os/textandloc/fontservices/textshaperplugin/IcuSource/layout/KhmerReordering.cpp
changeset 0 bde4ae8d615e
     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/os/textandloc/fontservices/textshaperplugin/IcuSource/layout/KhmerReordering.cpp	Fri Jun 15 03:10:57 2012 +0200
     1.3 @@ -0,0 +1,523 @@
     1.4 +/*
     1.5 + *
     1.6 + * (C) Copyright IBM Corp. 1998-2005 - All Rights Reserved 
     1.7 + *
     1.8 + * This file is a modification of the ICU file IndicReordering.cpp
     1.9 + * by Jens Herden and Javier Sola for Khmer language 
    1.10 + *
    1.11 + */
    1.12 +
    1.13 +#include "LETypes.h"
    1.14 +#include "KhmerReordering.h"
    1.15 +#include "LEGlyphStorage.h"
    1.16 +
    1.17 +
    1.18 +U_NAMESPACE_BEGIN
    1.19 +
    1.20 +// Characters that get refered to by name...
    1.21 +enum
    1.22 +{
    1.23 +    C_SIGN_ZWNJ     = 0x200C,
    1.24 +    C_SIGN_ZWJ      = 0x200D,
    1.25 +    C_DOTTED_CIRCLE = 0x25CC,
    1.26 +    C_RO            = 0x179A,
    1.27 +    C_VOWEL_AA      = 0x17B6,
    1.28 +    C_SIGN_NIKAHIT  = 0x17C6,
    1.29 +    C_VOWEL_E       = 0x17C1,
    1.30 +    C_COENG         = 0x17D2
    1.31 +};
    1.32 +
    1.33 +
    1.34 +enum
    1.35 +{
    1.36 +    // simple classes, they are used in the statetable (in this file) to control the length of a syllable
    1.37 +    // they are also used to know where a character should be placed (location in reference to the base character)
    1.38 +    // and also to know if a character, when independtly displayed, should be displayed with a dotted-circle to
    1.39 +    // indicate error in syllable construction 
    1.40 +    _xx = KhmerClassTable::CC_RESERVED,
    1.41 +    _sa = KhmerClassTable::CC_SIGN_ABOVE | KhmerClassTable::CF_DOTTED_CIRCLE | KhmerClassTable::CF_POS_ABOVE,
    1.42 +    _sp = KhmerClassTable::CC_SIGN_AFTER | KhmerClassTable::CF_DOTTED_CIRCLE| KhmerClassTable::CF_POS_AFTER,
    1.43 +    _c1 = KhmerClassTable::CC_CONSONANT | KhmerClassTable::CF_CONSONANT,
    1.44 +    _c2 = KhmerClassTable::CC_CONSONANT2 | KhmerClassTable::CF_CONSONANT,
    1.45 +    _c3 = KhmerClassTable::CC_CONSONANT3 | KhmerClassTable::CF_CONSONANT,
    1.46 +    _rb = KhmerClassTable::CC_ROBAT | KhmerClassTable::CF_POS_ABOVE | KhmerClassTable::CF_DOTTED_CIRCLE,
    1.47 +    _cs = KhmerClassTable::CC_CONSONANT_SHIFTER | KhmerClassTable::CF_DOTTED_CIRCLE | KhmerClassTable::CF_SHIFTER,
    1.48 +    _dl = KhmerClassTable::CC_DEPENDENT_VOWEL | KhmerClassTable::CF_POS_BEFORE | KhmerClassTable::CF_DOTTED_CIRCLE, 
    1.49 +    _db = KhmerClassTable::CC_DEPENDENT_VOWEL | KhmerClassTable::CF_POS_BELOW | KhmerClassTable::CF_DOTTED_CIRCLE,
    1.50 +    _da = KhmerClassTable::CC_DEPENDENT_VOWEL | KhmerClassTable::CF_POS_ABOVE | KhmerClassTable::CF_DOTTED_CIRCLE | KhmerClassTable::CF_ABOVE_VOWEL,
    1.51 +    _dr = KhmerClassTable::CC_DEPENDENT_VOWEL | KhmerClassTable::CF_POS_AFTER | KhmerClassTable::CF_DOTTED_CIRCLE,
    1.52 +    _co = KhmerClassTable::CC_COENG | KhmerClassTable::CF_COENG | KhmerClassTable::CF_DOTTED_CIRCLE,
    1.53 +    
    1.54 +    // split vowel
    1.55 +    _va = _da | KhmerClassTable::CF_SPLIT_VOWEL,
    1.56 +    _vr = _dr | KhmerClassTable::CF_SPLIT_VOWEL
    1.57 +};
    1.58 +
    1.59 +
    1.60 +// Character class tables 
    1.61 +// _xx character does not combine into syllable, such as numbers, puntuation marks, non-Khmer signs... 
