Update ICU to 54.1 step 1

source/i18n/collationkeys.cpp

Index: source/i18n/collationkeys.cpp
diff --git a/source/i18n/collationkeys.cpp b/source/i18n/collationkeys.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6006811377fec607d99b0f7e300033b9d5eaf399
--- /dev/null
+++ b/source/i18n/collationkeys.cpp
@@ -0,0 +1,695 @@
+/*
+*******************************************************************************
+* Copyright (C) 2012-2014, International Business Machines
+* Corporation and others.  All Rights Reserved.
+*******************************************************************************
+* collationkeys.cpp
+*
+* created on: 2012sep02
+* created by: Markus W. Scherer
+*/
+
+#include "unicode/utypes.h"
+
+#if !UCONFIG_NO_COLLATION
+
+#include "unicode/bytestream.h"
+#include "collation.h"
+#include "collationiterator.h"
+#include "collationkeys.h"
+#include "collationsettings.h"
+#include "uassert.h"
+
+U_NAMESPACE_BEGIN
+
+SortKeyByteSink::~SortKeyByteSink() {}
+
+void
+SortKeyByteSink::Append(const char *bytes, int32_t n) {
+    if (n <= 0 || bytes == NULL) {
+        return;
+    }
+    if (ignore_ > 0) {
+        int32_t ignoreRest = ignore_ - n;
+        if (ignoreRest >= 0) {
+            ignore_ = ignoreRest;
+            return;
+        } else {
+            bytes += ignore_;
+            n = -ignoreRest;
+            ignore_ = 0;
+        }
+    }
+    int32_t length = appended_;
+    appended_ += n;
+    if ((buffer_ + length) == bytes) {
+        return;  // the caller used GetAppendBuffer() and wrote the bytes already
+    }
+    int32_t available = capacity_ - length;
+    if (n <= available) {
+        uprv_memcpy(buffer_ + length, bytes, n);
+    } else {
+        AppendBeyondCapacity(bytes, n, length);
+    }
+}
+
+char *
+SortKeyByteSink::GetAppendBuffer(int32_t min_capacity,
+                                 int32_t desired_capacity_hint,
+                                 char *scratch,
+                                 int32_t scratch_capacity,
+                                 int32_t *result_capacity) {
+    if (min_capacity < 1 || scratch_capacity < min_capacity) {
+        *result_capacity = 0;
+        return NULL;
+    }
+    if (ignore_ > 0) {
+        // Do not write ignored bytes right at the end of the buffer.
+        *result_capacity = scratch_capacity;
+        return scratch;
+    }
+    int32_t available = capacity_ - appended_;
+    if (available >= min_capacity) {
+        *result_capacity = available;
+        return buffer_ + appended_;
+    } else if (Resize(desired_capacity_hint, appended_)) {
+        *result_capacity = capacity_ - appended_;
+        return buffer_ + appended_;
+    } else {
+        *result_capacity = scratch_capacity;
+        return scratch;
+    }
+}
+
+namespace {
+
+/**
+ * uint8_t byte buffer, similar to CharString but simpler.
