Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

1 files changed, 1260 insertions, 0 deletions

diff --git a/intl/icu/source/i18n/measunit_extra.cpp b/intl/icu/source/i18n/measunit_extra.cpp
new file mode 100644
index 0000000000..295d6a8ce8
--- /dev/null
+++ b/intl/icu/source/i18n/measunit_extra.cpp
@@ -0,0 +1,1260 @@
+// © 2020 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+
+// Extra functions for MeasureUnit not needed for all clients.
+// Separate .o file so that it can be removed for modularity.
+
+#include "unicode/utypes.h"
+
+#if !UCONFIG_NO_FORMATTING
+
+// Allow implicit conversion from char16_t* to UnicodeString for this file:
+// Helpful in toString methods and elsewhere.
+#define UNISTR_FROM_STRING_EXPLICIT
+
+#include "charstr.h"
+#include "cmemory.h"
+#include "cstring.h"
+#include "measunit_impl.h"
+#include "resource.h"
+#include "uarrsort.h"
+#include "uassert.h"
+#include "ucln_in.h"
+#include "umutex.h"
+#include "unicode/bytestrie.h"
+#include "unicode/bytestriebuilder.h"
+#include "unicode/localpointer.h"
+#include "unicode/stringpiece.h"
+#include "unicode/stringtriebuilder.h"
+#include "unicode/ures.h"
+#include "unicode/ustringtrie.h"
+#include "uresimp.h"
+#include "util.h"
+#include <cstdlib>
+
+U_NAMESPACE_BEGIN
+
+
+namespace {
+
+// TODO: Propose a new error code for this?
+constexpr UErrorCode kUnitIdentifierSyntaxError = U_ILLEGAL_ARGUMENT_ERROR;
+
+// Trie value offset for SI or binary prefixes. This is big enough to ensure we only
+// insert positive integers into the trie.
+constexpr int32_t kPrefixOffset = 64;
+static_assert(kPrefixOffset + UMEASURE_PREFIX_INTERNAL_MIN_BIN > 0,
+              "kPrefixOffset is too small for minimum UMeasurePrefix value");
+static_assert(kPrefixOffset + UMEASURE_PREFIX_INTERNAL_MIN_SI > 0,
+              "kPrefixOffset is too small for minimum UMeasurePrefix value");
+
+// Trie value offset for compound parts, e.g. "-per-", "-", "-and-".
+constexpr int32_t kCompoundPartOffset = 128;
+static_assert(kCompoundPartOffset > kPrefixOffset + UMEASURE_PREFIX_INTERNAL_MAX_BIN,
+              "Ambiguous token values: prefix tokens are overlapping with CompoundPart tokens");
+static_assert(kCompoundPartOffset > kPrefixOffset + UMEASURE_PREFIX_INTERNAL_MAX_SI,
+              "Ambiguous token values: prefix tokens are overlapping with CompoundPart tokens");
+
+enum CompoundPart {
+    // Represents "-per-"
+    COMPOUND_PART_PER = kCompoundPartOffset,
+    // Represents "-"
+    COMPOUND_PART_TIMES,
+    // Represents "-and-"
+    COMPOUND_PART_AND,
+};
+
+// Trie value offset for "per-".
+constexpr int32_t kInitialCompoundPartOffset = 192;
+
+enum InitialCompoundPart {
+    // Represents "per-", the only compound part that can appear at the start of
+    // an identifier.
+    INITIAL_COMPOUND_PART_PER = kInitialCompoundPartOffset,
+};
+
+// Trie value offset for powers like "square-", "cubic-", "pow2-" etc.
+constexpr int32_t kPowerPartOffset = 256;
+
+enum PowerPart {
+    POWER_PART_P2 = kPowerPartOffset + 2,
+    POWER_PART_P3,
+    POWER_PART_P4,
+    POWER_PART_P5,
+    POWER_PART_P6,
+    POWER_PART_P7,
+    POWER_PART_P8,
+    POWER_PART_P9,
+    POWER_PART_P10,
+    POWER_PART_P11,
+    POWER_PART_P12,
+    POWER_PART_P13,
+    POWER_PART_P14,
+    POWER_PART_P15,
+};
+
+// Trie value offset for simple units, e.g. "gram", "nautical-mile",
+// "fluid-ounce-imperial".
