/*
 * Copyright (c) 2009, 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 *******************************************************************************
 *   Copyright (C) 2009-2015, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *******************************************************************************
 */
package jdk.internal.icu.impl;

import java.io.IOException;
import java.nio.ByteBuffer;

import jdk.internal.icu.lang.UCharacter;
import jdk.internal.icu.text.Normalizer2;
import jdk.internal.icu.text.UTF16;
import jdk.internal.icu.util.CodePointTrie;
import jdk.internal.icu.util.VersionInfo;

// Original filename in ICU4J: Normalizer2Impl.java
public final class NormalizerImpl {
    public static final class Hangul {
        /* Korean Hangul and Jamo constants */
        public static final int JAMO_L_BASE=0x1100;     /* "lead" jamo */
        public static final int JAMO_V_BASE=0x1161;     /* "vowel" jamo */
        public static final int JAMO_T_BASE=0x11a7;     /* "trail" jamo */

        public static final int HANGUL_BASE=0xac00;
        public static final int HANGUL_END=0xd7a3;

        public static final int JAMO_L_COUNT=19;
        public static final int JAMO_V_COUNT=21;
        public static final int JAMO_T_COUNT=28;

        public static final int HANGUL_COUNT=JAMO_L_COUNT*JAMO_V_COUNT*JAMO_T_COUNT;
        public static final int HANGUL_LIMIT=HANGUL_BASE+HANGUL_COUNT;

        public static boolean isHangul(int c) {
            return HANGUL_BASE<=c && c<HANGUL_LIMIT;
        }
        public static boolean isHangulLV(int c) {
            c-=HANGUL_BASE;
            return 0<=c && c<HANGUL_COUNT && c%JAMO_T_COUNT==0;
        }

        /**
         * Decomposes c, which must be a Hangul syllable, into buffer
         * and returns the length of the decomposition (2 or 3).
         */
        public static int decompose(int c, Appendable buffer) {
            try {
                c-=HANGUL_BASE;
                int c2=c%JAMO_T_COUNT;
                c/=JAMO_T_COUNT;
                buffer.append((char)(JAMO_L_BASE+c/JAMO_V_COUNT));
                buffer.append((char)(JAMO_V_BASE+c%JAMO_V_COUNT));
                if(c2==0) {
                    return 2;
                } else {
                    buffer.append((char)(JAMO_T_BASE+c2));
                    return 3;
                }
            } catch(IOException e) {
                throw new InternalError(e);
            }
        }
    }

    /**
     * Writable buffer that takes care of canonical ordering.
     * Its Appendable methods behave like the C++ implementation's
     * appendZeroCC() methods.
     * <p>
     * If dest is a StringBuilder, then the buffer writes directly to it.
     * Otherwise, the buffer maintains a StringBuilder for intermediate text segments
     * until no further changes are necessary and whole segments are appended.
     * append() methods that take combining-class values always write to the StringBuilder.
     * Other append() methods flush and append to the Appendable.
     */
    public static final class ReorderingBuffer implements Appendable {
        public ReorderingBuffer(NormalizerImpl ni, Appendable dest, int destCapacity) {
            impl=ni;
            app=dest;
            if (app instanceof StringBuilder) {
                appIsStringBuilder=true;
                str=(StringBuilder)dest;
                // In Java, the constructor subsumes public void init(int destCapacity)
                str.ensureCapacity(destCapacity);
                reorderStart=0;
                if(str.length()==0) {
                    lastCC=0;
                } else {
                    setIterator();
                    lastCC=previousCC();
                    // Set reorderStart after the last code point with cc<=1 if there is one.
                    if(lastCC>1) {
                        while(previousCC()>1) {}
                    }
                    reorderStart=codePointLimit;
                }
            } else {
                appIsStringBuilder=false;
                str=new StringBuilder();
                reorderStart=0;
                lastCC=0;
            }
        }

        public boolean isEmpty() { return str.length()==0; }
        public int length() { return str.length(); }
        public int getLastCC() { return lastCC; }

        public StringBuilder getStringBuilder() { return str; }

        public boolean equals(CharSequence s, int start, int limit) {
            return UTF16Plus.equal(str, 0, str.length(), s, start, limit);
        }

        public void append(int c, int cc) {
            if(lastCC<=cc || cc==0) {
                str.appendCodePoint(c);
                lastCC=cc;
                if(cc<=1) {
                    reorderStart=str.length();
                }
            } else {
                insert(c, cc);
            }
        }
        public void append(CharSequence s, int start, int limit, boolean isNFD,
                           int leadCC, int trailCC) {
            if(start==limit) {
                return;
            }
            if(lastCC<=leadCC || leadCC==0) {
                if(trailCC<=1) {
                    reorderStart=str.length()+(limit-start);
                } else if(leadCC<=1) {
                    reorderStart=str.length()+1;  // Ok if not a code point boundary.
                }
                str.append(s, start, limit);
                lastCC=trailCC;
            } else {
                int c=Character.codePointAt(s, start);
                start+=Character.charCount(c);
                insert(c, leadCC);  // insert first code point
                while(start<limit) {
                    c=Character.codePointAt(s, start);
                    start+=Character.charCount(c);
                    if(start<limit) {
                        if (isNFD) {
                            leadCC = getCCFromYesOrMaybe(impl.getNorm16(c));
                        } else {
                            leadCC = impl.getCC(impl.getNorm16(c));
                        }
                    } else {
                        leadCC=trailCC;
                    }
                    append(c, leadCC);
                }
            }
        }
        // The following append() methods work like C++ appendZeroCC().
        // They assume that the cc or trailCC of their input is 0.
        // Most of them implement Appendable interface methods.
        @Override
        public ReorderingBuffer append(char c) {
            str.append(c);
            lastCC=0;
            reorderStart=str.length();
            return this;
        }
        public void appendZeroCC(int c) {
            str.appendCodePoint(c);
            lastCC=0;
            reorderStart=str.length();
        }
        @Override
        public ReorderingBuffer append(CharSequence s) {
            if(s.length()!=0) {
                str.append(s);
                lastCC=0;
                reorderStart=str.length();
            }
            return this;
        }
        @Override
        public ReorderingBuffer append(CharSequence s, int start, int limit) {
            if(start!=limit) {
                str.append(s, start, limit);
                lastCC=0;
                reorderStart=str.length();
            }
            return this;
        }
        /**
         * Flushes from the intermediate StringBuilder to the Appendable,
         * if they are different objects.
         * Used after recomposition.
         * Must be called at the end when writing to a non-StringBuilder Appendable.
         */
        public void flush() {
            if(appIsStringBuilder) {
                reorderStart=str.length();
            } else {
                try {
                    app.append(str);
                    str.setLength(0);
                    reorderStart=0;
                } catch(IOException e) {
                    throw new InternalError(e);  // Avoid declaring "throws IOException".
                }
            }
            lastCC=0;
        }
        /**
         * Flushes from the intermediate StringBuilder to the Appendable,
         * if they are different objects.
         * Then appends the new text to the Appendable or StringBuilder.
         * Normally used after quick check loops find a non-empty sequence.
         */
        public ReorderingBuffer flushAndAppendZeroCC(CharSequence s, int start, int limit) {
            if(appIsStringBuilder) {
                str.append(s, start, limit);
                reorderStart=str.length();
            } else {
                try {
                    app.append(str).append(s, start, limit);
                    str.setLength(0);
                    reorderStart=0;
                } catch(IOException e) {
                    throw new InternalError(e);  // Avoid declaring "throws IOException".
                }
            }
            lastCC=0;
            return this;
        }
        public void remove() {
            str.setLength(0);
            lastCC=0;
            reorderStart=0;
        }
        public void removeSuffix(int suffixLength) {
            int oldLength=str.length();
            str.delete(oldLength-suffixLength, oldLength);
            lastCC=0;
            reorderStart=str.length();
        }

        // Inserts c somewhere before the last character.
        // Requires 0<cc<lastCC which implies reorderStart<limit.
        private void insert(int c, int cc) {
            for(setIterator(), skipPrevious(); previousCC()>cc;) {}
            // insert c at codePointLimit, after the character with prevCC<=cc
            if(c<=0xffff) {
                str.insert(codePointLimit, (char)c);
                if(cc<=1) {
                    reorderStart=codePointLimit+1;
                }
            } else {
                str.insert(codePointLimit, Character.toChars(c));
                if(cc<=1) {
                    reorderStart=codePointLimit+2;
                }
            }
        }

        private final NormalizerImpl impl;
        private final Appendable app;
        private final StringBuilder str;
        private final boolean appIsStringBuilder;
        private int reorderStart;
        private int lastCC;

        // private backward iterator
        private void setIterator() { codePointStart=str.length(); }
        private void skipPrevious() {  // Requires 0<codePointStart.
            codePointLimit=codePointStart;
            codePointStart=str.offsetByCodePoints(codePointStart, -1);
        }
        private int previousCC() {  // Returns 0 if there is no previous character.
            codePointLimit=codePointStart;
            if(reorderStart>=codePointStart) {
                return 0;
            }
            int c=str.codePointBefore(codePointStart);
            codePointStart-=Character.charCount(c);
            return impl.getCCFromYesOrMaybeCP(c);
        }
        private int codePointStart, codePointLimit;
    }

    // TODO: Propose as public API on the UTF16 class.
    // TODO: Propose widening UTF16 methods that take char to take int.
    // TODO: Propose widening UTF16 methods that take String to take CharSequence.
    public static final class UTF16Plus {
        /**
         * Is this code point a lead surrogate (U+d800..U+dbff)?
         * @param c code unit or code point
         * @return true or false
         */
        public static boolean isLeadSurrogate(int c) { return (c & 0xfffffc00) == 0xd800; }
        /**
         * Assuming c is a surrogate code point (UTF16.isSurrogate(c)),
         * is it a lead surrogate?
         * @param c code unit or code point
         * @return true or false
         */
        public static boolean isSurrogateLead(int c) { return (c&0x400)==0; }