+ */
+class SortKeyLevel : public UMemory {
+public:
+    SortKeyLevel() : len(0), ok(TRUE) {}
+    ~SortKeyLevel() {}
+
+    /** @return FALSE if memory allocation failed */
+    UBool isOk() const { return ok; }
+    UBool isEmpty() const { return len == 0; }
+    int32_t length() const { return len; }
+    const uint8_t *data() const { return buffer.getAlias(); }
+    uint8_t operator[](int32_t index) const { return buffer[index]; }
+
+    uint8_t *data() { return buffer.getAlias(); }
+
+    void appendByte(uint32_t b);
+    void appendWeight16(uint32_t w);
+    void appendWeight32(uint32_t w);
+    void appendReverseWeight16(uint32_t w);
+
+    /** Appends all but the last byte to the sink. The last byte should be the 01 terminator. */
+    void appendTo(ByteSink &sink) const {
+        U_ASSERT(len > 0 && buffer[len - 1] == 1);
+        sink.Append(reinterpret_cast<const char *>(buffer.getAlias()), len - 1);
+    }
+
+private:
+    MaybeStackArray<uint8_t, 40> buffer;
+    int32_t len;
+    UBool ok;
+
+    UBool ensureCapacity(int32_t appendCapacity);
+
+    SortKeyLevel(const SortKeyLevel &other); // forbid copying of this class
+    SortKeyLevel &operator=(const SortKeyLevel &other); // forbid copying of this class
+};
+
+void SortKeyLevel::appendByte(uint32_t b) {
+    if(len < buffer.getCapacity() || ensureCapacity(1)) {
+        buffer[len++] = (uint8_t)b;
+    }
+}
+
+void
+SortKeyLevel::appendWeight16(uint32_t w) {
+    U_ASSERT((w & 0xffff) != 0);
+    uint8_t b0 = (uint8_t)(w >> 8);
+    uint8_t b1 = (uint8_t)w;
+    int32_t appendLength = (b1 == 0) ? 1 : 2;
+    if((len + appendLength) <= buffer.getCapacity() || ensureCapacity(appendLength)) {
+        buffer[len++] = b0;
+        if(b1 != 0) {
+            buffer[len++] = b1;
+        }
+    }
+}
+
+void
+SortKeyLevel::appendWeight32(uint32_t w) {
+    U_ASSERT(w != 0);
+    uint8_t bytes[4] = { (uint8_t)(w >> 24), (uint8_t)(w >> 16), (uint8_t)(w >> 8), (uint8_t)w };
+    int32_t appendLength = (bytes[1] == 0) ? 1 : (bytes[2] == 0) ? 2 : (bytes[3] == 0) ? 3 : 4;
+    if((len + appendLength) <= buffer.getCapacity() || ensureCapacity(appendLength)) {
+        buffer[len++] = bytes[0];
+        if(bytes[1] != 0) {
+            buffer[len++] = bytes[1];
+            if(bytes[2] != 0) {
+                buffer[len++] = bytes[2];
+                if(bytes[3] != 0) {
+                    buffer[len++] = bytes[3];
+                }
+            }
+        }
+    }
+}
+
+void
+SortKeyLevel::appendReverseWeight16(uint32_t w) {
+    U_ASSERT((w & 0xffff) != 0);
+    uint8_t b0 = (uint8_t)(w >> 8);
+    uint8_t b1 = (uint8_t)w;
+    int32_t appendLength = (b1 == 0) ? 1 : 2;
+    if((len + appendLength) <= buffer.getCapacity() || ensureCapacity(appendLength)) {
+        if(b1 == 0) {
+            buffer[len++] = b0;
+        } else {
+            buffer[len] = b1;
+            buffer[len + 1] = b0;
+            len += 2;
+        }
+    }
+}
+
+UBool SortKeyLevel::ensureCapacity(int32_t appendCapacity) {
+    if(!ok) {
+        return FALSE;
+    }
+    int32_t newCapacity = 2 * buffer.getCapacity();
+    int32_t altCapacity = len + 2 * appendCapacity;
+    if (newCapacity < altCapacity) {
+        newCapacity = altCapacity;
+    }
+    if (newCapacity < 200) {
+        newCapacity = 200;
+    }
+    if(buffer.resize(newCapacity, len)==NULL) {
+        return ok = FALSE;
+    }
+    return TRUE;
+}
+
+}  // namespace
+
+CollationKeys::LevelCallback::~LevelCallback() {}
+
+UBool
+CollationKeys::LevelCallback::needToWrite(Collation::Level /*level*/) { return TRUE; }
+
+/**
+ * Map from collation strength (UColAttributeValue)
+ * to a mask of Collation::Level bits up to that strength,
+ * excluding the CASE_LEVEL which is independent of the strength,
+ * and excluding IDENTICAL_LEVEL which this function does not write.