    1.62 +// _sa Sign placed above the base
    1.63 +// _sp Sign placed after the base
    1.64 +// _c1 Consonant of type 1 or independent vowel (independent vowels behave as type 1 consonants)
    1.65 +// _c2 Consonant of type 2 (only RO)
    1.66 +// _c3 Consonant of type 3 
    1.67 +// _rb Khmer sign robat u17CC. combining mark for subscript consonants
    1.68 +// _cd Consonant-shifter
    1.69 +// _dl Dependent vowel placed before the base (left of the base)
    1.70 +// _db Dependent vowel placed below the base 
    1.71 +// _da Dependent vowel placed above the base
    1.72 +// _dr Dependent vowel placed behind the base (right of the base)    
    1.73 +// _co Khmer combining mark COENG u17D2, combines with the consonant or independent vowel following 
    1.74 +//     it to create a subscript consonant or independent vowel   
    1.75 +// _va Khmer split vowel in wich the first part is before the base and the second one above the base
    1.76 +// _vr Khmer split vowel in wich the first part is before the base and the second one behind (right of) the base
    1.77 +
    1.78 +static const KhmerClassTable::CharClass khmerCharClasses[] =
    1.79 +{
    1.80 +    _c1, _c1, _c1, _c3, _c1, _c1, _c1, _c1, _c3, _c1, _c1, _c1, _c1, _c3, _c1, _c1, // 1780 - 178F
    1.81 +    _c1, _c1, _c1, _c1, _c3, _c1, _c1, _c1, _c1, _c3, _c2, _c1, _c1, _c1, _c3, _c3, // 1790 - 179F
    1.82 +    _c1, _c3, _c1, _c1, _c1, _c1, _c1, _c1, _c1, _c1, _c1, _c1, _c1, _c1, _c1, _c1, // 17A0 - 17AF
    1.83 +    _c1, _c1, _c1, _c1, _dr, _dr, _dr, _da, _da, _da, _da, _db, _db, _db, _va, _vr, // 17B0 - 17BF
    1.84 +    _vr, _dl, _dl, _dl, _vr, _vr, _sa, _sp, _sp, _cs, _cs, _sa, _rb, _sa, _sa, _sa, // 17C0 - 17CF
    1.85 +    _sa, _sa, _co, _sa, _xx, _xx, _xx, _xx, _xx, _xx, _xx, _xx, _xx, _sa, _xx, _xx, // 17D0 - 17DF
    1.86 +};                                                                                  
    1.87 +
    1.88 +
    1.89 +//
    1.90 +// Khmer Class Tables
    1.91 +//                   
    1.92 +
    1.93 +//
    1.94 +// The range of characters defined in the above table is defined here. FOr Khmer 1780 to 17DF
    1.95 +// Even if the Khmer range is bigger, all other characters are not combinable, and therefore treated
    1.96 +// as _xx
    1.97 +static const KhmerClassTable khmerClassTable = {0x1780, 0x17df, khmerCharClasses};
    1.98 +
    1.99 +
   1.100 +// Below we define how a character in the input string is either in the khmerCharClasses table
   1.101 +// (in which case we get its type back), a ZWJ or ZWNJ (two characters that may appear 
   1.102 +// within the syllable, but are not in the table) we also get their type back, or an unknown object
   1.103 +// in which case we get _xx (CC_RESERVED) back
   1.104 +KhmerClassTable::CharClass KhmerClassTable::getCharClass(LEUnicode ch) const