        /**
         * Compares two CharSequence subsequences for binary equality.
         * @param s1 first sequence
         * @param start1 start offset in first sequence
         * @param limit1 limit offset in first sequence
         * @param s2 second sequence
         * @param start2 start offset in second sequence
         * @param limit2 limit offset in second sequence
         * @return true if s1.subSequence(start1, limit1) contains the same text
         *              as s2.subSequence(start2, limit2)
         */
        public static boolean equal(CharSequence s1, int start1, int limit1,
                                    CharSequence s2, int start2, int limit2) {
            if((limit1-start1)!=(limit2-start2)) {
                return false;
            }
            if(s1==s2 && start1==start2) {
                return true;
            }
            while(start1<limit1) {
                if(s1.charAt(start1++)!=s2.charAt(start2++)) {
                    return false;
                }
            }
            return true;
        }
    }

    public NormalizerImpl() {}

    private static final class IsAcceptable implements ICUBinary.Authenticate {
        public boolean isDataVersionAcceptable(byte version[]) {
            return version[0]==4;
        }
    }
    private static final IsAcceptable IS_ACCEPTABLE = new IsAcceptable();
    private static final int DATA_FORMAT = 0x4e726d32;  // "Nrm2"

    public NormalizerImpl load(ByteBuffer bytes) {
        try {
            dataVersion=ICUBinary.readHeaderAndDataVersion(bytes, DATA_FORMAT, IS_ACCEPTABLE);
            int indexesLength=bytes.getInt()/4;  // inIndexes[IX_NORM_TRIE_OFFSET]/4
            if(indexesLength<=IX_MIN_LCCC_CP) {
                throw new InternalError("Normalizer2 data: not enough indexes");
            }
            int[] inIndexes=new int[indexesLength];
            inIndexes[0]=indexesLength*4;
            for(int i=1; i<indexesLength; ++i) {
                inIndexes[i]=bytes.getInt();
            }

            minDecompNoCP=inIndexes[IX_MIN_DECOMP_NO_CP];
            minCompNoMaybeCP=inIndexes[IX_MIN_COMP_NO_MAYBE_CP];
            minLcccCP=inIndexes[IX_MIN_LCCC_CP];

            minYesNo=inIndexes[IX_MIN_YES_NO];
            minYesNoMappingsOnly=inIndexes[IX_MIN_YES_NO_MAPPINGS_ONLY];
            minNoNo=inIndexes[IX_MIN_NO_NO];
            minNoNoCompBoundaryBefore=inIndexes[IX_MIN_NO_NO_COMP_BOUNDARY_BEFORE];
            minNoNoCompNoMaybeCC=inIndexes[IX_MIN_NO_NO_COMP_NO_MAYBE_CC];
            minNoNoEmpty=inIndexes[IX_MIN_NO_NO_EMPTY];
            limitNoNo=inIndexes[IX_LIMIT_NO_NO];
            minMaybeYes=inIndexes[IX_MIN_MAYBE_YES];
            assert((minMaybeYes&7)==0);  // 8-aligned for noNoDelta bit fields
            centerNoNoDelta=(minMaybeYes>>DELTA_SHIFT)-MAX_DELTA-1;

            // Read the normTrie.
            int offset=inIndexes[IX_NORM_TRIE_OFFSET];
            int nextOffset=inIndexes[IX_EXTRA_DATA_OFFSET];
            int triePosition = bytes.position();
            normTrie = CodePointTrie.Fast16.fromBinary(bytes);
            int trieLength = bytes.position() - triePosition;
            if(trieLength>(nextOffset-offset)) {
                throw new InternalError("Normalizer2 data: not enough bytes for normTrie");
            }
            ICUBinary.skipBytes(bytes, (nextOffset-offset)-trieLength);  // skip padding after trie bytes

            // Read the composition and mapping data.
            offset=nextOffset;
            nextOffset=inIndexes[IX_SMALL_FCD_OFFSET];
            int numChars=(nextOffset-offset)/2;
            if(numChars!=0) {
                maybeYesCompositions=ICUBinary.getString(bytes, numChars, 0);
                extraData=maybeYesCompositions.substring((MIN_NORMAL_MAYBE_YES-minMaybeYes)>>OFFSET_SHIFT);
            }

            // smallFCD: new in formatVersion 2
            offset=nextOffset;
            smallFCD=new byte[0x100];
            bytes.get(smallFCD);

            return this;
        } catch(IOException e) {
            throw new InternalError(e);
        }
    }
    public NormalizerImpl load(String name) {
        return load(ICUBinary.getRequiredData(name));
    }

    // The trie stores values for lead surrogate code *units*.
    // Surrogate code *points* are inert.
    public int getNorm16(int c) {
        return UTF16Plus.isLeadSurrogate(c) ? INERT : normTrie.get(c);
    }
    public int getRawNorm16(int c) { return normTrie.get(c); }
    public boolean isAlgorithmicNoNo(int norm16) { return limitNoNo<=norm16 && norm16<minMaybeYes; }
    public boolean isCompNo(int norm16) { return minNoNo<=norm16 && norm16<minMaybeYes; }
    public boolean isDecompYes(int norm16) { return norm16<minYesNo || minMaybeYes<=norm16; }

    public int getCC(int norm16) {
        if(norm16>=MIN_NORMAL_MAYBE_YES) {
            return getCCFromNormalYesOrMaybe(norm16);
        }
        if(norm16<minNoNo || limitNoNo<=norm16) {
            return 0;
        }
        return getCCFromNoNo(norm16);
    }
    public static int getCCFromNormalYesOrMaybe(int norm16) {
        return (norm16 >> OFFSET_SHIFT) & 0xff;
    }
    public static int getCCFromYesOrMaybe(int norm16) {
        return norm16>=MIN_NORMAL_MAYBE_YES ? getCCFromNormalYesOrMaybe(norm16) : 0;
    }
    public int getCCFromYesOrMaybeCP(int c) {
        if (c < minCompNoMaybeCP) { return 0; }
        return getCCFromYesOrMaybe(getNorm16(c));
    }

    /**
     * Returns the FCD data for code point c.
     * @param c A Unicode code point.
     * @return The lccc(c) in bits 15..8 and tccc(c) in bits 7..0.
     */
    public int getFCD16(int c) {
        if(c<minDecompNoCP) {
            return 0;
        } else if(c<=0xffff) {
            if(!singleLeadMightHaveNonZeroFCD16(c)) { return 0; }
        }
        return getFCD16FromNormData(c);
    }
    /** Returns true if the single-or-lead code unit c might have non-zero FCD data. */
    public boolean singleLeadMightHaveNonZeroFCD16(int lead) {
        // 0<=lead<=0xffff
        byte bits=smallFCD[lead>>8];
        if(bits==0) { return false; }
        return ((bits>>((lead>>5)&7))&1)!=0;
    }

    /** Gets the FCD value from the regular normalization data. */
    public int getFCD16FromNormData(int c) {
        int norm16=getNorm16(c);
        if (norm16 >= limitNoNo) {
            if(norm16>=MIN_NORMAL_MAYBE_YES) {
                // combining mark
                norm16=getCCFromNormalYesOrMaybe(norm16);
                return norm16|(norm16<<8);
            } else if(norm16>=minMaybeYes) {
                return 0;
            } else {  // isDecompNoAlgorithmic(norm16)
                int deltaTrailCC = norm16 & DELTA_TCCC_MASK;
                if (deltaTrailCC <= DELTA_TCCC_1) {
                    return deltaTrailCC >> OFFSET_SHIFT;
                }
                // Maps to an isCompYesAndZeroCC.
                c=mapAlgorithmic(c, norm16);
                norm16=getRawNorm16(c);
            }
        }
        if(norm16<=minYesNo || isHangulLVT(norm16)) {
            // no decomposition or Hangul syllable, all zeros
            return 0;
        }
        // c decomposes, get everything from the variable-length extra data
        int mapping=norm16>>OFFSET_SHIFT;
        int firstUnit=extraData.charAt(mapping);
        int fcd16=firstUnit>>8;  // tccc
        if((firstUnit&MAPPING_HAS_CCC_LCCC_WORD)!=0) {
            fcd16|=extraData.charAt(mapping-1)&0xff00;  // lccc
        }
        return fcd16;
    }

    /**
     * Gets the decomposition for one code point.
     * @param c code point
     * @return c's decomposition, if it has one; returns null if it does not have a decomposition
     */
    public String getDecomposition(int c) {
        int norm16;
        if(c<minDecompNoCP || isMaybeOrNonZeroCC(norm16=getNorm16(c))) {
            // c does not decompose
            return null;
        }
        int decomp = -1;
        if(isDecompNoAlgorithmic(norm16)) {
            // Maps to an isCompYesAndZeroCC.
            decomp=c=mapAlgorithmic(c, norm16);
            // The mapping might decompose further.
            norm16 = getRawNorm16(c);
        }
        if (norm16 < minYesNo) {
            if(decomp<0) {
                return null;
            } else {
                return UTF16.valueOf(decomp);
            }
        } else if(isHangulLV(norm16) || isHangulLVT(norm16)) {
            // Hangul syllable: decompose algorithmically
            StringBuilder buffer=new StringBuilder();
            Hangul.decompose(c, buffer);
            return buffer.toString();
        }
        // c decomposes, get everything from the variable-length extra data
        int mapping=norm16>>OFFSET_SHIFT;
        int length=extraData.charAt(mapping++)&MAPPING_LENGTH_MASK;
        return extraData.substring(mapping, mapping+length);
    }

    // Fixed norm16 values.
    public static final int MIN_YES_YES_WITH_CC=0xfe02;
    public static final int JAMO_VT=0xfe00;
    public static final int MIN_NORMAL_MAYBE_YES=0xfc00;
    public static final int JAMO_L=2;  // offset=1 hasCompBoundaryAfter=false
    public static final int INERT=1;  // offset=0 hasCompBoundaryAfter=true

    // norm16 bit 0 is comp-boundary-after.
    public static final int HAS_COMP_BOUNDARY_AFTER=1;
    public static final int OFFSET_SHIFT=1;

    // For algorithmic one-way mappings, norm16 bits 2..1 indicate the
    // tccc (0, 1, >1) for quick FCC boundary-after tests.
    public static final int DELTA_TCCC_0=0;
    public static final int DELTA_TCCC_1=2;
    public static final int DELTA_TCCC_GT_1=4;
    public static final int DELTA_TCCC_MASK=6;
    public static final int DELTA_SHIFT=3;

    public static final int MAX_DELTA=0x40;

    // Byte offsets from the start of the data, after the generic header.
    public static final int IX_NORM_TRIE_OFFSET=0;
    public static final int IX_EXTRA_DATA_OFFSET=1;
    public static final int IX_SMALL_FCD_OFFSET=2;
    public static final int IX_RESERVED3_OFFSET=3;
    public static final int IX_TOTAL_SIZE=7;
    public static final int MIN_CCC_LCCC_CP=0x300;
    // Code point thresholds for quick check codes.
    public static final int IX_MIN_DECOMP_NO_CP=8;
    public static final int IX_MIN_COMP_NO_MAYBE_CP=9;

    // Norm16 value thresholds for quick check combinations and types of extra data.