+ */
+static const uint32_t levelMasks[UCOL_STRENGTH_LIMIT] = {
+    2,          // UCOL_PRIMARY -> PRIMARY_LEVEL
+    6,          // UCOL_SECONDARY -> up to SECONDARY_LEVEL
+    0x16,       // UCOL_TERTIARY -> up to TERTIARY_LEVEL
+    0x36,       // UCOL_QUATERNARY -> up to QUATERNARY_LEVEL
+    0, 0, 0, 0,
+    0, 0, 0, 0,
+    0, 0, 0,
+    0x36        // UCOL_IDENTICAL -> up to QUATERNARY_LEVEL
+};
+
+void
+CollationKeys::writeSortKeyUpToQuaternary(CollationIterator &iter,
+                                          const UBool *compressibleBytes,
+                                          const CollationSettings &settings,
+                                          SortKeyByteSink &sink,
+                                          Collation::Level minLevel, LevelCallback &callback,
+                                          UBool preflight, UErrorCode &errorCode) {
+    if(U_FAILURE(errorCode)) { return; }
+
+    int32_t options = settings.options;
+    // Set of levels to process and write.
+    uint32_t levels = levelMasks[CollationSettings::getStrength(options)];
+    if((options & CollationSettings::CASE_LEVEL) != 0) {
+        levels |= Collation::CASE_LEVEL_FLAG;
+    }
+    // Minus the levels below minLevel.
+    levels &= ~(((uint32_t)1 << minLevel) - 1);
+    if(levels == 0) { return; }
+
+    uint32_t variableTop;
+    if((options & CollationSettings::ALTERNATE_MASK) == 0) {
+        variableTop = 0;
+    } else {
+        // +1 so that we can use "<" and primary ignorables test out early.
+        variableTop = settings.variableTop + 1;
+    }
+    const uint8_t *reorderTable = settings.reorderTable;
+
+    uint32_t tertiaryMask = CollationSettings::getTertiaryMask(options);
+
+    SortKeyLevel cases;
+    SortKeyLevel secondaries;
+    SortKeyLevel tertiaries;
+    SortKeyLevel quaternaries;
+
+    uint32_t compressedP1 = 0;  // 0==no compression; otherwise reordered compressible lead byte
+    int32_t commonCases = 0;
+    int32_t commonSecondaries = 0;
+    int32_t commonTertiaries = 0;
+    int32_t commonQuaternaries = 0;
+
+    uint32_t prevSecondary = 0;
+    UBool anyMergeSeparators = FALSE;
+
+    for(;;) {
+        // No need to keep all CEs in the buffer when we write a sort key.
+        iter.clearCEsIfNoneRemaining();
+        int64_t ce = iter.nextCE(errorCode);
+        uint32_t p = (uint32_t)(ce >> 32);
+        if(p < variableTop && p > Collation::MERGE_SEPARATOR_PRIMARY) {
+            // Variable CE, shift it to quaternary level.
+            // Ignore all following primary ignorables, and shift further variable CEs.
+            if(commonQuaternaries != 0) {
+                --commonQuaternaries;
+                while(commonQuaternaries >= QUAT_COMMON_MAX_COUNT) {
+                    quaternaries.appendByte(QUAT_COMMON_MIDDLE);
+                    commonQuaternaries -= QUAT_COMMON_MAX_COUNT;
+                }
+                // Shifted primary weights are lower than the common weight.
+                quaternaries.appendByte(QUAT_COMMON_LOW + commonQuaternaries);
+                commonQuaternaries = 0;
+            }
+            do {
+                if((levels & Collation::QUATERNARY_LEVEL_FLAG) != 0) {
+                    uint32_t p1 = p >> 24;
+                    if(reorderTable != NULL) { p1 = reorderTable[p1]; }
+                    if(p1 >= QUAT_SHIFTED_LIMIT_BYTE) {
+                        // Prevent shifted primary lead bytes from
+                        // overlapping with the common compression range.
