X-Git-Url: https://git.saurik.com/apple/icu.git/blobdiff_plain/48b980fed3435926e0b3a8d72ecb58be703a1c7a..729e4ab9bc6618bc3d8a898e575df7f4019e29ca:/icuSources/common/normalizer2impl.cpp

diff --git a/icuSources/common/normalizer2impl.cpp b/icuSources/common/normalizer2impl.cpp
new file mode 100644
index 00000000..52459be7
--- /dev/null
+++ b/icuSources/common/normalizer2impl.cpp
@@ -0,0 +1,2011 @@
+/*
+*******************************************************************************
+*
+*   Copyright (C) 2009-2010, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  normalizer2impl.cpp
+*   encoding:   US-ASCII
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2009nov22
+*   created by: Markus W. Scherer
+*/
+
+#include "unicode/utypes.h"
+
+#if !UCONFIG_NO_NORMALIZATION
+
+#include "unicode/normalizer2.h"
+#include "unicode/udata.h"
+#include "unicode/ustring.h"
+#include "cmemory.h"
+#include "mutex.h"
+#include "normalizer2impl.h"
+#include "uassert.h"
+#include "uhash.h"
+#include "uset_imp.h"
+#include "utrie2.h"
+#include "uvector.h"
+
+U_NAMESPACE_BEGIN
+
+// ReorderingBuffer -------------------------------------------------------- ***
+
+UBool ReorderingBuffer::init(int32_t destCapacity, UErrorCode &errorCode) {
+    int32_t length=str.length();
+    start=str.getBuffer(destCapacity);
+    if(start==NULL) {
+        // getBuffer() already did str.setToBogus()
+        errorCode=U_MEMORY_ALLOCATION_ERROR;
+        return FALSE;
+    }
+    limit=start+length;
+    remainingCapacity=str.getCapacity()-length;
+    reorderStart=start;
+    if(start==limit) {
+        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;
+    }
+    return TRUE;
+}
+
+UBool ReorderingBuffer::equals(const UChar *otherStart, const UChar *otherLimit) const {
+    int32_t length=(int32_t)(limit-start);
+    return
+        length==(int32_t)(otherLimit-otherStart) &&
+        0==u_memcmp(start, otherStart, length);
+}
+
+UBool ReorderingBuffer::appendSupplementary(UChar32 c, uint8_t cc, UErrorCode &errorCode) {
+    if(remainingCapacity<2 && !resize(2, errorCode)) {
+        return FALSE;
+    }
+    if(lastCC<=cc || cc==0) {
+        limit[0]=U16_LEAD(c);
+        limit[1]=U16_TRAIL(c);
+        limit+=2;
+        lastCC=cc;
+        if(cc<=1) {
+            reorderStart=limit;
+        }
+    } else {
+        insert(c, cc);
+    }
+    remainingCapacity-=2;
+    return TRUE;
+}
+
+UBool ReorderingBuffer::append(const UChar *s, int32_t length,
+                               uint8_t leadCC, uint8_t trailCC,
+                               UErrorCode &errorCode) {
+    if(length==0) {
+        return TRUE;
+    }
+    if(remainingCapacity<length && !resize(length, errorCode)) {
+        return FALSE;
+    }
+    remainingCapacity-=length;
+    if(lastCC<=leadCC || leadCC==0) {
+        if(trailCC<=1) {
+            reorderStart=limit+length;
+        } else if(leadCC<=1) {
+            reorderStart=limit+1;  // Ok if not a code point boundary.
+        }
+        const UChar *sLimit=s+length;
+        do { *limit++=*s++; } while(s!=sLimit);
+        lastCC=trailCC;
+    } else {
+        int32_t i=0;
+        UChar32 c;
+        U16_NEXT(s, i, length, c);
+        insert(c, leadCC);  // insert first code point
+        while(i<length) {
+            U16_NEXT(s, i, length, c);
+            if(i<length) {
+                // s must be in NFD, otherwise we need to use getCC().
+                leadCC=Normalizer2Impl::getCCFromYesOrMaybe(impl.getNorm16(c));
+            } else {
+                leadCC=trailCC;
+            }
+            append(c, leadCC, errorCode);
+        }
+    }
+    return TRUE;
+}
+
+UBool ReorderingBuffer::appendZeroCC(UChar32 c, UErrorCode &errorCode) {
+    int32_t cpLength=U16_LENGTH(c);
+    if(remainingCapacity<cpLength && !resize(cpLength, errorCode)) {
+        return FALSE;
+    }
+    remainingCapacity-=cpLength;
+    if(cpLength==1) {
+        *limit++=(UChar)c;
+    } else {
+        limit[0]=U16_LEAD(c);
+        limit[1]=U16_TRAIL(c);
+        limit+=2;
+    }
+    lastCC=0;
+    reorderStart=limit;
+    return TRUE;
+}
+
+UBool ReorderingBuffer::appendZeroCC(const UChar *s, const UChar *sLimit, UErrorCode &errorCode) {
+    if(s==sLimit) {
+        return TRUE;
+    }
+    int32_t length=(int32_t)(sLimit-s);
+    if(remainingCapacity<length && !resize(length, errorCode)) {
+        return FALSE;
+    }
+    u_memcpy(limit, s, length);
+    limit+=length;
+    remainingCapacity-=length;
+    lastCC=0;
+    reorderStart=limit;
+    return TRUE;
+}
+
+void ReorderingBuffer::remove() {
+    reorderStart=limit=start;
+    remainingCapacity=str.getCapacity();
+    lastCC=0;
+}
+
+void ReorderingBuffer::removeSuffix(int32_t suffixLength) {
+    if(suffixLength<(limit-start)) {
+        limit-=suffixLength;
+        remainingCapacity+=suffixLength;
+    } else {
+        limit=start;
+        remainingCapacity=str.getCapacity();
+    }
+    lastCC=0;
+    reorderStart=limit;
+}
+
+UBool ReorderingBuffer::resize(int32_t appendLength, UErrorCode &errorCode) {
+    int32_t reorderStartIndex=(int32_t)(reorderStart-start);
+    int32_t length=(int32_t)(limit-start);
+    str.releaseBuffer(length);
+    int32_t newCapacity=length+appendLength;
+    int32_t doubleCapacity=2*str.getCapacity();
+    if(newCapacity<doubleCapacity) {
+        newCapacity=doubleCapacity;
+    }
+    if(newCapacity<256) {
+        newCapacity=256;
+    }
+    start=str.getBuffer(newCapacity);
+    if(start==NULL) {
+        // getBuffer() already did str.setToBogus()
+        errorCode=U_MEMORY_ALLOCATION_ERROR;
+        return FALSE;
+    }
+    reorderStart=start+reorderStartIndex;
+    limit=start+length;
+    remainingCapacity=str.getCapacity()-length;
+    return TRUE;
+}
+
+void ReorderingBuffer::skipPrevious() {
+    codePointLimit=codePointStart;
+    UChar c=*--codePointStart;
+    if(U16_IS_TRAIL(c) && start<codePointStart && U16_IS_LEAD(*(codePointStart-1))) {
+        --codePointStart;
+    }
+}
+
+uint8_t ReorderingBuffer::previousCC() {
+    codePointLimit=codePointStart;
+    if(reorderStart>=codePointStart) {
+        return 0;
+    }
+    UChar32 c=*--codePointStart;
+    if(c<Normalizer2Impl::MIN_CCC_LCCC_CP) {
+        return 0;
+    }
+
+    UChar c2;
+    if(U16_IS_TRAIL(c) && start<codePointStart && U16_IS_LEAD(c2=*(codePointStart-1))) {
+        --codePointStart;
+        c=U16_GET_SUPPLEMENTARY(c2, c);
+    }
+    return Normalizer2Impl::getCCFromYesOrMaybe(impl.getNorm16(c));
+}
+
+// Inserts c somewhere before the last character.
+// Requires 0<cc<lastCC which implies reorderStart<limit.
+void ReorderingBuffer::insert(UChar32 c, uint8_t cc) {
+    for(setIterator(), skipPrevious(); previousCC()>cc;) {}
+    // insert c at codePointLimit, after the character with prevCC<=cc
+    UChar *q=limit;
+    UChar *r=limit+=U16_LENGTH(c);
+    do {
+        *--r=*--q;
+    } while(codePointLimit!=q);
+    writeCodePoint(q, c);
+    if(cc<=1) {
+        reorderStart=r;
+    }
+}
+
+// Normalizer2Impl --------------------------------------------------------- ***
+
+struct CanonIterData : public UMemory {
+    CanonIterData(UErrorCode &errorCode);
+    ~CanonIterData();
+    void addToStartSet(UChar32 origin, UChar32 decompLead, UErrorCode &errorCode);
+    UTrie2 *trie;
+    UVector canonStartSets;  // contains UnicodeSet *
+};
+
+Normalizer2Impl::~Normalizer2Impl() {
+    udata_close(memory);
+    utrie2_close(normTrie);
+    UTrie2Singleton(fcdTrieSingleton).deleteInstance();
+    delete (CanonIterData *)canonIterDataSingleton.fInstance;
+}
+
+UBool U_CALLCONV
+Normalizer2Impl::isAcceptable(void *context,
+                              const char * /* type */, const char * /*name*/,
+                              const UDataInfo *pInfo) {
+    if(
+        pInfo->size>=20 &&
+        pInfo->isBigEndian==U_IS_BIG_ENDIAN &&
+        pInfo->charsetFamily==U_CHARSET_FAMILY &&
+        pInfo->dataFormat[0]==0x4e &&    /* dataFormat="Nrm2" */
+        pInfo->dataFormat[1]==0x72 &&
+        pInfo->dataFormat[2]==0x6d &&
+        pInfo->dataFormat[3]==0x32 &&
+        pInfo->formatVersion[0]==1
+    ) {
+        Normalizer2Impl *me=(Normalizer2Impl *)context;
+        uprv_memcpy(me->dataVersion, pInfo->dataVersion, 4);
+        return TRUE;
+    } else {
+        return FALSE;
+    }
+}
+
+void
+Normalizer2Impl::load(const char *packageName, const char *name, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) {
+        return;
+    }
+    memory=udata_openChoice(packageName, "nrm", name, isAcceptable, this, &errorCode);
+    if(U_FAILURE(errorCode)) {
+        return;
+    }
+    const uint8_t *inBytes=(const uint8_t *)udata_getMemory(memory);
+    const int32_t *inIndexes=(const int32_t *)inBytes;
+    int32_t indexesLength=inIndexes[IX_NORM_TRIE_OFFSET]/4;
+    if(indexesLength<=IX_MIN_MAYBE_YES) {
+        errorCode=U_INVALID_FORMAT_ERROR;  // Not enough indexes.