    /** Mappings & compositions in [minYesNo..minYesNoMappingsOnly[. */
    public static final int IX_MIN_YES_NO=10;
    /** Mappings are comp-normalized. */
    public static final int IX_MIN_NO_NO=11;
    public static final int IX_LIMIT_NO_NO=12;
    public static final int IX_MIN_MAYBE_YES=13;

    /** Mappings only in [minYesNoMappingsOnly..minNoNo[. */
    public static final int IX_MIN_YES_NO_MAPPINGS_ONLY=14;
    /** Mappings are not comp-normalized but have a comp boundary before. */
    public static final int IX_MIN_NO_NO_COMP_BOUNDARY_BEFORE=15;
    /** Mappings do not have a comp boundary before. */
    public static final int IX_MIN_NO_NO_COMP_NO_MAYBE_CC=16;
    /** Mappings to the empty string. */
    public static final int IX_MIN_NO_NO_EMPTY=17;

    public static final int IX_MIN_LCCC_CP=18;
    public static final int IX_COUNT=20;

    public static final int MAPPING_HAS_CCC_LCCC_WORD=0x80;
    public static final int MAPPING_HAS_RAW_MAPPING=0x40;
    // unused bit 0x20;
    public static final int MAPPING_LENGTH_MASK=0x1f;

    public static final int COMP_1_LAST_TUPLE=0x8000;
    public static final int COMP_1_TRIPLE=1;
    public static final int COMP_1_TRAIL_LIMIT=0x3400;
    public static final int COMP_1_TRAIL_MASK=0x7ffe;
    public static final int COMP_1_TRAIL_SHIFT=9;  // 10-1 for the "triple" bit
    public static final int COMP_2_TRAIL_SHIFT=6;
    public static final int COMP_2_TRAIL_MASK=0xffc0;

    // higher-level functionality ------------------------------------------ ***

    /**
     * Decomposes s[src, limit[ and writes the result to dest.
     * limit can be NULL if src is NUL-terminated.
     * destLengthEstimate is the initial dest buffer capacity and can be -1.
     */
    public void decompose(CharSequence s, int src, int limit, StringBuilder dest,
                   int destLengthEstimate) {
        if(destLengthEstimate<0) {
            destLengthEstimate=limit-src;
        }
        dest.setLength(0);
        ReorderingBuffer buffer=new ReorderingBuffer(this, dest, destLengthEstimate);
        decompose(s, src, limit, buffer);
    }

    // Dual functionality:
    // buffer!=NULL: normalize
    // buffer==NULL: isNormalized/quickCheck/spanQuickCheckYes
    public int decompose(CharSequence s, int src, int limit,
                         ReorderingBuffer buffer) {
        int minNoCP=minDecompNoCP;

        int prevSrc;
        int c=0;
        int norm16=0;

        // only for quick check
        int prevBoundary=src;
        int prevCC=0;

        for(;;) {
            // count code units below the minimum or with irrelevant data for the quick check
            for(prevSrc=src; src!=limit;) {
                if( (c=s.charAt(src))<minNoCP ||
                    isMostDecompYesAndZeroCC(norm16=normTrie.bmpGet(c))
                ) {
                    ++src;
                } else if(!UTF16Plus.isLeadSurrogate(c)) {
                    break;
                } else {
                    char c2;
                    if ((src + 1) != limit && Character.isLowSurrogate(c2 = s.charAt(src + 1))) {
                        c = Character.toCodePoint((char)c, c2);
                        norm16 = normTrie.suppGet(c);
                        if (isMostDecompYesAndZeroCC(norm16)) {
                            src += 2;
                        } else {
                            break;
                        }
                    } else {
                        ++src;  // unpaired lead surrogate: inert
                    }
                }
            }
            // copy these code units all at once
            if(src!=prevSrc) {
                if(buffer!=null) {
                    buffer.flushAndAppendZeroCC(s, prevSrc, src);
                } else {
                    prevCC=0;
                    prevBoundary=src;
                }
            }
            if(src==limit) {
                break;
            }

            // Check one above-minimum, relevant code point.
            src+=Character.charCount(c);
            if(buffer!=null) {
                decompose(c, norm16, buffer);
            } else {
                if(isDecompYes(norm16)) {
                    int cc=getCCFromYesOrMaybe(norm16);
                    if(prevCC<=cc || cc==0) {
                        prevCC=cc;
                        if(cc<=1) {
                            prevBoundary=src;
                        }
                        continue;
                    }
                }
                return prevBoundary;  // "no" or cc out of order
            }
        }
        return src;
    }
    public void decomposeAndAppend(CharSequence s, boolean doDecompose, ReorderingBuffer buffer) {
        int limit=s.length();
        if(limit==0) {
            return;
        }
        if(doDecompose) {
            decompose(s, 0, limit, buffer);
            return;
        }
        // Just merge the strings at the boundary.
        int c=Character.codePointAt(s, 0);
        int src=0;
        int firstCC, prevCC, cc;
        firstCC=prevCC=cc=getCC(getNorm16(c));
        while(cc!=0) {
            prevCC=cc;
            src+=Character.charCount(c);
            if(src>=limit) {
                break;
            }
            c=Character.codePointAt(s, src);
            cc=getCC(getNorm16(c));
        };
        buffer.append(s, 0, src, false, firstCC, prevCC);
        buffer.append(s, src, limit);
    }

    // Very similar to composeQuickCheck(): Make the same changes in both places if relevant.
    // doCompose: normalize
    // !doCompose: isNormalized (buffer must be empty and initialized)
    public boolean compose(CharSequence s, int src, int limit,
                           boolean onlyContiguous,
                           boolean doCompose,
                           ReorderingBuffer buffer) {
        int prevBoundary=src;
        int minNoMaybeCP=minCompNoMaybeCP;

        for (;;) {
            // Fast path: Scan over a sequence of characters below the minimum "no or maybe" code point,
            // or with (compYes && ccc==0) properties.
            int prevSrc;
            int c = 0;
            int norm16 = 0;
            for (;;) {
                if (src == limit) {
                    if (prevBoundary != limit && doCompose) {
                        buffer.append(s, prevBoundary, limit);
                    }
                    return true;
                }
                if( (c=s.charAt(src))<minNoMaybeCP ||
                    isCompYesAndZeroCC(norm16=normTrie.bmpGet(c))
                ) {
                    ++src;
                } else {
                    prevSrc = src++;
                    if (!UTF16Plus.isLeadSurrogate(c)) {
                        break;
                    } else {
                        char c2;
                        if (src != limit && Character.isLowSurrogate(c2 = s.charAt(src))) {
                            ++src;
                            c = Character.toCodePoint((char)c, c2);
                            norm16 = normTrie.suppGet(c);
                            if (!isCompYesAndZeroCC(norm16)) {
                                break;
                            }
                        }
                    }
                }
            }
            // isCompYesAndZeroCC(norm16) is false, that is, norm16>=minNoNo.
            // The current character is either a "noNo" (has a mapping)
            // or a "maybeYes" (combines backward)
            // or a "yesYes" with ccc!=0.
            // It is not a Hangul syllable or Jamo L because those have "yes" properties.