   1.105 +{
   1.106 +
   1.107 +    if (ch == C_SIGN_ZWJ) {
   1.108 +        return CC_ZERO_WIDTH_J_MARK;
   1.109 +    }
   1.110 +
   1.111 +    if (ch == C_SIGN_ZWNJ) {
   1.112 +        return CC_ZERO_WIDTH_NJ_MARK;
   1.113 +    }
   1.114 +
   1.115 +    if (ch < firstChar || ch > lastChar) {
   1.116 +        return CC_RESERVED;
   1.117 +    }
   1.118 +    
   1.119 +    return classTable[ch - firstChar];
   1.120 +}
   1.121 +
   1.122 +const KhmerClassTable *KhmerClassTable::getKhmerClassTable()
   1.123 +{
   1.124 +    return &khmerClassTable;
   1.125 +}
   1.126 +
   1.127 +
   1.128 +
   1.129 +class ReorderingOutput : public UMemory {
   1.130 +private:
   1.131 +    le_int32 fOutIndex;
   1.132 +    LEUnicode *fOutChars;
   1.133 +
   1.134 +    LEGlyphStorage &fGlyphStorage;
   1.135 +
   1.136 +
   1.137 +public:
   1.138 +    ReorderingOutput(LEUnicode *outChars, LEGlyphStorage &glyphStorage)
   1.139 +        : fOutIndex(0), fOutChars(outChars), fGlyphStorage(glyphStorage)
   1.140 +    {
   1.141 +        // nothing else to do...
   1.142 +    }
   1.143 +
   1.144 +    ~ReorderingOutput()
   1.145 +    {
   1.146 +        // nothing to do here...
   1.147 +    }
   1.148 +
   1.149 +    void writeChar(LEUnicode ch, le_uint32 charIndex, const LETag *charTags)
   1.150 +    {
   1.151 +        LEErrorCode success = LE_NO_ERROR;
   1.152 +
   1.153 +        fOutChars[fOutIndex] = ch;
   1.154 +
   1.155 +        fGlyphStorage.setCharIndex(fOutIndex, charIndex, success);
   1.156 +        fGlyphStorage.setAuxData(fOutIndex, (void *) charTags, success);
   1.157 +
   1.158 +        fOutIndex += 1;
   1.159 +    }
   1.160 +
   1.161 +    le_int32 getOutputIndex()
   1.162 +    {
   1.163 +        return fOutIndex;
   1.164 +    }
   1.165 +};
   1.166 +
   1.167 +
   1.168 +static const LETag emptyTag       = 0x00000000; // ''
   1.169 +//TODO remove unused flags
   1.170 +//static const LETag nuktFeatureTag = LE_NUKT_FEATURE_TAG;
   1.171 +//static const LETag akhnFeatureTag = LE_AKHN_FEATURE_TAG;
   1.172 +//static const LETag rphfFeatureTag = LE_RPHF_FEATURE_TAG;
   1.173 +static const LETag blwfFeatureTag = LE_BLWF_FEATURE_TAG;
   1.174 +//static const LETag halfFeatureTag = LE_HALF_FEATURE_TAG;
   1.175 +static const LETag pstfFeatureTag = LE_PSTF_FEATURE_TAG;
   1.176 +//static const LETag vatuFeatureTag = LE_VATU_FEATURE_TAG;
   1.177 +static const LETag presFeatureTag = LE_PRES_FEATURE_TAG;
   1.178 +static const LETag blwsFeatureTag = LE_BLWS_FEATURE_TAG;
   1.179 +static const LETag abvsFeatureTag = LE_ABVS_FEATURE_TAG;
   1.180 +static const LETag pstsFeatureTag = LE_PSTS_FEATURE_TAG;
   1.181 +//static const LETag halnFeatureTag = LE_HALN_FEATURE_TAG;
   1.182 +
   1.183 +static const LETag blwmFeatureTag = LE_BLWM_FEATURE_TAG;
   1.184 +static const LETag abvmFeatureTag = LE_ABVM_FEATURE_TAG;