+        return;
+    }
+
+    minDecompNoCP=inIndexes[IX_MIN_DECOMP_NO_CP];
+    minCompNoMaybeCP=inIndexes[IX_MIN_COMP_NO_MAYBE_CP];
+
+    minYesNo=inIndexes[IX_MIN_YES_NO];
+    minNoNo=inIndexes[IX_MIN_NO_NO];
+    limitNoNo=inIndexes[IX_LIMIT_NO_NO];
+    minMaybeYes=inIndexes[IX_MIN_MAYBE_YES];
+
+    int32_t offset=inIndexes[IX_NORM_TRIE_OFFSET];
+    int32_t nextOffset=inIndexes[IX_EXTRA_DATA_OFFSET];
+    normTrie=utrie2_openFromSerialized(UTRIE2_16_VALUE_BITS,
+                                       inBytes+offset, nextOffset-offset, NULL,
+                                       &errorCode);
+    if(U_FAILURE(errorCode)) {
+        return;
+    }
+
+    offset=nextOffset;
+    maybeYesCompositions=(const uint16_t *)(inBytes+offset);
+    extraData=maybeYesCompositions+(MIN_NORMAL_MAYBE_YES-minMaybeYes);
+}
+
+uint8_t Normalizer2Impl::getTrailCCFromCompYesAndZeroCC(const UChar *cpStart, const UChar *cpLimit) const {
+    UChar32 c;
+    if(cpStart==(cpLimit-1)) {
+        c=*cpStart;
+    } else {
+        c=U16_GET_SUPPLEMENTARY(cpStart[0], cpStart[1]);
+    }
+    uint16_t prevNorm16=getNorm16(c);
+    if(prevNorm16<=minYesNo) {
+        return 0;  // yesYes and Hangul LV/LVT have ccc=tccc=0
+    } else {
+        return (uint8_t)(*getMapping(prevNorm16)>>8);  // tccc from yesNo
+    }
+}
+
+U_CDECL_BEGIN
+
+static UBool U_CALLCONV
+enumPropertyStartsRange(const void *context, UChar32 start, UChar32 /*end*/, uint32_t /*value*/) {
+    /* add the start code point to the USet */
+    const USetAdder *sa=(const USetAdder *)context;
+    sa->add(sa->set, start);
+    return TRUE;
+}
+
+static uint32_t U_CALLCONV
+segmentStarterMapper(const void * /*context*/, uint32_t value) {
+    return value&CANON_NOT_SEGMENT_STARTER;
+}
+
+U_CDECL_END
+
+void
+Normalizer2Impl::addPropertyStarts(const USetAdder *sa, UErrorCode & /*errorCode*/) const {
+    /* add the start code point of each same-value range of each trie */
+    utrie2_enum(normTrie, NULL, enumPropertyStartsRange, sa);
+
+    /* add Hangul LV syllables and LV+1 because of skippables */
+    for(UChar c=Hangul::HANGUL_BASE; c<Hangul::HANGUL_LIMIT; c+=Hangul::JAMO_T_COUNT) {
+        sa->add(sa->set, c);
+        sa->add(sa->set, c+1);
+    }
+    sa->add(sa->set, Hangul::HANGUL_LIMIT); /* add Hangul+1 to continue with other properties */
+}
+
+void
+Normalizer2Impl::addCanonIterPropertyStarts(const USetAdder *sa, UErrorCode &errorCode) const {
+    /* add the start code point of each same-value range of the canonical iterator data trie */
+    if(ensureCanonIterData(errorCode)) {
+        // currently only used for the SEGMENT_STARTER property
+        utrie2_enum(((CanonIterData *)canonIterDataSingleton.fInstance)->trie,
+                    segmentStarterMapper, enumPropertyStartsRange, sa);
+    }
+}
+
+const UChar *
+Normalizer2Impl::copyLowPrefixFromNulTerminated(const UChar *src,
+                                                UChar32 minNeedDataCP,
+                                                ReorderingBuffer *buffer,
+                                                UErrorCode &errorCode) const {
+    // Make some effort to support NUL-terminated strings reasonably.
+    // Take the part of the fast quick check loop that does not look up
+    // data and check the first part of the string.
+    // After this prefix, determine the string length to simplify the rest
+    // of the code.
+    const UChar *prevSrc=src;
+    UChar c;
+    while((c=*src++)<minNeedDataCP && c!=0) {}
+    // Back out the last character for full processing.
+    // Copy this prefix.
+    if(--src!=prevSrc) {
+        if(buffer!=NULL) {
+            buffer->appendZeroCC(prevSrc, src, errorCode);
+        }
+    }
+    return src;
+}
+
+// Dual functionality:
+// buffer!=NULL: normalize
+// buffer==NULL: isNormalized/spanQuickCheckYes
+const UChar *
+Normalizer2Impl::decompose(const UChar *src, const UChar *limit,
+                           ReorderingBuffer *buffer,
+                           UErrorCode &errorCode) const {
+    UChar32 minNoCP=minDecompNoCP;
+    if(limit==NULL) {
+        src=copyLowPrefixFromNulTerminated(src, minNoCP, buffer, errorCode);
+        if(U_FAILURE(errorCode)) {
+            return src;
+        }
+        limit=u_strchr(src, 0);
+    }
+
+    const UChar *prevSrc;
+    UChar32 c=0;
+    uint16_t norm16=0;
+
+    // only for quick check
+    const UChar *prevBoundary=src;
+    uint8_t prevCC=0;
+
+    for(;;) {
+        // count code units below the minimum or with irrelevant data for the quick check
+        for(prevSrc=src; src!=limit;) {
+            if( (c=*src)<minNoCP ||
+                isMostDecompYesAndZeroCC(norm16=UTRIE2_GET16_FROM_U16_SINGLE_LEAD(normTrie, c))
+            ) {
+                ++src;
+            } else if(!U16_IS_SURROGATE(c)) {
+                break;
+            } else {
+                UChar c2;
+                if(U16_IS_SURROGATE_LEAD(c)) {
+                    if((src+1)!=limit && U16_IS_TRAIL(c2=src[1])) {
+                        c=U16_GET_SUPPLEMENTARY(c, c2);
+                    }
+                } else /* trail surrogate */ {
+                    if(prevSrc<src && U16_IS_LEAD(c2=*(src-1))) {
+                        --src;
+                        c=U16_GET_SUPPLEMENTARY(c2, c);
+                    }
+                }
+                if(isMostDecompYesAndZeroCC(norm16=getNorm16(c))) {
+                    src+=U16_LENGTH(c);
+                } else {
+                    break;
+                }
+            }
+        }
+        // copy these code units all at once
+        if(src!=prevSrc) {
+            if(buffer!=NULL) {
+                if(!buffer->appendZeroCC(prevSrc, src, errorCode)) {
+                    break;
+                }
+            } else {
+                prevCC=0;
+                prevBoundary=src;
+            }
+        }
+        if(src==limit) {
+            break;
+        }
+
+        // Check one above-minimum, relevant code point.
+        src+=U16_LENGTH(c);
+        if(buffer!=NULL) {
+            if(!decompose(c, norm16, *buffer, errorCode)) {
+                break;
+            }
+        } else {
+            if(isDecompYes(norm16)) {
+                uint8_t 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;
+}
+
+// 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.
+UBool Normalizer2Impl::decomposeShort(const UChar *src, const UChar *limit,
+                                      ReorderingBuffer &buffer,
+                                      UErrorCode &errorCode) const {
+    while(src<limit) {
+        UChar32 c;
+        uint16_t norm16;
+        UTRIE2_U16_NEXT16(normTrie, src, limit, c, norm16);
+        if(!decompose(c, norm16, buffer, errorCode)) {
+            return FALSE;
+        }
+    }
+    return TRUE;
+}
+
+UBool Normalizer2Impl::decompose(UChar32 c, uint16_t norm16,
+                                 ReorderingBuffer &buffer,
+                                 UErrorCode &errorCode) const {
+    // Only loops for 1:1 algorithmic mappings.
