Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1683 insertions, 0 deletions

diff --git a/intl/icu/source/i18n/collationdatabuilder.cpp b/intl/icu/source/i18n/collationdatabuilder.cpp
new file mode 100644
index 0000000000..7c6f1b881e
--- /dev/null
+++ b/intl/icu/source/i18n/collationdatabuilder.cpp
@@ -0,0 +1,1683 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+*******************************************************************************
+* Copyright (C) 2012-2015, International Business Machines
+* Corporation and others.  All Rights Reserved.
+*******************************************************************************
+* collationdatabuilder.cpp
+*
+* (replaced the former ucol_elm.cpp)
+*
+* created on: 2012apr01
+* created by: Markus W. Scherer
+*/
+
+#include "unicode/utypes.h"
+
+#if !UCONFIG_NO_COLLATION
+
+#include "unicode/localpointer.h"
+#include "unicode/uchar.h"
+#include "unicode/ucharstrie.h"
+#include "unicode/ucharstriebuilder.h"
+#include "unicode/uniset.h"
+#include "unicode/unistr.h"
+#include "unicode/usetiter.h"
+#include "unicode/utf16.h"
+#include "cmemory.h"
+#include "collation.h"
+#include "collationdata.h"
+#include "collationdatabuilder.h"
+#include "collationfastlatinbuilder.h"
+#include "collationiterator.h"
+#include "normalizer2impl.h"
+#include "utrie2.h"
+#include "uvectr32.h"
+#include "uvectr64.h"
+#include "uvector.h"
+
+U_NAMESPACE_BEGIN
+
+CollationDataBuilder::CEModifier::~CEModifier() {}
+
+/**
+ * Build-time context and CE32 for a code point.
+ * If a code point has contextual mappings, then the default (no-context) mapping
+ * and all conditional mappings are stored in a singly-linked list
+ * of ConditionalCE32, sorted by context strings.
+ *
+ * Context strings sort by prefix length, then by prefix, then by contraction suffix.
+ * Context strings must be unique and in ascending order.
+ */
+struct ConditionalCE32 : public UMemory {
+    ConditionalCE32()
+            : context(),
+              ce32(0), defaultCE32(Collation::NO_CE32), builtCE32(Collation::NO_CE32),
+              next(-1) {}
+    ConditionalCE32(const UnicodeString &ct, uint32_t ce)
+            : context(ct),
+              ce32(ce), defaultCE32(Collation::NO_CE32), builtCE32(Collation::NO_CE32),
+              next(-1) {}
+
+    inline UBool hasContext() const { return context.length() > 1; }
+    inline int32_t prefixLength() const { return context.charAt(0); }
+
+    /**
+     * "\0" for the first entry for any code point, with its default CE32.
+     *
+     * Otherwise one unit with the length of the prefix string,
+     * then the prefix string, then the contraction suffix.
+     */
+    UnicodeString context;
+    /**
+     * CE32 for the code point and its context.
+     * Can be special (e.g., for an expansion) but not contextual (prefix or contraction tag).
+     */
+    uint32_t ce32;
+    /**
+     * Default CE32 for all contexts with this same prefix.
+     * Initially NO_CE32. Set only while building runtime data structures,
+     * and only on one of the nodes of a sub-list with the same prefix.
+     */
+    uint32_t defaultCE32;
+    /**
+     * CE32 for the built contexts.
+     * When fetching CEs from the builder, the contexts are built into their runtime form
+     * so that the normal collation implementation can process them.
+     * The result is cached in the list head. It is reset when the contexts are modified.
+     * All of these builtCE32 are invalidated by clearContexts(),
+     * via incrementing the contextsEra.
+     */
+    uint32_t builtCE32;
+    /**
+     * The "era" of building intermediate contexts when the above builtCE32 was set.
+     * When the array of cached, temporary contexts overflows, then clearContexts()
+     * removes them all and invalidates the builtCE32 that used to point to built tries.
+     */
+    int32_t era = -1;
+    /**
+     * Index of the next ConditionalCE32.
+     * Negative for the end of the list.
+     */
+    int32_t next;
+    // Note: We could create a separate class for all of the contextual mappings for
+    // a code point, with the builtCE32, the era, and a list of the actual mappings.
+    // The class that represents one mapping would then not need to
+    // store those fields in each element.
+};
+
+U_CDECL_BEGIN
+
+void U_CALLCONV
+uprv_deleteConditionalCE32(void *obj) {
+    delete static_cast<ConditionalCE32 *>(obj);
+}
+
+U_CDECL_END
+
+/**
+ * Build-time collation element and character iterator.
+ * Uses the runtime CollationIterator for fetching CEs for a string
+ * but reads from the builder's unfinished data structures.
+ * In particular, this class reads from the unfinished trie
+ * and has to avoid CollationIterator::nextCE() and redirect other
+ * calls to data->getCE32() and data->getCE32FromSupplementary().
+ *
+ * We do this so that we need not implement the collation algorithm
+ * again for the builder and make it behave exactly like the runtime code.
+ * That would be more difficult to test and maintain than this indirection.
+ *
+ * Some CE32 tags (for example, the DIGIT_TAG) do not occur in the builder data,
+ * so the data accesses from those code paths need not be modified.
+ *
+ * This class iterates directly over whole code points
+ * so that the CollationIterator does not need the finished trie
+ * for handling the LEAD_SURROGATE_TAG.
+ */
+class DataBuilderCollationIterator : public CollationIterator {
+public:
+    DataBuilderCollationIterator(CollationDataBuilder &b);
+
+    virtual ~DataBuilderCollationIterator();
+
+    int32_t fetchCEs(const UnicodeString &str, int32_t start, int64_t ces[], int32_t cesLength);
+
+    virtual void resetToOffset(int32_t newOffset) override;
+    virtual int32_t getOffset() const override;
+
+    virtual UChar32 nextCodePoint(UErrorCode &errorCode) override;
+    virtual UChar32 previousCodePoint(UErrorCode &errorCode) override;
+
+protected:
+    virtual void forwardNumCodePoints(int32_t num, UErrorCode &errorCode) override;
+    virtual void backwardNumCodePoints(int32_t num, UErrorCode &errorCode) override;
+
+    virtual uint32_t getDataCE32(UChar32 c) const override;
+    virtual uint32_t getCE32FromBuilderData(uint32_t ce32, UErrorCode &errorCode) override;
+
+    CollationDataBuilder &builder;
+    CollationData builderData;
+    uint32_t jamoCE32s[CollationData::JAMO_CE32S_LENGTH];
+    const UnicodeString *s;
+    int32_t pos;
+};
+
+DataBuilderCollationIterator::DataBuilderCollationIterator(CollationDataBuilder &b)
+        : CollationIterator(&builderData, /*numeric=*/ false),
+          builder(b), builderData(b.nfcImpl),
+          s(nullptr), pos(0) {
+    builderData.base = builder.base;
+    // Set all of the jamoCE32s[] to indirection CE32s.
+    for(int32_t j = 0; j < CollationData::JAMO_CE32S_LENGTH; ++j) {  // Count across Jamo types.
+        UChar32 jamo = CollationDataBuilder::jamoCpFromIndex(j);
+        jamoCE32s[j] = Collation::makeCE32FromTagAndIndex(Collation::BUILDER_DATA_TAG, jamo) |
+                CollationDataBuilder::IS_BUILDER_JAMO_CE32;
+    }
+    builderData.jamoCE32s = jamoCE32s;
+}
+
+DataBuilderCollationIterator::~DataBuilderCollationIterator() {}
+
+int32_t
+DataBuilderCollationIterator::fetchCEs(const UnicodeString &str, int32_t start,
+                                       int64_t ces[], int32_t cesLength) {
+    // Set the pointers each time, in case they changed due to reallocation.
+    builderData.ce32s = reinterpret_cast<const uint32_t *>(builder.ce32s.getBuffer());
+    builderData.ces = builder.ce64s.getBuffer();
+    builderData.contexts = builder.contexts.getBuffer();
+    // Modified copy of CollationIterator::nextCE() and CollationIterator::nextCEFromCE32().
+    reset();
+    s = &str;
+    pos = start;
+    UErrorCode errorCode = U_ZERO_ERROR;
+    while(U_SUCCESS(errorCode) && pos < s->length()) {
+        // No need to keep all CEs in the iterator buffer.