+constexpr int32_t kSimpleUnitOffset = 512;
+
+const struct UnitPrefixStrings {
+    const char* const string;
+    UMeasurePrefix value;
+} gUnitPrefixStrings[] = {
+    // SI prefixes
+    { "yotta", UMEASURE_PREFIX_YOTTA },
+    { "zetta", UMEASURE_PREFIX_ZETTA },
+    { "exa", UMEASURE_PREFIX_EXA },
+    { "peta", UMEASURE_PREFIX_PETA },
+    { "tera", UMEASURE_PREFIX_TERA },
+    { "giga", UMEASURE_PREFIX_GIGA },
+    { "mega", UMEASURE_PREFIX_MEGA },
+    { "kilo", UMEASURE_PREFIX_KILO },
+    { "hecto", UMEASURE_PREFIX_HECTO },
+    { "deka", UMEASURE_PREFIX_DEKA },
+    { "deci", UMEASURE_PREFIX_DECI },
+    { "centi", UMEASURE_PREFIX_CENTI },
+    { "milli", UMEASURE_PREFIX_MILLI },
+    { "micro", UMEASURE_PREFIX_MICRO },
+    { "nano", UMEASURE_PREFIX_NANO },
+    { "pico", UMEASURE_PREFIX_PICO },
+    { "femto", UMEASURE_PREFIX_FEMTO },
+    { "atto", UMEASURE_PREFIX_ATTO },
+    { "zepto", UMEASURE_PREFIX_ZEPTO },
+    { "yocto", UMEASURE_PREFIX_YOCTO },
+    // Binary prefixes
+    { "yobi", UMEASURE_PREFIX_YOBI },
+    { "zebi", UMEASURE_PREFIX_ZEBI },
+    { "exbi", UMEASURE_PREFIX_EXBI },
+    { "pebi", UMEASURE_PREFIX_PEBI },
+    { "tebi", UMEASURE_PREFIX_TEBI },
+    { "gibi", UMEASURE_PREFIX_GIBI },
+    { "mebi", UMEASURE_PREFIX_MEBI },
+    { "kibi", UMEASURE_PREFIX_KIBI },
+};
+
+/**
+ * A ResourceSink that collects simple unit identifiers from the keys of the
+ * convertUnits table into an array, and adds these values to a TrieBuilder,
+ * with associated values being their index into this array plus a specified
+ * offset.
+ *
+ * Example code:
+ *
+ *     UErrorCode status = U_ZERO_ERROR;
+ *     BytesTrieBuilder b(status);
+ *     int32_t ARR_SIZE = 200;
+ *     const char *unitIdentifiers[ARR_SIZE];
+ *     int32_t *unitCategories[ARR_SIZE];
+ *     SimpleUnitIdentifiersSink identifierSink(gSerializedUnitCategoriesTrie, unitIdentifiers,
+ *                                              unitCategories, ARR_SIZE, b, kTrieValueOffset);
+ *     LocalUResourceBundlePointer unitsBundle(ures_openDirect(nullptr, "units", &status));
+ *     ures_getAllItemsWithFallback(unitsBundle.getAlias(), "convertUnits", identifierSink, status);
+ */
+class SimpleUnitIdentifiersSink : public icu::ResourceSink {
+  public:
+    /**
+     * Constructor.
+     * @param quantitiesTrieData The data for constructing a quantitiesTrie,
+     *     which maps from a simple unit identifier to an index into the
+     *     gCategories array.
+     * @param out Array of char* to which pointers to the simple unit
+     *     identifiers will be saved. (Does not take ownership.)
+     * @param outCategories Array of int32_t to which category indexes will be
+     *     saved: this corresponds to simple unit IDs saved to `out`, mapping
+     *     from the ID to the value produced by the quantitiesTrie (which is an
+     *     index into the gCategories array).
+     * @param outSize The size of `out` and `outCategories`.
+     * @param trieBuilder The trie builder to which the simple unit identifier
+     *     should be added. The trie builder must outlive this resource sink.
+     * @param trieValueOffset This is added to the index of the identifier in
+     *     the `out` array, before adding to `trieBuilder` as the value
+     *     associated with the identifier.
+     */
+    explicit SimpleUnitIdentifiersSink(StringPiece quantitiesTrieData, const char **out,
+                                       int32_t *outCategories, int32_t outSize,
+                                       BytesTrieBuilder &trieBuilder, int32_t trieValueOffset)
+        : outArray(out), outCategories(outCategories), outSize(outSize), trieBuilder(trieBuilder),
+          trieValueOffset(trieValueOffset), quantitiesTrieData(quantitiesTrieData), outIndex(0) {}
+
+    /**
+     * Adds the table keys found in value to the output vector.
+     * @param key The key of the resource passed to `value`: the second
+     *     parameter of the ures_getAllItemsWithFallback() call.
+     * @param value Should be a ResourceTable value, if
+     *     ures_getAllItemsWithFallback() was called correctly for this sink.
+     * @param noFallback Ignored.
+     * @param status The standard ICU error code output parameter.
+     */
+    void put(const char * /*key*/, ResourceValue &value, UBool /*noFallback*/, UErrorCode &status) override {
+        ResourceTable table = value.getTable(status);
+        if (U_FAILURE(status)) return;
+
+        if (outIndex + table.getSize() > outSize) {
+            status = U_INDEX_OUTOFBOUNDS_ERROR;
+            return;
+        }
+
+        BytesTrie quantitiesTrie(quantitiesTrieData.data());
+
+        // Collect keys from the table resource.