   1.185 +static const LETag distFeatureTag = LE_DIST_FEATURE_TAG;
   1.186 +
   1.187 +static const LETag prefFeatureTag = LE_PREF_FEATURE_TAG;
   1.188 +static const LETag abvfFeatureTag = LE_ABVF_FEATURE_TAG;
   1.189 +static const LETag cligFeatureTag = LE_CLIG_FEATURE_TAG;
   1.190 +static const LETag mkmkFeatureTag = LE_MKMK_FEATURE_TAG;
   1.191 +
   1.192 +// These are in the order in which the features need to be applied
   1.193 +// for correct processing
   1.194 +static const LETag featureOrder[] =
   1.195 +{
   1.196 +    // Shaping features
   1.197 +    prefFeatureTag, blwfFeatureTag, abvfFeatureTag, pstfFeatureTag, 
   1.198 +    presFeatureTag, blwsFeatureTag, abvsFeatureTag, pstsFeatureTag,
   1.199 +    cligFeatureTag, 
   1.200 +    
   1.201 +    // Positioning features
   1.202 +    distFeatureTag, blwmFeatureTag, abvmFeatureTag, mkmkFeatureTag,
   1.203 +    emptyTag
   1.204 +};
   1.205 +
   1.206 +static const LETag tagPref[] = 
   1.207 +{
   1.208 +    prefFeatureTag, presFeatureTag, 
   1.209 +    cligFeatureTag, 
   1.210 +    
   1.211 +    // Positioning features
   1.212 +    distFeatureTag, 
   1.213 +    emptyTag
   1.214 +};
   1.215 +
   1.216 +static const LETag tagAbvf[] = 
   1.217 +{
   1.218 +    abvfFeatureTag, abvsFeatureTag, 
   1.219 +    cligFeatureTag, 
   1.220 +    
   1.221 +    // Positioning features
   1.222 +    distFeatureTag, abvmFeatureTag, mkmkFeatureTag,
   1.223 +    emptyTag
   1.224 +};
   1.225 +
   1.226 +static const LETag tagPstf[] = 
   1.227 +{
   1.228 +    blwfFeatureTag, blwsFeatureTag, 
   1.229 +    prefFeatureTag, presFeatureTag, 
   1.230 +    
   1.231 +    pstfFeatureTag, pstsFeatureTag, 
   1.232 +    cligFeatureTag, 
   1.233 +    
   1.234 +    // Positioning features
   1.235 +    distFeatureTag, blwmFeatureTag, 
   1.236 +    emptyTag
   1.237 +};
   1.238 +
   1.239 +static const LETag tagBlwf[] = 
   1.240 +{
   1.241 +    blwfFeatureTag, blwsFeatureTag, 
   1.242 +    cligFeatureTag, 
   1.243 +    
   1.244 +    // Positioning features
   1.245 +    distFeatureTag, blwmFeatureTag, mkmkFeatureTag,
   1.246 +    emptyTag
   1.247 +};
   1.248 +
   1.249 +
   1.250 +// TODO do we need all of them?
   1.251 +static const LETag tagDefault[] = 
   1.252 +{
   1.253 +    // Shaping feature
   1.254 +    prefFeatureTag, blwfFeatureTag, /*abvfFeatureTag,*/ /*pstfFeatureTag, */
   1.255 +    presFeatureTag, blwsFeatureTag, /*abvsFeatureTag,*/ /*pstsFeatureTag,*/
   1.256 +    cligFeatureTag, 
   1.257 +    
   1.258 +    // Positioning features
   1.259 +    distFeatureTag, abvmFeatureTag, blwmFeatureTag, mkmkFeatureTag,
   1.260 +    emptyTag
   1.261 +};
   1.262 +
   1.263 +
   1.264 +
   1.265 +// The stateTable is used to calculate the end (the length) of a well
   1.266 +// formed Khmer Syllable. 
