty( $startChar ) &&
                                                $lastClass < $class &&
                                                $class > 0 &&
                                                isset( $utfCanonicalComp[$pair] ) ) {
                                                $startChar = $utfCanonicalComp[$pair];
                                                $class = 0;
                                        } else {
                                                $combining .= $c;
                                        }
                                        $lastClass = $class;
                                        $lastHangul = 0;
                                        continue;
                                }
                        }
                        # New start char
                        if( $lastClass == 0 ) {
                                if( isset( $utfCanonicalComp[$pair] ) ) {
                                        $startChar = $utfCanonicalComp[$pair];
                                        $lastHangul = 0;
                                        continue;
                                }
                                if( $n >= $x1 && $n <= $x2 ) {
                                        # WARNING: Hangul code is painfully slow.
                                        # I apologize for this ugly, ugly code; however
                                        # performance is even more teh suck if we call
                                        # out to nice clean functions. Lookup tables are
                                        # marginally faster, but require a lot of space.
                                        #
                                        if( $c >= UTF8_HANGUL_VBASE &&
                                                $c <= UTF8_HANGUL_VEND &&
                                                $startChar >= UTF8_HANGUL_LBASE &&
                                                $startChar <= UTF8_HANGUL_LEND ) {
                                                #
                                                #$lIndex = utf8ToCodepoint( $startChar ) - UNICODE_HANGUL_LBASE;
                                                #$vIndex = utf8ToCodepoint( $c ) - UNICODE_HANGUL_VBASE;
                                                $lIndex = ord( $startChar{2} ) - 0x80;
                                                $vIndex = ord( $c{2}         ) - 0xa1;

                                                $hangulPoint = UNICODE_HANGUL_FIRST +
                                                        UNICODE_HANGUL_TCOUNT *
                                                        (UNICODE_HANGUL_VCOUNT * $lIndex + $vIndex);
                                                
                                                # Hardcode the limited-range UTF-8 conversion:
                                                $startChar = chr( $hangulPoint >> 12 & 0x0f | 0xe0 ) .
                                                                         chr( $hangulPoint >>  6 & 0x3f | 0x80 ) .
                                                                         chr( $hangulPoint       & 0x3f | 0x80 );
                                                $lastHangul = 0;
                                                continue;
                                        } elseif( $c >= UTF8_HANGUL_TBASE &&
                                                          $c <= UTF8_HANGUL_TEND &&
                                                          $startChar >= UTF8_HANGUL_FIRST &&
                                                          $startChar <= UTF8_HANGUL_LAST &&
                                                          !$lastHangul ) {
                                                # $tIndex = utf8ToCodepoint( $c ) - UNICODE_HANGUL_TBASE;
                                                $tIndex = ord( $c{2} ) - 0xa7;
                                                if( $tIndex < 0 ) $tIndex = ord( $c{2} ) - 0x80 + (0x11c0 - 0x11a7);
                                                
                                                # Increment the code point by $tIndex, without
                                                # the function overhead of decoding and recoding UTF-8
                                                #
                                                $tail = ord( $startChar{2} ) + $tIndex;
                                                if( $tail > 0xbf ) {
                                                        $tail -= 0x40;
                                                        $mid = ord( $startChar{1} ) + 1;
                                                        if( $mid > 0xbf ) {
                                                                $startChar{0} = chr( ord( $startChar{0} ) + 1 );
                                                                $mid -= 0x40;
                                                        }
                                                        $startChar{1} = chr( $mid );
                                                }
                                                $startChar{2} = chr( $tail );
                                                
                                                # If there's another jamo char after this, *don't* try to merge it.
                                                $lastHangul = 1;
                                                continue;
                                        }
                                }
                        }
                        $out .= $startChar;
                        $out .= $combining;
                        $startChar = $c;
                        $combining = '';
                        $lastClass = 0;
                        $lastHangul = 0;
                }
                $out .= $startChar . $combining;
                return $out;
        }
        
        function placebo( $string ) {
                $len = strlen( $string );
                $out = '';
                for( $i = 0; $i < $len; $i++ ) {
                        $out .= $string{$i};
                }
                return $out;
        }
}

?>