+        const char *simpleUnitID;
+        for (int32_t i = 0; table.getKeyAndValue(i, simpleUnitID, value); ++i) {
+            U_ASSERT(i < table.getSize());
+            U_ASSERT(outIndex < outSize);
+            if (uprv_strcmp(simpleUnitID, "kilogram") == 0) {
+                // For parsing, we use "gram", the prefixless metric mass unit. We
+                // thus ignore the SI Base Unit of Mass: it exists due to being the
+                // mass conversion target unit, but not needed for MeasureUnit
+                // parsing.
+                continue;
+            }
+            outArray[outIndex] = simpleUnitID;
+            trieBuilder.add(simpleUnitID, trieValueOffset + outIndex, status);
+
+            // Find the base target unit for this simple unit
+            ResourceTable table = value.getTable(status);
+            if (U_FAILURE(status)) { return; }
+            if (!table.findValue("target", value)) {
+                status = U_INVALID_FORMAT_ERROR;
+                break;
+            }
+            int32_t len;
+            const char16_t* uTarget = value.getString(len, status);
+            CharString target;
+            target.appendInvariantChars(uTarget, len, status);
+            if (U_FAILURE(status)) { return; }
+            quantitiesTrie.reset();
+            UStringTrieResult result = quantitiesTrie.next(target.data(), target.length());
+            if (!USTRINGTRIE_HAS_VALUE(result)) {
+                status = U_INVALID_FORMAT_ERROR;
+                break;
+            }
+            outCategories[outIndex] = quantitiesTrie.getValue();
+
+            outIndex++;
+        }
+    }
+
+  private:
+    const char **outArray;
+    int32_t *outCategories;
+    int32_t outSize;
+    BytesTrieBuilder &trieBuilder;
+    int32_t trieValueOffset;
+
+    StringPiece quantitiesTrieData;
+
+    int32_t outIndex;
+};
+
+/**
+ * A ResourceSink that collects information from `unitQuantities` in the `units`
+ * resource to provide key->value lookups from base unit to category, as well as
+ * preserving ordering information for these categories. See `units.txt`.
+ *
+ * For example: "kilogram" -> "mass", "meter-per-second" -> "speed".
+ *
+ * In C++ unitQuantity values are collected in order into a char16_t* array, while
+ * unitQuantity keys are added added to a TrieBuilder, with associated values
+ * being the index into the aforementioned char16_t* array.
+ */
+class CategoriesSink : public icu::ResourceSink {
+  public:
+    /**
+     * Constructor.
+     * @param out Array of char16_t* to which unitQuantity values will be saved.
+     *     The pointers returned  not owned: they point directly at the resource
+     *     strings in static memory.
+     * @param outSize The size of the `out` array.
+     * @param trieBuilder The trie builder to which the keys (base units) of
+     *     each unitQuantity will be added, each with value being the offset
+     *     into `out`.
+     */
+    explicit CategoriesSink(const char16_t **out, int32_t &outSize, BytesTrieBuilder &trieBuilder)
+        : outQuantitiesArray(out), outSize(outSize), trieBuilder(trieBuilder), outIndex(0) {}
+
+    void put(const char * /*key*/, ResourceValue &value, UBool /*noFallback*/, UErrorCode &status) override {
+        ResourceArray array = value.getArray(status);
+        if (U_FAILURE(status)) {
+            return;
+        }
+
+        if (outIndex + array.getSize() > outSize) {
+            status = U_INDEX_OUTOFBOUNDS_ERROR;
+            return;
+        }
+
+        for (int32_t i = 0; array.getValue(i, value); ++i) {
+            U_ASSERT(outIndex < outSize);
+            ResourceTable table = value.getTable(status);
+            if (U_FAILURE(status)) {
+                return;
+            }
+            if (table.getSize() != 1) {
+                status = U_INVALID_FORMAT_ERROR;
+                return;
+            }
+            const char *key;
+            table.getKeyAndValue(0, key, value);
+            int32_t uTmpLen;
+            outQuantitiesArray[outIndex] = value.getString(uTmpLen, status);
+            trieBuilder.add(key, outIndex, status);
+            outIndex++;
+        }
+    }
+
+  private:
+    const char16_t **outQuantitiesArray;
+    int32_t &outSize;
+    BytesTrieBuilder &trieBuilder;
+
+    int32_t outIndex;
+};
+
+icu::UInitOnce gUnitExtrasInitOnce {};
+
+// Array of simple unit IDs.
+//
+// The array memory itself is owned by this pointer, but the individual char* in
+// that array point at static memory. (Note that these char* are also returned
+// by SingleUnitImpl::getSimpleUnitID().)
+const char **gSimpleUnits = nullptr;
+
+// Maps from the value associated with each simple unit ID to an index into the
+// gCategories array.