+    for(;;) {
+        // get the decomposition and the lead and trail cc's
+        if(isDecompYes(norm16)) {
+            // c does not decompose
+            return buffer.append(c, getCCFromYesOrMaybe(norm16), errorCode);
+        } else if(isHangul(norm16)) {
+            // Hangul syllable: decompose algorithmically
+            UChar jamos[3];
+            return buffer.appendZeroCC(jamos, jamos+Hangul::decompose(c, jamos), errorCode);
+        } else if(isDecompNoAlgorithmic(norm16)) {
+            c=mapAlgorithmic(c, norm16);
+            norm16=getNorm16(c);
+        } else {
+            // c decomposes, get everything from the variable-length extra data
+            const uint16_t *mapping=getMapping(norm16);
+            uint16_t firstUnit=*mapping++;
+            int32_t length=firstUnit&MAPPING_LENGTH_MASK;
+            uint8_t leadCC, trailCC;
+            trailCC=(uint8_t)(firstUnit>>8);
+            if(firstUnit&MAPPING_HAS_CCC_LCCC_WORD) {
+                leadCC=(uint8_t)(*mapping++>>8);
+            } else {
+                leadCC=0;
+            }
+            return buffer.append((const UChar *)mapping, length, leadCC, trailCC, errorCode);
+        }
+    }
+}
+
+const UChar *
+Normalizer2Impl::getDecomposition(UChar32 c, UChar buffer[4], int32_t &length) const {
+    const UChar *decomp=NULL;
+    uint16_t norm16;
+    for(;;) {
+        if(c<minDecompNoCP || isDecompYes(norm16=getNorm16(c))) {
+            // c does not decompose
+            return decomp;
+        } else if(isHangul(norm16)) {
+            // Hangul syllable: decompose algorithmically
+            length=Hangul::decompose(c, buffer);
+            return buffer;
+        } else if(isDecompNoAlgorithmic(norm16)) {
+            c=mapAlgorithmic(c, norm16);
+            decomp=buffer;
+            length=0;
+            U16_APPEND_UNSAFE(buffer, length, c);
+        } else {
+            // c decomposes, get everything from the variable-length extra data
+            const uint16_t *mapping=getMapping(norm16);
+            uint16_t firstUnit=*mapping++;
+            length=firstUnit&MAPPING_LENGTH_MASK;
+            if(firstUnit&MAPPING_HAS_CCC_LCCC_WORD) {
+                ++mapping;
+            }
+            return (const UChar *)mapping;
+        }
+    }
+}
+
+void Normalizer2Impl::decomposeAndAppend(const UChar *src, const UChar *limit,
+                                         UBool doDecompose,
+                                         ReorderingBuffer &buffer,
+                                         UErrorCode &errorCode) const {
+    if(doDecompose) {
+        decompose(src, limit, &buffer, errorCode);
+        return;
+    }
+    // Just merge the strings at the boundary.
+    ForwardUTrie2StringIterator iter(normTrie, src, limit);
+    uint8_t firstCC, prevCC, cc;
+    firstCC=prevCC=cc=getCC(iter.next16());
+    while(cc!=0) {
+        prevCC=cc;
+        cc=getCC(iter.next16());
+    };
+    buffer.append(src, (int32_t)(iter.codePointStart-src), firstCC, prevCC, errorCode) &&
+        buffer.appendZeroCC(iter.codePointStart, limit, errorCode);
+}
+
+// Note: hasDecompBoundary() could be implemented as aliases to
+// hasFCDBoundaryBefore() and hasFCDBoundaryAfter()
+// at the cost of building the FCD trie for a decomposition normalizer.
+UBool Normalizer2Impl::hasDecompBoundary(UChar32 c, UBool before) const {
+    for(;;) {
+        if(c<minDecompNoCP) {
+            return TRUE;
+        }
+        uint16_t norm16=getNorm16(c);
+        if(isHangul(norm16) || isDecompYesAndZeroCC(norm16)) {
+            return TRUE;
+        } else if(norm16>MIN_NORMAL_MAYBE_YES) {
+            return FALSE;  // ccc!=0
+        } else if(isDecompNoAlgorithmic(norm16)) {
+            c=mapAlgorithmic(c, norm16);
+        } else {
+            // c decomposes, get everything from the variable-length extra data
+            const uint16_t *mapping=getMapping(norm16);
+            uint16_t firstUnit=*mapping++;
+            if((firstUnit&MAPPING_LENGTH_MASK)==0) {
+                return FALSE;
+            }
+            if(!before) {
+                // 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 || (*mapping&0xff00)==0;
+        }
+    }
+}
+
+/*
+ * Finds the recomposition result for
+ * a forward-combining "lead" character,
+ * specified with a pointer to its compositions list,
+ * and a backward-combining "trail" character.
+ *
+ * If the lead and trail characters combine, then this function returns
+ * the following "compositeAndFwd" value:
+ * Bits 21..1  composite character
+ * Bit      0  set if the composite is a forward-combining starter
+ * otherwise it returns -1.
+ *
+ * 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.
+ *
+ * The list is sorted by ascending trail characters (there are no duplicates).
+ * A linear search is used.
+ *
+ * See normalizer2impl.h for a more detailed description
+ * of the compositions list format.
+ */
+int32_t Normalizer2Impl::combine(const uint16_t *list, UChar32 trail) {
+    uint16_t key1, firstUnit;
+    if(trail<COMP_1_TRAIL_LIMIT) {
+        // trail character is 0..33FF
+        // result entry may have 2 or 3 units
+        key1=(uint16_t)(trail<<1);
+        while(key1>(firstUnit=*list)) {
+            list+=2+(firstUnit&COMP_1_TRIPLE);
+        }
+        if(key1==(firstUnit&COMP_1_TRAIL_MASK)) {
+            if(firstUnit&COMP_1_TRIPLE) {
+                return ((int32_t)list[1]<<16)|list[2];
+            } else {
+                return list[1];
+            }
+        }
+    } else {
+        // trail character is 3400..10FFFF
+        // result entry has 3 units
+        key1=(uint16_t)(COMP_1_TRAIL_LIMIT+
+                        (((trail>>COMP_1_TRAIL_SHIFT))&
+                          ~COMP_1_TRIPLE));
+        uint16_t key2=(uint16_t)(trail<<COMP_2_TRAIL_SHIFT);
+        uint16_t secondUnit;
+        for(;;) {
+            if(key1>(firstUnit=*list)) {
+                list+=2+(firstUnit&COMP_1_TRIPLE);
+            } else if(key1==(firstUnit&COMP_1_TRAIL_MASK)) {
+                if(key2>(secondUnit=list[1])) {
+                    if(firstUnit&COMP_1_LAST_TUPLE) {
+                        break;
+                    } else {
+                        list+=3;
+                    }
+                } else if(key2==(secondUnit&COMP_2_TRAIL_MASK)) {
+                    return ((int32_t)(secondUnit&~COMP_2_TRAIL_MASK)<<16)|list[2];
+                } else {
+                    break;
+                }
+            } else {
+                break;
+            }
+        }
+    }
+    return -1;
+}
+
+/**
+  * @param list some character's compositions list
+  * @param set recursively receives the composites from these compositions
+  */
+void Normalizer2Impl::addComposites(const uint16_t *list, UnicodeSet &set) const {
+    uint16_t firstUnit;
+    int32_t compositeAndFwd;
+    do {
+        firstUnit=*list;
+        if((firstUnit&COMP_1_TRIPLE)==0) {
+            compositeAndFwd=list[1];
+            list+=2;
+        } else {
+            compositeAndFwd=(((int32_t)list[1]&~COMP_2_TRAIL_MASK)<<16)|list[2];
+            list+=3;
+        }
+        UChar32 composite=compositeAndFwd>>1;
+        if((compositeAndFwd&1)!=0) {
+            addComposites(getCompositionsListForComposite(getNorm16(composite)), set);
+        }
+        set.add(composite);
+    } while((firstUnit&COMP_1_LAST_TUPLE)==0);
+}
+
+/*
+ * 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.
+ */
+void Normalizer2Impl::recompose(ReorderingBuffer &buffer, int32_t recomposeStartIndex,
+                                UBool onlyContiguous) const {
+    UChar *p=buffer.getStart()+recomposeStartIndex;
+    UChar *limit=buffer.getLimit();
+    if(p==limit) {
+        return;
+    }
+
+    UChar *starter, *pRemove, *q, *r;
+    const uint16_t *compositionsList;
+    UChar32 c, compositeAndFwd;
+    uint16_t norm16;
+    uint8_t cc, prevCC;
+    UBool 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=NULL;  // used as indicator for whether we have a forward-combining starter
+    starter=NULL;
+    starterIsSupplementary=FALSE;
+    prevCC=0;
+
+    for(;;) {
+        UTRIE2_U16_NEXT16(normTrie, p, limit, c, norm16);
+        cc=getCCFromYesOrMaybe(norm16);
+        if( // this character combines backward and
+            isMaybe(norm16) &&
+            // we have seen a starter that combines forward and
+            compositionsList!=NULL &&
+            // 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.
+                    UChar prev=(UChar)(*starter-Hangul::JAMO_L_BASE);
+                    if(prev<Hangul::JAMO_L_COUNT) {
+                        pRemove=p-1;
+                        UChar syllable=(UChar)
+                            (Hangul::HANGUL_BASE+
+                             (prev*Hangul::JAMO_V_COUNT+(c-Hangul::JAMO_V_BASE))*
+                             Hangul::JAMO_T_COUNT);
+                        UChar t;
+                        if(p!=limit && (t=(UChar)(*p-Hangul::JAMO_T_BASE))<Hangul::JAMO_T_COUNT) {
+                            ++p;
+                            syllable+=t;  // The next character was a Jamo T.
+                        }
+                        *starter=syllable;
+                        // remove the Jamo V/T
+                        q=pRemove;
+                        r=p;
+                        while(r<limit) {
+                            *q++=*r++;
+                        }
+                        limit=q;
+                        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==limit) {
+                    break;
+                }
+                compositionsList=NULL;
+                continue;
+            } else if((compositeAndFwd=combine(compositionsList, c))>=0) {
+                // The starter and the combining mark (c) do combine.