+        clearCEs();
+        UChar32 c = s->char32At(pos);
+        pos += U16_LENGTH(c);
+        uint32_t ce32 = utrie2_get32(builder.trie, c);
+        const CollationData *d;
+        if(ce32 == Collation::FALLBACK_CE32) {
+            d = builder.base;
+            ce32 = builder.base->getCE32(c);
+        } else {
+            d = &builderData;
+        }
+        appendCEsFromCE32(d, c, ce32, /*forward=*/ true, errorCode);
+        U_ASSERT(U_SUCCESS(errorCode));
+        for(int32_t i = 0; i < getCEsLength(); ++i) {
+            int64_t ce = getCE(i);
+            if(ce != 0) {
+                if(cesLength < Collation::MAX_EXPANSION_LENGTH) {
+                    ces[cesLength] = ce;
+                }
+                ++cesLength;
+            }
+        }
+    }
+    return cesLength;
+}
+
+void
+DataBuilderCollationIterator::resetToOffset(int32_t newOffset) {
+    reset();
+    pos = newOffset;
+}
+
+int32_t
+DataBuilderCollationIterator::getOffset() const {
+    return pos;
+}
+
+UChar32
+DataBuilderCollationIterator::nextCodePoint(UErrorCode & /*errorCode*/) {
+    if(pos == s->length()) {
+        return U_SENTINEL;
+    }
+    UChar32 c = s->char32At(pos);
+    pos += U16_LENGTH(c);
+    return c;
+}
+
+UChar32
+DataBuilderCollationIterator::previousCodePoint(UErrorCode & /*errorCode*/) {
+    if(pos == 0) {
+        return U_SENTINEL;
+    }
+    UChar32 c = s->char32At(pos - 1);
+    pos -= U16_LENGTH(c);
+    return c;
+}
+
+void
+DataBuilderCollationIterator::forwardNumCodePoints(int32_t num, UErrorCode & /*errorCode*/) {
+    pos = s->moveIndex32(pos, num);
+}
+
+void
+DataBuilderCollationIterator::backwardNumCodePoints(int32_t num, UErrorCode & /*errorCode*/) {
+    pos = s->moveIndex32(pos, -num);
+}
+
+uint32_t
+DataBuilderCollationIterator::getDataCE32(UChar32 c) const {
+    return utrie2_get32(builder.trie, c);
+}
+
+uint32_t
+DataBuilderCollationIterator::getCE32FromBuilderData(uint32_t ce32, UErrorCode &errorCode) {
+    if (U_FAILURE(errorCode)) { return 0; }
+    U_ASSERT(Collation::hasCE32Tag(ce32, Collation::BUILDER_DATA_TAG));
+    if((ce32 & CollationDataBuilder::IS_BUILDER_JAMO_CE32) != 0) {
+        UChar32 jamo = Collation::indexFromCE32(ce32);
+        return utrie2_get32(builder.trie, jamo);
+    } else {
+        ConditionalCE32 *cond = builder.getConditionalCE32ForCE32(ce32);
+        if (cond == nullptr) {
+            errorCode = U_INTERNAL_PROGRAM_ERROR;
+            // TODO: ICU-21531 figure out why this happens.
+            return 0;
+        }
+        if(cond->builtCE32 == Collation::NO_CE32 || cond->era != builder.contextsEra) {
+            // Build the context-sensitive mappings into their runtime form and cache the result.
+            cond->builtCE32 = builder.buildContext(cond, errorCode);
+            if(errorCode == U_BUFFER_OVERFLOW_ERROR) {
+                errorCode = U_ZERO_ERROR;
+                builder.clearContexts();
+                cond->builtCE32 = builder.buildContext(cond, errorCode);
+            }
+            cond->era = builder.contextsEra;
+            builderData.contexts = builder.contexts.getBuffer();
+        }
+        return cond->builtCE32;
+    }
+}
+
+// ------------------------------------------------------------------------- ***
+
+CollationDataBuilder::CollationDataBuilder(UBool icu4xMode, UErrorCode &errorCode)
+        : nfcImpl(*Normalizer2Factory::getNFCImpl(errorCode)),
+          base(nullptr), baseSettings(nullptr),
+          trie(nullptr),
+          ce32s(errorCode), ce64s(errorCode), conditionalCE32s(errorCode),
+          modified(false),
+          icu4xMode(icu4xMode),
+          fastLatinEnabled(false), fastLatinBuilder(nullptr),
+          collIter(nullptr) {
+    // Reserve the first CE32 for U+0000.
+    if (!icu4xMode) {
+        ce32s.addElement(0, errorCode);
+    }
+    conditionalCE32s.setDeleter(uprv_deleteConditionalCE32);
+}
+
+CollationDataBuilder::~CollationDataBuilder() {
+    utrie2_close(trie);
+    delete fastLatinBuilder;
+    delete collIter;
+}
+
+void
+CollationDataBuilder::initForTailoring(const CollationData *b, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return; }
+    if(trie != nullptr) {
+        errorCode = U_INVALID_STATE_ERROR;
+        return;
+    }
+    if(b == nullptr) {
+        errorCode = U_ILLEGAL_ARGUMENT_ERROR;
+        return;
+    }
+    base = b;
+
+    // For a tailoring, the default is to fall back to the base.
+    // For ICU4X, use the same value for fallback as for the default
+    // to avoid having to have different blocks for the two.
+    trie = utrie2_open(Collation::FALLBACK_CE32, icu4xMode ? Collation::FALLBACK_CE32 : Collation::FFFD_CE32, &errorCode);
+
+    if (!icu4xMode) {
+        // Set the Latin-1 letters block so that it is allocated first in the data array,
+        // to try to improve locality of reference when sorting Latin-1 text.
+        // Do not use utrie2_setRange32() since that will not actually allocate blocks
+        // that are filled with the default value.
+        // ASCII (0..7F) is already preallocated anyway.
+        for(UChar32 c = 0xc0; c <= 0xff; ++c) {
+            utrie2_set32(trie, c, Collation::FALLBACK_CE32, &errorCode);
+        }
+
+        // Hangul syllables are not tailorable (except via tailoring Jamos).
+        // Always set the Hangul tag to help performance.
+        // Do this here, rather than in buildMappings(),
+        // so that we see the HANGUL_TAG in various assertions.
+        uint32_t hangulCE32 = Collation::makeCE32FromTagAndIndex(Collation::HANGUL_TAG, 0);
+        utrie2_setRange32(trie, Hangul::HANGUL_BASE, Hangul::HANGUL_END, hangulCE32, true, &errorCode);
+
+        // Copy the set contents but don't copy/clone the set as a whole because
+        // that would copy the isFrozen state too.
+        unsafeBackwardSet.addAll(*b->unsafeBackwardSet);
+    }
+
+    if(U_FAILURE(errorCode)) { return; }
+}
+
+UBool
+CollationDataBuilder::maybeSetPrimaryRange(UChar32 start, UChar32 end,
+                                           uint32_t primary, int32_t step,
+                                           UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return false; }
+    U_ASSERT(start <= end);
+    // TODO: Do we need to check what values are currently set for start..end?
+    // An offset range is worth it only if we can achieve an overlap between
+    // adjacent UTrie2 blocks of 32 code points each.
+    // An offset CE is also a little more expensive to look up and compute
+    // than a simple CE.
+    // If the range spans at least three UTrie2 block boundaries (> 64 code points),
+    // then we take it.
+    // If the range spans one or two block boundaries and there are
+    // at least 4 code points on either side, then we take it.
+    // (We could additionally require a minimum range length of, say, 16.)
+    int32_t blockDelta = (end >> 5) - (start >> 5);
+    if(2 <= step && step <= 0x7f &&
+            (blockDelta >= 3 ||
+            (blockDelta > 0 && (start & 0x1f) <= 0x1c && (end & 0x1f) >= 3))) {
+        int64_t dataCE = ((int64_t)primary << 32) | (start << 8) | step;
+        if(isCompressiblePrimary(primary)) { dataCE |= 0x80; }
+        int32_t index = addCE(dataCE, errorCode);
+        if(U_FAILURE(errorCode)) { return 0; }
+        if(index > Collation::MAX_INDEX) {
+            errorCode = U_BUFFER_OVERFLOW_ERROR;
+            return 0;
+        }
+        uint32_t offsetCE32 = Collation::makeCE32FromTagAndIndex(Collation::OFFSET_TAG, index);
+        utrie2_setRange32(trie, start, end, offsetCE32, true, &errorCode);
+        modified = true;
+        return true;
+    } else {
+        return false;
+    }
+}
+
+uint32_t
+CollationDataBuilder::setPrimaryRangeAndReturnNext(UChar32 start, UChar32 end,
+                                                   uint32_t primary, int32_t step,
+                                                   UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return 0; }
+    UBool isCompressible = isCompressiblePrimary(primary);
+    if(maybeSetPrimaryRange(start, end, primary, step, errorCode)) {
+        return Collation::incThreeBytePrimaryByOffset(primary, isCompressible,
+                                                      (end - start + 1) * step);
+    } else {
+        // Short range: Set individual CE32s.
+        for(;;) {
+            utrie2_set32(trie, start, Collation::makeLongPrimaryCE32(primary), &errorCode);
+            ++start;
+            primary = Collation::incThreeBytePrimaryByOffset(primary, isCompressible, step);
+            if(start > end) { return primary; }
+        }
+        modified = true;
+    }
+}
+
+uint32_t
+CollationDataBuilder::getCE32FromOffsetCE32(UBool fromBase, UChar32 c, uint32_t ce32) const {
+    int32_t i = Collation::indexFromCE32(ce32);
+    int64_t dataCE = fromBase ? base->ces[i] : ce64s.elementAti(i);
+    uint32_t p = Collation::getThreeBytePrimaryForOffsetData(c, dataCE);
+    return Collation::makeLongPrimaryCE32(p);
+}
+
+UBool
+CollationDataBuilder::isCompressibleLeadByte(uint32_t b) const {
+    return base->isCompressibleLeadByte(b);
+}
+
+UBool
+CollationDataBuilder::isAssigned(UChar32 c) const {
+    return Collation::isAssignedCE32(utrie2_get32(trie, c));
+}
+
+uint32_t
+CollationDataBuilder::getLongPrimaryIfSingleCE(UChar32 c) const {
+    uint32_t ce32 = utrie2_get32(trie, c);
+    if(Collation::isLongPrimaryCE32(ce32)) {
+        return Collation::primaryFromLongPrimaryCE32(ce32);
+    } else {
+        return 0;
+    }
+}
+
+int64_t
+CollationDataBuilder::getSingleCE(UChar32 c, UErrorCode &errorCode) const {
+    if(U_FAILURE(errorCode)) { return 0; }
+    // Keep parallel with CollationData::getSingleCE().