+                        quaternaries.appendByte(QUAT_SHIFTED_LIMIT_BYTE);
+                    }
+                    quaternaries.appendWeight32((p1 << 24) | (p & 0xffffff));
+                }
+                do {
+                    ce = iter.nextCE(errorCode);
+                    p = (uint32_t)(ce >> 32);
+                } while(p == 0);
+            } while(p < variableTop && p > Collation::MERGE_SEPARATOR_PRIMARY);
+        }
+        // ce could be primary ignorable, or NO_CE, or the merge separator,
+        // or a regular primary CE, but it is not variable.
+        // If ce==NO_CE, then write nothing for the primary level but
+        // terminate compression on all levels and then exit the loop.
+        if(p > Collation::NO_CE_PRIMARY && (levels & Collation::PRIMARY_LEVEL_FLAG) != 0) {
+            uint32_t p1 = p >> 24;
+            if(reorderTable != NULL) { p1 = reorderTable[p1]; }
+            if(p1 != compressedP1) {
+                if(compressedP1 != 0) {
+                    if(p1 < compressedP1) {
+                        // No primary compression terminator
+                        // at the end of the level or merged segment.
+                        if(p1 > Collation::MERGE_SEPARATOR_BYTE) {
+                            sink.Append(Collation::PRIMARY_COMPRESSION_LOW_BYTE);
+                        }
+                    } else {
+                        sink.Append(Collation::PRIMARY_COMPRESSION_HIGH_BYTE);
+                    }
+                }
+                sink.Append(p1);
+                // Test the un-reordered lead byte for compressibility but
+                // remember the reordered lead byte.
+                if(compressibleBytes[p >> 24]) {
+                    compressedP1 = p1;
+                } else {
+                    compressedP1 = 0;
+                }
+            }
+            char p2 = (char)(p >> 16);
+            if(p2 != 0) {
+                char buffer[3] = { p2, (char)(p >> 8), (char)p };
+                sink.Append(buffer, (buffer[1] == 0) ? 1 : (buffer[2] == 0) ? 2 : 3);
+            }
+            // Optimization for internalNextSortKeyPart():
+            // When the primary level overflows we can stop because we need not
+            // calculate (preflight) the whole sort key length.
+            if(!preflight && sink.Overflowed()) {
+                if(U_SUCCESS(errorCode) && !sink.IsOk()) {
+                    errorCode = U_MEMORY_ALLOCATION_ERROR;
+                }
+                return;
+            }
+        }
+
+        uint32_t lower32 = (uint32_t)ce;
+        if(lower32 == 0) { continue; }  // completely ignorable, no secondary/case/tertiary/quaternary
+
+        if((levels & Collation::SECONDARY_LEVEL_FLAG) != 0) {
+            uint32_t s = lower32 >> 16;
+            if(s == 0) {
+                // secondary ignorable
+            } else if(s == Collation::COMMON_WEIGHT16) {
+                ++commonSecondaries;
+            } else if((options & CollationSettings::BACKWARD_SECONDARY) == 0) {
+                if(commonSecondaries != 0) {
+                    --commonSecondaries;
+                    while(commonSecondaries >= SEC_COMMON_MAX_COUNT) {
+                        secondaries.appendByte(SEC_COMMON_MIDDLE);
+                        commonSecondaries -= SEC_COMMON_MAX_COUNT;
+                    }
+                    uint32_t b;
+                    if(s < Collation::COMMON_WEIGHT16) {
+                        b = SEC_COMMON_LOW + commonSecondaries;
+                    } else {
+                        b = SEC_COMMON_HIGH - commonSecondaries;
+                    }
+                    secondaries.appendByte(b);
+                    commonSecondaries = 0;
+                }
+                secondaries.appendWeight16(s);
+            } else {
+                if(commonSecondaries != 0) {
+                    --commonSecondaries;
+                    // Append reverse weights. The level will be re-reversed later.