+int32_t *gSimpleUnitCategories = nullptr;
+
+char *gSerializedUnitExtrasStemTrie = nullptr;
+
+// Array of char16_t* pointing at the unit categories (aka "quantities", aka
+// "types"), as found in the `unitQuantities` resource. The array memory itself
+// is owned by this pointer, but the individual char16_t* in that array point at
+// static memory.
+const char16_t **gCategories = nullptr;
+// Number of items in `gCategories`.
+int32_t gCategoriesCount = 0;
+// Serialized BytesTrie for mapping from base units to indices into gCategories.
+char *gSerializedUnitCategoriesTrie = nullptr;
+
+UBool U_CALLCONV cleanupUnitExtras() {
+    uprv_free(gSerializedUnitCategoriesTrie);
+    gSerializedUnitCategoriesTrie = nullptr;
+    uprv_free(gCategories);
+    gCategories = nullptr;
+    uprv_free(gSerializedUnitExtrasStemTrie);
+    gSerializedUnitExtrasStemTrie = nullptr;
+    uprv_free(gSimpleUnitCategories);
+    gSimpleUnitCategories = nullptr;
+    uprv_free(gSimpleUnits);
+    gSimpleUnits = nullptr;
+    gUnitExtrasInitOnce.reset();
+    return true;
+}
+
+void U_CALLCONV initUnitExtras(UErrorCode& status) {
+    ucln_i18n_registerCleanup(UCLN_I18N_UNIT_EXTRAS, cleanupUnitExtras);
+    LocalUResourceBundlePointer unitsBundle(ures_openDirect(nullptr, "units", &status));
+
+    // Collect unitQuantities information into gSerializedUnitCategoriesTrie and gCategories.
+    const char *CATEGORY_TABLE_NAME = "unitQuantities";
+    LocalUResourceBundlePointer unitQuantities(
+        ures_getByKey(unitsBundle.getAlias(), CATEGORY_TABLE_NAME, nullptr, &status));
+    if (U_FAILURE(status)) { return; }
+    gCategoriesCount = unitQuantities.getAlias()->fSize;
+    size_t quantitiesMallocSize = sizeof(char16_t *) * gCategoriesCount;
+    gCategories = static_cast<const char16_t **>(uprv_malloc(quantitiesMallocSize));
+    if (gCategories == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    uprv_memset(gCategories, 0, quantitiesMallocSize);
+    BytesTrieBuilder quantitiesBuilder(status);
+    CategoriesSink categoriesSink(gCategories, gCategoriesCount, quantitiesBuilder);
+    ures_getAllItemsWithFallback(unitsBundle.getAlias(), CATEGORY_TABLE_NAME, categoriesSink, status);
+    StringPiece resultQuantities = quantitiesBuilder.buildStringPiece(USTRINGTRIE_BUILD_FAST, status);
+    if (U_FAILURE(status)) { return; }
+    // Copy the result into the global constant pointer
+    size_t numBytesQuantities = resultQuantities.length();
+    gSerializedUnitCategoriesTrie = static_cast<char *>(uprv_malloc(numBytesQuantities));
+    if (gSerializedUnitCategoriesTrie == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    uprv_memcpy(gSerializedUnitCategoriesTrie, resultQuantities.data(), numBytesQuantities);
+
+    // Build the BytesTrie that Parser needs for parsing unit identifiers.
+
+    BytesTrieBuilder b(status);
+    if (U_FAILURE(status)) { return; }
+
+    // Add SI and binary prefixes
+    for (const auto& unitPrefixInfo : gUnitPrefixStrings) {
+        b.add(unitPrefixInfo.string, unitPrefixInfo.value + kPrefixOffset, status);
+    }
+    if (U_FAILURE(status)) { return; }
+
+    // Add syntax parts (compound, power prefixes)
+    b.add("-per-", COMPOUND_PART_PER, status);
+    b.add("-", COMPOUND_PART_TIMES, status);
+    b.add("-and-", COMPOUND_PART_AND, status);
+    b.add("per-", INITIAL_COMPOUND_PART_PER, status);
+    b.add("square-", POWER_PART_P2, status);
+    b.add("cubic-", POWER_PART_P3, status);
+    b.add("pow2-", POWER_PART_P2, status);
+    b.add("pow3-", POWER_PART_P3, status);
+    b.add("pow4-", POWER_PART_P4, status);
+    b.add("pow5-", POWER_PART_P5, status);
+    b.add("pow6-", POWER_PART_P6, status);
+    b.add("pow7-", POWER_PART_P7, status);
+    b.add("pow8-", POWER_PART_P8, status);
+    b.add("pow9-", POWER_PART_P9, status);
+    b.add("pow10-", POWER_PART_P10, status);
+    b.add("pow11-", POWER_PART_P11, status);
+    b.add("pow12-", POWER_PART_P12, status);
+    b.add("pow13-", POWER_PART_P13, status);
+    b.add("pow14-", POWER_PART_P14, status);
+    b.add("pow15-", POWER_PART_P15, status);
+    if (U_FAILURE(status)) { return; }
+
+    // Add sanctioned simple units by offset: simple units all have entries in
+    // units/convertUnits resources.