+                UChar32 composite=compositeAndFwd>>1;
+
+                // Replace the starter with the composite, remove the combining mark.
+                pRemove=p-U16_LENGTH(c);  // pRemove & p: start & limit of the combining mark
+                if(starterIsSupplementary) {
+                    if(U_IS_SUPPLEMENTARY(composite)) {
+                        // both are supplementary
+                        starter[0]=U16_LEAD(composite);
+                        starter[1]=U16_TRAIL(composite);
+                    } else {
+                        *starter=(UChar)composite;
+                        // The composite is shorter than the starter,
+                        // move the intermediate characters forward one.
+                        starterIsSupplementary=FALSE;
+                        q=starter+1;
+                        r=q+1;
+                        while(r<pRemove) {
+                            *q++=*r++;
+                        }
+                        --pRemove;
+                    }
+                } else if(U_IS_SUPPLEMENTARY(composite)) {
+                    // The composite is longer than the starter,
+                    // move the intermediate characters back one.
+                    starterIsSupplementary=TRUE;
+                    ++starter;  // temporarily increment for the loop boundary
+                    q=pRemove;
+                    r=++pRemove;
+                    while(starter<q) {
+                        *--r=*--q;
+                    }
+                    *starter=U16_TRAIL(composite);
+                    *--starter=U16_LEAD(composite);  // undo the temporary increment
+                } else {
+                    // both are on the BMP
+                    *starter=(UChar)composite;
+                }
+
+                /* remove the combining mark by moving the following text over it */
+                if(pRemove<p) {
+                    q=pRemove;
+                    r=p;
+                    while(r<limit) {
+                        *q++=*r++;
+                    }
+                    limit=q;
+                    p=pRemove;
+                }
+                // Keep prevCC because we removed the combining mark.
+
+                if(p==limit) {
+                    break;
+                }
+                // Is the composite a starter that combines forward?
+                if(compositeAndFwd&1) {
+                    compositionsList=
+                        getCompositionsListForComposite(getNorm16(composite));
+                } else {
+                    compositionsList=NULL;
+                }
+
+                // We combined; continue with looking for compositions.
+                continue;
+            }
+        }
+
+        // no combination this time
+        prevCC=cc;
+        if(p==limit) {
+            break;
+        }
+
+        // If c did not combine, then check if it is a starter.
+        if(cc==0) {
+            // Found a new starter.
+            if((compositionsList=getCompositionsListForDecompYes(norm16))!=NULL) {
+                // It may combine with something, prepare for it.
+                if(U_IS_BMP(c)) {
+                    starterIsSupplementary=FALSE;
+                    starter=p-1;
+                } else {
+                    starterIsSupplementary=TRUE;
+                    starter=p-2;
+                }
+            }
+        } else if(onlyContiguous) {
+            // FCC: no discontiguous compositions; any intervening character blocks.
+            compositionsList=NULL;
+        }
+    }
+    buffer.setReorderingLimit(limit);
+}
+
+// Very similar to composeQuickCheck(): Make the same changes in both places if relevant.
+// doCompose: normalize
+// !doCompose: isNormalized (buffer must be empty and initialized)
+UBool
+Normalizer2Impl::compose(const UChar *src, const UChar *limit,
+                         UBool onlyContiguous,
+                         UBool doCompose,
+                         ReorderingBuffer &buffer,
+                         UErrorCode &errorCode) const {
+    /*
+     * prevBoundary points to the last character before the current one
+     * that has a composition boundary before it with ccc==0 and quick check "yes".
+     * Keeping track of prevBoundary saves us looking for a composition boundary
+     * when we find a "no" or "maybe".
+     *
+     * When we back out from prevSrc back to prevBoundary,
+     * then we also remove those same characters (which had been simply copied
+     * or canonically-order-inserted) from the ReorderingBuffer.
+     * Therefore, at all times, the [prevBoundary..prevSrc[ source units
+     * must correspond 1:1 to destination units at the end of the destination buffer.
+     */
+    const UChar *prevBoundary=src;
+    UChar32 minNoMaybeCP=minCompNoMaybeCP;
+    if(limit==NULL) {
+        src=copyLowPrefixFromNulTerminated(src, minNoMaybeCP,
+                                           doCompose ? &buffer : NULL,
+                                           errorCode);
+        if(U_FAILURE(errorCode)) {
+            return FALSE;
+        }
+        if(prevBoundary<src) {
+            // Set prevBoundary to the last character in the prefix.
+            prevBoundary=src-1;
+        }
+        limit=u_strchr(src, 0);
+    }
+
+    const UChar *prevSrc;
+    UChar32 c=0;
+    uint16_t norm16=0;
+
+    // only for isNormalized
+    uint8_t prevCC=0;
+
+    for(;;) {
+        // count code units below the minimum or with irrelevant data for the quick check
+        for(prevSrc=src; src!=limit;) {
+            if( (c=*src)<minNoMaybeCP ||
+                isCompYesAndZeroCC(norm16=UTRIE2_GET16_FROM_U16_SINGLE_LEAD(normTrie, c))
+            ) {
+                ++src;
+            } else if(!U16_IS_SURROGATE(c)) {
+                break;
+            } else {
+                UChar c2;
+                if(U16_IS_SURROGATE_LEAD(c)) {
+                    if((src+1)!=limit && U16_IS_TRAIL(c2=src[1])) {
+                        c=U16_GET_SUPPLEMENTARY(c, c2);
+                    }
+                } else /* trail surrogate */ {
+                    if(prevSrc<src && U16_IS_LEAD(c2=*(src-1))) {
+                        --src;
+                        c=U16_GET_SUPPLEMENTARY(c2, c);
+                    }
+                }
+                if(isCompYesAndZeroCC(norm16=getNorm16(c))) {
+                    src+=U16_LENGTH(c);
+                } else {
+                    break;
+                }
+            }
+        }
+        // copy these code units all at once
+        if(src!=prevSrc) {
+            if(doCompose) {
+                if(!buffer.appendZeroCC(prevSrc, src, errorCode)) {
+                    break;
+                }
+            } else {
+                prevCC=0;
+            }
+            if(src==limit) {
+                break;
+            }
+            // Set prevBoundary to the last character in the quick check loop.
+            prevBoundary=src-1;
+            if( U16_IS_TRAIL(*prevBoundary) && prevSrc<prevBoundary &&
+                U16_IS_LEAD(*(prevBoundary-1))
+            ) {
+                --prevBoundary;
+            }
+            // The start of the current character (c).
+            prevSrc=src;
+        } else if(src==limit) {
+            break;
+        }
+
+        src+=U16_LENGTH(c);
+        /*
+         * isCompYesAndZeroCC(norm16) is false, that is, norm16>=minNoNo.
+         * c is either a "noNo" (has a mapping) or a "maybeYes" (combines backward)
+         * or has ccc!=0.
+         * Check for Jamo V/T, then for regular characters.
+         * c is not a Hangul syllable or Jamo L because those have "yes" properties.
+         */
+        if(isJamoVT(norm16) && prevBoundary!=prevSrc) {
+            UChar prev=*(prevSrc-1);
+            UBool needToDecompose=FALSE;
+            if(c<Hangul::JAMO_T_BASE) {
+                // c is a Jamo Vowel, compose with previous Jamo L and following Jamo T.
+                prev=(UChar)(prev-Hangul::JAMO_L_BASE);
+                if(prev<Hangul::JAMO_L_COUNT) {
+                    if(!doCompose) {
+                        return FALSE;
+                    }
+                    UChar syllable=(UChar)
+                        (Hangul::HANGUL_BASE+
+                         (prev*Hangul::JAMO_V_COUNT+(c-Hangul::JAMO_V_BASE))*
+                         Hangul::JAMO_T_COUNT);
+                    UChar t;
+                    if(src!=limit && (t=(UChar)(*src-Hangul::JAMO_T_BASE))<Hangul::JAMO_T_COUNT) {
+                        ++src;
+                        syllable+=t;  // The next character was a Jamo T.
+                        prevBoundary=src;
+                        buffer.setLastChar(syllable);
+                        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 -- or else our replacing
+                    // two input characters (L+V) with one output character (LV syllable)
+                    // would violate the invariant that [prevBoundary..prevSrc[ has the same
+                    // length as what we appended to the buffer since prevBoundary.
+                    needToDecompose=TRUE;
+                }
+            } else if(Hangul::isHangulWithoutJamoT(prev)) {
+                // c is a Jamo Trailing consonant,
+                // compose with previous Hangul LV that does not contain a Jamo T.
+                if(!doCompose) {
+                    return FALSE;
+                }
+                buffer.setLastChar((UChar)(prev+c-Hangul::JAMO_T_BASE));
+                prevBoundary=src;
+                continue;
+            }
+            if(!needToDecompose) {
+                // The Jamo V/T did not compose into a Hangul syllable.