+                    int32_t remainder = commonSecondaries % SEC_COMMON_MAX_COUNT;
+                    uint32_t b;
+                    if(prevSecondary < Collation::COMMON_WEIGHT16) {
+                        b = SEC_COMMON_LOW + remainder;
+                    } else {
+                        b = SEC_COMMON_HIGH - remainder;
+                    }
+                    secondaries.appendByte(b);
+                    commonSecondaries -= remainder;
+                    // commonSecondaries is now a multiple of SEC_COMMON_MAX_COUNT.
+                    while(commonSecondaries > 0) {  // same as >= SEC_COMMON_MAX_COUNT
+                        secondaries.appendByte(SEC_COMMON_MIDDLE);
+                        commonSecondaries -= SEC_COMMON_MAX_COUNT;
+                    }
+                    // commonSecondaries == 0
+                }
+                // Reduce separators so that we can look for byte<=1 later.
+                if(s <= Collation::MERGE_SEPARATOR_WEIGHT16) {
+                    if(s == Collation::MERGE_SEPARATOR_WEIGHT16) {
+                        anyMergeSeparators = TRUE;
+                    }
+                    secondaries.appendByte((s >> 8) - 1);
+                } else {
+                    secondaries.appendReverseWeight16(s);
+                }
+                prevSecondary = s;
+            }
+        }
+
+        if((levels & Collation::CASE_LEVEL_FLAG) != 0) {
+            if((CollationSettings::getStrength(options) == UCOL_PRIMARY) ?
+                    p == 0 : lower32 <= 0xffff) {
+                // Primary+caseLevel: Ignore case level weights of primary ignorables.
+                // Otherwise: Ignore case level weights of secondary ignorables.
+                // For details see the comments in the CollationCompare class.
+            } else {
+                uint32_t c = (lower32 >> 8) & 0xff;  // case bits & tertiary lead byte
+                U_ASSERT((c & 0xc0) != 0xc0);
+                if((c & 0xc0) == 0 && c > Collation::MERGE_SEPARATOR_BYTE) {
+                    ++commonCases;
+                } else {
+                    if((options & CollationSettings::UPPER_FIRST) == 0) {
+                        // lowerFirst: Compress common weights to nibbles 1..7..13, mixed=14, upper=15.
+                        if(commonCases != 0) {
+                            --commonCases;
+                            while(commonCases >= CASE_LOWER_FIRST_COMMON_MAX_COUNT) {
+                                cases.appendByte(CASE_LOWER_FIRST_COMMON_MIDDLE << 4);
+                                commonCases -= CASE_LOWER_FIRST_COMMON_MAX_COUNT;
+                            }
+                            uint32_t b;
+                            if(c <= Collation::MERGE_SEPARATOR_BYTE) {
+                                b = CASE_LOWER_FIRST_COMMON_LOW + commonCases;
+                            } else {
+                                b = CASE_LOWER_FIRST_COMMON_HIGH - commonCases;
+                            }
+                            cases.appendByte(b << 4);
+                            commonCases = 0;
+                        }
+                        if(c > Collation::MERGE_SEPARATOR_BYTE) {
+                            c = (CASE_LOWER_FIRST_COMMON_HIGH + (c >> 6)) << 4;  // 14 or 15
+                        }
+                    } else {
+                        // upperFirst: Compress common weights to nibbles 3..15, mixed=2, upper=1.
+                        // The compressed common case weights only go up from the "low" value
+                        // because with upperFirst the common weight is the highest one.