+    UBool fromBase = false;
+    uint32_t ce32 = utrie2_get32(trie, c);
+    if(ce32 == Collation::FALLBACK_CE32) {
+        fromBase = true;
+        ce32 = base->getCE32(c);
+    }
+    while(Collation::isSpecialCE32(ce32)) {
+        switch(Collation::tagFromCE32(ce32)) {
+        case Collation::LATIN_EXPANSION_TAG:
+        case Collation::BUILDER_DATA_TAG:
+        case Collation::PREFIX_TAG:
+        case Collation::CONTRACTION_TAG:
+        case Collation::HANGUL_TAG:
+        case Collation::LEAD_SURROGATE_TAG:
+            errorCode = U_UNSUPPORTED_ERROR;
+            return 0;
+        case Collation::FALLBACK_TAG:
+        case Collation::RESERVED_TAG_3:
+            errorCode = U_INTERNAL_PROGRAM_ERROR;
+            return 0;
+        case Collation::LONG_PRIMARY_TAG:
+            return Collation::ceFromLongPrimaryCE32(ce32);
+        case Collation::LONG_SECONDARY_TAG:
+            return Collation::ceFromLongSecondaryCE32(ce32);
+        case Collation::EXPANSION32_TAG:
+            if(Collation::lengthFromCE32(ce32) == 1) {
+                int32_t i = Collation::indexFromCE32(ce32);
+                ce32 = fromBase ? base->ce32s[i] : ce32s.elementAti(i);
+                break;
+            } else {
+                errorCode = U_UNSUPPORTED_ERROR;
+                return 0;
+            }
+        case Collation::EXPANSION_TAG: {
+            if(Collation::lengthFromCE32(ce32) == 1) {
+                int32_t i = Collation::indexFromCE32(ce32);
+                return fromBase ? base->ces[i] : ce64s.elementAti(i);
+            } else {
+                errorCode = U_UNSUPPORTED_ERROR;
+                return 0;
+            }
+        }
+        case Collation::DIGIT_TAG:
+            // Fetch the non-numeric-collation CE32 and continue.
+            ce32 = ce32s.elementAti(Collation::indexFromCE32(ce32));
+            break;
+        case Collation::U0000_TAG:
+            U_ASSERT(c == 0);
+            // Fetch the normal ce32 for U+0000 and continue.
+            ce32 = fromBase ? base->ce32s[0] : ce32s.elementAti(0);
+            break;
+        case Collation::OFFSET_TAG:
+            ce32 = getCE32FromOffsetCE32(fromBase, c, ce32);
+            break;
+        case Collation::IMPLICIT_TAG:
+            return Collation::unassignedCEFromCodePoint(c);
+        }
+    }
+    return Collation::ceFromSimpleCE32(ce32);
+}
+
+int32_t
+CollationDataBuilder::addCE(int64_t ce, UErrorCode &errorCode) {
+    int32_t length = ce64s.size();
+    for(int32_t i = 0; i < length; ++i) {
+        if(ce == ce64s.elementAti(i)) { return i; }
+    }
+    ce64s.addElement(ce, errorCode);
+    return length;
+}
+
+int32_t
+CollationDataBuilder::addCE32(uint32_t ce32, UErrorCode &errorCode) {
+    int32_t length = ce32s.size();
+    for(int32_t i = 0; i < length; ++i) {
+        if(ce32 == (uint32_t)ce32s.elementAti(i)) { return i; }
+    }
+    ce32s.addElement((int32_t)ce32, errorCode);  
+    return length;
+}
+
+int32_t
+CollationDataBuilder::addConditionalCE32(const UnicodeString &context, uint32_t ce32,
+                                         UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return -1; }
+    U_ASSERT(!context.isEmpty());
+    int32_t index = conditionalCE32s.size();
+    if(index > Collation::MAX_INDEX) {
+        errorCode = U_BUFFER_OVERFLOW_ERROR;
+        return -1;
+    }
+    LocalPointer<ConditionalCE32> cond(new ConditionalCE32(context, ce32), errorCode);
+    conditionalCE32s.adoptElement(cond.orphan(), errorCode);
+    if(U_FAILURE(errorCode)) {
+        return -1;
+    }
+    return index;
+}
+
+void
+CollationDataBuilder::add(const UnicodeString &prefix, const UnicodeString &s,
+                          const int64_t ces[], int32_t cesLength,
+                          UErrorCode &errorCode) {
+    uint32_t ce32 = encodeCEs(ces, cesLength, errorCode);
+    addCE32(prefix, s, ce32, errorCode);
+}
+
+void
+CollationDataBuilder::addCE32(const UnicodeString &prefix, const UnicodeString &s,
+                              uint32_t ce32, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return; }
+    if(s.isEmpty()) {
+        errorCode = U_ILLEGAL_ARGUMENT_ERROR;
+        return;
+    }
+    if(trie == nullptr || utrie2_isFrozen(trie)) {
+        errorCode = U_INVALID_STATE_ERROR;
+        return;
+    }
+    UChar32 c = s.char32At(0);
+    int32_t cLength = U16_LENGTH(c);
+    uint32_t oldCE32 = utrie2_get32(trie, c);
+    UBool hasContext = !prefix.isEmpty() || s.length() > cLength;
+
+    if (icu4xMode) {
+        if (base && c >= 0x1100 && c < 0x1200) {
+            // Omit jamo tailorings.
+            // TODO(https://github.com/unicode-org/icu4x/issues/1941).
+        }
+        const Normalizer2* nfdNormalizer = Normalizer2::getNFDInstance(errorCode);
+        UnicodeString sInNfd;
+        nfdNormalizer->normalize(s, sInNfd, errorCode);
+        if (s != sInNfd) {
+            // s is not in NFD, so it cannot match in ICU4X, since ICU4X only
+            // does NFD lookups.
+            // Now check that we're only rejecting known cases.
+            if (s.length() == 2) {
+                char16_t second = s.charAt(1);
+                if (second == 0x0F73 || second == 0x0F75 || second == 0x0F81) {
+                    // Second is a special decomposing Tibetan vowel sign.
+                    // These also get added in the decomposed form, so ignoring
+                    // this instance is OK.
+                    return;
+                }
+                if (c == 0xFDD1 && second == 0xAC00) {
+                    // This strange contraction exists in the root and
+                    // doesn't have a decomposed counterpart there.
+                    // This won't match in ICU4X anyway and is very strange:
+                    // Unassigned Arabic presentation form contracting with
+                    // the very first Hangul syllable. Let's ignore this
+                    // explicitly.
+                    return;
+                }
+            }
+            // Unknown case worth investigating if ever found.
+            errorCode = U_UNSUPPORTED_ERROR;
+            return;
+        }
+
+        if (!prefix.isEmpty()) {
+            UnicodeString prefixInNfd;
+            nfdNormalizer->normalize(prefix, prefixInNfd, errorCode);
+            if (prefix != prefixInNfd) {
+                errorCode = U_UNSUPPORTED_ERROR;
+                return;
+            }
+
+            int32_t count = prefix.countChar32();
+            if (count > 2) {
+                // Prefix too long for ICU4X.
+                errorCode = U_UNSUPPORTED_ERROR;
+                return;
+            }
+            UChar32 utf32[4];
+            int32_t len = prefix.toUTF32(utf32, 4, errorCode);
+            if (len != count) {
+                errorCode = U_INVALID_STATE_ERROR;
+                return;
+            }
+            UChar32 c = utf32[0];
+            if (u_getCombiningClass(c)) {
+                // Prefix must start with as starter for ICU4X.
+                errorCode = U_UNSUPPORTED_ERROR;
+                return;
+            }
+            // XXX: Korean searchjl has jamo in prefix, so commenting out this
+            // check for now. ICU4X currently ignores non-root jamo tables anyway.
+            // searchjl was added in
+            // https://unicode-org.atlassian.net/browse/CLDR-3560
+            // Contractions were changed to prefixes in
+            // https://unicode-org.atlassian.net/browse/CLDR-6546
+            //
+            // if ((c >= 0x1100 && c < 0x1200) || (c >= 0xAC00 && c < 0xD7A4)) {
+            //     errorCode = U_UNSUPPORTED_ERROR;
+            //     return;
+            // }
+            if ((len > 1) && !(utf32[1] == 0x3099 || utf32[1] == 0x309A)) {
+                // Second character in prefix, if present, must be a kana voicing mark for ICU4X.
+                errorCode = U_UNSUPPORTED_ERROR;
+                return;
+            }
+        }
+
+        if (s.length() > cLength) {
+            // Check that there's no modern Hangul in contractions.