            // Medium-fast path: Handle cases that do not require full decomposition and recomposition.
            if (!isMaybeOrNonZeroCC(norm16)) {  // minNoNo <= norm16 < minMaybeYes
                if (!doCompose) {
                    return false;
                }
                // Fast path for mapping a character that is immediately surrounded by boundaries.
                // In this case, we need not decompose around the current character.
                if (isDecompNoAlgorithmic(norm16)) {
                    // Maps to a single isCompYesAndZeroCC character
                    // which also implies hasCompBoundaryBefore.
                    if (norm16HasCompBoundaryAfter(norm16, onlyContiguous) ||
                            hasCompBoundaryBefore(s, src, limit)) {
                        if (prevBoundary != prevSrc) {
                            buffer.append(s, prevBoundary, prevSrc);
                        }
                        buffer.append(mapAlgorithmic(c, norm16), 0);
                        prevBoundary = src;
                        continue;
                    }
                } else if (norm16 < minNoNoCompBoundaryBefore) {
                    // The mapping is comp-normalized which also implies hasCompBoundaryBefore.
                    if (norm16HasCompBoundaryAfter(norm16, onlyContiguous) ||
                            hasCompBoundaryBefore(s, src, limit)) {
                        if (prevBoundary != prevSrc) {
                            buffer.append(s, prevBoundary, prevSrc);
                        }
                        int mapping = norm16 >> OFFSET_SHIFT;
                        int length = extraData.charAt(mapping++) & MAPPING_LENGTH_MASK;
                        buffer.append(extraData, mapping, mapping + length);
                        prevBoundary = src;
                        continue;
                    }
                } else if (norm16 >= minNoNoEmpty) {
                    // The current character maps to nothing.
                    // Simply omit it from the output if there is a boundary before _or_ after it.
                    // The character itself implies no boundaries.
                    if (hasCompBoundaryBefore(s, src, limit) ||
                            hasCompBoundaryAfter(s, prevBoundary, prevSrc, onlyContiguous)) {
                        if (prevBoundary != prevSrc) {
                            buffer.append(s, prevBoundary, prevSrc);
                        }
                        prevBoundary = src;
                        continue;
                    }
                }
                // Other "noNo" type, or need to examine more text around this character:
                // Fall through to the slow path.
            } else if (isJamoVT(norm16) && prevBoundary != prevSrc) {
                char prev=s.charAt(prevSrc-1);
                if(c<Hangul.JAMO_T_BASE) {
                    // The current character is a Jamo Vowel,
                    // compose with previous Jamo L and following Jamo T.
                    char l = (char)(prev-Hangul.JAMO_L_BASE);
                    if(l<Hangul.JAMO_L_COUNT) {
                        if (!doCompose) {
                            return false;
                        }
                        int t;
                        if (src != limit &&
                                0 < (t = (s.charAt(src) - Hangul.JAMO_T_BASE)) &&
                                t < Hangul.JAMO_T_COUNT) {
                            // The next character is a Jamo T.
                            ++src;
                        } else if (hasCompBoundaryBefore(s, src, limit)) {
                            // No Jamo T follows, not even via decomposition.
                            t = 0;
                        } else {
                            t = -1;
                        }
                        if (t >= 0) {
                            int syllable = Hangul.HANGUL_BASE +
                                (l*Hangul.JAMO_V_COUNT + (c-Hangul.JAMO_V_BASE)) *
                                Hangul.JAMO_T_COUNT + t;
                            --prevSrc;  // Replace the Jamo L as well.
                            if (prevBoundary != prevSrc) {
                                buffer.append(s, prevBoundary, prevSrc);
                            }
                            buffer.append((char)syllable);
                            prevBoundary = src;
                            continue;
                        }
                        // If we see L+V+x where x!=T then we drop to the slow path,
                        // decompose and recompose.
                        // This is to deal with NFKC finding normal L and V but a
                        // compatibility variant of a T.
                        // We need to either fully compose that combination here
                        // (which would complicate the code and may not work with strange custom data)
                        // or use the slow path.
                    }
                } else if (Hangul.isHangulLV(prev)) {
                    // The current character is a Jamo Trailing consonant,
                    // compose with previous Hangul LV that does not contain a Jamo T.
                    if (!doCompose) {
                        return false;
                    }
                    int syllable = prev + c - Hangul.JAMO_T_BASE;
                    --prevSrc;  // Replace the Hangul LV as well.
                    if (prevBoundary != prevSrc) {
                        buffer.append(s, prevBoundary, prevSrc);
                    }
                    buffer.append((char)syllable);
                    prevBoundary = src;
                    continue;
                }
                // No matching context, or may need to decompose surrounding text first:
                // Fall through to the slow path.
            } else if (norm16 > JAMO_VT) {  // norm16 >= MIN_YES_YES_WITH_CC
                // One or more combining marks that do not combine-back:
                // Check for canonical order, copy unchanged if ok and
                // if followed by a character with a boundary-before.
                int cc = getCCFromNormalYesOrMaybe(norm16);  // cc!=0
                if (onlyContiguous /* FCC */ && getPreviousTrailCC(s, prevBoundary, prevSrc) > cc) {
                    // Fails FCD test, need to decompose and contiguously recompose.
                    if (!doCompose) {
                        return false;
                    }
                } else {
                    // If !onlyContiguous (not FCC), then we ignore the tccc of
                    // the previous character which passed the quick check "yes && ccc==0" test.
                    int n16;
                    for (;;) {
                        if (src == limit) {
                            if (doCompose) {
                                buffer.append(s, prevBoundary, limit);
                            }
                            return true;
                        }
                        int prevCC = cc;
                        c = Character.codePointAt(s, src);
                        n16 = normTrie.get(c);
                        if (n16 >= MIN_YES_YES_WITH_CC) {
                            cc = getCCFromNormalYesOrMaybe(n16);
                            if (prevCC > cc) {
                                if (!doCompose) {
                                    return false;
                                }
                                break;
                            }
                        } else {
                            break;
                        }
                        src += Character.charCount(c);
                    }
                    // p is after the last in-order combining mark.
                    // If there is a boundary here, then we continue with no change.
                    if (norm16HasCompBoundaryBefore(n16)) {
                        if (isCompYesAndZeroCC(n16)) {
                            src += Character.charCount(c);
                        }
                        continue;
                    }
                    // Use the slow path. There is no boundary in [prevSrc, src[.
                }
            }

            // Slow path: Find the nearest boundaries around the current character,
            // decompose and recompose.
            if (prevBoundary != prevSrc && !norm16HasCompBoundaryBefore(norm16)) {
                c = Character.codePointBefore(s, prevSrc);
                norm16 = normTrie.get(c);
                if (!norm16HasCompBoundaryAfter(norm16, onlyContiguous)) {
                    prevSrc -= Character.charCount(c);
                }
            }
            if (doCompose && prevBoundary != prevSrc) {
                buffer.append(s, prevBoundary, prevSrc);
            }
            int recomposeStartIndex=buffer.length();
            // We know there is not a boundary here.
            decomposeShort(s, prevSrc, src, false /* !stopAtCompBoundary */, onlyContiguous,
                           buffer);
            // Decompose until the next boundary.
            src = decomposeShort(s, src, limit, true /* stopAtCompBoundary */, onlyContiguous,
                                 buffer);
            recompose(buffer, recomposeStartIndex, onlyContiguous);
            if(!doCompose) {
                if(!buffer.equals(s, prevSrc, src)) {
                    return false;
                }
                buffer.remove();
            }
            prevBoundary=src;
        }
    }

    /**
     * Very similar to compose(): Make the same changes in both places if relevant.
     * doSpan: spanQuickCheckYes (ignore bit 0 of the return value)
     * !doSpan: quickCheck
     * @return bits 31..1: spanQuickCheckYes (==s.length() if "yes") and
     *         bit 0: set if "maybe"; otherwise, if the span length&lt;s.length()
     *         then the quick check result is "no"
     */
    public int composeQuickCheck(CharSequence s, int src, int limit,
                                 boolean onlyContiguous, boolean doSpan) {
        int qcResult=0;
        int prevBoundary=src;
        int minNoMaybeCP=minCompNoMaybeCP;

        for(;;) {
            // Fast path: Scan over a sequence of characters below the minimum "no or maybe" code point,
            // or with (compYes && ccc==0) properties.
            int prevSrc;
            int c = 0;
            int norm16 = 0;
            for (;;) {
                if(src==limit) {
                    return (src<<1)|qcResult;  // "yes" or "maybe"
                }
                if( (c=s.charAt(src))<minNoMaybeCP ||
                    isCompYesAndZeroCC(norm16=normTrie.bmpGet(c))
                ) {
                    ++src;
                } else {
                    prevSrc = src++;
                    if (!UTF16Plus.isLeadSurrogate(c)) {
                        break;
                    } else {
                        char c2;
                        if (src != limit && Character.isLowSurrogate(c2 = s.charAt(src))) {
                            ++src;
                            c = Character.toCodePoint((char)c, c2);
                            norm16 = normTrie.suppGet(c);
                            if (!isCompYesAndZeroCC(norm16)) {
                                break;
                            }
                        }
                    }
                }
            }
            // isCompYesAndZeroCC(norm16) is false, that is, norm16>=minNoNo.
            // The current character is either a "noNo" (has a mapping)
            // or a "maybeYes" (combines backward)
            // or a "yesYes" with ccc!=0.
            // It is not a Hangul syllable or Jamo L because those have "yes" properties.

            int prevNorm16 = INERT;
            if (prevBoundary != prevSrc) {
                prevBoundary = prevSrc;
                if (!norm16HasCompBoundaryBefore(norm16)) {
                    c = Character.codePointBefore(s, prevSrc);
                    int n16 = getNorm16(c);
                    if (!norm16HasCompBoundaryAfter(n16, onlyContiguous)) {
                        prevBoundary -= Character.charCount(c);
                        prevNorm16 = n16;
                    }
                }
            }

            if(isMaybeOrNonZeroCC(norm16)) {
                int cc=getCCFromYesOrMaybe(norm16);
                if (onlyContiguous /* FCC */ && cc != 0 &&
                        getTrailCCFromCompYesAndZeroCC(prevNorm16) > cc) {
                    // The [prevBoundary..prevSrc[ character
                    // passed the quick check "yes && ccc==0" test
                    // but is out of canonical order with the current combining mark.
                } else {
                    // If !onlyContiguous (not FCC), then we ignore the tccc of
                    // the previous character which passed the quick check "yes && ccc==0" test.
                    for (;;) {
                        if (norm16 < MIN_YES_YES_WITH_CC) {
                            if (!doSpan) {
                                qcResult = 1;
                            } else {
                                return prevBoundary << 1;  // spanYes does not care to know it's "maybe"
                            }
                        }
                        if (src == limit) {
                            return (src<<1) | qcResult;  // "yes" or "maybe"
                        }
                        int prevCC = cc;
                        c = Character.codePointAt(s, src);
                        norm16 = getNorm16(c);
                        if (isMaybeOrNonZeroCC(norm16)) {
                            cc = getCCFromYesOrMaybe(norm16);
                            if (!(prevCC <= cc || cc == 0)) {
                                break;
                            }
                        } else {
                            break;
                        }
                        src += Character.charCount(c);
                    }
                    // src is after the last in-order combining mark.
                    if (isCompYesAndZeroCC(norm16)) {
                        prevBoundary = src;
                        src += Character.charCount(c);
                        continue;
                    }
                }
            }
            return prevBoundary<<1;  // "no"
        }
    }
    public void composeAndAppend(CharSequence s,
                                 boolean doCompose,
                                 boolean onlyContiguous,
                                 ReorderingBuffer buffer) {
        int src=0, limit=s.length();
        if(!buffer.isEmpty()) {
            int firstStarterInSrc=findNextCompBoundary(s, 0, limit, onlyContiguous);
            if(0!=firstStarterInSrc) {
                int lastStarterInDest=findPreviousCompBoundary(buffer.getStringBuilder(),
                                                               buffer.length(), onlyContiguous);
                StringBuilder middle=new StringBuilder((buffer.length()-lastStarterInDest)+
                                                       firstStarterInSrc+16);
                middle.append(buffer.getStringBuilder(), lastStarterInDest, buffer.length());
                buffer.removeSuffix(buffer.length()-lastStarterInDest);
                middle.append(s, 0, firstStarterInSrc);
                compose(middle, 0, middle.length(), onlyContiguous, true, buffer);
                src=firstStarterInSrc;
            }
        }
        if(doCompose) {
            compose(s, src, limit, onlyContiguous, true, buffer);
        } else {
            buffer.append(s, src, limit);
        }
    }
    // Dual functionality:
    // buffer!=NULL: normalize
    // buffer==NULL: isNormalized/quickCheck/spanQuickCheckYes
    public int makeFCD(CharSequence s, int src, int limit, ReorderingBuffer buffer) {
        // Note: In this function we use buffer->appendZeroCC() because we track
        // the lead and trail combining classes here, rather than leaving it to
        // the ReorderingBuffer.
        // The exception is the call to decomposeShort() which uses the buffer
        // in the normal way.