+    LocalUResourceBundlePointer convertUnits(
+        ures_getByKey(unitsBundle.getAlias(), "convertUnits", nullptr, &status));
+    if (U_FAILURE(status)) { return; }
+
+    // Allocate enough space: with identifierSink below skipping kilogram, we're
+    // probably allocating one more than needed.
+    int32_t simpleUnitsCount = convertUnits.getAlias()->fSize;
+    int32_t arrayMallocSize = sizeof(char *) * simpleUnitsCount;
+    gSimpleUnits = static_cast<const char **>(uprv_malloc(arrayMallocSize));
+    if (gSimpleUnits == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    uprv_memset(gSimpleUnits, 0, arrayMallocSize);
+    arrayMallocSize = sizeof(int32_t) * simpleUnitsCount;
+    gSimpleUnitCategories = static_cast<int32_t *>(uprv_malloc(arrayMallocSize));
+    if (gSimpleUnitCategories == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    uprv_memset(gSimpleUnitCategories, 0, arrayMallocSize);
+
+    // Populate gSimpleUnits and build the associated trie.
+    SimpleUnitIdentifiersSink identifierSink(resultQuantities, gSimpleUnits, gSimpleUnitCategories,
+                                             simpleUnitsCount, b, kSimpleUnitOffset);
+    ures_getAllItemsWithFallback(unitsBundle.getAlias(), "convertUnits", identifierSink, status);
+
+    // Build the CharsTrie
+    // TODO: Use SLOW or FAST here?
+    StringPiece result = b.buildStringPiece(USTRINGTRIE_BUILD_FAST, status);
+    if (U_FAILURE(status)) { return; }
+
+    // Copy the result into the global constant pointer
+    size_t numBytes = result.length();
+    gSerializedUnitExtrasStemTrie = static_cast<char *>(uprv_malloc(numBytes));
+    if (gSerializedUnitExtrasStemTrie == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    uprv_memcpy(gSerializedUnitExtrasStemTrie, result.data(), numBytes);
+}
+
+class Token {
+public:
+    Token(int32_t match) : fMatch(match) {}
+
+    enum Type {
+        TYPE_UNDEFINED,
+        TYPE_PREFIX,
+        // Token type for "-per-", "-", and "-and-".
+        TYPE_COMPOUND_PART,
+        // Token type for "per-".
+        TYPE_INITIAL_COMPOUND_PART,
+        TYPE_POWER_PART,
+        TYPE_SIMPLE_UNIT,
+    };
+
+    // Calling getType() is invalid, resulting in an assertion failure, if Token
+    // value isn't positive.
+    Type getType() const {
+        U_ASSERT(fMatch > 0);
+        if (fMatch < kCompoundPartOffset) {
+            return TYPE_PREFIX;
+        }
+        if (fMatch < kInitialCompoundPartOffset) {
+            return TYPE_COMPOUND_PART;
+        }
+        if (fMatch < kPowerPartOffset) {
+            return TYPE_INITIAL_COMPOUND_PART;
+        }
+        if (fMatch < kSimpleUnitOffset) {
+            return TYPE_POWER_PART;
+        }
+        return TYPE_SIMPLE_UNIT;
+    }
+
+    UMeasurePrefix getUnitPrefix() const {
+        U_ASSERT(getType() == TYPE_PREFIX);
+        return static_cast<UMeasurePrefix>(fMatch - kPrefixOffset);
+    }
+
+    // Valid only for tokens with type TYPE_COMPOUND_PART.
+    int32_t getMatch() const {
+        U_ASSERT(getType() == TYPE_COMPOUND_PART);
+        return fMatch;
+    }
+
+    int32_t getInitialCompoundPart() const {
+        // Even if there is only one InitialCompoundPart value, we have this
+        // function for the simplicity of code consistency.
+        U_ASSERT(getType() == TYPE_INITIAL_COMPOUND_PART);
+        // Defensive: if this assert fails, code using this function also needs
+        // to change.
+        U_ASSERT(fMatch == INITIAL_COMPOUND_PART_PER);
+        return fMatch;
+    }
+
+    int8_t getPower() const {
+        U_ASSERT(getType() == TYPE_POWER_PART);
+        return static_cast<int8_t>(fMatch - kPowerPartOffset);
+    }
+
+    int32_t getSimpleUnitIndex() const {
+        U_ASSERT(getType() == TYPE_SIMPLE_UNIT);
+        return fMatch - kSimpleUnitOffset;
+    }
+
+private:
+    int32_t fMatch;
+};
+
+class Parser {
+public:
+    /**
+     * Factory function for parsing the given identifier.
+     *
+     * @param source The identifier to parse. This function does not make a copy
+     * of source: the underlying string that source points at, must outlive the
+     * parser.