   1.267 +//
   1.268 +// Each horizontal line is ordered exactly the same way as the values in KhmerClassTable
   1.269 +// CharClassValues in KhmerReordering.h This coincidence of values allows the
   1.270 +// follow up of the table.
   1.271 +//
   1.272 +// Each line corresponds to a state, which does not necessarily need to be a type
   1.273 +// of component... for example, state 2 is a base, with is always a first character
   1.274 +// in the syllable, but the state could be produced a consonant of any type when
   1.275 +// it is the first character that is analysed (in ground state).
   1.276 +//
   1.277 +// Differentiating 3 types of consonants is necessary in order to 
   1.278 +// forbid the use of certain combinations, such as having a second
   1.279 +// coeng after a coeng RO, 
   1.280 +// The inexistent possibility of having a type 3 after another type 3 is permitted,
   1.281 +// eliminating it would very much complicate the table, and it does not create typing
   1.282 +// problems, as the case above.
   1.283 +//
   1.284 +// The table is quite complex, in order to limit the number of coeng consonants
   1.285 +// to 2 (by means of the table).
   1.286 +//
   1.287 +// There a peculiarity, as far as Unicode is concerned:
   1.288 +// - The consonant-shifter is considered in two possible different 
   1.289 +//   locations, the one considered in Unicode 3.0 and the one considered in
   1.290 +//   Unicode 4.0. (there is a backwards compatibility problem in this standard).
   1.291 +
   1.292 +
   1.293 +// xx    independent character, such as a number, punctuation sign or non-khmer char
   1.294 +//
   1.295 +// c1    Khmer consonant of type 1 or an independent vowel
   1.296 +//       that is, a letter in which the subscript for is only under the
   1.297 +//       base, not taking any space to the right or to the left
   1.298 +//
   1.299 +// c2    Khmer consonant of type 2, the coeng form takes space under
   1.300 +//       and to the left of the base (only RO is of this type)
   1.301 +//
   1.302 +// c3    Khmer consonant of type 3. Its subscript form takes space under
   1.303 +//       and to the right of the base. 
   1.304 +//
   1.305 +// cs    Khmer consonant shifter         
   1.306 +//
   1.307 +// rb    Khmer robat
   1.308 +//
   1.309 +// co    coeng character (u17D2)
   1.310 +//
   1.311 +// dv    dependent vowel (including split vowels, they are treated in the same way).
   1.312 +//       even if dv is not defined above, the component that is really tested for is
   1.313 +//       KhmerClassTable::CC_DEPENDENT_VOWEL, which is common to all dependent vowels
   1.314 +//
   1.315 +// zwj   Zero Width joiner
   1.316 +//
   1.317 +// zwnj  Zero width non joiner  
   1.318 +//
   1.319 +// sa    above sign
   1.320 +//
   1.321 +// sp    post sign    
   1.322 +// 
   1.323 +// there are lines with equal content but for an easier understanding 
   1.324 +// (and maybe change in the future) we did not join them
   1.325 +//
   1.326 +static const le_int8 khmerStateTable[][KhmerClassTable::CC_COUNT] =
   1.327 +{
   1.328 +
   1.329 +//   xx  c1  c2  c3 zwnj cs  rb  co  dv  sa  sp zwj  
   1.330 +    { 1,  2,  2,  2,  1,  1,  1,  6,  1,  1,  1,  2}, //  0 - ground state
   1.331 +    {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1}, //  1 - exit state (or sign to the right of the syllable)
   1.332 +    {-1, -1, -1, -1,  3,  4,  5,  6, 16, 17,  1, -1}, //  2 - Base consonant    
   1.333 +    {-1, -1, -1, -1, -1,  4, -1, -1, 16, -1, -1, -1}, //  3 - First ZWNJ before a register shifter