        // Tracks the last FCD-safe boundary, before lccc=0 or after properly-ordered tccc<=1.
        // Similar to the prevBoundary in the compose() implementation.
        int prevBoundary=src;
        int prevSrc;
        int c=0;
        int prevFCD16=0;
        int fcd16=0;

        for(;;) {
            // count code units with lccc==0
            for(prevSrc=src; src!=limit;) {
                if((c=s.charAt(src))<minLcccCP) {
                    prevFCD16=~c;
                    ++src;
                } else if(!singleLeadMightHaveNonZeroFCD16(c)) {
                    prevFCD16=0;
                    ++src;
                } else {
                    if (UTF16Plus.isLeadSurrogate(c)) {
                        char c2;
                        if ((src + 1) != limit && Character.isLowSurrogate(c2 = s.charAt(src + 1))) {
                            c = Character.toCodePoint((char)c, c2);
                        }
                    }
                    if((fcd16=getFCD16FromNormData(c))<=0xff) {
                        prevFCD16=fcd16;
                        src+=Character.charCount(c);
                    } else {
                        break;
                    }
                }
            }
            // copy these code units all at once
            if(src!=prevSrc) {
                if(src==limit) {
                    if(buffer!=null) {
                        buffer.flushAndAppendZeroCC(s, prevSrc, src);
                    }
                    break;
                }
                prevBoundary=src;
                // We know that the previous character's lccc==0.
                if(prevFCD16<0) {
                    // Fetching the fcd16 value was deferred for this below-minLcccCP code point.
                    int prev=~prevFCD16;
                    if(prev<minDecompNoCP) {
                        prevFCD16=0;
                    } else {
                        prevFCD16=getFCD16FromNormData(prev);
                        if(prevFCD16>1) {
                            --prevBoundary;
                        }
                    }
                } else {
                    int p=src-1;
                    if( Character.isLowSurrogate(s.charAt(p)) && prevSrc<p &&
                        Character.isHighSurrogate(s.charAt(p-1))
                    ) {
                        --p;
                        // Need to fetch the previous character's FCD value because
                        // prevFCD16 was just for the trail surrogate code point.
                        prevFCD16=getFCD16FromNormData(Character.toCodePoint(s.charAt(p), s.charAt(p+1)));
                        // Still known to have lccc==0 because its lead surrogate unit had lccc==0.
                    }
                    if(prevFCD16>1) {
                        prevBoundary=p;
                    }
                }
                if(buffer!=null) {
                    // The last lccc==0 character is excluded from the
                    // flush-and-append call in case it needs to be modified.
                    buffer.flushAndAppendZeroCC(s, prevSrc, prevBoundary);
                    buffer.append(s, prevBoundary, src);
                }
                // The start of the current character (c).
                prevSrc=src;
            } else if(src==limit) {
                break;
            }

            src+=Character.charCount(c);
            // The current character (c) at [prevSrc..src[ has a non-zero lead combining class.
            // Check for proper order, and decompose locally if necessary.
            if((prevFCD16&0xff)<=(fcd16>>8)) {
                // proper order: prev tccc <= current lccc
                if((fcd16&0xff)<=1) {
                    prevBoundary=src;
                }
                if(buffer!=null) {
                    buffer.appendZeroCC(c);
                }
                prevFCD16=fcd16;
                continue;
            } else if(buffer==null) {
                return prevBoundary;  // quick check "no"
            } else {
                /*
                 * Back out the part of the source that we copied or appended
                 * already but is now going to be decomposed.
                 * prevSrc is set to after what was copied/appended.
                 */
                buffer.removeSuffix(prevSrc-prevBoundary);
                /*
                 * Find the part of the source that needs to be decomposed,
                 * up to the next safe boundary.
                 */
                src=findNextFCDBoundary(s, src, limit);
                /*
                 * The source text does not fulfill the conditions for FCD.
                 * Decompose and reorder a limited piece of the text.
                 */
                decomposeShort(s, prevBoundary, src, false, false, buffer);
                prevBoundary=src;
                prevFCD16=0;
            }
        }
        return src;
    }

    public boolean hasDecompBoundaryBefore(int c) {
        return c < minLcccCP || (c <= 0xffff && !singleLeadMightHaveNonZeroFCD16(c)) ||
            norm16HasDecompBoundaryBefore(getNorm16(c));
    }
    public boolean norm16HasDecompBoundaryBefore(int norm16) {
        if (norm16 < minNoNoCompNoMaybeCC) {
            return true;
        }
        if (norm16 >= limitNoNo) {
            return norm16 <= MIN_NORMAL_MAYBE_YES || norm16 == JAMO_VT;
        }
        // c decomposes, get everything from the variable-length extra data
        int mapping=norm16>>OFFSET_SHIFT;
        int firstUnit=extraData.charAt(mapping);
        // true if leadCC==0 (hasFCDBoundaryBefore())
        return (firstUnit&MAPPING_HAS_CCC_LCCC_WORD)==0 || (extraData.charAt(mapping-1)&0xff00)==0;
    }
    public boolean hasDecompBoundaryAfter(int c) {
        if (c < minDecompNoCP) {
            return true;
        }
        if (c <= 0xffff && !singleLeadMightHaveNonZeroFCD16(c)) {
            return true;
        }
        return norm16HasDecompBoundaryAfter(getNorm16(c));
    }
    public boolean norm16HasDecompBoundaryAfter(int norm16) {
        if(norm16 <= minYesNo || isHangulLVT(norm16)) {
            return true;
        }
        if (norm16 >= limitNoNo) {
            if (isMaybeOrNonZeroCC(norm16)) {
                return norm16 <= MIN_NORMAL_MAYBE_YES || norm16 == JAMO_VT;
            }
            // Maps to an isCompYesAndZeroCC.
            return (norm16 & DELTA_TCCC_MASK) <= DELTA_TCCC_1;
        }
        // c decomposes, get everything from the variable-length extra data
        int mapping=norm16>>OFFSET_SHIFT;
        int firstUnit=extraData.charAt(mapping);
        // decomp after-boundary: same as hasFCDBoundaryAfter(),
        // fcd16<=1 || trailCC==0
        if(firstUnit>0x1ff) {
            return false;  // trailCC>1
        }
        if(firstUnit<=0xff) {
            return true;  // trailCC==0
        }
        // if(trailCC==1) test leadCC==0, same as checking for before-boundary
        // true if leadCC==0 (hasFCDBoundaryBefore())
        return (firstUnit&MAPPING_HAS_CCC_LCCC_WORD)==0 || (extraData.charAt(mapping-1)&0xff00)==0;
    }
    public boolean isDecompInert(int c) { return isDecompYesAndZeroCC(getNorm16(c)); }

    public boolean hasCompBoundaryBefore(int c) {
        return c<minCompNoMaybeCP || norm16HasCompBoundaryBefore(getNorm16(c));
    }
    public boolean hasCompBoundaryAfter(int c, boolean onlyContiguous) {
        return norm16HasCompBoundaryAfter(getNorm16(c), onlyContiguous);
    }

    private boolean isMaybe(int norm16) { return minMaybeYes<=norm16 && norm16<=JAMO_VT; }
    private boolean isMaybeOrNonZeroCC(int norm16) { return norm16>=minMaybeYes; }
    private static boolean isInert(int norm16) { return norm16==INERT; }
    private static boolean isJamoVT(int norm16) { return norm16==JAMO_VT; }
    private int hangulLVT() { return minYesNoMappingsOnly|HAS_COMP_BOUNDARY_AFTER; }
    private boolean isHangulLV(int norm16) { return norm16==minYesNo; }
    private boolean isHangulLVT(int norm16) {
        return norm16==hangulLVT();
    }
    private boolean isCompYesAndZeroCC(int norm16) { return norm16<minNoNo; }
    // UBool isCompYes(uint16_t norm16) const {
    //     return norm16>=MIN_YES_YES_WITH_CC || norm16<minNoNo;
    // }
    // UBool isCompYesOrMaybe(uint16_t norm16) const {
    //     return norm16<minNoNo || minMaybeYes<=norm16;
    // }
    // private boolean hasZeroCCFromDecompYes(int norm16) {
    //     return norm16<=MIN_NORMAL_MAYBE_YES || norm16==JAMO_VT;
    // }
    private boolean isDecompYesAndZeroCC(int norm16) {
        return norm16<minYesNo ||
               norm16==JAMO_VT ||
               (minMaybeYes<=norm16 && norm16<=MIN_NORMAL_MAYBE_YES);
    }
    /**
     * A little faster and simpler than isDecompYesAndZeroCC() but does not include
     * the MaybeYes which combine-forward and have ccc=0.
     * (Standard Unicode 10 normalization does not have such characters.)
     */
    private boolean isMostDecompYesAndZeroCC(int norm16) {
        return norm16<minYesNo || norm16==MIN_NORMAL_MAYBE_YES || norm16==JAMO_VT;
    }
    private boolean isDecompNoAlgorithmic(int norm16) { return norm16>=limitNoNo; }