+            for (int32_t i = 0; i < s.length(); ++i) {
+                char16_t c = s.charAt(i);
+                if ((c >= 0x1100 && c < 0x1100 + 19) || (c >= 0x1161 && c < 0x1161 + 21) || (c >= 0x11A7 && c < 0x11A7 + 28) || (c >= 0xAC00 && c < 0xD7A4)) {
+                    errorCode = U_UNSUPPORTED_ERROR;
+                    return;
+                }
+            }
+        }
+    }
+
+    if(oldCE32 == Collation::FALLBACK_CE32) {
+        // First tailoring for c.
+        // If c has contextual base mappings or if we add a contextual mapping,
+        // then copy the base mappings.
+        // Otherwise we just override the base mapping.
+        uint32_t baseCE32 = base->getFinalCE32(base->getCE32(c));
+        if(hasContext || Collation::ce32HasContext(baseCE32)) {
+            oldCE32 = copyFromBaseCE32(c, baseCE32, true, errorCode);
+            utrie2_set32(trie, c, oldCE32, &errorCode);
+            if(U_FAILURE(errorCode)) { return; }
+        }
+    }
+    if(!hasContext) {
+        // No prefix, no contraction.
+        if(!isBuilderContextCE32(oldCE32)) {
+            utrie2_set32(trie, c, ce32, &errorCode);
+        } else {
+            ConditionalCE32 *cond = getConditionalCE32ForCE32(oldCE32);
+            cond->builtCE32 = Collation::NO_CE32;
+            cond->ce32 = ce32;
+        }
+    } else {
+        ConditionalCE32 *cond;
+        if(!isBuilderContextCE32(oldCE32)) {
+            // Replace the simple oldCE32 with a builder context CE32
+            // pointing to a new ConditionalCE32 list head.
+            int32_t index = addConditionalCE32(UnicodeString((char16_t)0), oldCE32, errorCode);
+            if(U_FAILURE(errorCode)) { return; }
+            uint32_t contextCE32 = makeBuilderContextCE32(index);
+            utrie2_set32(trie, c, contextCE32, &errorCode);
+            contextChars.add(c);
+            cond = getConditionalCE32(index);
+        } else {
+            cond = getConditionalCE32ForCE32(oldCE32);
+            cond->builtCE32 = Collation::NO_CE32;
+        }
+        UnicodeString suffix(s, cLength);
+        UnicodeString context((char16_t)prefix.length());
+        context.append(prefix).append(suffix);
+        unsafeBackwardSet.addAll(suffix);
+        for(;;) {
+            // invariant: context > cond->context
+            int32_t next = cond->next;
+            if(next < 0) {
+                // Append a new ConditionalCE32 after cond.
+                int32_t index = addConditionalCE32(context, ce32, errorCode);
+                if(U_FAILURE(errorCode)) { return; }
+                cond->next = index;
+                break;
+            }
+            ConditionalCE32 *nextCond = getConditionalCE32(next);
+            int8_t cmp = context.compare(nextCond->context);
+            if(cmp < 0) {
+                // Insert a new ConditionalCE32 between cond and nextCond.
+                int32_t index = addConditionalCE32(context, ce32, errorCode);
+                if(U_FAILURE(errorCode)) { return; }
+                cond->next = index;
+                getConditionalCE32(index)->next = next;
+                break;
+            } else if(cmp == 0) {
+                // Same context as before, overwrite its ce32.
+                nextCond->ce32 = ce32;
+                break;
+            }
+            cond = nextCond;
+        }
+    }
+    modified = true;
+}
+
+uint32_t
+CollationDataBuilder::encodeOneCEAsCE32(int64_t ce) {
+    uint32_t p = (uint32_t)(ce >> 32);
+    uint32_t lower32 = (uint32_t)ce;
+    uint32_t t = (uint32_t)(ce & 0xffff);
+    U_ASSERT((t & 0xc000) != 0xc000);  // Impossible case bits 11 mark special CE32s.
+    if((ce & INT64_C(0xffff00ff00ff)) == 0) {
+        // normal form ppppsstt
+        return p | (lower32 >> 16) | (t >> 8);
+    } else if((ce & INT64_C(0xffffffffff)) == Collation::COMMON_SEC_AND_TER_CE) {
+        // long-primary form ppppppC1
+        return Collation::makeLongPrimaryCE32(p);
+    } else if(p == 0 && (t & 0xff) == 0) {
+        // long-secondary form ssssttC2
+        return Collation::makeLongSecondaryCE32(lower32);
+    }
+    return Collation::NO_CE32;
+}
+
+uint32_t
+CollationDataBuilder::encodeOneCE(int64_t ce, UErrorCode &errorCode) {
+    // Try to encode one CE as one CE32.
+    uint32_t ce32 = encodeOneCEAsCE32(ce);
+    if(ce32 != Collation::NO_CE32) { return ce32; }
+    int32_t index = addCE(ce, errorCode);
+    if(U_FAILURE(errorCode)) { return 0; }
+    if(index > Collation::MAX_INDEX) {
+        errorCode = U_BUFFER_OVERFLOW_ERROR;
+        return 0;
+    }
+    return Collation::makeCE32FromTagIndexAndLength(Collation::EXPANSION_TAG, index, 1);
+}
+
+uint32_t
+CollationDataBuilder::encodeCEs(const int64_t ces[], int32_t cesLength,
+                                UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return 0; }
+    if(cesLength < 0 || cesLength > Collation::MAX_EXPANSION_LENGTH) {
+        errorCode = U_ILLEGAL_ARGUMENT_ERROR;
+        return 0;
+    }
+    if(trie == nullptr || utrie2_isFrozen(trie)) {
+        errorCode = U_INVALID_STATE_ERROR;
+        return 0;
+    }
+    if(cesLength == 0) {
+        // Convenience: We cannot map to nothing, but we can map to a completely ignorable CE.
+        // Do this here so that callers need not do it.
+        return encodeOneCEAsCE32(0);
+    } else if(cesLength == 1) {
+        return encodeOneCE(ces[0], errorCode);
+    } else if(cesLength == 2 && !icu4xMode) {
+        // Try to encode two CEs as one CE32.
+        // Turn this off for ICU4X, because without the canonical closure
+        // these are so rare that it doesn't make sense to spend a branch
+        // on checking this tag when using the data.
+        int64_t ce0 = ces[0];
+        int64_t ce1 = ces[1];
+        uint32_t p0 = (uint32_t)(ce0 >> 32);
+        if((ce0 & INT64_C(0xffffffffff00ff)) == Collation::COMMON_SECONDARY_CE &&
+                (ce1 & INT64_C(0xffffffff00ffffff)) == Collation::COMMON_TERTIARY_CE &&
+                p0 != 0) {
+            // Latin mini expansion
+            return
+                p0 |
+                (((uint32_t)ce0 & 0xff00u) << 8) |
+                (uint32_t)(ce1 >> 16) |
+                Collation::SPECIAL_CE32_LOW_BYTE |
+                Collation::LATIN_EXPANSION_TAG;
+        }
+    }
+    // Try to encode two or more CEs as CE32s.
+    int32_t newCE32s[Collation::MAX_EXPANSION_LENGTH];
+    for(int32_t i = 0;; ++i) {
+        if(i == cesLength) {
+            return encodeExpansion32(newCE32s, cesLength, errorCode);
+        }
+        uint32_t ce32 = encodeOneCEAsCE32(ces[i]);
+        if(ce32 == Collation::NO_CE32) { break; }
+        newCE32s[i] = (int32_t)ce32;
+    }
+    return encodeExpansion(ces, cesLength, errorCode);
+}
+
+uint32_t
+CollationDataBuilder::encodeExpansion(const int64_t ces[], int32_t length, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return 0; }
+    // See if this sequence of CEs has already been stored.
+    int64_t first = ces[0];
+    int32_t ce64sMax = ce64s.size() - length;
+    for(int32_t i = 0; i <= ce64sMax; ++i) {
+        if(first == ce64s.elementAti(i)) {
+            if(i > Collation::MAX_INDEX) {
+                errorCode = U_BUFFER_OVERFLOW_ERROR;
+                return 0;
+            }
+            for(int32_t j = 1;; ++j) {
+                if(j == length) {
+                    return Collation::makeCE32FromTagIndexAndLength(
+                            Collation::EXPANSION_TAG, i, length);
+                }
+                if(ce64s.elementAti(i + j) != ces[j]) { break; }
+            }
+        }
+    }
+    // Store the new sequence.
+    int32_t i = ce64s.size();
+    if(i > Collation::MAX_INDEX) {
+        errorCode = U_BUFFER_OVERFLOW_ERROR;
+        return 0;
+    }
+    for(int32_t j = 0; j < length; ++j) {
+        ce64s.addElement(ces[j], errorCode);
+    }
+    return Collation::makeCE32FromTagIndexAndLength(Collation::EXPANSION_TAG, i, length);
+}
+
+uint32_t
+CollationDataBuilder::encodeExpansion32(const int32_t newCE32s[], int32_t length,
+                                        UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return 0; }
+    // See if this sequence of CE32s has already been stored.