+                if(doCompose) {
+                    if(!buffer.appendBMP((UChar)c, 0, errorCode)) {
+                        break;
+                    }
+                } else {
+                    prevCC=0;
+                }
+                continue;
+            }
+        }
+        /*
+         * Source buffer pointers:
+         *
+         *  all done      quick check   current char  not yet
+         *                "yes" but     (c)           processed
+         *                may combine
+         *                forward
+         * [-------------[-------------[-------------[-------------[
+         * |             |             |             |             |
+         * orig. src     prevBoundary  prevSrc       src           limit
+         *
+         *
+         * Destination buffer pointers inside the ReorderingBuffer:
+         *
+         *  all done      might take    not filled yet
+         *                characters for
+         *                reordering
+         * [-------------[-------------[-------------[
+         * |             |             |             |
+         * start         reorderStart  limit         |
+         *                             +remainingCap.+
+         */
+        if(norm16>=MIN_YES_YES_WITH_CC) {
+            uint8_t cc=(uint8_t)norm16;  // cc!=0
+            if( onlyContiguous &&  // FCC
+                (doCompose ? buffer.getLastCC() : prevCC)==0 &&
+                prevBoundary<prevSrc &&
+                // buffer.getLastCC()==0 && prevBoundary<prevSrc tell us that
+                // [prevBoundary..prevSrc[ (which is exactly one character under these conditions)
+                // passed the quick check "yes && ccc==0" test.
+                // Check whether the last character was a "yesYes" or a "yesNo".
+                // If a "yesNo", then we get its trailing ccc from its
+                // mapping and check for canonical order.
+                // All other cases are ok.
+                getTrailCCFromCompYesAndZeroCC(prevBoundary, prevSrc)>cc
+            ) {
+                // Fails FCD test, need to decompose and contiguously recompose.
+                if(!doCompose) {
+                    return FALSE;
+                }
+            } else if(doCompose) {
+                if(!buffer.append(c, cc, errorCode)) {
+                    break;
+                }
+                continue;
+            } else if(prevCC<=cc) {
+                prevCC=cc;
+                continue;
+            } else {
+                return FALSE;
+            }
+        } else if(!doCompose && !isMaybeOrNonZeroCC(norm16)) {
+            return FALSE;
+        }
+
+        /*
+         * Find appropriate boundaries around this character,
+         * decompose the source text from between the boundaries,
+         * and recompose it.
+         *
+         * We may need to remove the last few characters from the ReorderingBuffer
+         * to account for source text that was copied or appended
+         * but needs to take part in the recomposition.
+         */
+
+        /*
+         * Find the last composition boundary in [prevBoundary..src[.
+         * It is either the decomposition of the current character (at prevSrc),
+         * or prevBoundary.
+         */
+        if(hasCompBoundaryBefore(c, norm16)) {
+            prevBoundary=prevSrc;
+        } else if(doCompose) {
+            buffer.removeSuffix((int32_t)(prevSrc-prevBoundary));
+        }
+
+        // Find the next composition boundary in [src..limit[ -
+        // modifies src to point to the next starter.
+        src=(UChar *)findNextCompBoundary(src, limit);
+
+        // Decompose [prevBoundary..src[ into the buffer and then recompose that part of it.
+        int32_t recomposeStartIndex=buffer.length();
+        if(!decomposeShort(prevBoundary, src, buffer, errorCode)) {
+            break;
+        }
+        recompose(buffer, recomposeStartIndex, onlyContiguous);
+        if(!doCompose) {
+            if(!buffer.equals(prevBoundary, src)) {
+                return FALSE;
+            }
+            buffer.remove();
+            prevCC=0;
+        }
+
+        // Move to the next starter. We never need to look back before this point again.
+        prevBoundary=src;
+    }
+    return TRUE;
+}
+
+// Very similar to compose(): Make the same changes in both places if relevant.
+// pQCResult==NULL: spanQuickCheckYes
+// pQCResult!=NULL: quickCheck (*pQCResult must be UNORM_YES)
+const UChar *
+Normalizer2Impl::composeQuickCheck(const UChar *src, const UChar *limit,
+                                   UBool onlyContiguous,
+                                   UNormalizationCheckResult *pQCResult) const {
+    /*
+     * prevBoundary points to the last character before the current one
+     * that has a composition boundary before it with ccc==0 and quick check "yes".
+     */
+    const UChar *prevBoundary=src;
+    UChar32 minNoMaybeCP=minCompNoMaybeCP;
+    if(limit==NULL) {
+        UErrorCode errorCode=U_ZERO_ERROR;
+        src=copyLowPrefixFromNulTerminated(src, minNoMaybeCP, NULL, errorCode);
+        if(prevBoundary<src) {
+            // Set prevBoundary to the last character in the prefix.
+            prevBoundary=src-1;
+        }
+        limit=u_strchr(src, 0);
+    }
+
+    const UChar *prevSrc;
+    UChar32 c=0;
+    uint16_t norm16=0;
+    uint8_t prevCC=0;
+
+    for(;;) {
+        // count code units below the minimum or with irrelevant data for the quick check
+        for(prevSrc=src;;) {
+            if(src==limit) {
+                return src;
+            }
+            if( (c=*src)<minNoMaybeCP ||
+                isCompYesAndZeroCC(norm16=UTRIE2_GET16_FROM_U16_SINGLE_LEAD(normTrie, c))
+            ) {
+                ++src;
+            } else if(!U16_IS_SURROGATE(c)) {
+                break;
+            } else {
+                UChar c2;
+                if(U16_IS_SURROGATE_LEAD(c)) {
+                    if((src+1)!=limit && U16_IS_TRAIL(c2=src[1])) {
+                        c=U16_GET_SUPPLEMENTARY(c, c2);
+                    }
+                } else /* trail surrogate */ {
+                    if(prevSrc<src && U16_IS_LEAD(c2=*(src-1))) {
+                        --src;
+                        c=U16_GET_SUPPLEMENTARY(c2, c);
+                    }
+                }
+                if(isCompYesAndZeroCC(norm16=getNorm16(c))) {
+                    src+=U16_LENGTH(c);
+                } else {
+                    break;
+                }
+            }
+        }
+        if(src!=prevSrc) {
+            // Set prevBoundary to the last character in the quick check loop.
+            prevBoundary=src-1;
+            if( U16_IS_TRAIL(*prevBoundary) && prevSrc<prevBoundary &&
+                U16_IS_LEAD(*(prevBoundary-1))
+            ) {
+                --prevBoundary;
+            }
+            prevCC=0;
+            // The start of the current character (c).
+            prevSrc=src;
+        }
+
+        src+=U16_LENGTH(c);
+        /*
+         * isCompYesAndZeroCC(norm16) is false, that is, norm16>=minNoNo.
+         * c is either a "noNo" (has a mapping) or a "maybeYes" (combines backward)
+         * or has ccc!=0.
+         */
+        if(isMaybeOrNonZeroCC(norm16)) {
+            uint8_t cc=getCCFromYesOrMaybe(norm16);
+            if( onlyContiguous &&  // FCC
+                cc!=0 &&
+                prevCC==0 &&
+                prevBoundary<prevSrc &&
+                // prevCC==0 && prevBoundary<prevSrc tell us that
+                // [prevBoundary..prevSrc[ (which is exactly one character under these conditions)
+                // passed the quick check "yes && ccc==0" test.
+                // Check whether the last character was a "yesYes" or a "yesNo".
+                // If a "yesNo", then we get its trailing ccc from its
+                // mapping and check for canonical order.
+                // All other cases are ok.
+                getTrailCCFromCompYesAndZeroCC(prevBoundary, prevSrc)>cc
+            ) {
+                // Fails FCD test.
+            } else if(prevCC<=cc || cc==0) {
+                prevCC=cc;
+                if(norm16<MIN_YES_YES_WITH_CC) {
+                    if(pQCResult!=NULL) {
+                        *pQCResult=UNORM_MAYBE;
+                    } else {
+                        return prevBoundary;
+                    }
+                }
+                continue;
+            }
+        }
+        if(pQCResult!=NULL) {
+            *pQCResult=UNORM_NO;
+        }
+        return prevBoundary;
+    }
+}
+
+void Normalizer2Impl::composeAndAppend(const UChar *src, const UChar *limit,
+                                       UBool doCompose,
+                                       UBool onlyContiguous,
+                                       ReorderingBuffer &buffer,
+                                       UErrorCode &errorCode) const {
+    if(!buffer.isEmpty()) {
+        const UChar *firstStarterInSrc=findNextCompBoundary(src, limit);
+        if(src!=firstStarterInSrc) {
+            const UChar *lastStarterInDest=findPreviousCompBoundary(buffer.getStart(),
+                                                                    buffer.getLimit());
+            UnicodeString middle(lastStarterInDest,
+                                 (int32_t)(buffer.getLimit()-lastStarterInDest));
+            buffer.removeSuffix((int32_t)(buffer.getLimit()-lastStarterInDest));
+            middle.append(src, (int32_t)(firstStarterInSrc-src));
+            const UChar *middleStart=middle.getBuffer();
+            compose(middleStart, middleStart+middle.length(), onlyContiguous,
+                    TRUE, buffer, errorCode);
+            if(U_FAILURE(errorCode)) {
+                return;
+            }
+            src=firstStarterInSrc;
+        }
+    }
+    if(doCompose) {
+        compose(src, limit, onlyContiguous, TRUE, buffer, errorCode);
+    } else {
+        buffer.appendZeroCC(src, limit, errorCode);
+    }
+}
+
+/**
+ * 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.