+                        if(commonCases != 0) {
+                            --commonCases;
+                            while(commonCases >= CASE_UPPER_FIRST_COMMON_MAX_COUNT) {
+                                cases.appendByte(CASE_UPPER_FIRST_COMMON_LOW << 4);
+                                commonCases -= CASE_UPPER_FIRST_COMMON_MAX_COUNT;
+                            }
+                            cases.appendByte((CASE_UPPER_FIRST_COMMON_LOW + commonCases) << 4);
+                            commonCases = 0;
+                        }
+                        if(c > Collation::MERGE_SEPARATOR_BYTE) {
+                            c = (CASE_UPPER_FIRST_COMMON_LOW - (c >> 6)) << 4;  // 2 or 1
+                        }
+                    }
+                    // c is a separator byte 01 or 02,
+                    // or a left-shifted nibble 0x10, 0x20, ... 0xf0.
+                    cases.appendByte(c);
+                }
+            }
+        }
+
+        if((levels & Collation::TERTIARY_LEVEL_FLAG) != 0) {
+            uint32_t t = lower32 & tertiaryMask;
+            U_ASSERT((lower32 & 0xc000) != 0xc000);
+            if(t == Collation::COMMON_WEIGHT16) {
+                ++commonTertiaries;
+            } else if((tertiaryMask & 0x8000) == 0) {
+                // Tertiary weights without case bits.
+                // Move lead bytes 06..3F to C6..FF for a large common-weight range.
+                if(commonTertiaries != 0) {
+                    --commonTertiaries;
+                    while(commonTertiaries >= TER_ONLY_COMMON_MAX_COUNT) {
+                        tertiaries.appendByte(TER_ONLY_COMMON_MIDDLE);
+                        commonTertiaries -= TER_ONLY_COMMON_MAX_COUNT;
+                    }
+                    uint32_t b;
+                    if(t < Collation::COMMON_WEIGHT16) {
+                        b = TER_ONLY_COMMON_LOW + commonTertiaries;
+                    } else {
+                        b = TER_ONLY_COMMON_HIGH - commonTertiaries;
+                    }
+                    tertiaries.appendByte(b);
+                    commonTertiaries = 0;
+                }
+                if(t > Collation::COMMON_WEIGHT16) { t += 0xc000; }
+                tertiaries.appendWeight16(t);
+            } else if((options & CollationSettings::UPPER_FIRST) == 0) {
+                // Tertiary weights with caseFirst=lowerFirst.
+                // Move lead bytes 06..BF to 46..FF for the common-weight range.
+                if(commonTertiaries != 0) {
+                    --commonTertiaries;
+                    while(commonTertiaries >= TER_LOWER_FIRST_COMMON_MAX_COUNT) {
+                        tertiaries.appendByte(TER_LOWER_FIRST_COMMON_MIDDLE);
+                        commonTertiaries -= TER_LOWER_FIRST_COMMON_MAX_COUNT;
+                    }
+                    uint32_t b;
+                    if(t < Collation::COMMON_WEIGHT16) {
+                        b = TER_LOWER_FIRST_COMMON_LOW + commonTertiaries;
+                    } else {
+                        b = TER_LOWER_FIRST_COMMON_HIGH - commonTertiaries;
+                    }
+                    tertiaries.appendByte(b);
+                    commonTertiaries = 0;
+                }
+                if(t > Collation::COMMON_WEIGHT16) { t += 0x4000; }
+                tertiaries.appendWeight16(t);
+            } else {
+                // Tertiary weights with caseFirst=upperFirst.
+                // Do not change the artificial uppercase weight of a tertiary CE (0.0.ut),
+                // to keep tertiary CEs well-formed.
+                // Their case+tertiary weights must be greater than those of
+                // primary and secondary CEs.
+                //
+                // Separators    01..02 -> 01..02  (unchanged)
+                // Lowercase     03..04 -> 83..84  (includes uncased)
+                // Common weight     05 -> 85..C5  (common-weight compression range)
+                // Lowercase     06..3F -> C6..FF
+                // Mixed case    43..7F -> 43..7F
+                // Uppercase     83..BF -> 03..3F
+                // Tertiary CE   86..BF -> C6..FF
+                if(t <= Collation::MERGE_SEPARATOR_WEIGHT16) {
+                    // Keep separators unchanged.
