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 * accompanied this code).

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package java.util.regex;

import java.util.Objects;

final class Grapheme {

    /**

     * Look for the next extended grapheme cluster boundary in a CharSequence.

     * It assumes the start of the char sequence at offset {@code off} is a boundary.

     * <p>

     * See Unicode Standard Annex #29 Unicode Text Segmentation for the specification

     * for the extended grapheme cluster boundary rules. The following implementation

     * is based on version 12.0 of the annex.

     * (http://www.unicode.org/reports/tr29/tr29-35.html)

     *

     * @param src the {@code CharSequence} to be scanned

     * @param off offset to start looking for the next boundary in the src

     * @param limit limit offset in the src (exclusive)

     * @return the next grapheme boundary

     */

    static int nextBoundary(CharSequence src, int off, int limit) {

        Objects.checkFromToIndex(off, limit, src.length());

        int ch0 = Character.codePointAt(src, off);

        int ret = off + Character.charCount(ch0);

        // indicates whether gb11 or gb12 is underway

        int t0 = getType(ch0);

        int riCount = t0 == RI ? 1 : 0;

        boolean gb11 = t0 == EXTENDED_PICTOGRAPHIC;

        while (ret < limit) {

            int ch1 = Character.codePointAt(src, ret);

            int t1 = getType(ch1);

            if (gb11 && t0 == ZWJ && t1 == EXTENDED_PICTOGRAPHIC) {

                // continue for gb11

            } else if (riCount % 2 == 1 && t0 == RI && t1 == RI) {

                // continue for gb12

            } else if (rules[t0][t1]) {

                if (ret > off) {

                    break;

                } else {

                    gb11 = t1 == EXTENDED_PICTOGRAPHIC;

                    riCount = 0;

                }

            }

            riCount += (t1 == RI) ? 1 : 0;

            t0 = t1;

            ret += Character.charCount(ch1);

        }

        return ret;

    }

    // types

    private static final int OTHER = 0;

    private static final int CR = 1;

    private static final int LF = 2;

    private static final int CONTROL = 3;

    private static final int EXTEND = 4;

    private static final int ZWJ = 5;

    private static final int RI = 6;

    private static final int PREPEND = 7;

    private static final int SPACINGMARK = 8;

    private static final int L = 9;

    private static final int V = 10;

    private static final int T = 11;

    private static final int LV = 12;

    private static final int LVT = 13;

    private static final int EXTENDED_PICTOGRAPHIC = 14;

    private static final int FIRST_TYPE = 0;

    private static final int LAST_TYPE = 14;

    private static boolean[][] rules;

    static {

        rules = new boolean[LAST_TYPE + 1][LAST_TYPE + 1];

        // GB 999 Any + Any  -> default

        for (int i = FIRST_TYPE; i <= LAST_TYPE; i++)

            for (int j = FIRST_TYPE; j <= LAST_TYPE; j++)

                rules[i][j] = true;

        // GB 6 L x (L | V | LV | VT)

        rules[L][L] = false;

        rules[L][V] = false;

        rules[L][LV] = false;

        rules[L][LVT] = false;

        // GB 7 (LV | V) x (V | T)

        rules[LV][V] = false;

        rules[LV][T] = false;

        rules[V][V] = false;

        rules[V][T] = false;

        // GB 8 (LVT | T) x T

        rules[LVT][T] = false;

        rules[T][T] = false;

        // GB 9 x (Extend|ZWJ)

        // GB 9a x Spacing Mark

        // GB 9b Prepend x

        for (int i = FIRST_TYPE; i <= LAST_TYPE; i++) {

            rules[i][EXTEND] = false;

            rules[i][ZWJ] = false;

            rules[i][SPACINGMARK] = false;

            rules[PREPEND][i] = false;

        }

        // GB 4  (Control | CR | LF) +

        // GB 5  + (Control | CR | LF)

        for (int i = FIRST_TYPE; i <= LAST_TYPE; i++)

            for (int j = CR; j <= CONTROL; j++) {

                rules[i][j] = true;

                rules[j][i] = true;

            }

        // GB 3 CR x LF

        rules[CR][LF] = false;

        // GB 11 Exended_Pictographic x (Extend|ZWJ)

        rules[EXTENDED_PICTOGRAPHIC][EXTEND] = false;

        rules[EXTENDED_PICTOGRAPHIC][ZWJ] = false;

    }

    // Hangul syllables

    private static final int SYLLABLE_BASE = 0xAC00;

    private static final int LCOUNT = 19;

    private static final int VCOUNT = 21;

    private static final int TCOUNT = 28;

    private static final int NCOUNT = VCOUNT * TCOUNT; // 588

    private static final int SCOUNT = LCOUNT * NCOUNT; // 11172

    // #tr29: SpacingMark exceptions: The following (which have

    // General_Category = Spacing_Mark and would otherwise be included)