+ */
+UBool Normalizer2Impl::hasCompBoundaryBefore(UChar32 c, uint16_t norm16) const {
+    for(;;) {
+        if(isCompYesAndZeroCC(norm16)) {
+            return TRUE;
+        } else if(isMaybeOrNonZeroCC(norm16)) {
+            return FALSE;
+        } else if(isDecompNoAlgorithmic(norm16)) {
+            c=mapAlgorithmic(c, norm16);
+            norm16=getNorm16(c);
+        } else {
+            // c decomposes, get everything from the variable-length extra data
+            const uint16_t *mapping=getMapping(norm16);
+            uint16_t firstUnit=*mapping++;
+            if((firstUnit&MAPPING_LENGTH_MASK)==0) {
+                return FALSE;
+            }
+            if((firstUnit&MAPPING_HAS_CCC_LCCC_WORD) && (*mapping++&0xff00)) {
+                return FALSE;  // non-zero leadCC
+            }
+            int32_t i=0;
+            UChar32 c;
+            U16_NEXT_UNSAFE(mapping, i, c);
+            return isCompYesAndZeroCC(getNorm16(c));
+        }
+    }
+}
+
+UBool Normalizer2Impl::hasCompBoundaryAfter(UChar32 c, UBool onlyContiguous, UBool testInert) const {
+    for(;;) {
+        uint16_t norm16=getNorm16(c);
+        if(isInert(norm16)) {
+            return TRUE;
+        } else if(norm16<=minYesNo) {
+            // Hangul LVT (==minYesNo) has a boundary after it.
+            // Hangul LV and non-inert yesYes characters combine forward.
+            return isHangul(norm16) && !Hangul::isHangulWithoutJamoT((UChar)c);
+        } else if(norm16>= (testInert ? minNoNo : minMaybeYes)) {
+            return FALSE;
+        } else if(isDecompNoAlgorithmic(norm16)) {
+            c=mapAlgorithmic(c, norm16);
+        } else {
+            // c decomposes, get everything from the variable-length extra data.
+            // If testInert, then c must be a yesNo character which has lccc=0,
+            // otherwise it could be a noNo.
+            const uint16_t *mapping=getMapping(norm16);
+            uint16_t firstUnit=*mapping;
+            // TRUE if
+            //      c is not deleted, and
+            //      it and its decomposition do not combine forward, and it has a starter, and
+            //      if FCC then trailCC<=1
+            return
+                (firstUnit&MAPPING_LENGTH_MASK)!=0 &&
+                (firstUnit&(MAPPING_PLUS_COMPOSITION_LIST|MAPPING_NO_COMP_BOUNDARY_AFTER))==0 &&
+                (!onlyContiguous || firstUnit<=0x1ff);
+        }
+    }
+}
+
+const UChar *Normalizer2Impl::findPreviousCompBoundary(const UChar *start, const UChar *p) const {
+    BackwardUTrie2StringIterator iter(normTrie, start, p);
+    uint16_t norm16;
+    do {
+        norm16=iter.previous16();
+    } while(!hasCompBoundaryBefore(iter.codePoint, norm16));
+    // We could also test hasCompBoundaryAfter() and return iter.codePointLimit,
+    // but that's probably not worth the extra cost.
+    return iter.codePointStart;
+}
+
+const UChar *Normalizer2Impl::findNextCompBoundary(const UChar *p, const UChar *limit) const {
+    ForwardUTrie2StringIterator iter(normTrie, p, limit);
+    uint16_t norm16;
+    do {
+        norm16=iter.next16();
+    } while(!hasCompBoundaryBefore(iter.codePoint, norm16));
+    return iter.codePointStart;
+}
+
+class FCDTrieSingleton : public UTrie2Singleton {
+public:
+    FCDTrieSingleton(SimpleSingleton &s, Normalizer2Impl &ni, UErrorCode &ec) :
+        UTrie2Singleton(s), impl(ni), errorCode(ec) {}
+    UTrie2 *getInstance(UErrorCode &errorCode) {
+        return UTrie2Singleton::getInstance(createInstance, this, errorCode);
+    }
+    static void *createInstance(const void *context, UErrorCode &errorCode);
+    UBool rangeHandler(UChar32 start, UChar32 end, uint32_t value) {
+        if(value!=0) {
+            impl.setFCD16FromNorm16(start, end, (uint16_t)value, newFCDTrie, errorCode);
+        }
+        return U_SUCCESS(errorCode);
+    }
+
+    Normalizer2Impl &impl;
+    UTrie2 *newFCDTrie;
+    UErrorCode &errorCode;
+};
+
+U_CDECL_BEGIN
+
+// Set the FCD value for a range of same-norm16 characters.
+static UBool U_CALLCONV
+enumRangeHandler(const void *context, UChar32 start, UChar32 end, uint32_t value) {
+    return ((FCDTrieSingleton *)context)->rangeHandler(start, end, value);
+}
+
+// Collect (OR together) the FCD values for a range of supplementary characters,
+// for their lead surrogate code unit.
+static UBool U_CALLCONV
+enumRangeOrValue(const void *context, UChar32 /*start*/, UChar32 /*end*/, uint32_t value) {
+    *((uint32_t *)context)|=value;
+    return TRUE;
+}
+
+U_CDECL_END
+
+void *FCDTrieSingleton::createInstance(const void *context, UErrorCode &errorCode) {
+    FCDTrieSingleton *me=(FCDTrieSingleton *)context;
+    me->newFCDTrie=utrie2_open(0, 0, &errorCode);
+    if(U_SUCCESS(errorCode)) {
+        utrie2_enum(me->impl.getNormTrie(), NULL, enumRangeHandler, me);
+        for(UChar lead=0xd800; lead<0xdc00; ++lead) {
+            uint32_t oredValue=utrie2_get32(me->newFCDTrie, lead);
+            utrie2_enumForLeadSurrogate(me->newFCDTrie, lead, NULL, enumRangeOrValue, &oredValue);
+            if(oredValue!=0) {
+                // Set a "bad" value for makeFCD() to break the quick check loop
+                // and look up the value for the supplementary code point.
+                // If there is any lccc, then set the worst-case lccc of 1.
+                // The ORed-together value's tccc is already the worst case.
+                if(oredValue>0xff) {
+                    oredValue=0x100|(oredValue&0xff);
+                }
+                utrie2_set32ForLeadSurrogateCodeUnit(me->newFCDTrie, lead, oredValue, &errorCode);
+            }
+        }
+        utrie2_freeze(me->newFCDTrie, UTRIE2_16_VALUE_BITS, &errorCode);
+        if(U_SUCCESS(errorCode)) {
+            return me->newFCDTrie;
+        }
+    }
+    utrie2_close(me->newFCDTrie);
+    return NULL;
+}
+
+void Normalizer2Impl::setFCD16FromNorm16(UChar32 start, UChar32 end, uint16_t norm16,
+                                         UTrie2 *newFCDTrie, UErrorCode &errorCode) const {
+    // Only loops for 1:1 algorithmic mappings.
+    for(;;) {
+        if(norm16>=MIN_NORMAL_MAYBE_YES) {
+            norm16&=0xff;
+            norm16|=norm16<<8;
+        } else if(norm16<=minYesNo || minMaybeYes<=norm16) {
+            // no decomposition or Hangul syllable, all zeros
+            break;
+        } else if(limitNoNo<=norm16) {
+            int32_t delta=norm16-(minMaybeYes-MAX_DELTA-1);
+            if(start==end) {
+                start+=delta;
+                norm16=getNorm16(start);
+            } else {
+                // the same delta leads from different original characters to different mappings
+                do {
+                    UChar32 c=start+delta;
+                    setFCD16FromNorm16(c, c, getNorm16(c), newFCDTrie, errorCode);
+                } while(++start<=end);
+                break;
+            }
+        } else {
+            // c decomposes, get everything from the variable-length extra data
+            const uint16_t *mapping=getMapping(norm16);
+            uint16_t firstUnit=*mapping;
+            if((firstUnit&MAPPING_LENGTH_MASK)==0) {
+                // A character that is deleted (maps to an empty string) must
+                // get the worst-case lccc and tccc values because arbitrary
+                // characters on both sides will become adjacent.
+                norm16=0x1ff;
+            } else {
+                if(firstUnit&MAPPING_HAS_CCC_LCCC_WORD) {
+                    norm16=mapping[1]&0xff00;  // lccc
+                } else {
+                    norm16=0;
+                }
+                norm16|=firstUnit>>8;  // tccc
+            }
+        }
+        utrie2_setRange32(newFCDTrie, start, end, norm16, TRUE, &errorCode);
+        break;
+    }
+}
+
+const UTrie2 *Normalizer2Impl::getFCDTrie(UErrorCode &errorCode) const {
+    // Logically const: Synchronized instantiation.
+    Normalizer2Impl *me=const_cast<Normalizer2Impl *>(this);
+    return FCDTrieSingleton(me->fcdTrieSingleton, *me, errorCode).getInstance(errorCode);
+}
+
+// Dual functionality:
+// buffer!=NULL: normalize
+// buffer==NULL: isNormalized/quickCheck/spanQuickCheckYes
+const UChar *
+Normalizer2Impl::makeFCD(const UChar *src, const UChar *limit,
+                         ReorderingBuffer *buffer,
+                         UErrorCode &errorCode) const {
+    // Tracks the last FCD-safe boundary, before lccc=0 or after properly-ordered tccc<=1.
+    // Similar to the prevBoundary in the compose() implementation.
+    const UChar *prevBoundary=src;
+    int32_t prevFCD16=0;
+    if(limit==NULL) {
+        src=copyLowPrefixFromNulTerminated(src, MIN_CCC_LCCC_CP, buffer, errorCode);
+        if(U_FAILURE(errorCode)) {
+            return src;
+        }
+        if(prevBoundary<src) {
+            prevBoundary=src;
+            // We know that the previous character's lccc==0.
+            // Fetching the fcd16 value was deferred for this below-U+0300 code point.
+            prevFCD16=getFCD16FromSingleLead(*(src-1));
+            if(prevFCD16>1) {
+                --prevBoundary;
+            }
+        }
+        limit=u_strchr(src, 0);
+    }
+
+    // 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.