+                } else if(lower32 > 0xffff) {
+                    // Invert case bits of primary & secondary CEs.
+                    t ^= 0xc000;
+                    if(t < (TER_UPPER_FIRST_COMMON_HIGH << 8)) {
+                        t -= 0x4000;
+                    }
+                } else {
+                    // Keep uppercase bits of tertiary CEs.
+                    U_ASSERT(0x8600 <= t && t <= 0xbfff);
+                    t += 0x4000;
+                }
+                if(commonTertiaries != 0) {
+                    --commonTertiaries;
+                    while(commonTertiaries >= TER_UPPER_FIRST_COMMON_MAX_COUNT) {
+                        tertiaries.appendByte(TER_UPPER_FIRST_COMMON_MIDDLE);
+                        commonTertiaries -= TER_UPPER_FIRST_COMMON_MAX_COUNT;
+                    }
+                    uint32_t b;
+                    if(t < (TER_UPPER_FIRST_COMMON_LOW << 8)) {
+                        b = TER_UPPER_FIRST_COMMON_LOW + commonTertiaries;
+                    } else {
+                        b = TER_UPPER_FIRST_COMMON_HIGH - commonTertiaries;
+                    }
+                    tertiaries.appendByte(b);
+                    commonTertiaries = 0;
+                }
+                tertiaries.appendWeight16(t);
+            }
+        }
+
+        if((levels & Collation::QUATERNARY_LEVEL_FLAG) != 0) {
+            uint32_t q = lower32 & 0xffff;
+            if((q & 0xc0) == 0 && q > Collation::MERGE_SEPARATOR_WEIGHT16) {
+                ++commonQuaternaries;
+            } else if(q <= Collation::MERGE_SEPARATOR_WEIGHT16 &&
+                    (options & CollationSettings::ALTERNATE_MASK) == 0 &&
+                    (quaternaries.isEmpty() ||
+                        quaternaries[quaternaries.length() - 1] == Collation::MERGE_SEPARATOR_BYTE)) {
+                // If alternate=non-ignorable and there are only
+                // common quaternary weights between two separators,
+                // then we need not write anything between these separators.
+                // The only weights greater than the merge separator and less than the common weight
+                // are shifted primary weights, which are not generated for alternate=non-ignorable.
+                // There are also exactly as many quaternary weights as tertiary weights,
+                // so level length differences are handled already on tertiary level.
+                // Any above-common quaternary weight will compare greater regardless.
+                quaternaries.appendByte(q >> 8);
+            } else {
+                if(q <= Collation::MERGE_SEPARATOR_WEIGHT16) {
+                    q >>= 8;
+                } else {
+                    q = 0xfc + ((q >> 6) & 3);
+                }
+                if(commonQuaternaries != 0) {
+                    --commonQuaternaries;
+                    while(commonQuaternaries >= QUAT_COMMON_MAX_COUNT) {
+                        quaternaries.appendByte(QUAT_COMMON_MIDDLE);
+                        commonQuaternaries -= QUAT_COMMON_MAX_COUNT;
+                    }
+                    uint32_t b;
+                    if(q < QUAT_COMMON_LOW) {
+                        b = QUAT_COMMON_LOW + commonQuaternaries;
+                    } else {
+                        b = QUAT_COMMON_HIGH - commonQuaternaries;
+                    }
+                    quaternaries.appendByte(b);
+                    commonQuaternaries = 0;
+                }
+                quaternaries.appendByte(q);
+            }
+        }
+
+        if((lower32 >> 24) == Collation::LEVEL_SEPARATOR_BYTE) { break; }  // ce == NO_CE
+    }
+
+    if(U_FAILURE(errorCode)) { return; }
+
+    // Append the beyond-primary levels.