    // For use with isCompYes().
    // Perhaps the compiler can combine the two tests for MIN_YES_YES_WITH_CC.
    // static uint8_t getCCFromYes(uint16_t norm16) {
    //     return norm16>=MIN_YES_YES_WITH_CC ? getCCFromNormalYesOrMaybe(norm16) : 0;
    // }
    private int getCCFromNoNo(int norm16) {
        int mapping=norm16>>OFFSET_SHIFT;
        if((extraData.charAt(mapping)&MAPPING_HAS_CCC_LCCC_WORD)!=0) {
            return extraData.charAt(mapping-1)&0xff;
        } else {
            return 0;
        }
    }
    int getTrailCCFromCompYesAndZeroCC(int norm16) {
        if(norm16<=minYesNo) {
            return 0;  // yesYes and Hangul LV have ccc=tccc=0
        } else {
            // For Hangul LVT we harmlessly fetch a firstUnit with tccc=0 here.
            return extraData.charAt(norm16>>OFFSET_SHIFT)>>8;  // tccc from yesNo
        }
    }

    // Requires algorithmic-NoNo.
    private int mapAlgorithmic(int c, int norm16) {
        return c+(norm16>>DELTA_SHIFT)-centerNoNoDelta;
    }

    // Requires minYesNo<norm16<limitNoNo.
    // private int getMapping(int norm16) { return extraData+(norm16>>OFFSET_SHIFT); }

    /**
     * @return index into maybeYesCompositions, or -1
     */
    private int getCompositionsListForDecompYes(int norm16) {
        if(norm16<JAMO_L || MIN_NORMAL_MAYBE_YES<=norm16) {
            return -1;
        } else {
            if((norm16-=minMaybeYes)<0) {
                // norm16<minMaybeYes: index into extraData which is a substring at
                //     maybeYesCompositions[MIN_NORMAL_MAYBE_YES-minMaybeYes]
                // same as (MIN_NORMAL_MAYBE_YES-minMaybeYes)+norm16
                norm16+=MIN_NORMAL_MAYBE_YES;  // for yesYes; if Jamo L: harmless empty list
            }
            return norm16>>OFFSET_SHIFT;
        }
    }
    /**
     * @return index into maybeYesCompositions
     */
    private int getCompositionsListForComposite(int norm16) {
        // A composite has both mapping & compositions list.
        int list=((MIN_NORMAL_MAYBE_YES-minMaybeYes)+norm16)>>OFFSET_SHIFT;
        int firstUnit=maybeYesCompositions.charAt(list);
        return list+  // mapping in maybeYesCompositions
            1+  // +1 to skip the first unit with the mapping length
            (firstUnit&MAPPING_LENGTH_MASK);  // + mapping length
    }

    // Decompose a short piece of text which is likely to contain characters that
    // fail the quick check loop and/or where the quick check loop's overhead
    // is unlikely to be amortized.
    // Called by the compose() and makeFCD() implementations.
    // Public in Java for collation implementation code.
    private int decomposeShort(
            CharSequence s, int src, int limit,
            boolean stopAtCompBoundary, boolean onlyContiguous,
            ReorderingBuffer buffer) {
        while(src<limit) {
            int c=Character.codePointAt(s, src);
            if (stopAtCompBoundary && c < minCompNoMaybeCP) {
                return src;
            }
            int norm16 = getNorm16(c);
            if (stopAtCompBoundary && norm16HasCompBoundaryBefore(norm16)) {
                return src;
            }
            src+=Character.charCount(c);
            decompose(c, norm16, buffer);
            if (stopAtCompBoundary && norm16HasCompBoundaryAfter(norm16, onlyContiguous)) {
                return src;
            }
        }
        return src;
    }
    private void decompose(int c, int norm16, ReorderingBuffer buffer) {
        // get the decomposition and the lead and trail cc's
        if (norm16 >= limitNoNo) {
            if (isMaybeOrNonZeroCC(norm16)) {
                buffer.append(c, getCCFromYesOrMaybe(norm16));
                return;
            }
            // Maps to an isCompYesAndZeroCC.
            c=mapAlgorithmic(c, norm16);
            norm16=getRawNorm16(c);
        }
        if (norm16 < minYesNo) {
            // c does not decompose
            buffer.append(c, 0);
        } else if(isHangulLV(norm16) || isHangulLVT(norm16)) {
            // Hangul syllable: decompose algorithmically
            Hangul.decompose(c, buffer);
        } else {
            // c decomposes, get everything from the variable-length extra data
            int mapping=norm16>>OFFSET_SHIFT;
            int firstUnit=extraData.charAt(mapping);
            int length=firstUnit&MAPPING_LENGTH_MASK;
            int leadCC, trailCC;
            trailCC=firstUnit>>8;
            if((firstUnit&MAPPING_HAS_CCC_LCCC_WORD)!=0) {
                leadCC=extraData.charAt(mapping-1)>>8;
            } else {
                leadCC=0;
            }
            ++mapping;  // skip over the firstUnit
            buffer.append(extraData, mapping, mapping+length, true, leadCC, trailCC);
        }
    }

    /**
     * Finds the recomposition result for
     * a forward-combining "lead" character,
     * specified with a pointer to its compositions list,
     * and a backward-combining "trail" character.
     *
     * <p>If the lead and trail characters combine, then this function returns
     * the following "compositeAndFwd" value:
     * <pre>
     * Bits 21..1  composite character
     * Bit      0  set if the composite is a forward-combining starter
     * </pre>
     * otherwise it returns -1.
     *
     * <p>The compositions list has (trail, compositeAndFwd) pair entries,
     * encoded as either pairs or triples of 16-bit units.
     * The last entry has the high bit of its first unit set.
     *
     * <p>The list is sorted by ascending trail characters (there are no duplicates).
     * A linear search is used.
     *
     * <p>See normalizer2impl.h for a more detailed description
     * of the compositions list format.
     */
    private static int combine(String compositions, int list, int trail) {
        int key1, firstUnit;
        if(trail<COMP_1_TRAIL_LIMIT) {
            // trail character is 0..33FF
            // result entry may have 2 or 3 units
            key1=(trail<<1);
            while(key1>(firstUnit=compositions.charAt(list))) {
                list+=2+(firstUnit&COMP_1_TRIPLE);
            }
            if(key1==(firstUnit&COMP_1_TRAIL_MASK)) {
                if((firstUnit&COMP_1_TRIPLE)!=0) {
                    return (compositions.charAt(list+1)<<16)|compositions.charAt(list+2);
                } else {
                    return compositions.charAt(list+1);
                }
            }
        } else {
            // trail character is 3400..10FFFF
            // result entry has 3 units
            key1=COMP_1_TRAIL_LIMIT+(((trail>>COMP_1_TRAIL_SHIFT))&~COMP_1_TRIPLE);
            int key2=(trail<<COMP_2_TRAIL_SHIFT)&0xffff;
            int secondUnit;
            for(;;) {
                if(key1>(firstUnit=compositions.charAt(list))) {
                    list+=2+(firstUnit&COMP_1_TRIPLE);
                } else if(key1==(firstUnit&COMP_1_TRAIL_MASK)) {
                    if(key2>(secondUnit=compositions.charAt(list+1))) {
                        if((firstUnit&COMP_1_LAST_TUPLE)!=0) {
                            break;
                        } else {
                            list+=3;
                        }
                    } else if(key2==(secondUnit&COMP_2_TRAIL_MASK)) {
                        return ((secondUnit&~COMP_2_TRAIL_MASK)<<16)|compositions.charAt(list+2);
                    } else {
                        break;
                    }
                } else {
                    break;
                }
            }
        }
        return -1;
    }

    /*
     * Recomposes the buffer text starting at recomposeStartIndex
     * (which is in NFD - decomposed and canonically ordered),
     * and truncates the buffer contents.
     *
     * Note that recomposition never lengthens the text:
     * Any character consists of either one or two code units;
     * a composition may contain at most one more code unit than the original starter,
     * while the combining mark that is removed has at least one code unit.
     */
    private void recompose(ReorderingBuffer buffer, int recomposeStartIndex,
                           boolean onlyContiguous) {
        StringBuilder sb=buffer.getStringBuilder();
        int p=recomposeStartIndex;
        if(p==sb.length()) {
            return;
        }

        int starter, pRemove;
        int compositionsList;
        int c, compositeAndFwd;
        int norm16;
        int cc, prevCC;
        boolean starterIsSupplementary;

        // Some of the following variables are not used until we have a forward-combining starter
        // and are only initialized now to avoid compiler warnings.
        compositionsList=-1;  // used as indicator for whether we have a forward-combining starter
        starter=-1;
        starterIsSupplementary=false;
        prevCC=0;

        for(;;) {
            c=sb.codePointAt(p);
            p+=Character.charCount(c);
            norm16=getNorm16(c);
            cc=getCCFromYesOrMaybe(norm16);
            if( // this character combines backward and
                isMaybe(norm16) &&
                // we have seen a starter that combines forward and
                compositionsList>=0 &&
                // the backward-combining character is not blocked
                (prevCC<cc || prevCC==0)
            ) {
                if(isJamoVT(norm16)) {
                    // c is a Jamo V/T, see if we can compose it with the previous character.
                    if(c<Hangul.JAMO_T_BASE) {
                        // c is a Jamo Vowel, compose with previous Jamo L and following Jamo T.
                        char prev=(char)(sb.charAt(starter)-Hangul.JAMO_L_BASE);
                        if(prev<Hangul.JAMO_L_COUNT) {
                            pRemove=p-1;
                            char syllable=(char)
                                (Hangul.HANGUL_BASE+
                                 (prev*Hangul.JAMO_V_COUNT+(c-Hangul.JAMO_V_BASE))*
                                 Hangul.JAMO_T_COUNT);
                            char t;
                            if(p!=sb.length() && (t=(char)(sb.charAt(p)-Hangul.JAMO_T_BASE))<Hangul.JAMO_T_COUNT) {
                                ++p;
                                syllable+=t;  // The next character was a Jamo T.
                            }
                            sb.setCharAt(starter, syllable);
                            // remove the Jamo V/T
                            sb.delete(pRemove, p);
                            p=pRemove;
                        }
                    }
                    /*
                     * No "else" for Jamo T:
                     * Since the input is in NFD, there are no Hangul LV syllables that
                     * a Jamo T could combine with.
                     * All Jamo Ts are combined above when handling Jamo Vs.
                     */
                    if(p==sb.length()) {
                        break;
                    }
                    compositionsList=-1;
                    continue;
                } else if((compositeAndFwd=combine(maybeYesCompositions, compositionsList, c))>=0) {
                    // The starter and the combining mark (c) do combine.
                    int composite=compositeAndFwd>>1;