   1.334 +                                                      //      It can only be followed by a shifter or a vowel
   1.335 +    {-1, -1, -1, -1, 15, -1, -1,  6, 16, 17,  1, 14}, //  4 - First register shifter             
   1.336 +    {-1, -1, -1, -1, -1, -1, -1, -1, 20, -1,  1, -1}, //  5 - Robat
   1.337 +    {-1,  7,  8,  9, -1, -1, -1, -1, -1, -1, -1, -1}, //  6 - First Coeng
   1.338 +    {-1, -1, -1, -1, 12, 13, -1, 10, 16, 17,  1, 14}, //  7 - First consonant of type 1 after coeng 
   1.339 +    {-1, -1, -1, -1, 12, 13, -1, -1, 16, 17,  1, 14}, //  8 - First consonant of type 2 after coeng
   1.340 +    {-1, -1, -1, -1, 12, 13, -1, 10, 16, 17,  1, 14}, //  9 - First consonant or type 3 after ceong
   1.341 +    {-1, 11, 11, 11, -1, -1, -1, -1, -1, -1, -1, -1}, // 10 - Second Coeng (no register shifter before)
   1.342 +    {-1, -1, -1, -1, 15, -1, -1, -1, 16, 17,  1, 14}, // 11 - Second coeng consonant (or ind. vowel) no register shifter before 
   1.343 +    {-1, -1,  1, -1, -1, 13, -1, -1, 16, -1, -1, -1}, // 12 - Second ZWNJ before a register shifter
   1.344 +    {-1, -1, -1, -1, 15, -1, -1, -1, 16, 17,  1, 14}, // 13 - Second register shifter 
   1.345 +    {-1, -1, -1, -1, -1, -1, -1, -1, 16, -1, -1, -1}, // 14 - ZWJ before vowel    
   1.346 +    {-1, -1, -1, -1, -1, -1, -1, -1, 16, -1, -1, -1}, // 15 - ZWNJ before vowel
   1.347 +    {-1, -1, -1, -1, -1, -1, -1, -1, -1, 17,  1, 18}, // 16 - dependent vowel 
   1.348 +    {-1, -1,  1, -1, -1, -1, -1, -1, -1, -1,  1, 18}, // 17 - sign above
   1.349 +    {-1, -1, -1, -1, -1, -1, -1, 19, -1, -1, -1, -1}, // 18 - ZWJ after vowel    
   1.350 +    {-1,  1, -1,  1, -1, -1, -1, -1, -1, -1, -1, -1}, // 19 - Third coeng 
   1.351 +    {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  1, -1}, // 20 - dependent vowel after a Robat
   1.352 +
   1.353 +};         
   1.354 +
   1.355 +
   1.356 +const LETag *KhmerReordering::getFeatureOrder()
   1.357 +{
   1.358 +    return featureOrder;
   1.359 +}
   1.360 +
   1.361 +
   1.362 +// Given an input string of characters and a location in which to start looking
   1.363 +// calculate, using the state table, which one is the last character of the syllable
   1.364 +// that starts in the starting position.
   1.365 +le_int32 KhmerReordering::findSyllable(const KhmerClassTable *classTable, const LEUnicode *chars, le_int32 prev, le_int32 charCount)
   1.366 +{
   1.367 +    le_int32 cursor = prev;
   1.368 +    le_int8 state = 0;
   1.369 +
   1.370 +    while (cursor < charCount) {
   1.371 +        KhmerClassTable::CharClass charClass = (classTable->getCharClass(chars[cursor]) & KhmerClassTable::CF_CLASS_MASK);
   1.372 +
   1.373 +        state = khmerStateTable[state][charClass];
   1.374 +
   1.375 +        if (state < 0) {
   1.376 +            break;
   1.377 +        }
   1.378 +
   1.379 +        cursor += 1;
   1.380 +    }
   1.381 +
   1.382 +    return cursor;
   1.383 +}
   1.384 +
   1.385 +
   1.386 +// This is the real reordering function as applied to the Khmer language
   1.387 +
   1.388 +le_int32 KhmerReordering::reorder(const LEUnicode *chars, le_int32 charCount, le_int32 /*scriptCode*/,
   1.389 +                                  LEUnicode *outChars, LEGlyphStorage &glyphStorage)
   1.390 +{
   1.391 +    const KhmerClassTable *classTable = KhmerClassTable::getKhmerClassTable();
   1.392 +
   1.393 +    ReorderingOutput output(outChars, glyphStorage);
   1.394 +    KhmerClassTable::CharClass charClass;
   1.395 +    le_int32 i, prev = 0, coengRo;
   1.396 +
   1.397 +    
   1.398 +    // This loop only exits when we reach the end of a run, which may contain 
   1.399 +    // several syllables.