+     * @param status ICU error code.
+     */
+    static Parser from(StringPiece source, UErrorCode& status) {
+        if (U_FAILURE(status)) {
+            return Parser();
+        }
+        umtx_initOnce(gUnitExtrasInitOnce, &initUnitExtras, status);
+        if (U_FAILURE(status)) {
+            return Parser();
+        }
+        return Parser(source);
+    }
+
+    MeasureUnitImpl parse(UErrorCode& status) {
+        MeasureUnitImpl result;
+
+        if (U_FAILURE(status)) {
+            return result;
+        }
+        if (fSource.empty()) {
+            // The dimenionless unit: nothing to parse. leave result as is.
+            return result;
+        }
+
+        while (hasNext()) {
+            bool sawAnd = false;
+
+            SingleUnitImpl singleUnit = nextSingleUnit(sawAnd, status);
+            if (U_FAILURE(status)) {
+                return result;
+            }
+
+            bool added = result.appendSingleUnit(singleUnit, status);
+            if (U_FAILURE(status)) {
+                return result;
+            }
+
+            if (sawAnd && !added) {
+                // Two similar units are not allowed in a mixed unit.
+                status = kUnitIdentifierSyntaxError;
+                return result;
+            }
+
+            if (result.singleUnits.length() >= 2) {
+                // nextSingleUnit fails appropriately for "per" and "and" in the
+                // same identifier. It doesn't fail for other compound units
+                // (COMPOUND_PART_TIMES). Consequently we take care of that
+                // here.
+                UMeasureUnitComplexity complexity =
+                    sawAnd ? UMEASURE_UNIT_MIXED : UMEASURE_UNIT_COMPOUND;
+                if (result.singleUnits.length() == 2) {
+                    // After appending two singleUnits, the complexity will be `UMEASURE_UNIT_COMPOUND`
+                    U_ASSERT(result.complexity == UMEASURE_UNIT_COMPOUND);
+                    result.complexity = complexity;
+                } else if (result.complexity != complexity) {
+                    // Can't have mixed compound units
+                    status = kUnitIdentifierSyntaxError;
+                    return result;
+                }
+            }
+        }
+
+        return result;
+    }
+
+private:
+    // Tracks parser progress: the offset into fSource.
+    int32_t fIndex = 0;
+
+    // Since we're not owning this memory, whatever is passed to the constructor
+    // should live longer than this Parser - and the parser shouldn't return any
+    // references to that string.
+    StringPiece fSource;
+    BytesTrie fTrie;
+
+    // Set to true when we've seen a "-per-" or a "per-", after which all units
+    // are in the denominator. Until we find an "-and-", at which point the
+    // identifier is invalid pending TODO(CLDR-13701).
+    bool fAfterPer = false;
+
+    Parser() : fSource(""), fTrie(u"") {}
+
+    Parser(StringPiece source)
+        : fSource(source), fTrie(gSerializedUnitExtrasStemTrie) {}
+
+    inline bool hasNext() const {
+        return fIndex < fSource.length();
+    }
+
+    // Returns the next Token parsed from fSource, advancing fIndex to the end
+    // of that token in fSource. In case of U_FAILURE(status), the token
+    // returned will cause an abort if getType() is called on it.
+    Token nextToken(UErrorCode& status) {
+        fTrie.reset();
+        int32_t match = -1;
+        // Saves the position in the fSource string for the end of the most
+        // recent matching token.
+        int32_t previ = -1;
+        // Find the longest token that matches a value in the trie:
+        while (fIndex < fSource.length()) {
+            auto result = fTrie.next(fSource.data()[fIndex++]);
+            if (result == USTRINGTRIE_NO_MATCH) {
+                break;
+            } else if (result == USTRINGTRIE_NO_VALUE) {
+                continue;
+            }
+            U_ASSERT(USTRINGTRIE_HAS_VALUE(result));
+            match = fTrie.getValue();
+            previ = fIndex;
+            if (result == USTRINGTRIE_FINAL_VALUE) {
+                break;
+            }
+            U_ASSERT(result == USTRINGTRIE_INTERMEDIATE_VALUE);
+            // continue;
+        }
+
+        if (match < 0) {
+            status = kUnitIdentifierSyntaxError;
+        } else {
+            fIndex = previ;
+        }
+        return Token(match);
+    }
+
+    /**
+     * Returns the next "single unit" via result.
+     *
+     * If a "-per-" was parsed, the result will have appropriate negative
+     * dimensionality.
+     *
+     * Returns an error if we parse both compound units and "-and-", since mixed
+     * compound units are not yet supported - TODO(CLDR-13701).
+     *
+     * @param result Will be overwritten by the result, if status shows success.
+     * @param sawAnd If an "-and-" was parsed prior to finding the "single
+     * unit", sawAnd is set to true. If not, it is left as is.
+     * @param status ICU error code.
