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[mediawiki.git] / includes / libs / normal / UtfNormal.php

<?php
/**
 * Unicode normalization routines
 *
 * Copyright © 2004 Brion Vibber <brion@pobox.com>
 * https://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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup UtfNormal
 */

/**
 * @defgroup UtfNormal UtfNormal
 */

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

/**
 * Unicode normalization routines for working with UTF-8 strings.
 * Currently assumes that input strings are valid UTF-8!
 *
 * Not as fast as I'd like, but should be usable for most purposes.
 * UtfNormal::toNFC() will bail early if given ASCII text or text
 * it can quickly determine is already normalized.
 *
 * All functions can be called static.
 *
 * See description of forms at http://www.unicode.org/reports/tr15/
 *
 * @ingroup UtfNormal
 */
class UtfNormal {
        /**
         * For using the ICU wrapper
         */
        const UNORM_NONE = 1;
        const UNORM_NFD = 2;
        const UNORM_NFKD = 3;
        const UNORM_NFC = 4;
        const UNORM_NFKC = 5;
        const UNORM_FCD = 6;
        const UNORM_DEFAULT = self::UNORM_NFC;

        public static $utfCombiningClass = null;
        public static $utfCanonicalComp = null;
        public static $utfCanonicalDecomp = null;

        # Load compatibility decompositions on demand if they are needed.
        public static $utfCompatibilityDecomp = null;
        public static $utfCheckNFC;

        /**
         * The ultimate convenience function! Clean up invalid UTF-8 sequences,
         * and convert to normal form C, canonical composition.
         *
         * Fast return for pure ASCII strings; some lesser optimizations for
         * strings containing only known-good characters. Not as fast as toNFC().
         *
         * @param string $string a UTF-8 string
         * @return string a clean, shiny, normalized UTF-8 string
         */
        static function cleanUp( $string ) {
                if ( NORMALIZE_ICU ) {
                        $string = self::replaceForNativeNormalize( $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", self::UNORM_NFC ), "\x01" );
                } elseif ( NORMALIZE_INTL ) {
                        $string = self::replaceForNativeNormalize( $string );
                        $norm = normalizer_normalize( $string, Normalizer::FORM_C );
                        if ( $norm === null || $norm === false ) {
                                # normalizer_normalize will either return false or null
                                # (depending on which doc you read) if invalid utf8 string.
                                # quickIsNFCVerify cleans up invalid sequences.

                                if ( UtfNormal::quickIsNFCVerify( $string ) ) {
                                        # if that's true, the string is actually already normal.
                                        return $string;
                                } else {
                                        # Now we are valid but non-normal
                                        return normalizer_normalize( $string, Normalizer::FORM_C );
                                }
                        } else {
                                return $norm;
                        }
                } elseif ( UtfNormal::quickIsNFCVerify( $string ) ) {
                        # Side effect -- $string has had UTF-8 errors cleaned up.
                        return $string;
                } else {
                        return UtfNormal::NFC( $string );
                }
        }

        /**
         * Convert a UTF-8 string to normal form C, canonical composition.
         * Fast return for pure ASCII strings; some lesser optimizations for
         * strings containing only known-good characters.
         *
         * @param string $string a valid UTF-8 string. Input is not validated.
         * @return string a UTF-8 string in normal form C
         */
        static function toNFC( $string ) {
                if ( NORMALIZE_INTL )
                        return normalizer_normalize( $string, Normalizer::FORM_C );
                elseif ( NORMALIZE_ICU )
                        return utf8_normalize( $string, self::UNORM_NFC );
                elseif ( UtfNormal::quickIsNFC( $string ) )
                        return $string;
                else
                        return UtfNormal::NFC( $string );
        }

        /**
         * Convert a UTF-8 string to normal form D, canonical decomposition.
         * Fast return for pure ASCII strings.
         *
         * @param string $string a valid UTF-8 string. Input is not validated.
         * @return string a UTF-8 string in normal form D
         */
        static function toNFD( $string ) {
                if ( NORMALIZE_INTL )
                        return normalizer_normalize( $string, Normalizer::FORM_D );
                elseif ( NORMALIZE_ICU )
                        return utf8_normalize( $string, self::UNORM_NFD );
                elseif ( preg_match( '/[\x80-\xff]/', $string ) )
                        return UtfNormal::NFD( $string );
                else
                        return $string;
        }

        /**
         * Convert a UTF-8 string to normal form KC, compatibility composition.
         * This may cause irreversible information loss, use judiciously.
         * Fast return for pure ASCII strings.
         *
         * @param string $string a valid UTF-8 string. Input is not validated.
         * @return string a UTF-8 string in normal form KC
         */
        static function toNFKC( $string ) {
                if ( NORMALIZE_INTL )
                        return normalizer_normalize( $string, Normalizer::FORM_KC );
                elseif ( NORMALIZE_ICU )
                        return utf8_normalize( $string, self::UNORM_NFKC );
                elseif ( preg_match( '/[\x80-\xff]/', $string ) )
                        return UtfNormal::NFKC( $string );
                else
                        return $string;
        }

        /**
         * Convert a UTF-8 string to normal form KD, compatibility decomposition.
         * This may cause irreversible information loss, use judiciously.
         * Fast return for pure ASCII strings.
         *
         * @param string $string a valid UTF-8 string. Input is not validated.
         * @return string a UTF-8 string in normal form KD
         */
        static function toNFKD( $string ) {
                if ( NORMALIZE_INTL )
                        return normalizer_normalize( $string, Normalizer::FORM_KD );
                elseif ( NORMALIZE_ICU )
                        return utf8_normalize( $string, self::UNORM_NFKD );
                elseif ( preg_match( '/[\x80-\xff]/', $string ) )
                        return UtfNormal::NFKD( $string );
                else
                        return $string;
        }