   1.400 +    while (prev < charCount) {
   1.401 +        le_int32 syllable = findSyllable(classTable, chars, prev, charCount);
   1.402 +   
   1.403 +        // write a pre vowel or the pre part of a split vowel first
   1.404 +        // and look out for coeng + ro. RO is the only vowel of type 2, and
   1.405 +        // therefore the only one that requires saving space before the base.
   1.406 +        coengRo = -1;  // There is no Coeng Ro, if found this value will change
   1.407 +        for (i = prev; i < syllable; i += 1) {
   1.408 +            charClass = classTable->getCharClass(chars[i]);
   1.409 +            
   1.410 +            // if a split vowel, write the pre part. In Khmer the pre part
   1.411 +            // is the same for all split vowels, same glyph as pre vowel C_VOWEL_E
   1.412 +            if (charClass & KhmerClassTable::CF_SPLIT_VOWEL) {
   1.413 +                output.writeChar(C_VOWEL_E, i, &tagPref[0]);
   1.414 +                break; // there can be only one vowel
   1.415 +            }
   1.416 +            
   1.417 +            // if a vowel with pos before write it out
   1.418 +            if (charClass & KhmerClassTable::CF_POS_BEFORE) {
   1.419 +                output.writeChar(chars[i], i, &tagPref[0]);
   1.420 +                break; // there can be only one vowel 
   1.421 +            }
   1.422 +            
   1.423 +            // look for coeng + ro and remember position
   1.424 +            // works because coeng + ro is always in front of a vowel (if there is a vowel) 
   1.425 +            // and because CC_CONSONANT2 is enough to identify it, as it is the only consonant
   1.426 +            // with this flag
   1.427 +            if ( (charClass & KhmerClassTable::CF_COENG) && (i + 1 < syllable) &&
   1.428 +                 ( (classTable->getCharClass(chars[i + 1]) & KhmerClassTable::CF_CLASS_MASK) == KhmerClassTable::CC_CONSONANT2) )
   1.429 +            {
   1.430 +                    coengRo = i;
   1.431 +            }
   1.432 +        }
   1.433 +        
   1.434 +        // write coeng + ro if found
   1.435 +        if (coengRo > -1) {
   1.436 +            output.writeChar(C_COENG, coengRo, &tagPref[0]);
   1.437 +            output.writeChar(C_RO, coengRo + 1, &tagPref[0]);
   1.438 +        }
   1.439 +        
   1.440 +        // shall we add a dotted circle?
   1.441 +        // If in the position in which the base should be (first char in the string) there is
   1.442 +        // a character that has the Dotted circle flag (a character that cannot be a base)
   1.443 +        // then write a dotted circle
   1.444 +        if (classTable->getCharClass(chars[prev]) & KhmerClassTable::CF_DOTTED_CIRCLE) {
   1.445 +            output.writeChar(C_DOTTED_CIRCLE, prev, &tagDefault[0]);        
   1.446 +        }        
   1.447 +
   1.448 +        // copy what is left to the output, skipping before vowels and coeng Ro if they are present
   1.449 +        for (i = prev; i < syllable; i += 1) {
   1.450 +            charClass = classTable->getCharClass(chars[i]);
   1.451 +            
   1.452 +            // skip a before vowel, it was already processed
   1.453 +            if (charClass & KhmerClassTable::CF_POS_BEFORE) {
   1.454 +                continue;
   1.455 +            }
   1.456 +            
   1.457 +            // skip coeng + ro, it was already processed
   1.458 +            if (i == coengRo) {
   1.459 +                i += 1;
   1.460 +                continue;
   1.461 +            }
   1.462 +            
   1.463 +            switch (charClass & KhmerClassTable::CF_POS_MASK) {
   1.464 +                case KhmerClassTable::CF_POS_ABOVE :
   1.465 +                    output.writeChar(chars[i], i, &tagAbvf[0]);
   1.466 +                    break;