+
+    const UTrie2 *trie=fcdTrie();
+
+    const UChar *prevSrc;
+    UChar32 c=0;
+    uint16_t fcd16=0;
+
+    for(;;) {
+        // count code units with lccc==0
+        for(prevSrc=src; src!=limit;) {
+            if((c=*src)<MIN_CCC_LCCC_CP) {
+                prevFCD16=~c;
+                ++src;
+            } else if((fcd16=UTRIE2_GET16_FROM_U16_SINGLE_LEAD(trie, c))<=0xff) {
+                prevFCD16=fcd16;
+                ++src;
+            } else if(!U16_IS_SURROGATE(c)) {
+                break;
+            } else {
+                UChar c2;
+                if(U16_IS_SURROGATE_LEAD(c)) {
+                    if((src+1)!=limit && U16_IS_TRAIL(c2=src[1])) {
+                        c=U16_GET_SUPPLEMENTARY(c, c2);
+                    }
+                } else /* trail surrogate */ {
+                    if(prevSrc<src && U16_IS_LEAD(c2=*(src-1))) {
+                        --src;
+                        c=U16_GET_SUPPLEMENTARY(c2, c);
+                    }
+                }
+                if((fcd16=getFCD16(c))<=0xff) {
+                    prevFCD16=fcd16;
+                    src+=U16_LENGTH(c);
+                } else {
+                    break;
+                }
+            }
+        }
+        // copy these code units all at once
+        if(src!=prevSrc) {
+            if(buffer!=NULL && !buffer->appendZeroCC(prevSrc, src, errorCode)) {
+                break;
+            }
+            if(src==limit) {
+                break;
+            }
+            prevBoundary=src;
+            // We know that the previous character's lccc==0.
+            if(prevFCD16<0) {
+                // Fetching the fcd16 value was deferred for this below-U+0300 code point.
+                prevFCD16=getFCD16FromSingleLead((UChar)~prevFCD16);
+                if(prevFCD16>1) {
+                    --prevBoundary;
+                }
+            } else {
+                const UChar *p=src-1;
+                if(U16_IS_TRAIL(*p) && prevSrc<p && U16_IS_LEAD(*(p-1))) {
+                    --p;
+                    // Need to fetch the previous character's FCD value because
+                    // prevFCD16 was just for the trail surrogate code point.
+                    prevFCD16=getFCD16FromSurrogatePair(p[0], p[1]);
+                    // Still known to have lccc==0 because its lead surrogate unit had lccc==0.
+                }
+                if(prevFCD16>1) {
+                    prevBoundary=p;
+                }
+            }
+            // The start of the current character (c).
+            prevSrc=src;
+        } else if(src==limit) {
+            break;
+        }
+
+        src+=U16_LENGTH(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, errorCode)) {
+                break;
+            }
+            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((int32_t)(prevSrc-prevBoundary));
+            /*
+             * Find the part of the source that needs to be decomposed,
+             * up to the next safe boundary.
+             */
+            src=findNextFCDBoundary(src, limit);
+            /*
+             * The source text does not fulfill the conditions for FCD.
+             * Decompose and reorder a limited piece of the text.
+             */
+            if(!decomposeShort(prevBoundary, src, *buffer, errorCode)) {
+                break;
+            }
+            prevBoundary=src;
+            prevFCD16=0;
+        }
+    }
+    return src;
+}
+
+void Normalizer2Impl::makeFCDAndAppend(const UChar *src, const UChar *limit,
+                                       UBool doMakeFCD,
+                                       ReorderingBuffer &buffer,
+                                       UErrorCode &errorCode) const {
+    if(!buffer.isEmpty()) {
+        const UChar *firstBoundaryInSrc=findNextFCDBoundary(src, limit);
+        if(src!=firstBoundaryInSrc) {
+            const UChar *lastBoundaryInDest=findPreviousFCDBoundary(buffer.getStart(),
+                                                                    buffer.getLimit());
+            UnicodeString middle(lastBoundaryInDest,
+                                 (int32_t)(buffer.getLimit()-lastBoundaryInDest));
+            buffer.removeSuffix((int32_t)(buffer.getLimit()-lastBoundaryInDest));
+            middle.append(src, (int32_t)(firstBoundaryInSrc-src));
+            const UChar *middleStart=middle.getBuffer();
+            makeFCD(middleStart, middleStart+middle.length(), &buffer, errorCode);
+            if(U_FAILURE(errorCode)) {
+                return;
+            }
+            src=firstBoundaryInSrc;
+        }
+    }
+    if(doMakeFCD) {
+        makeFCD(src, limit, &buffer, errorCode);
+    } else {
+        buffer.appendZeroCC(src, limit, errorCode);
+    }
+}
+
+const UChar *Normalizer2Impl::findPreviousFCDBoundary(const UChar *start, const UChar *p) const {
+    BackwardUTrie2StringIterator iter(fcdTrie(), start, p);
+    uint16_t fcd16;
+    do {
+        fcd16=iter.previous16();
+    } while(fcd16>0xff);
+    return iter.codePointStart;
+}
+
+const UChar *Normalizer2Impl::findNextFCDBoundary(const UChar *p, const UChar *limit) const {
+    ForwardUTrie2StringIterator iter(fcdTrie(), p, limit);
+    uint16_t fcd16;
+    do {
+        fcd16=iter.next16();
+    } while(fcd16>0xff);
+    return iter.codePointStart;
+}
+
+// CanonicalIterator data -------------------------------------------------- ***
+
+CanonIterData::CanonIterData(UErrorCode &errorCode) :
+        trie(utrie2_open(0, 0, &errorCode)),
+        canonStartSets(uhash_deleteUObject, NULL, errorCode) {}
+
+CanonIterData::~CanonIterData() {
+    utrie2_close(trie);
+}
+
+void CanonIterData::addToStartSet(UChar32 origin, UChar32 decompLead, UErrorCode &errorCode) {
+    uint32_t canonValue=utrie2_get32(trie, decompLead);
+    if((canonValue&(CANON_HAS_SET|CANON_VALUE_MASK))==0 && origin!=0) {
+        // origin is the first character whose decomposition starts with
+        // the character for which we are setting the value.
+        utrie2_set32(trie, decompLead, canonValue|origin, &errorCode);
+    } else {
+        // origin is not the first character, or it is U+0000.
+        UnicodeSet *set;
+        if((canonValue&CANON_HAS_SET)==0) {
+            set=new UnicodeSet;
+            if(set==NULL) {
+                errorCode=U_MEMORY_ALLOCATION_ERROR;
+                return;
+            }
+            UChar32 firstOrigin=(UChar32)(canonValue&CANON_VALUE_MASK);
+            canonValue=(canonValue&~CANON_VALUE_MASK)|CANON_HAS_SET|(uint32_t)canonStartSets.size();
+            utrie2_set32(trie, decompLead, canonValue, &errorCode);
+            canonStartSets.addElement(set, errorCode);
+            if(firstOrigin!=0) {
+                set->add(firstOrigin);
+            }
+        } else {
+            set=(UnicodeSet *)canonStartSets[(int32_t)(canonValue&CANON_VALUE_MASK)];
+        }
+        set->add(origin);
+    }
+}
+
+class CanonIterDataSingleton {
+public:
+    CanonIterDataSingleton(SimpleSingleton &s, Normalizer2Impl &ni, UErrorCode &ec) :
+        singleton(s), impl(ni), errorCode(ec) {}
+    CanonIterData *getInstance(UErrorCode &errorCode) {
+        void *duplicate;
+        CanonIterData *instance=
+            (CanonIterData *)singleton.getInstance(createInstance, this, duplicate, errorCode);
+        delete (CanonIterData *)duplicate;
+        return instance;
+    }
+    static void *createInstance(const void *context, UErrorCode &errorCode);
+    UBool rangeHandler(UChar32 start, UChar32 end, uint32_t value) {
+        if(value!=0) {
+            impl.makeCanonIterDataFromNorm16(start, end, (uint16_t)value, *newData, errorCode);
+        }
+        return U_SUCCESS(errorCode);
+    }
+
+private:
+    SimpleSingleton &singleton;
+    Normalizer2Impl &impl;
+    CanonIterData *newData;
+    UErrorCode &errorCode;
+};
+
+U_CDECL_BEGIN
+
+// Call Normalizer2Impl::makeCanonIterDataFromNorm16() for a range of same-norm16 characters.
+static UBool U_CALLCONV
+enumCIDRangeHandler(const void *context, UChar32 start, UChar32 end, uint32_t value) {
+    return ((CanonIterDataSingleton *)context)->rangeHandler(start, end, value);
+}
+
+U_CDECL_END
+
+void *CanonIterDataSingleton::createInstance(const void *context, UErrorCode &errorCode) {
+    CanonIterDataSingleton *me=(CanonIterDataSingleton *)context;
+    me->newData=new CanonIterData(errorCode);
+    if(me->newData==NULL) {
+        errorCode=U_MEMORY_ALLOCATION_ERROR;
+        return NULL;
+    }
+    if(U_SUCCESS(errorCode)) {
+        utrie2_enum(me->impl.getNormTrie(), NULL, enumCIDRangeHandler, me);
+        utrie2_freeze(me->newData->trie, UTRIE2_32_VALUE_BITS, &errorCode);
+        if(U_SUCCESS(errorCode)) {
+            return me->newData;
+        }
+    }
+    delete me->newData;
+    return NULL;
+}
+
+void Normalizer2Impl::makeCanonIterDataFromNorm16(UChar32 start, UChar32 end, uint16_t norm16,
+                                                  CanonIterData &newData,
+                                                  UErrorCode &errorCode) const {
+    if(norm16==0 || (minYesNo<=norm16 && norm16<minNoNo)) {
+        // Inert, or 2-way mapping (including Hangul syllable).