+    int32_t first = newCE32s[0];
+    int32_t ce32sMax = ce32s.size() - length;
+    for(int32_t i = 0; i <= ce32sMax; ++i) {
+        if(first == ce32s.elementAti(i)) {
+            if(i > Collation::MAX_INDEX) {
+                errorCode = U_BUFFER_OVERFLOW_ERROR;
+                return 0;
+            }
+            for(int32_t j = 1;; ++j) {
+                if(j == length) {
+                    return Collation::makeCE32FromTagIndexAndLength(
+                            Collation::EXPANSION32_TAG, i, length);
+                }
+                if(ce32s.elementAti(i + j) != newCE32s[j]) { break; }
+            }
+        }
+    }
+    // Store the new sequence.
+    int32_t i = ce32s.size();
+    if(i > Collation::MAX_INDEX) {
+        errorCode = U_BUFFER_OVERFLOW_ERROR;
+        return 0;
+    }
+    for(int32_t j = 0; j < length; ++j) {
+        ce32s.addElement(newCE32s[j], errorCode);
+    }
+    return Collation::makeCE32FromTagIndexAndLength(Collation::EXPANSION32_TAG, i, length);
+}
+
+uint32_t
+CollationDataBuilder::copyFromBaseCE32(UChar32 c, uint32_t ce32, UBool withContext,
+                                       UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return 0; }
+    if(!Collation::isSpecialCE32(ce32)) { return ce32; }
+    switch(Collation::tagFromCE32(ce32)) {
+    case Collation::LONG_PRIMARY_TAG:
+    case Collation::LONG_SECONDARY_TAG:
+    case Collation::LATIN_EXPANSION_TAG:
+        // copy as is
+        break;
+    case Collation::EXPANSION32_TAG: {
+        const uint32_t *baseCE32s = base->ce32s + Collation::indexFromCE32(ce32);
+        int32_t length = Collation::lengthFromCE32(ce32);
+        ce32 = encodeExpansion32(
+            reinterpret_cast<const int32_t *>(baseCE32s), length, errorCode);
+        break;
+    }
+    case Collation::EXPANSION_TAG: {
+        const int64_t *baseCEs = base->ces + Collation::indexFromCE32(ce32);
+        int32_t length = Collation::lengthFromCE32(ce32);
+        ce32 = encodeExpansion(baseCEs, length, errorCode);
+        break;
+    }
+    case Collation::PREFIX_TAG: {
+        // Flatten prefixes and nested suffixes (contractions)
+        // into a linear list of ConditionalCE32.
+        const char16_t *p = base->contexts + Collation::indexFromCE32(ce32);
+        ce32 = CollationData::readCE32(p);  // Default if no prefix match.
+        if(!withContext) {
+            return copyFromBaseCE32(c, ce32, false, errorCode);
+        }
+        ConditionalCE32 head;
+        UnicodeString context((char16_t)0);
+        int32_t index;
+        if(Collation::isContractionCE32(ce32)) {
+            index = copyContractionsFromBaseCE32(context, c, ce32, &head, errorCode);
+        } else {
+            ce32 = copyFromBaseCE32(c, ce32, true, errorCode);
+            head.next = index = addConditionalCE32(context, ce32, errorCode);
+        }
+        if(U_FAILURE(errorCode)) { return 0; }
+        ConditionalCE32 *cond = getConditionalCE32(index);  // the last ConditionalCE32 so far
+        UCharsTrie::Iterator prefixes(p + 2, 0, errorCode);
+        while(prefixes.next(errorCode)) {
+            context = prefixes.getString();
+            context.reverse();
+            context.insert(0, (char16_t)context.length());
+            ce32 = (uint32_t)prefixes.getValue();
+            if(Collation::isContractionCE32(ce32)) {
+                index = copyContractionsFromBaseCE32(context, c, ce32, cond, errorCode);
+            } else {
+                ce32 = copyFromBaseCE32(c, ce32, true, errorCode);
+                cond->next = index = addConditionalCE32(context, ce32, errorCode);
+            }
+            if(U_FAILURE(errorCode)) { return 0; }
+            cond = getConditionalCE32(index);
+        }
+        ce32 = makeBuilderContextCE32(head.next);
+        contextChars.add(c);
+        break;
+    }
+    case Collation::CONTRACTION_TAG: {
+        if(!withContext) {
+            const char16_t *p = base->contexts + Collation::indexFromCE32(ce32);
+            ce32 = CollationData::readCE32(p);  // Default if no suffix match.
+            return copyFromBaseCE32(c, ce32, false, errorCode);
+        }
+        ConditionalCE32 head;
+        UnicodeString context((char16_t)0);
+        copyContractionsFromBaseCE32(context, c, ce32, &head, errorCode);
+        ce32 = makeBuilderContextCE32(head.next);
+        contextChars.add(c);
+        break;
+    }
+    case Collation::HANGUL_TAG:
+        errorCode = U_UNSUPPORTED_ERROR;  // We forbid tailoring of Hangul syllables.
+        break;
+    case Collation::OFFSET_TAG:
+        ce32 = getCE32FromOffsetCE32(true, c, ce32);
+        break;
+    case Collation::IMPLICIT_TAG:
+        ce32 = encodeOneCE(Collation::unassignedCEFromCodePoint(c), errorCode);
+        break;
+    default:
+        UPRV_UNREACHABLE_EXIT;  // require ce32 == base->getFinalCE32(ce32)
+    }
+    return ce32;
+}
+
+int32_t
+CollationDataBuilder::copyContractionsFromBaseCE32(UnicodeString &context, UChar32 c, uint32_t ce32,
+                                                   ConditionalCE32 *cond, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return 0; }
+    const char16_t *p = base->contexts + Collation::indexFromCE32(ce32);
+    int32_t index;
+    if((ce32 & Collation::CONTRACT_SINGLE_CP_NO_MATCH) != 0) {
+        // No match on the single code point.
+        // We are underneath a prefix, and the default mapping is just
+        // a fallback to the mappings for a shorter prefix.
+        U_ASSERT(context.length() > 1);
+        index = -1;
+    } else {
+        ce32 = CollationData::readCE32(p);  // Default if no suffix match.
+        U_ASSERT(!Collation::isContractionCE32(ce32));
+        ce32 = copyFromBaseCE32(c, ce32, true, errorCode);
+        cond->next = index = addConditionalCE32(context, ce32, errorCode);
+        if(U_FAILURE(errorCode)) { return 0; }
+        cond = getConditionalCE32(index);
+    }
+
+    int32_t suffixStart = context.length();
+    UCharsTrie::Iterator suffixes(p + 2, 0, errorCode);
+    while(suffixes.next(errorCode)) {
+        context.append(suffixes.getString());
+        ce32 = copyFromBaseCE32(c, (uint32_t)suffixes.getValue(), true, errorCode);
+        cond->next = index = addConditionalCE32(context, ce32, errorCode);
+        if(U_FAILURE(errorCode)) { return 0; }
+        // No need to update the unsafeBackwardSet because the tailoring set
+        // is already a copy of the base set.
+        cond = getConditionalCE32(index);
+        context.truncate(suffixStart);
+    }
+    U_ASSERT(index >= 0);
+    return index;
+}
+
+class CopyHelper {
+public:
+    CopyHelper(const CollationDataBuilder &s, CollationDataBuilder &d,
+               const CollationDataBuilder::CEModifier &m, UErrorCode &initialErrorCode)
+            : src(s), dest(d), modifier(m),
+              errorCode(initialErrorCode) {}
+
+    UBool copyRangeCE32(UChar32 start, UChar32 end, uint32_t ce32) {
+        ce32 = copyCE32(ce32);
+        utrie2_setRange32(dest.trie, start, end, ce32, true, &errorCode);
+        if(CollationDataBuilder::isBuilderContextCE32(ce32)) {
+            dest.contextChars.add(start, end);
+        }
+        return U_SUCCESS(errorCode);
+    }
+
+    uint32_t copyCE32(uint32_t ce32) {
+        if(!Collation::isSpecialCE32(ce32)) {
+            int64_t ce = modifier.modifyCE32(ce32);
+            if(ce != Collation::NO_CE) {
+                ce32 = dest.encodeOneCE(ce, errorCode);
+            }
+        } else {
+            int32_t tag = Collation::tagFromCE32(ce32);
+            if(tag == Collation::EXPANSION32_TAG) {
+                const uint32_t *srcCE32s = reinterpret_cast<uint32_t *>(src.ce32s.getBuffer());
+                srcCE32s += Collation::indexFromCE32(ce32);
+                int32_t length = Collation::lengthFromCE32(ce32);
+                // Inspect the source CE32s. Just copy them if none are modified.
+                // Otherwise copy to modifiedCEs, with modifications.
+                UBool isModified = false;
+                for(int32_t i = 0; i < length; ++i) {
+                    ce32 = srcCE32s[i];
+                    int64_t ce;
+                    if(Collation::isSpecialCE32(ce32) ||
+                            (ce = modifier.modifyCE32(ce32)) == Collation::NO_CE) {
+                        if(isModified) {
+                            modifiedCEs[i] = Collation::ceFromCE32(ce32);
+                        }
+                    } else {
+                        if(!isModified) {
+                            for(int32_t j = 0; j < i; ++j) {
+                                modifiedCEs[j] = Collation::ceFromCE32(srcCE32s[j]);
+                            }
+                            isModified = true;
+                        }
+                        modifiedCEs[i] = ce;
+                    }
+                }
+                if(isModified) {
+                    ce32 = dest.encodeCEs(modifiedCEs, length, errorCode);
+                } else {
+                    ce32 = dest.encodeExpansion32(
+                        reinterpret_cast<const int32_t *>(srcCE32s), length, errorCode);
+                }
+            } else if(tag == Collation::EXPANSION_TAG) {
+                const int64_t *srcCEs = src.ce64s.getBuffer();
+                srcCEs += Collation::indexFromCE32(ce32);
+                int32_t length = Collation::lengthFromCE32(ce32);
+                // Inspect the source CEs. Just copy them if none are modified.