        /**
         * Load the basic composition data if necessary
         * @private
         */
        static function loadData() {
                if ( !isset( self::$utfCombiningClass ) ) {
                        require_once __DIR__ . '/UtfNormalData.inc';
                }
        }

        /**
         * Returns true if the string is _definitely_ in NFC.
         * Returns false if not or uncertain.
         * @param string $string a valid UTF-8 string. Input is not validated.
         * @return bool
         */
        static 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();
                $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 );
                                $i++;
                        }
                        if ( isset( self::$utfCheckNFC[$c] ) ) {
                                # If it's NO or MAYBE, bail and do the slow check.
                                return false;
                        }
                        if ( isset( self::$utfCombiningClass[$c] ) ) {
                                # Combining character? We might have to do sorting, at least.
                                return false;
                        }
                }

                return true;
        }

        /**
         * Returns true if the string is _definitely_ in NFC.
         * Returns false if not or uncertain.
         * @param string $string a UTF-8 string, altered on output to be valid UTF-8 safe for XML.
         * @return bool
         */
        static function quickIsNFCVerify( &$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();

                        $utfCheckOrCombining = array_merge( self::$utfCheckNFC, self::$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.
                $matches = array();
                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; ) {
                                $remaining = $tailBytes[$c = $str[++$i]];
                                if ( $remaining ) {
                                        # 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!
        /**
         * @param $string string
         * @return string
         * @private
         */
        static function NFC( $string ) {
                return UtfNormal::fastCompose( UtfNormal::NFD( $string ) );
        }

        /**
         * @param $string string
         * @return string
         * @private
         */
        static function NFD( $string ) {
                UtfNormal::loadData();

                return UtfNormal::fastCombiningSort(
                        UtfNormal::fastDecompose( $string, self::$utfCanonicalDecomp ) );
        }

        /**
         * @param $string string
         * @return string
         * @private
         */
        static function NFKC( $string ) {
                return UtfNormal::fastCompose( UtfNormal::NFKD( $string ) );
        }

        /**
         * @param $string string
         * @return string
         * @private
         */
        static function NFKD( $string ) {
                if ( !isset( self::$utfCompatibilityDecomp ) ) {
                        require_once 'UtfNormalDataK.inc';
                }

                return self::fastCombiningSort(
                        self::fastDecompose( $string, self::$utfCompatibilityDecomp ) );
        }

        /**
         * Perform decomposition of a UTF-8 string into either D or KD form
         * (depending on which decomposition map is passed to us).
         * Input is assumed to be *valid* UTF-8. Invalid code will break.
         * @private
         * @param string $string valid UTF-8 string
         * @param array $map hash of expanded decomposition map
         * @return string a UTF-8 string decomposed, not yet normalized (needs sorting)
         */
        static 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;
        }

        /**
         * Sorts combining characters into canonical order. This is the
         * final step in creating decomposed normal forms D and KD.
         * @private
         * @param string $string a valid, decomposed UTF-8 string. Input is not validated.
         * @return string a UTF-8 string with combining characters sorted in canonical order
         */
        static function fastCombiningSort( $string ) {
                UtfNormal::loadData();
                $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 );
                                        $i++;
                                }
                                if ( isset( self::$utfCombiningClass[$c] ) ) {
                                        $lastClass = self::$utfCombiningClass[$c];
                                        if ( isset( $combiners[$lastClass] ) ) {
                                                $combiners[$lastClass] .= $c;
                                        } else {
                                                $combiners[$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;
        }

        /**
         * Produces canonically composed sequences, i.e. normal form C or KC.
         *
         * @private
         * @param string $string a valid UTF-8 string in sorted normal form D or KD.
         *   Input is not validated.
         * @return string a UTF-8 string with canonical precomposed characters used
         *   where possible.
         */
        static function fastCompose( $string ) {
                UtfNormal::loadData();
                $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 ( $n > 0x80 ) {
                                if ( isset( self::$utfCombiningClass[$c] ) ) {
                                        # A combining char; see what we can do with it
                                        $class = self::$utfCombiningClass[$c];
                                        if ( !empty( $startChar ) &&
                                                $lastClass < $class &&
                                                $class > 0 &&
                                                isset( self::$utfCanonicalComp[$pair] )
                                        ) {
                                                $startChar = self::$utfCanonicalComp[$pair];
                                                $class = 0;
                                        } else {
                                                $combining .= $c;
                                        }
                                        $lastClass = $class;
                                        $lastHangul = 0;
                                        continue;
                                }
                        }
                        # New start char
                        if ( $lastClass == 0 ) {
                                if ( isset( self::$utfCanonicalComp[$pair] ) ) {
                                        $startChar = self::$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;
        }

        /**
         * This is just used for the benchmark, comparing how long it takes to
         * interate through a string without really doing anything of substance.
         * @param $string string
         * @return string
         */
        static function placebo( $string ) {
                $len = strlen( $string );
                $out = '';
                for ( $i = 0; $i < $len; $i++ ) {
                        $out .= $string[$i];
                }

                return $out;
        }

        /**
         * Function to replace some characters that we don't want
         * but most of the native normalize functions keep.
         *
         * @param string $string The string
         * @return String String with the character codes replaced.
         */
        private static function replaceForNativeNormalize( $string ) {
                $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 );

                return $string;
        }
}