+     */
+    SingleUnitImpl nextSingleUnit(bool &sawAnd, UErrorCode &status) {
+        SingleUnitImpl result;
+        if (U_FAILURE(status)) {
+            return result;
+        }
+
+        // state:
+        // 0 = no tokens seen yet (will accept power, SI or binary prefix, or simple unit)
+        // 1 = power token seen (will not accept another power token)
+        // 2 = SI or binary prefix token seen (will not accept a power, or SI or binary prefix token)
+        int32_t state = 0;
+
+        bool atStart = fIndex == 0;
+        Token token = nextToken(status);
+        if (U_FAILURE(status)) {
+            return result;
+        }
+
+        if (atStart) {
+            // Identifiers optionally start with "per-".
+            if (token.getType() == Token::TYPE_INITIAL_COMPOUND_PART) {
+                U_ASSERT(token.getInitialCompoundPart() == INITIAL_COMPOUND_PART_PER);
+                fAfterPer = true;
+                result.dimensionality = -1;
+
+                token = nextToken(status);
+                if (U_FAILURE(status)) {
+                    return result;
+                }
+            }
+        } else {
+            // All other SingleUnit's are separated from previous SingleUnit's
+            // via a compound part:
+            if (token.getType() != Token::TYPE_COMPOUND_PART) {
+                status = kUnitIdentifierSyntaxError;
+                return result;
+            }
+
+            switch (token.getMatch()) {
+            case COMPOUND_PART_PER:
+                if (sawAnd) {
+                    // Mixed compound units not yet supported,
+                    // TODO(CLDR-13701).
+                    status = kUnitIdentifierSyntaxError;
+                    return result;
+                }
+                fAfterPer = true;
+                result.dimensionality = -1;
+                break;
+
+            case COMPOUND_PART_TIMES:
+                if (fAfterPer) {
+                    result.dimensionality = -1;
+                }
+                break;
+
+            case COMPOUND_PART_AND:
+                if (fAfterPer) {
+                    // Can't start with "-and-", and mixed compound units
+                    // not yet supported, TODO(CLDR-13701).
+                    status = kUnitIdentifierSyntaxError;
+                    return result;
+                }
+                sawAnd = true;
+                break;
+            }
+
+            token = nextToken(status);
+            if (U_FAILURE(status)) {
+                return result;
+            }
+        }
+
+        // Read tokens until we have a complete SingleUnit or we reach the end.
+        while (true) {
+            switch (token.getType()) {
+                case Token::TYPE_POWER_PART:
+                    if (state > 0) {
+                        status = kUnitIdentifierSyntaxError;
+                        return result;
+                    }
+                    result.dimensionality *= token.getPower();
+                    state = 1;
+                    break;
+
+                case Token::TYPE_PREFIX:
+                    if (state > 1) {
+                        status = kUnitIdentifierSyntaxError;
+                        return result;
+                    }
+                    result.unitPrefix = token.getUnitPrefix();
+                    state = 2;
+                    break;
+
+                case Token::TYPE_SIMPLE_UNIT:
+                    result.index = token.getSimpleUnitIndex();
+                    return result;
+
+                default:
+                    status = kUnitIdentifierSyntaxError;
+                    return result;
+            }
+
+            if (!hasNext()) {
+                // We ran out of tokens before finding a complete single unit.
+                status = kUnitIdentifierSyntaxError;
+                return result;
+            }
+            token = nextToken(status);
+            if (U_FAILURE(status)) {
+                return result;
+            }
+        }
+
+        return result;
+    }
+};
+
+// Sorting function wrapping SingleUnitImpl::compareTo for use with uprv_sortArray.
+int32_t U_CALLCONV
+compareSingleUnits(const void* /*context*/, const void* left, const void* right) {
+    auto realLeft = static_cast<const SingleUnitImpl* const*>(left);
+    auto realRight = static_cast<const SingleUnitImpl* const*>(right);
+    return (*realLeft)->compareTo(**realRight);
+}
+
+// Returns an index into the gCategories array, for the "unitQuantity" (aka
+// "type" or "category") associated with the given base unit identifier. Returns
+// -1 on failure, together with U_UNSUPPORTED_ERROR.