+                // Otherwise copy to modifiedCEs, with modifications.
+                UBool isModified = false;
+                for(int32_t i = 0; i < length; ++i) {
+                    int64_t srcCE = srcCEs[i];
+                    int64_t ce = modifier.modifyCE(srcCE);
+                    if(ce == Collation::NO_CE) {
+                        if(isModified) {
+                            modifiedCEs[i] = srcCE;
+                        }
+                    } else {
+                        if(!isModified) {
+                            for(int32_t j = 0; j < i; ++j) {
+                                modifiedCEs[j] = srcCEs[j];
+                            }
+                            isModified = true;
+                        }
+                        modifiedCEs[i] = ce;
+                    }
+                }
+                if(isModified) {
+                    ce32 = dest.encodeCEs(modifiedCEs, length, errorCode);
+                } else {
+                    ce32 = dest.encodeExpansion(srcCEs, length, errorCode);
+                }
+            } else if(tag == Collation::BUILDER_DATA_TAG) {
+                // Copy the list of ConditionalCE32.
+                ConditionalCE32 *cond = src.getConditionalCE32ForCE32(ce32);
+                U_ASSERT(!cond->hasContext());
+                int32_t destIndex = dest.addConditionalCE32(
+                        cond->context, copyCE32(cond->ce32), errorCode);
+                ce32 = CollationDataBuilder::makeBuilderContextCE32(destIndex);
+                while(cond->next >= 0) {
+                    cond = src.getConditionalCE32(cond->next);
+                    ConditionalCE32 *prevDestCond = dest.getConditionalCE32(destIndex);
+                    destIndex = dest.addConditionalCE32(
+                            cond->context, copyCE32(cond->ce32), errorCode);
+                    int32_t suffixStart = cond->prefixLength() + 1;
+                    dest.unsafeBackwardSet.addAll(cond->context.tempSubString(suffixStart));
+                    prevDestCond->next = destIndex;
+                }
+            } else {
+                // Just copy long CEs and Latin mini expansions (and other expected values) as is,
+                // assuming that the modifier would not modify them.
+                U_ASSERT(tag == Collation::LONG_PRIMARY_TAG ||
+                        tag == Collation::LONG_SECONDARY_TAG ||
+                        tag == Collation::LATIN_EXPANSION_TAG ||
+                        tag == Collation::HANGUL_TAG);
+            }
+        }
+        return ce32;
+    }
+
+    const CollationDataBuilder &src;
+    CollationDataBuilder &dest;
+    const CollationDataBuilder::CEModifier &modifier;
+    int64_t modifiedCEs[Collation::MAX_EXPANSION_LENGTH];
+    UErrorCode errorCode;
+};
+
+U_CDECL_BEGIN
+
+static UBool U_CALLCONV
+enumRangeForCopy(const void *context, UChar32 start, UChar32 end, uint32_t value) {
+    return
+        value == Collation::UNASSIGNED_CE32 || value == Collation::FALLBACK_CE32 ||
+        ((CopyHelper *)context)->copyRangeCE32(start, end, value);
+}
+
+U_CDECL_END
+
+void
+CollationDataBuilder::copyFrom(const CollationDataBuilder &src, const CEModifier &modifier,
+                               UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return; }
+    if(trie == nullptr || utrie2_isFrozen(trie)) {
+        errorCode = U_INVALID_STATE_ERROR;
+        return;
+    }
+    CopyHelper helper(src, *this, modifier, errorCode);
+    utrie2_enum(src.trie, nullptr, enumRangeForCopy, &helper);
+    errorCode = helper.errorCode;
+    // Update the contextChars and the unsafeBackwardSet while copying,
+    // in case a character had conditional mappings in the source builder
+    // and they were removed later.
+    modified |= src.modified;
+}
+
+void
+CollationDataBuilder::optimize(const UnicodeSet &set, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode) || set.isEmpty()) { return; }
+    UnicodeSetIterator iter(set);
+    while(iter.next() && !iter.isString()) {
+        UChar32 c = iter.getCodepoint();
+        uint32_t ce32 = utrie2_get32(trie, c);
+        if(ce32 == Collation::FALLBACK_CE32) {
+            ce32 = base->getFinalCE32(base->getCE32(c));
+            ce32 = copyFromBaseCE32(c, ce32, true, errorCode);
+            utrie2_set32(trie, c, ce32, &errorCode);
+        }
+    }
+    modified = true;
+}
+
+void
+CollationDataBuilder::suppressContractions(const UnicodeSet &set, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode) || set.isEmpty()) { return; }
+    UnicodeSetIterator iter(set);
+    while(iter.next() && !iter.isString()) {
+        UChar32 c = iter.getCodepoint();
+        uint32_t ce32 = utrie2_get32(trie, c);
+        if(ce32 == Collation::FALLBACK_CE32) {
+            ce32 = base->getFinalCE32(base->getCE32(c));
+            if(Collation::ce32HasContext(ce32)) {
+                ce32 = copyFromBaseCE32(c, ce32, false /* without context */, errorCode);
+                utrie2_set32(trie, c, ce32, &errorCode);
+            }
+        } else if(isBuilderContextCE32(ce32)) {
+            ce32 = getConditionalCE32ForCE32(ce32)->ce32;
+            // Simply abandon the list of ConditionalCE32.
+            // The caller will copy this builder in the end,
+            // eliminating unreachable data.
+            utrie2_set32(trie, c, ce32, &errorCode);
+            contextChars.remove(c);
+        }
+    }
+    modified = true;
+}
+
+UBool
+CollationDataBuilder::getJamoCE32s(uint32_t jamoCE32s[], UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return false; }
+    UBool anyJamoAssigned = base == nullptr;  // always set jamoCE32s in the base data
+    UBool needToCopyFromBase = false;
+    for(int32_t j = 0; j < CollationData::JAMO_CE32S_LENGTH; ++j) {  // Count across Jamo types.
+        UChar32 jamo = jamoCpFromIndex(j);
+        UBool fromBase = false;
+        uint32_t ce32 = utrie2_get32(trie, jamo);
+        anyJamoAssigned |= Collation::isAssignedCE32(ce32);
+        // TODO: Try to prevent [optimize [Jamo]] from counting as anyJamoAssigned.
+        // (As of CLDR 24 [2013] the Korean tailoring does not optimize conjoining Jamo.)
+        if(ce32 == Collation::FALLBACK_CE32) {
+            fromBase = true;
+            ce32 = base->getCE32(jamo);
+        }
+        if(Collation::isSpecialCE32(ce32)) {
+            switch(Collation::tagFromCE32(ce32)) {
+            case Collation::LONG_PRIMARY_TAG:
+            case Collation::LONG_SECONDARY_TAG:
+            case Collation::LATIN_EXPANSION_TAG:
+                // Copy the ce32 as-is.
+                break;
+            case Collation::EXPANSION32_TAG:
+            case Collation::EXPANSION_TAG:
+            case Collation::PREFIX_TAG:
+            case Collation::CONTRACTION_TAG:
+                if(fromBase) {
+                    // Defer copying until we know if anyJamoAssigned.
+                    ce32 = Collation::FALLBACK_CE32;
+                    needToCopyFromBase = true;
+                }
+                break;
+            case Collation::IMPLICIT_TAG:
+                // An unassigned Jamo should only occur in tests with incomplete bases.