+    UBool ok = TRUE;
+    if((levels & Collation::SECONDARY_LEVEL_FLAG) != 0) {
+        if(!callback.needToWrite(Collation::SECONDARY_LEVEL)) { return; }
+        ok &= secondaries.isOk();
+        sink.Append(Collation::LEVEL_SEPARATOR_BYTE);
+        uint8_t *secs = secondaries.data();
+        int32_t length = secondaries.length() - 1;  // Ignore the trailing NO_CE.
+        if((options & CollationSettings::BACKWARD_SECONDARY) != 0) {
+            // The backwards secondary level compares secondary weights backwards
+            // within segments separated by the merge separator (U+FFFE, weight 02).
+            // The separator weights 01 & 02 were reduced to 00 & 01 so that
+            // we do not accidentally separate at a _second_ weight byte of 02.
+            int32_t start = 0;
+            for(;;) {
+                // Find the merge separator or the NO_CE terminator.
+                int32_t limit;
+                if(anyMergeSeparators) {
+                    limit = start;
+                    while(secs[limit] > 1) { ++limit; }
+                } else {
+                    limit = length;
+                }
+                // Reverse this segment.
+                if(start < limit) {
+                    uint8_t *p = secs + start;
+                    uint8_t *q = secs + limit - 1;
+                    while(p < q) {
+                        uint8_t s = *p;
+                        *p++ = *q;
+                        *q-- = s;
+                    }
+                }
+                // Did we reach the end of the string?
+                if(secs[limit] == 0) { break; }
+                // Restore the merge separator.
+                secs[limit] = 2;
+                // Skip the merge separator and continue.
+                start = limit + 1;
+            }
+        }
+        sink.Append(reinterpret_cast<char *>(secs), length);
+    }
+
+    if((levels & Collation::CASE_LEVEL_FLAG) != 0) {
+        if(!callback.needToWrite(Collation::CASE_LEVEL)) { return; }
+        ok &= cases.isOk();
+        sink.Append(Collation::LEVEL_SEPARATOR_BYTE);
+        // Write pairs of nibbles as bytes, except separator bytes as themselves.
+        int32_t length = cases.length() - 1;  // Ignore the trailing NO_CE.
+        uint8_t b = 0;
+        for(int32_t i = 0; i < length; ++i) {
+            uint8_t c = (uint8_t)cases[i];
+            if(c <= Collation::MERGE_SEPARATOR_BYTE) {
+                U_ASSERT(c != 0);
+                if(b != 0) {
+                    sink.Append(b);
+                    b = 0;
+                }
+                sink.Append(c);
+            } else {
+                U_ASSERT((c & 0xf) == 0);
+                if(b == 0) {
+                    b = c;
+                } else {
+                    sink.Append(b | (c >> 4));
+                    b = 0;
+                }
+            }
+        }
+        if(b != 0) {
+            sink.Append(b);
+        }
+    }
+
+    if((levels & Collation::TERTIARY_LEVEL_FLAG) != 0) {
+        if(!callback.needToWrite(Collation::TERTIARY_LEVEL)) { return; }
+        ok &= tertiaries.isOk();
+        sink.Append(Collation::LEVEL_SEPARATOR_BYTE);
+        tertiaries.appendTo(sink);
+    }
+
+    if((levels & Collation::QUATERNARY_LEVEL_FLAG) != 0) {
+        if(!callback.needToWrite(Collation::QUATERNARY_LEVEL)) { return; }
+        ok &= quaternaries.isOk();
+        sink.Append(Collation::LEVEL_SEPARATOR_BYTE);
+        quaternaries.appendTo(sink);
+    }
+
+    if(!ok || !sink.IsOk()) {
+        errorCode = U_MEMORY_ALLOCATION_ERROR;
+    }
+}
+
+U_NAMESPACE_END
+
+#endif  // !UCONFIG_NO_COLLATION