   1.467 +                
   1.468 +                case KhmerClassTable::CF_POS_AFTER :
   1.469 +                    output.writeChar(chars[i], i, &tagPstf[0]);
   1.470 +                    break;
   1.471 +                
   1.472 +                case KhmerClassTable::CF_POS_BELOW :
   1.473 +                    output.writeChar(chars[i], i, &tagBlwf[0]);
   1.474 +                    break;
   1.475 +                
   1.476 +                default:
   1.477 +                    // assign the correct flags to a coeng consonant
   1.478 +                    // Consonants of type 3 are taged as Post forms and those type 1 as below forms
   1.479 +                    if ( (charClass & KhmerClassTable::CF_COENG) && i + 1 < syllable ) {
   1.480 +                        if ( (classTable->getCharClass(chars[i + 1]) & KhmerClassTable::CF_CLASS_MASK) 
   1.481 +                              == KhmerClassTable::CC_CONSONANT3) {
   1.482 +                            output.writeChar(chars[i], i, &tagPstf[0]);
   1.483 +                            i += 1;
   1.484 +                            output.writeChar(chars[i], i, &tagPstf[0]);
   1.485 +                        }
   1.486 +                        else {
   1.487 +                            output.writeChar(chars[i], i, &tagBlwf[0]);
   1.488 +                            i += 1;
   1.489 +                            output.writeChar(chars[i], i, &tagBlwf[0]);
   1.490 +                        }
   1.491 +                        break;
   1.492 +                    }
   1.493 +                    // if a shifter is followed by an above vowel change the shifter to below form,
   1.494 +                    // an above vowel can have two possible positions i + 1 or i + 3 
   1.495 +                    // (position i+1 corresponds to unicode 3, position i+3 to Unicode 4)
   1.496 +                    // and there is an extra rule for C_VOWEL_AA + C_SIGN_NIKAHIT also for two
   1.497 +                    // different positions, right after the shifter or after a vowel (Unicode 4)
   1.498 +                    if ( (charClass & KhmerClassTable::CF_SHIFTER) && (i + 1 < syllable) ) {
   1.499 +                        if ((classTable->getCharClass(chars[i + 1]) & KhmerClassTable::CF_ABOVE_VOWEL)
   1.500 +                            || (i + 2 < syllable
   1.501 +                                && ( (classTable->getCharClass(chars[i + 1]) & KhmerClassTable::CF_CLASS_MASK) == C_VOWEL_AA)
   1.502 +                                && ( (classTable->getCharClass(chars[i + 2]) & KhmerClassTable::CF_CLASS_MASK) == C_SIGN_NIKAHIT))
   1.503 +                            || (i + 3 < syllable && (classTable->getCharClass(chars[i + 3]) & KhmerClassTable::CF_ABOVE_VOWEL))
   1.504 +                            || (i + 4 < syllable
   1.505 +                                && ( (classTable->getCharClass(chars[i + 3]) & KhmerClassTable::CF_CLASS_MASK) == C_VOWEL_AA)
   1.506 +                                && ( (classTable->getCharClass(chars[i + 4]) & KhmerClassTable::CF_CLASS_MASK) == C_SIGN_NIKAHIT) ) ) 
   1.507 +                        {
   1.508 +                            output.writeChar(chars[i], i, &tagBlwf[0]);
   1.509 +                            break;
   1.510 +                        }
   1.511 +                        
   1.512 +                    }
   1.513 +                    // default - any other characters
   1.514 +                    output.writeChar(chars[i], i, &tagDefault[0]);
   1.515 +                    break;
   1.516 +            } // switch
   1.517 +        } // for
   1.518 +
   1.519 +        prev = syllable; // move the pointer to the start of next syllable
   1.520 +    }
   1.521 +
   1.522 +    return output.getOutputIndex();
   1.523 +}
   1.524 +
   1.525 +
   1.526 +U_NAMESPACE_END