+                U_ASSERT(fromBase);
+                ce32 = Collation::FALLBACK_CE32;
+                needToCopyFromBase = true;
+                break;
+            case Collation::OFFSET_TAG:
+                ce32 = getCE32FromOffsetCE32(fromBase, jamo, ce32);
+                break;
+            case Collation::FALLBACK_TAG:
+            case Collation::RESERVED_TAG_3:
+            case Collation::BUILDER_DATA_TAG:
+            case Collation::DIGIT_TAG:
+            case Collation::U0000_TAG:
+            case Collation::HANGUL_TAG:
+            case Collation::LEAD_SURROGATE_TAG:
+                errorCode = U_INTERNAL_PROGRAM_ERROR;
+                return false;
+            }
+        }
+        jamoCE32s[j] = ce32;
+    }
+    if(anyJamoAssigned && needToCopyFromBase) {
+        for(int32_t j = 0; j < CollationData::JAMO_CE32S_LENGTH; ++j) {
+            if(jamoCE32s[j] == Collation::FALLBACK_CE32) {
+                UChar32 jamo = jamoCpFromIndex(j);
+                jamoCE32s[j] = copyFromBaseCE32(jamo, base->getCE32(jamo),
+                                                /*withContext=*/ true, errorCode);
+            }
+        }
+    }
+    return anyJamoAssigned && U_SUCCESS(errorCode);
+}
+
+void
+CollationDataBuilder::setDigitTags(UErrorCode &errorCode) {
+    UnicodeSet digits(UNICODE_STRING_SIMPLE("[:Nd:]"), errorCode);
+    if(U_FAILURE(errorCode)) { return; }
+    UnicodeSetIterator iter(digits);
+    while(iter.next()) {
+        U_ASSERT(!iter.isString());
+        UChar32 c = iter.getCodepoint();
+        uint32_t ce32 = utrie2_get32(trie, c);
+        if(ce32 != Collation::FALLBACK_CE32 && ce32 != Collation::UNASSIGNED_CE32) {
+            int32_t index = addCE32(ce32, errorCode);
+            if(U_FAILURE(errorCode)) { return; }
+            if(index > Collation::MAX_INDEX) {
+                errorCode = U_BUFFER_OVERFLOW_ERROR;
+                return;
+            }
+            ce32 = Collation::makeCE32FromTagIndexAndLength(
+                    Collation::DIGIT_TAG, index, u_charDigitValue(c));
+            utrie2_set32(trie, c, ce32, &errorCode);
+        }
+    }
+}
+
+U_CDECL_BEGIN
+
+static UBool U_CALLCONV
+enumRangeLeadValue(const void *context, UChar32 /*start*/, UChar32 /*end*/, uint32_t value) {
+    int32_t *pValue = (int32_t *)context;
+    if(value == Collation::UNASSIGNED_CE32) {
+        value = Collation::LEAD_ALL_UNASSIGNED;
+    } else if(value == Collation::FALLBACK_CE32) {
+        value = Collation::LEAD_ALL_FALLBACK;
+    } else {
+        *pValue = Collation::LEAD_MIXED;
+        return false;
+    }
+    if(*pValue < 0) {
+        *pValue = (int32_t)value;
+    } else if(*pValue != (int32_t)value) {
+        *pValue = Collation::LEAD_MIXED;
+        return false;
+    }
+    return true;
+}
+
+U_CDECL_END
+
+void
+CollationDataBuilder::setLeadSurrogates(UErrorCode &errorCode) {
+    for(char16_t lead = 0xd800; lead < 0xdc00; ++lead) {
+        int32_t value = -1;
+        utrie2_enumForLeadSurrogate(trie, lead, nullptr, enumRangeLeadValue, &value);
+        utrie2_set32ForLeadSurrogateCodeUnit(
+            trie, lead,
+            Collation::makeCE32FromTagAndIndex(Collation::LEAD_SURROGATE_TAG, 0) | (uint32_t)value,
+            &errorCode);
+    }
+}
+
+void
+CollationDataBuilder::build(CollationData &data, UErrorCode &errorCode) {
+    buildMappings(data, errorCode);
+    if(base != nullptr) {
+        data.numericPrimary = base->numericPrimary;
+        data.compressibleBytes = base->compressibleBytes;
+        data.numScripts = base->numScripts;
+        data.scriptsIndex = base->scriptsIndex;
+        data.scriptStarts = base->scriptStarts;
+        data.scriptStartsLength = base->scriptStartsLength;
+    }
+    buildFastLatinTable(data, errorCode);
+}
+
+void
+CollationDataBuilder::buildMappings(CollationData &data, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return; }
+    if(trie == nullptr || utrie2_isFrozen(trie)) {
+        errorCode = U_INVALID_STATE_ERROR;
+        return;
+    }
+
+    buildContexts(errorCode);
+
+    uint32_t jamoCE32s[CollationData::JAMO_CE32S_LENGTH];
+    int32_t jamoIndex = -1;
+    if(getJamoCE32s(jamoCE32s, errorCode)) {
+        jamoIndex = ce32s.size();
+        for(int32_t i = 0; i < CollationData::JAMO_CE32S_LENGTH; ++i) {
+            ce32s.addElement((int32_t)jamoCE32s[i], errorCode);
+        }
+        // Small optimization: Use a bit in the Hangul ce32
+        // to indicate that none of the Jamo CE32s are isSpecialCE32()
+        // (as it should be in the root collator).
+        // It allows CollationIterator to avoid recursive function calls and per-Jamo tests.
+        // In order to still have good trie compression and keep this code simple,
+        // we only set this flag if a whole block of 588 Hangul syllables starting with
+        // a common leading consonant (Jamo L) has this property.
+        UBool isAnyJamoVTSpecial = false;
+        for(int32_t i = Hangul::JAMO_L_COUNT; i < CollationData::JAMO_CE32S_LENGTH; ++i) {
+            if(Collation::isSpecialCE32(jamoCE32s[i])) {
+                isAnyJamoVTSpecial = true;
+                break;
+            }
+        }
+        uint32_t hangulCE32 = Collation::makeCE32FromTagAndIndex(Collation::HANGUL_TAG, 0);
+        UChar32 c = Hangul::HANGUL_BASE;
+        for(int32_t i = 0; i < Hangul::JAMO_L_COUNT; ++i) {  // iterate over the Jamo L
+            uint32_t ce32 = hangulCE32;
+            if(!isAnyJamoVTSpecial && !Collation::isSpecialCE32(jamoCE32s[i])) {
+                ce32 |= Collation::HANGUL_NO_SPECIAL_JAMO;
+            }
+            UChar32 limit = c + Hangul::JAMO_VT_COUNT;
+            utrie2_setRange32(trie, c, limit - 1, ce32, true, &errorCode);
+            c = limit;
+        }
+    } else {
+        // Copy the Hangul CE32s from the base in blocks per Jamo L,
+        // assuming that HANGUL_NO_SPECIAL_JAMO is set or not set for whole blocks.
+        for(UChar32 c = Hangul::HANGUL_BASE; c < Hangul::HANGUL_LIMIT;) {
+            uint32_t ce32 = base->getCE32(c);
+            U_ASSERT(Collation::hasCE32Tag(ce32, Collation::HANGUL_TAG));
+            UChar32 limit = c + Hangul::JAMO_VT_COUNT;
+            utrie2_setRange32(trie, c, limit - 1, ce32, true, &errorCode);
+            c = limit;
+        }
+    }
+
+    setDigitTags(errorCode);
+    setLeadSurrogates(errorCode);
+
+    if (!icu4xMode) {
+        // For U+0000, move its normal ce32 into CE32s[0] and set U0000_TAG.
+        ce32s.setElementAt((int32_t)utrie2_get32(trie, 0), 0);
+        utrie2_set32(trie, 0, Collation::makeCE32FromTagAndIndex(Collation::U0000_TAG, 0), &errorCode);
+    }
+
+    utrie2_freeze(trie, UTRIE2_32_VALUE_BITS, &errorCode);
+    if(U_FAILURE(errorCode)) { return; }
+
+    // Mark each lead surrogate as "unsafe"
+    // if any of its 1024 associated supplementary code points is "unsafe".
+    UChar32 c = 0x10000;
+    for(char16_t lead = 0xd800; lead < 0xdc00; ++lead, c += 0x400) {
+        if(unsafeBackwardSet.containsSome(c, c + 0x3ff)) {
+            unsafeBackwardSet.add(lead);
+        }
+    }
+    unsafeBackwardSet.freeze();
+
+    data.trie = trie;
+    data.ce32s = reinterpret_cast<const uint32_t *>(ce32s.getBuffer());
+    data.ces = ce64s.getBuffer();
+    data.contexts = contexts.getBuffer();
+
+    data.ce32sLength = ce32s.size();
+    data.cesLength = ce64s.size();
+    data.contextsLength = contexts.length();
+
+    data.base = base;
+    if(jamoIndex >= 0) {
+        data.jamoCE32s = data.ce32s + jamoIndex;
+    } else {
+        data.jamoCE32s = base->jamoCE32s;
+    }
+    data.unsafeBackwardSet = &unsafeBackwardSet;
+}
+
+void
+CollationDataBuilder::clearContexts() {
+    contexts.remove();
+    // Incrementing the contexts build "era" invalidates all of the builtCE32
+    // from before this clearContexts() call.
+    // Simpler than finding and resetting all of those fields.
+    ++contextsEra;
+}
+
+void
+CollationDataBuilder::buildContexts(UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return; }
+    // Ignore abandoned lists and the cached builtCE32,
+    // and build all contexts from scratch.
+    clearContexts();
+    UnicodeSetIterator iter(contextChars);
+    while(U_SUCCESS(errorCode) && iter.next()) {
+        U_ASSERT(!iter.isString());
+        UChar32 c = iter.getCodepoint();
+        uint32_t ce32 = utrie2_get32(trie, c);
+        if(!isBuilderContextCE32(ce32)) {
+            // Impossible: No context data for c in contextChars.
+            errorCode = U_INTERNAL_PROGRAM_ERROR;
+            return;
+        }
+        ConditionalCE32 *cond = getConditionalCE32ForCE32(ce32);
+        ce32 = buildContext(cond, errorCode);
+        utrie2_set32(trie, c, ce32, &errorCode);
+    }
+}
+
+uint32_t
+CollationDataBuilder::buildContext(ConditionalCE32 *head, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return 0; }
+    // The list head must have no context.
+    U_ASSERT(!head->hasContext());
+    // The list head must be followed by one or more nodes that all do have context.
+    U_ASSERT(head->next >= 0);
+    UCharsTrieBuilder prefixBuilder(errorCode);
+    UCharsTrieBuilder contractionBuilder(errorCode);
+    // This outer loop goes from each prefix to the next.