    // are specifically excluded

    private static boolean isExcludedSpacingMark(int cp) {

       return  cp == 0x102B || cp == 0x102C || cp == 0x1038 ||

               cp >= 0x1062 && cp <= 0x1064 ||

               cp >= 0x1062 && cp <= 0x106D ||

               cp == 0x1083 ||

               cp >= 0x1087 && cp <= 0x108C ||

               cp == 0x108F ||

               cp >= 0x109A && cp <= 0x109C ||

               cp == 0x1A61 || cp == 0x1A63 || cp == 0x1A64 ||

               cp == 0xAA7B || cp == 0xAA7D;

    }

    @SuppressWarnings("fallthrough")

    private static int getType(int cp) {

        if (cp < 0x007F) { // ASCII

            if (cp < 32) { // Control characters

                if (cp == 0x000D)

                    return CR;

                if (cp == 0x000A)

                    return LF;

                return CONTROL;

            }

            return OTHER;

        }

        if (EmojiData.isExtendedPictographic(cp)) {

            return EXTENDED_PICTOGRAPHIC;

        }

        int type = Character.getType(cp);

        switch(type) {

        case Character.UNASSIGNED:

            // NOTE: #tr29 lists "Unassigned and Default_Ignorable_Code_Point" as Control

            // but GraphemeBreakTest.txt lists u+0378/reserved-0378 as "Other"

            // so type it as "Other" to make the test happy

            if (cp == 0x0378)

                return OTHER;

        case Character.CONTROL:

        case Character.LINE_SEPARATOR:

        case Character.PARAGRAPH_SEPARATOR:

        case Character.SURROGATE:

            return CONTROL;

        case Character.FORMAT:

            if (cp == 0x200C ||

                cp >= 0xE0020 && cp <= 0xE007F)

                return EXTEND;

            if (cp == 0x200D)

                return ZWJ;

            if (cp >= 0x0600 && cp <= 0x0605 ||

                cp == 0x06DD || cp == 0x070F || cp == 0x08E2 ||

                cp == 0x110BD || cp == 0x110CD)

                return PREPEND;

            return CONTROL;

        case Character.NON_SPACING_MARK:

        case Character.ENCLOSING_MARK:

            // NOTE:

            // #tr29 "plus a few General_Category = Spacing_Mark needed for

            // canonical equivalence."

            // but for "extended grapheme clusters" support, there is no

            // need actually to diff "extend" and "spackmark" given GB9, GB9a

            return EXTEND;

        case  Character.COMBINING_SPACING_MARK:

            if (isExcludedSpacingMark(cp))

                return OTHER;

            // NOTE:

            // 0x11720 and 0x11721 are mentioned in #tr29 as

            // OTHER_LETTER but it appears their category has been updated to

            // COMBING_SPACING_MARK already (verified in ver.8)

            return SPACINGMARK;

        case Character.OTHER_SYMBOL:

            if (cp >= 0x1F1E6 && cp <= 0x1F1FF)

                return RI;

            return OTHER;

        case Character.MODIFIER_LETTER:

        case Character.MODIFIER_SYMBOL:

            // WARNING:

            // not mentioned in #tr29 but listed in GraphemeBreakProperty.txt

            if (cp == 0xFF9E || cp == 0xFF9F ||

                cp >= 0x1F3FB && cp <= 0x1F3FF)

                return EXTEND;

            return OTHER;

        case Character.OTHER_LETTER:

            if (cp == 0x0E33 || cp == 0x0EB3)

                return SPACINGMARK;

            // hangul jamo

            if (cp >= 0x1100 && cp <= 0x11FF) {

                if (cp <= 0x115F)

                    return L;

                if (cp <= 0x11A7)

                    return V;

                return T;

            }

            // hangul syllables

            int sindex = cp - SYLLABLE_BASE;

            if (sindex >= 0 && sindex < SCOUNT) {

                if (sindex % TCOUNT == 0)

                    return LV;

                return LVT;

            }

            //  hangul jamo_extended A

            if (cp >= 0xA960 && cp <= 0xA97C)

                return L;

            //  hangul jamo_extended B

            if (cp >= 0xD7B0 && cp <= 0xD7C6)

                return V;

            if (cp >= 0xD7CB && cp <= 0xD7FB)

                return T;

            // Prepend

            switch (cp) {

                case 0x0D4E:

                case 0x111C2:

                case 0x111C3:

                case 0x1193F:

                case 0x11941:

                case 0x11A3A:

                case 0x11A84:

                case 0x11A85:

                case 0x11A86:

                case 0x11A87:

                case 0x11A88:

                case 0x11A89:

                case 0x11D46:

                    return PREPEND;

            }

        }

        return OTHER;

    }

}