                    // Remove the combining mark.
                    pRemove=p-Character.charCount(c);  // pRemove & p: start & limit of the combining mark
                    sb.delete(pRemove, p);
                    p=pRemove;
                    // Replace the starter with the composite.
                    if(starterIsSupplementary) {
                        if(composite>0xffff) {
                            // both are supplementary
                            sb.setCharAt(starter, UTF16.getLeadSurrogate(composite));
                            sb.setCharAt(starter+1, UTF16.getTrailSurrogate(composite));
                        } else {
                            sb.setCharAt(starter, (char)c);
                            sb.deleteCharAt(starter+1);
                            // The composite is shorter than the starter,
                            // move the intermediate characters forward one.
                            starterIsSupplementary=false;
                            --p;
                        }
                    } else if(composite>0xffff) {
                        // The composite is longer than the starter,
                        // move the intermediate characters back one.
                        starterIsSupplementary=true;
                        sb.setCharAt(starter, UTF16.getLeadSurrogate(composite));
                        sb.insert(starter+1, UTF16.getTrailSurrogate(composite));
                        ++p;
                    } else {
                        // both are on the BMP
                        sb.setCharAt(starter, (char)composite);
                    }

                    // Keep prevCC because we removed the combining mark.

                    if(p==sb.length()) {
                        break;
                    }
                    // Is the composite a starter that combines forward?
                    if((compositeAndFwd&1)!=0) {
                        compositionsList=
                            getCompositionsListForComposite(getRawNorm16(composite));
                    } else {
                        compositionsList=-1;
                    }

                    // We combined; continue with looking for compositions.
                    continue;
                }
            }

            // no combination this time
            prevCC=cc;
            if(p==sb.length()) {
                break;
            }

            // If c did not combine, then check if it is a starter.
            if(cc==0) {
                // Found a new starter.
                if((compositionsList=getCompositionsListForDecompYes(norm16))>=0) {
                    // It may combine with something, prepare for it.
                    if(c<=0xffff) {
                        starterIsSupplementary=false;
                        starter=p-1;
                    } else {
                        starterIsSupplementary=true;
                        starter=p-2;
                    }
                }
            } else if(onlyContiguous) {
                // FCC: no discontiguous compositions; any intervening character blocks.
                compositionsList=-1;
            }
        }
        buffer.flush();
    }

    /**
     * Does c have a composition boundary before it?
     * True if its decomposition begins with a character that has
     * ccc=0 && NFC_QC=Yes (isCompYesAndZeroCC()).
     * As a shortcut, this is true if c itself has ccc=0 && NFC_QC=Yes
     * (isCompYesAndZeroCC()) so we need not decompose.
     */
    private boolean hasCompBoundaryBefore(int c, int norm16) {
        return c<minCompNoMaybeCP || norm16HasCompBoundaryBefore(norm16);
    }
    private boolean norm16HasCompBoundaryBefore(int norm16) {
        return norm16 < minNoNoCompNoMaybeCC || isAlgorithmicNoNo(norm16);
    }
    private boolean hasCompBoundaryBefore(CharSequence s, int src, int limit) {
        return src == limit || hasCompBoundaryBefore(Character.codePointAt(s, src));
    }
    private boolean norm16HasCompBoundaryAfter(int norm16, boolean onlyContiguous) {
        return (norm16 & HAS_COMP_BOUNDARY_AFTER) != 0 &&
            (!onlyContiguous || isTrailCC01ForCompBoundaryAfter(norm16));
    }
    private boolean hasCompBoundaryAfter(CharSequence s, int start, int p, boolean onlyContiguous) {
        return start == p || hasCompBoundaryAfter(Character.codePointBefore(s, p), onlyContiguous);
    }
    /** For FCC: Given norm16 HAS_COMP_BOUNDARY_AFTER, does it have tccc<=1? */
    private boolean isTrailCC01ForCompBoundaryAfter(int norm16) {
        return isInert(norm16) || (isDecompNoAlgorithmic(norm16) ?
            (norm16 & DELTA_TCCC_MASK) <= DELTA_TCCC_1 : extraData.charAt(norm16 >> OFFSET_SHIFT) <= 0x1ff);
    }

    private int findPreviousCompBoundary(CharSequence s, int p, boolean onlyContiguous) {
        while(p>0) {
            int c=Character.codePointBefore(s, p);
            int norm16 = getNorm16(c);
            if (norm16HasCompBoundaryAfter(norm16, onlyContiguous)) {
                break;
            }
            p-=Character.charCount(c);
            if(hasCompBoundaryBefore(c, norm16)) {
                break;
            }
        }
        return p;
    }
    private int findNextCompBoundary(CharSequence s, int p, int limit, boolean onlyContiguous) {
        while(p<limit) {
            int c=Character.codePointAt(s, p);
            int norm16=normTrie.get(c);
            if(hasCompBoundaryBefore(c, norm16)) {
                break;
            }
            p+=Character.charCount(c);
            if (norm16HasCompBoundaryAfter(norm16, onlyContiguous)) {
                break;
            }
        }
        return p;
    }


    private int findNextFCDBoundary(CharSequence s, int p, int limit) {
        while(p<limit) {
            int c=Character.codePointAt(s, p);
            int norm16;
            if (c < minLcccCP || norm16HasDecompBoundaryBefore(norm16 = getNorm16(c))) {
                break;
            }
            p+=Character.charCount(c);
            if (norm16HasDecompBoundaryAfter(norm16)) {
                break;
            }
        }
        return p;
    }

    /**
     * Get the canonical decomposition
     * sherman  for ComposedCharIter
     */
    public static int getDecompose(int chars[], String decomps[]) {
        Normalizer2 impl = Normalizer2.getNFDInstance();

        int length=0;
        int norm16 = 0;
        int ch = -1;
        int i = 0;

        while (++ch < 0x2fa1e) {   //no cannoical above 0x3ffff
            //TBD !!!! the hack code heres save us about 50ms for startup
            //need a better solution/lookup
            if (ch == 0x30ff)
                ch = 0xf900;
            else if (ch == 0x115bc)
                ch = 0x1d15e;
            else if (ch == 0x1d1c1)
                ch = 0x2f800;

            String s = impl.getDecomposition(ch);

            if(s != null && i < chars.length) {
                chars[i] = ch;
                decomps[i++] = s;
            }
        }
        return i;
    }

    //------------------------------------------------------
    // special method for Collation (RBTableBuilder.build())
    //------------------------------------------------------
    private static boolean needSingleQuotation(char c) {
        return (c >= 0x0009 && c <= 0x000D) ||
               (c >= 0x0020 && c <= 0x002F) ||
               (c >= 0x003A && c <= 0x0040) ||
               (c >= 0x005B && c <= 0x0060) ||
               (c >= 0x007B && c <= 0x007E);
    }

    public static String canonicalDecomposeWithSingleQuotation(String string) {
       Normalizer2 impl = Normalizer2.getNFDInstance();
       char[] src = string.toCharArray();
       int    srcIndex = 0;
       int    srcLimit = src.length;
       char[] dest = new char[src.length * 3];  //MAX_BUF_SIZE_DECOMPOSE = 3
       int    destIndex = 0;
       int    destLimit = dest.length;

        int prevSrc;
        String norm;
        int reorderStartIndex, length;
        char c1, c2;
        int cp;
        int minNoMaybe = 0x00c0;
        int cc, prevCC, trailCC;
        char[] p;
        int pStart;

        // initialize
        reorderStartIndex = 0;
        prevCC = 0;
        norm = null;
        cp = 0;
        pStart = 0;

        cc = trailCC = -1; // initialize to bogus value
        c1 = 0;
        for (;;) {
            prevSrc=srcIndex;
            //quick check (1)less than minNoMaybe (2)no decomp (3)hangual
            while (srcIndex != srcLimit &&
                   ((c1 = src[srcIndex]) < minNoMaybe ||
                    (norm = impl.getDecomposition(cp = string.codePointAt(srcIndex))) == null ||
                    (c1 >= '\uac00' && c1 <= '\ud7a3'))) { // Hangul Syllables
                prevCC = 0;
                srcIndex += (cp < 0x10000) ? 1 : 2;
            }

            // copy these code units all at once
            if (srcIndex != prevSrc) {
                length = srcIndex - prevSrc;
                if ((destIndex + length) <= destLimit) {
                    System.arraycopy(src,prevSrc,dest,destIndex,length);
                }

                destIndex += length;
                reorderStartIndex = destIndex;
            }

            // end of source reached?
            if (srcIndex == srcLimit) {
                break;
            }

            // cp already contains *src and norm32 is set for it, increment src
            srcIndex += (cp < 0x10000) ? 1 : 2;

            if (cp < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
                c2 = 0;
                length = 1;

                if (Character.isHighSurrogate(c1)
                    || Character.isLowSurrogate(c1)) {
                    norm = null;
                }
            } else {
                length = 2;
                c2 = src[srcIndex-1];
            }