+    // For each prefix it finds the one or more same-prefix entries (firstCond..lastCond).
+    // If there are multiple suffixes for the same prefix,
+    // then an inner loop builds a contraction trie for them.
+    for(ConditionalCE32 *cond = head;; cond = getConditionalCE32(cond->next)) {
+        if(U_FAILURE(errorCode)) { return 0; }  // early out for memory allocation errors
+        // After the list head, the prefix or suffix can be empty, but not both.
+        U_ASSERT(cond == head || cond->hasContext());
+        int32_t prefixLength = cond->prefixLength();
+        UnicodeString prefix(cond->context, 0, prefixLength + 1);
+        // Collect all contraction suffixes for one prefix.
+        ConditionalCE32 *firstCond = cond;
+        ConditionalCE32 *lastCond;
+        do {
+            lastCond = cond;
+            // Clear the defaultCE32 fields as we go.
+            // They are left over from building a previous version of this list of contexts.
+            //
+            // One of the code paths below may copy a preceding defaultCE32
+            // into its emptySuffixCE32.
+            // If a new suffix has been inserted before what used to be
+            // the firstCond for its prefix, then that previous firstCond could still
+            // contain an outdated defaultCE32 from an earlier buildContext() and
+            // result in an incorrect emptySuffixCE32.
+            // So we reset all defaultCE32 before reading and setting new values.
+            cond->defaultCE32 = Collation::NO_CE32;
+        } while(cond->next >= 0 &&
+                (cond = getConditionalCE32(cond->next))->context.startsWith(prefix));
+        uint32_t ce32;
+        int32_t suffixStart = prefixLength + 1;  // == prefix.length()
+        if(lastCond->context.length() == suffixStart) {
+            // One prefix without contraction suffix.
+            U_ASSERT(firstCond == lastCond);
+            ce32 = lastCond->ce32;
+            cond = lastCond;
+        } else {
+            // Build the contractions trie.
+            contractionBuilder.clear();
+            // Entry for an empty suffix, to be stored before the trie.
+            uint32_t emptySuffixCE32 = 0;
+            uint32_t flags = 0;
+            if(firstCond->context.length() == suffixStart) {
+                // There is a mapping for the prefix and the single character c. (p|c)
+                // If no other suffix matches, then we return this value.
+                emptySuffixCE32 = firstCond->ce32;
+                cond = getConditionalCE32(firstCond->next);
+            } else {
+                // There is no mapping for the prefix and just the single character.
+                // (There is no p|c, only p|cd, p|ce etc.)
+                flags |= Collation::CONTRACT_SINGLE_CP_NO_MATCH;
+                // When the prefix matches but none of the prefix-specific suffixes,
+                // then we fall back to the mappings with the next-longest prefix,
+                // and ultimately to mappings with no prefix.
+                // Each fallback might be another set of contractions.
+                // For example, if there are mappings for ch, p|cd, p|ce, but not for p|c,
+                // then in text "pch" we find the ch contraction.
+                for(cond = head;; cond = getConditionalCE32(cond->next)) {
+                    int32_t length = cond->prefixLength();
+                    if(length == prefixLength) { break; }
+                    if(cond->defaultCE32 != Collation::NO_CE32 &&
+                            (length==0 || prefix.endsWith(cond->context, 1, length))) {
+                        emptySuffixCE32 = cond->defaultCE32;
+                    }
+                }
+                cond = firstCond;
+            }
+            // Optimization: Set a flag when
+            // the first character of every contraction suffix has lccc!=0.
+            // Short-circuits contraction matching when a normal letter follows.
+            flags |= Collation::CONTRACT_NEXT_CCC;
+            // Add all of the non-empty suffixes into the contraction trie.
+            for(;;) {
+                UnicodeString suffix(cond->context, suffixStart);
+                uint16_t fcd16 = nfcImpl.getFCD16(suffix.char32At(0));
+                if(fcd16 <= 0xff) {
+                    flags &= ~Collation::CONTRACT_NEXT_CCC;
+                }
+                fcd16 = nfcImpl.getFCD16(suffix.char32At(suffix.length() - 1));
+                if(fcd16 > 0xff) {
+                    // The last suffix character has lccc!=0, allowing for discontiguous contractions.
+                    flags |= Collation::CONTRACT_TRAILING_CCC;
+                }
+                if (icu4xMode && (flags & Collation::CONTRACT_HAS_STARTER) == 0) {
+                    for (int32_t i = 0; i < suffix.length();) {
+                        UChar32 c = suffix.char32At(i);
+                            if (!u_getCombiningClass(c)) {
+                                flags |= Collation::CONTRACT_HAS_STARTER;
+                                break;
+                            }
+                        if (c > 0xFFFF) {
+                            i += 2;
+                        } else {
+                            ++i;
+                        }
+                    }
+                }
+                contractionBuilder.add(suffix, (int32_t)cond->ce32, errorCode);
+                if(cond == lastCond) { break; }
+                cond = getConditionalCE32(cond->next);
+            }
+            int32_t index = addContextTrie(emptySuffixCE32, contractionBuilder, errorCode);
+            if(U_FAILURE(errorCode)) { return 0; }
+            if(index > Collation::MAX_INDEX) {
+                errorCode = U_BUFFER_OVERFLOW_ERROR;
+                return 0;
+            }
+            ce32 = Collation::makeCE32FromTagAndIndex(Collation::CONTRACTION_TAG, index) | flags;
+        }
+        U_ASSERT(cond == lastCond);
+        firstCond->defaultCE32 = ce32;
+        if(prefixLength == 0) {
+            if(cond->next < 0) {
+                // No non-empty prefixes, only contractions.
+                return ce32;
+            }
+        } else {
+            prefix.remove(0, 1);  // Remove the length unit.
+            prefix.reverse();
+            prefixBuilder.add(prefix, (int32_t)ce32, errorCode);
+            if(cond->next < 0) { break; }
+        }
+    }
+    U_ASSERT(head->defaultCE32 != Collation::NO_CE32);
+    int32_t index = addContextTrie(head->defaultCE32, prefixBuilder, errorCode);
+    if(U_FAILURE(errorCode)) { return 0; }
+    if(index > Collation::MAX_INDEX) {
+        errorCode = U_BUFFER_OVERFLOW_ERROR;
+        return 0;
+    }
+    return Collation::makeCE32FromTagAndIndex(Collation::PREFIX_TAG, index);
+}
+
+int32_t
+CollationDataBuilder::addContextTrie(uint32_t defaultCE32, UCharsTrieBuilder &trieBuilder,
+                                     UErrorCode &errorCode) {
+    UnicodeString context;
+    context.append((char16_t)(defaultCE32 >> 16)).append((char16_t)defaultCE32);
+    UnicodeString trieString;
+    context.append(trieBuilder.buildUnicodeString(USTRINGTRIE_BUILD_SMALL, trieString, errorCode));
+    if(U_FAILURE(errorCode)) { return -1; }
+    int32_t index = contexts.indexOf(context);
+    if(index < 0) {
+        index = contexts.length();
+        contexts.append(context);
+    }
+    return index;
+}
+
+void
+CollationDataBuilder::buildFastLatinTable(CollationData &data, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode) || !fastLatinEnabled) { return; }
+
+    delete fastLatinBuilder;
+    fastLatinBuilder = new CollationFastLatinBuilder(errorCode);
+    if(fastLatinBuilder == nullptr) {
+        errorCode = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    if(fastLatinBuilder->forData(data, errorCode)) {
+        const uint16_t *table = fastLatinBuilder->getTable();
+        int32_t length = fastLatinBuilder->lengthOfTable();
+        if(base != nullptr && length == base->fastLatinTableLength &&
+                uprv_memcmp(table, base->fastLatinTable, length * 2) == 0) {
+            // Same fast Latin table as in the base, use that one instead.
+            delete fastLatinBuilder;
+            fastLatinBuilder = nullptr;
+            table = base->fastLatinTable;
+        }
+        data.fastLatinTable = table;
+        data.fastLatinTableLength = length;
+    } else {
+        delete fastLatinBuilder;
+        fastLatinBuilder = nullptr;
+    }
+}
+
+int32_t
+CollationDataBuilder::getCEs(const UnicodeString &s, int64_t ces[], int32_t cesLength) {
+    return getCEs(s, 0, ces, cesLength);
+}
+
+int32_t
+CollationDataBuilder::getCEs(const UnicodeString &prefix, const UnicodeString &s,
+                             int64_t ces[], int32_t cesLength) {
+    int32_t prefixLength = prefix.length();
+    if(prefixLength == 0) {
+        return getCEs(s, 0, ces, cesLength);
+    } else {
+        return getCEs(prefix + s, prefixLength, ces, cesLength);
+    }
+}
+
+int32_t
+CollationDataBuilder::getCEs(const UnicodeString &s, int32_t start,
+                             int64_t ces[], int32_t cesLength) {
+    if(collIter == nullptr) {
+        collIter = new DataBuilderCollationIterator(*this);
+        if(collIter == nullptr) { return 0; }
+    }
+    return collIter->fetchCEs(s, start, ces, cesLength);
+}
+
+U_NAMESPACE_END
+
+#endif  // !UCONFIG_NO_COLLATION