+        // We do not write a canonStartSet for any yesNo character.
+        // Composites from 2-way mappings are added at runtime from the
+        // starter's compositions list, and the other characters in
+        // 2-way mappings get CANON_NOT_SEGMENT_STARTER set because they are
+        // "maybe" characters.
+        return;
+    }
+    for(UChar32 c=start; c<=end; ++c) {
+        uint32_t oldValue=utrie2_get32(newData.trie, c);
+        uint32_t newValue=oldValue;
+        if(norm16>=minMaybeYes) {
+            // not a segment starter if it occurs in a decomposition or has cc!=0
+            newValue|=CANON_NOT_SEGMENT_STARTER;
+            if(norm16<MIN_NORMAL_MAYBE_YES) {
+                newValue|=CANON_HAS_COMPOSITIONS;
+            }
+        } else if(norm16<minYesNo) {
+            newValue|=CANON_HAS_COMPOSITIONS;
+        } else {
+            // c has a one-way decomposition
+            UChar32 c2=c;
+            uint16_t norm16_2=norm16;
+            while(limitNoNo<=norm16_2 && norm16_2<minMaybeYes) {
+                c2=mapAlgorithmic(c2, norm16_2);
+                norm16_2=getNorm16(c2);
+            }
+            if(minYesNo<=norm16_2 && norm16_2<limitNoNo) {
+                // c decomposes, get everything from the variable-length extra data
+                const uint16_t *mapping=getMapping(norm16_2);
+                uint16_t firstUnit=*mapping++;
+                int32_t length=firstUnit&MAPPING_LENGTH_MASK;
+                if((firstUnit&MAPPING_HAS_CCC_LCCC_WORD)!=0) {
+                    if(c==c2 && (*mapping&0xff)!=0) {
+                        newValue|=CANON_NOT_SEGMENT_STARTER;  // original c has cc!=0
+                    }
+                    ++mapping;
+                }
+                // Skip empty mappings (no characters in the decomposition).
+                if(length!=0) {
+                    // add c to first code point's start set
+                    int32_t i=0;
+                    U16_NEXT_UNSAFE(mapping, i, c2);
+                    newData.addToStartSet(c, c2, errorCode);
+                    // Set CANON_NOT_SEGMENT_STARTER for each remaining code point of a
+                    // one-way mapping. A 2-way mapping is possible here after
+                    // intermediate algorithmic mapping.
+                    if(norm16_2>=minNoNo) {
+                        while(i<length) {
+                            U16_NEXT_UNSAFE(mapping, i, c2);
+                            uint32_t c2Value=utrie2_get32(newData.trie, c2);
+                            if((c2Value&CANON_NOT_SEGMENT_STARTER)==0) {
+                                utrie2_set32(newData.trie, c2, c2Value|CANON_NOT_SEGMENT_STARTER,
+                                             &errorCode);
+                            }
+                        }
+                    }
+                }
+            } else {
+                // c decomposed to c2 algorithmically; c has cc==0
+                newData.addToStartSet(c, c2, errorCode);
+            }
+        }
+        if(newValue!=oldValue) {
+            utrie2_set32(newData.trie, c, newValue, &errorCode);
+        }
+    }
+}
+
+UBool Normalizer2Impl::ensureCanonIterData(UErrorCode &errorCode) const {
+    // Logically const: Synchronized instantiation.
+    Normalizer2Impl *me=const_cast<Normalizer2Impl *>(this);
+    CanonIterDataSingleton(me->canonIterDataSingleton, *me, errorCode).getInstance(errorCode);
+    return U_SUCCESS(errorCode);
+}
+
+int32_t Normalizer2Impl::getCanonValue(UChar32 c) const {
+    return (int32_t)utrie2_get32(((CanonIterData *)canonIterDataSingleton.fInstance)->trie, c);
+}
+
+const UnicodeSet &Normalizer2Impl::getCanonStartSet(int32_t n) const {
+    return *(const UnicodeSet *)(
+        ((CanonIterData *)canonIterDataSingleton.fInstance)->canonStartSets[n]);
+}
+
+UBool Normalizer2Impl::isCanonSegmentStarter(UChar32 c) const {
+    return getCanonValue(c)>=0;
+}
+
+UBool Normalizer2Impl::getCanonStartSet(UChar32 c, UnicodeSet &set) const {
+    int32_t canonValue=getCanonValue(c)&~CANON_NOT_SEGMENT_STARTER;
+    if(canonValue==0) {
+        return FALSE;
+    }
+    set.clear();
+    int32_t value=canonValue&CANON_VALUE_MASK;
+    if((canonValue&CANON_HAS_SET)!=0) {
+        set.addAll(getCanonStartSet(value));
+    } else if(value!=0) {
+        set.add(value);
+    }
+    if((canonValue&CANON_HAS_COMPOSITIONS)!=0) {
+        uint16_t norm16=getNorm16(c);
+        if(norm16==JAMO_L) {
+            UChar32 syllable=
+                (UChar32)(Hangul::HANGUL_BASE+(c-Hangul::JAMO_L_BASE)*Hangul::JAMO_VT_COUNT);
+            set.add(syllable, syllable+Hangul::JAMO_VT_COUNT-1);
+        } else {
+            addComposites(getCompositionsList(norm16), set);
+        }
+    }
+    return TRUE;
+}
+
+U_NAMESPACE_END
+
+// Normalizer2 data swapping ----------------------------------------------- ***
+
+U_NAMESPACE_USE
+
+U_CAPI int32_t U_EXPORT2
+unorm2_swap(const UDataSwapper *ds,
+            const void *inData, int32_t length, void *outData,
+            UErrorCode *pErrorCode) {
+    const UDataInfo *pInfo;
+    int32_t headerSize;
+
+    const uint8_t *inBytes;
+    uint8_t *outBytes;
+
+    const int32_t *inIndexes;
+    int32_t indexes[Normalizer2Impl::IX_MIN_MAYBE_YES+1];
+
+    int32_t i, offset, nextOffset, size;
+
+    /* udata_swapDataHeader checks the arguments */
+    headerSize=udata_swapDataHeader(ds, inData, length, outData, pErrorCode);
+    if(pErrorCode==NULL || U_FAILURE(*pErrorCode)) {
+        return 0;
+    }
+
+    /* check data format and format version */
+    pInfo=(const UDataInfo *)((const char *)inData+4);
+    if(!(
+        pInfo->dataFormat[0]==0x4e &&   /* dataFormat="Nrm2" */
+        pInfo->dataFormat[1]==0x72 &&
+        pInfo->dataFormat[2]==0x6d &&
+        pInfo->dataFormat[3]==0x32 &&
+        pInfo->formatVersion[0]==1
+    )) {
+        udata_printError(ds, "unorm2_swap(): data format %02x.%02x.%02x.%02x (format version %02x) is not recognized as Normalizer2 data\n",
+                         pInfo->dataFormat[0], pInfo->dataFormat[1],
+                         pInfo->dataFormat[2], pInfo->dataFormat[3],
+                         pInfo->formatVersion[0]);
+        *pErrorCode=U_UNSUPPORTED_ERROR;
+        return 0;
+    }
+
+    inBytes=(const uint8_t *)inData+headerSize;
+    outBytes=(uint8_t *)outData+headerSize;
+
+    inIndexes=(const int32_t *)inBytes;
+
+    if(length>=0) {
+        length-=headerSize;
+        if(length<(int32_t)sizeof(indexes)) {
+            udata_printError(ds, "unorm2_swap(): too few bytes (%d after header) for Normalizer2 data\n",
+                             length);
+            *pErrorCode=U_INDEX_OUTOFBOUNDS_ERROR;
+            return 0;
+        }
+    }
+
+    /* read the first few indexes */
+    for(i=0; i<=Normalizer2Impl::IX_MIN_MAYBE_YES; ++i) {
+        indexes[i]=udata_readInt32(ds, inIndexes[i]);
+    }
+
+    /* get the total length of the data */
+    size=indexes[Normalizer2Impl::IX_TOTAL_SIZE];
+
+    if(length>=0) {
+        if(length<size) {
+            udata_printError(ds, "unorm2_swap(): too few bytes (%d after header) for all of Normalizer2 data\n",
+                             length);
+            *pErrorCode=U_INDEX_OUTOFBOUNDS_ERROR;
+            return 0;
+        }
+
+        /* copy the data for inaccessible bytes */
+        if(inBytes!=outBytes) {
+            uprv_memcpy(outBytes, inBytes, size);
+        }
+
+        offset=0;
+
+        /* swap the int32_t indexes[] */
+        nextOffset=indexes[Normalizer2Impl::IX_NORM_TRIE_OFFSET];
+        ds->swapArray32(ds, inBytes, nextOffset-offset, outBytes, pErrorCode);
+        offset=nextOffset;
+
+        /* swap the UTrie2 */
+        nextOffset=indexes[Normalizer2Impl::IX_EXTRA_DATA_OFFSET];
+        utrie2_swap(ds, inBytes+offset, nextOffset-offset, outBytes+offset, pErrorCode);
+        offset=nextOffset;
+
+        /* swap the uint16_t extraData[] */
+        nextOffset=indexes[Normalizer2Impl::IX_EXTRA_DATA_OFFSET+1];
+        ds->swapArray16(ds, inBytes+offset, nextOffset-offset, outBytes+offset, pErrorCode);
+        offset=nextOffset;
+
+        U_ASSERT(offset==size);
+    }
+
+    return headerSize+size;
+}
+
+#endif  // !UCONFIG_NO_NORMALIZATION