          // get the decomposition and the lead and trail cc's
          if (norm == null) {
              // cp does not decompose
              cc = trailCC = UCharacter.getCombiningClass(cp);
              p = null;
              pStart = -1;
          } else {

                pStart = 0;
                p = norm.toCharArray();
                length = p.length;
                int cpNum = norm.codePointCount(0, length);
                cc= UCharacter.getCombiningClass(norm.codePointAt(0));
                trailCC= UCharacter.getCombiningClass(norm.codePointAt(cpNum-1));
                if (length == 1) {
                    // fastpath a single code unit from decomposition
                    c1 = p[pStart];
                    c2 = 0;
                    p = null;
                    pStart = -1;
                }
            }

            if((destIndex + length * 3) >= destLimit) {  // 2 SingleQuotations
                // buffer overflow
                char[] tmpBuf = new char[destLimit * 2];
                System.arraycopy(dest, 0, tmpBuf, 0, destIndex);
                dest = tmpBuf;
                destLimit = dest.length;
            }

            // append the decomposition to the destination buffer, assume length>0
            {
                int reorderSplit = destIndex;
                if (p == null) {
                    // fastpath: single code point
                    if (needSingleQuotation(c1)) {
                        //if we need single quotation, no need to consider "prevCC"
                        //and it must NOT be a supplementary pair
                        dest[destIndex++] = '\'';
                        dest[destIndex++] = c1;
                        dest[destIndex++] = '\'';
                        trailCC = 0;
                    } else if(cc != 0 && cc < prevCC) {
                        // (c1, c2) is out of order with respect to the preceding
                        //  text
                        destIndex += length;
                        trailCC = insertOrdered(dest, reorderStartIndex,
                                                reorderSplit, destIndex, c1, c2, cc);
                    } else {
                        // just append (c1, c2)
                        dest[destIndex++] = c1;
                        if(c2 != 0) {
                            dest[destIndex++] = c2;
                        }
                    }
                } else {
                    // general: multiple code points (ordered by themselves)
                    // from decomposition
                    if (needSingleQuotation(p[pStart])) {
                        dest[destIndex++] = '\'';
                        dest[destIndex++] = p[pStart++];
                        dest[destIndex++] = '\'';
                        length--;
                        do {
                            dest[destIndex++] = p[pStart++];
                        } while(--length > 0);
                    } else if (cc != 0 && cc < prevCC) {
                        destIndex += length;
                        trailCC = mergeOrdered(dest, reorderStartIndex,
                                               reorderSplit, p, pStart,
                                               pStart+length);
                    } else {
                        // just append the decomposition
                        do {
                            dest[destIndex++] = p[pStart++];
                        } while (--length > 0);
                    }
                }
            }
            prevCC = trailCC;
            if(prevCC == 0) {
                reorderStartIndex = destIndex;
            }
        }

        return new String(dest, 0, destIndex);
    }

    /**
     * simpler, single-character version of mergeOrdered() -
     * bubble-insert one single code point into the preceding string
     * which is already canonically ordered
     * (c, c2) may or may not yet have been inserted at src[current]..src[p]
     *
     * it must be p=current+lengthof(c, c2) i.e. p=current+(c2==0 ? 1 : 2)
     *
     * before: src[start]..src[current] is already ordered, and
     *         src[current]..src[p]     may or may not hold (c, c2) but
     *                          must be exactly the same length as (c, c2)
     * after: src[start]..src[p] is ordered
     *
     * @return the trailing combining class
     */
    private static int/*unsigned byte*/ insertOrdered(char[] source,
                                                      int start,
                                                      int current, int p,
                                                      char c1, char c2,
                                                      int/*unsigned byte*/ cc) {
        int back, preBack;
        int r;
        int prevCC, trailCC=cc;

        if (start<current && cc!=0) {
            // search for the insertion point where cc>=prevCC
            preBack=back=current;

            PrevArgs prevArgs = new PrevArgs();
            prevArgs.current  = current;
            prevArgs.start    = start;
            prevArgs.src      = source;
            prevArgs.c1       = c1;
            prevArgs.c2       = c2;

            // get the prevCC
            prevCC=getPrevCC(prevArgs);
            preBack = prevArgs.current;

            if(cc<prevCC) {
                // this will be the last code point, so keep its cc
                trailCC=prevCC;
                back=preBack;
                while(start<preBack) {
                    prevCC=getPrevCC(prevArgs);
                    preBack=prevArgs.current;
                    if(cc>=prevCC) {
                        break;
                    }
                    back=preBack;
                }

                // this is where we are right now with all these indicies:
                // [start]..[pPreBack] 0..? code points that we can ignore
                // [pPreBack]..[pBack] 0..1 code points with prevCC<=cc
                // [pBack]..[current] 0..n code points with >cc, move up to insert (c, c2)
                // [current]..[p]         1 code point (c, c2) with cc

                // move the code units in between up
                r=p;
                do {
                    source[--r]=source[--current];
                } while (back!=current);
            }
        }

        // insert (c1, c2)
        source[current] = c1;
        if (c2!=0) {
            source[(current+1)] = c2;
        }

        // we know the cc of the last code point
        return trailCC;
    }
    /**
     * merge two UTF-16 string parts together
     * to canonically order (order by combining classes) their concatenation
     *
     * the two strings may already be adjacent, so that the merging is done
     * in-place if the two strings are not adjacent, then the buffer holding the
     * first one must be large enough
     * the second string may or may not be ordered in itself
     *
     * before: [start]..[current] is already ordered, and
     *         [next]..[limit]    may be ordered in itself, but
     *                          is not in relation to [start..current[
     * after: [start..current+(limit-next)[ is ordered
     *
     * the algorithm is a simple bubble-sort that takes the characters from
     * src[next++] and inserts them in correct combining class order into the
     * preceding part of the string
     *
     * since this function is called much less often than the single-code point
     * insertOrdered(), it just uses that for easier maintenance
     *
     * @return the trailing combining class
     */
    private static int /*unsigned byte*/ mergeOrdered(char[] source,
                                                      int start,
                                                      int current,
                                                      char[] data,
                                                        int next,
                                                        int limit) {
            int r;
            int /*unsigned byte*/ cc, trailCC=0;
            boolean adjacent;

            adjacent= current==next;
            NextCCArgs ncArgs = new NextCCArgs();
            ncArgs.source = data;
            ncArgs.next   = next;
            ncArgs.limit  = limit;

            if(start!=current) {

                while(ncArgs.next<ncArgs.limit) {
                    cc=getNextCC(ncArgs);
                    if(cc==0) {
                        // does not bubble back
                        trailCC=0;
                        if(adjacent) {
                            current=ncArgs.next;
                        } else {
                            data[current++]=ncArgs.c1;
                            if(ncArgs.c2!=0) {
                                data[current++]=ncArgs.c2;
                            }
                        }
                        break;
                    } else {
                        r=current+(ncArgs.c2==0 ? 1 : 2);
                        trailCC=insertOrdered(source,start, current, r,
                                              ncArgs.c1, ncArgs.c2, cc);
                        current=r;
                    }
                }
            }

            if(ncArgs.next==ncArgs.limit) {
                // we know the cc of the last code point
                return trailCC;
            } else {
                if(!adjacent) {
                    // copy the second string part
                    do {
                        source[current++]=data[ncArgs.next++];
                    } while(ncArgs.next!=ncArgs.limit);
                    ncArgs.limit=current;
                }
                PrevArgs prevArgs = new PrevArgs();
                prevArgs.src   = data;
                prevArgs.start = start;
                prevArgs.current =  ncArgs.limit;
                return getPrevCC(prevArgs);
            }

    }
    private static final class PrevArgs{
        char[] src;
        int start;
        int current;
        char c1;
        char c2;
    }

    private static final class NextCCArgs{
        char[] source;
        int next;
        int limit;
        char c1;
        char c2;
    }
    private static int /*unsigned byte*/ getNextCC(NextCCArgs args) {
        args.c1=args.source[args.next++];
        args.c2=0;

        if (UTF16.isTrailSurrogate(args.c1)) {
            /* unpaired second surrogate */
            return 0;
        } else if (!UTF16.isLeadSurrogate(args.c1)) {
            return UCharacter.getCombiningClass(args.c1);
        } else if (args.next!=args.limit &&
                        UTF16.isTrailSurrogate(args.c2=args.source[args.next])){
            ++args.next;
            return UCharacter.getCombiningClass(Character.toCodePoint(args.c1, args.c2));
        } else {
            /* unpaired first surrogate */
            args.c2=0;
            return 0;
        }
    }
    private static int /*unsigned*/ getPrevCC(PrevArgs args) {
        args.c1=args.src[--args.current];
        args.c2=0;

        if (args.c1 < MIN_CCC_LCCC_CP) {
            return 0;
        } else if (UTF16.isLeadSurrogate(args.c1)) {
            /* unpaired first surrogate */
            return 0;
        } else if (!UTF16.isTrailSurrogate(args.c1)) {
            return UCharacter.getCombiningClass(args.c1);
        } else if (args.current!=args.start &&
                    UTF16.isLeadSurrogate(args.c2=args.src[args.current-1])) {
            --args.current;
            return UCharacter.getCombiningClass(Character.toCodePoint(args.c2, args.c1));
        } else {
            /* unpaired second surrogate */
            args.c2=0;
            return 0;
        }
    }

    private int getPreviousTrailCC(CharSequence s, int start, int p) {
        if (start == p) {
            return 0;
        }
        return getFCD16(Character.codePointBefore(s, p));
    }

    private VersionInfo dataVersion;

    // BMP code point thresholds for quick check loops looking at single UTF-16 code units.
    private int minDecompNoCP;
    private int minCompNoMaybeCP;
    private int minLcccCP;

    // Norm16 value thresholds for quick check combinations and types of extra data.
    private int minYesNo;
    private int minYesNoMappingsOnly;
    private int minNoNo;
    private int minNoNoCompBoundaryBefore;
    private int minNoNoCompNoMaybeCC;
    private int minNoNoEmpty;
    private int limitNoNo;
    private int centerNoNoDelta;
    private int minMaybeYes;

    private CodePointTrie.Fast16 normTrie;
    private String maybeYesCompositions;
    private String extraData;  // mappings and/or compositions for yesYes, yesNo & noNo characters
    private byte[] smallFCD;  // [0x100] one bit per 32 BMP code points, set if any FCD!=0
}