+int32_t getUnitCategoryIndex(BytesTrie &trie, StringPiece baseUnitIdentifier, UErrorCode &status) {
+    UStringTrieResult result = trie.reset().next(baseUnitIdentifier.data(), baseUnitIdentifier.length());
+    if (!USTRINGTRIE_HAS_VALUE(result)) {
+        status = U_UNSUPPORTED_ERROR;
+        return -1;
+    }
+
+    return trie.getValue();
+}
+
+} // namespace
+
+U_CAPI int32_t U_EXPORT2
+umeas_getPrefixPower(UMeasurePrefix unitPrefix) {
+    if (unitPrefix >= UMEASURE_PREFIX_INTERNAL_MIN_BIN &&
+        unitPrefix <= UMEASURE_PREFIX_INTERNAL_MAX_BIN) {
+        return unitPrefix - UMEASURE_PREFIX_INTERNAL_ONE_BIN;
+    }
+    U_ASSERT(unitPrefix >= UMEASURE_PREFIX_INTERNAL_MIN_SI &&
+             unitPrefix <= UMEASURE_PREFIX_INTERNAL_MAX_SI);
+    return unitPrefix - UMEASURE_PREFIX_ONE;
+}
+
+U_CAPI int32_t U_EXPORT2
+umeas_getPrefixBase(UMeasurePrefix unitPrefix) {
+    if (unitPrefix >= UMEASURE_PREFIX_INTERNAL_MIN_BIN &&
+        unitPrefix <= UMEASURE_PREFIX_INTERNAL_MAX_BIN) {
+        return 1024;
+    }
+    U_ASSERT(unitPrefix >= UMEASURE_PREFIX_INTERNAL_MIN_SI &&
+             unitPrefix <= UMEASURE_PREFIX_INTERNAL_MAX_SI);
+    return 10;
+}
+
+CharString U_I18N_API getUnitQuantity(const MeasureUnitImpl &baseMeasureUnitImpl, UErrorCode &status) {
+    CharString result;
+    MeasureUnitImpl baseUnitImpl = baseMeasureUnitImpl.copy(status);
+    UErrorCode localStatus = U_ZERO_ERROR;
+    umtx_initOnce(gUnitExtrasInitOnce, &initUnitExtras, status);
+    if (U_FAILURE(status)) {
+        return result;
+    }
+    BytesTrie trie(gSerializedUnitCategoriesTrie);
+
+    baseUnitImpl.serialize(status);
+    StringPiece identifier = baseUnitImpl.identifier.data();
+    int32_t idx = getUnitCategoryIndex(trie, identifier, localStatus);
+    if (U_FAILURE(status)) {
+        return result;
+    }
+
+    // In case the base unit identifier did not match any entry.
+    if (U_FAILURE(localStatus)) {
+        localStatus = U_ZERO_ERROR;
+        baseUnitImpl.takeReciprocal(status);
+        baseUnitImpl.serialize(status);
+        identifier.set(baseUnitImpl.identifier.data());
+        idx = getUnitCategoryIndex(trie, identifier, localStatus);
+
+        if (U_FAILURE(status)) {
+            return result;
+        }
+    }
+
+    // In case the reciprocal of the base unit identifier did not match any entry.
+    MeasureUnitImpl simplifiedUnit = baseMeasureUnitImpl.copyAndSimplify(status);
+    if (U_FAILURE(status)) {
+        return result;
+    }
+    if (U_FAILURE(localStatus)) {
+        localStatus = U_ZERO_ERROR;
+        simplifiedUnit.serialize(status);
+        identifier.set(simplifiedUnit.identifier.data());
+        idx = getUnitCategoryIndex(trie, identifier, localStatus);
+
+        if (U_FAILURE(status)) {
+            return result;
+        }
+    }
+
+    // In case the simplified base unit identifier did not match any entry.
+    if (U_FAILURE(localStatus)) {
+        localStatus = U_ZERO_ERROR;
+        simplifiedUnit.takeReciprocal(status);
+        simplifiedUnit.serialize(status);
+        identifier.set(simplifiedUnit.identifier.data());
+        idx = getUnitCategoryIndex(trie, identifier, localStatus);
+
+        if (U_FAILURE(status)) {
+            return result;
+        }
+    }
+
+    // If there is no match at all, throw an exception.
+    if (U_FAILURE(localStatus)) {
+        status = U_INVALID_FORMAT_ERROR;
+        return result;
+    }
+
+    if (idx < 0 || idx >= gCategoriesCount) {
+        status = U_INVALID_FORMAT_ERROR;
+        return result;
+    }
+
+    result.appendInvariantChars(gCategories[idx], u_strlen(gCategories[idx]), status);
+    return result;
+}
+
+// In ICU4J, this is MeasureUnit.getSingleUnitImpl().
+SingleUnitImpl SingleUnitImpl::forMeasureUnit(const MeasureUnit& measureUnit, UErrorCode& status) {
+    MeasureUnitImpl temp;
+    const MeasureUnitImpl& impl = MeasureUnitImpl::forMeasureUnit(measureUnit, temp, status);
+    if (U_FAILURE(status)) {
+        return {};
+    }
+    if (impl.singleUnits.length() == 0) {
+        return {};
+    }
+    if (impl.singleUnits.length() == 1) {
+        return *impl.singleUnits[0];
+    }
+    status = U_ILLEGAL_ARGUMENT_ERROR;
+    return {};
+}
+
+MeasureUnit SingleUnitImpl::build(UErrorCode& status) const {
+    MeasureUnitImpl temp;
+    temp.appendSingleUnit(*this, status);
+    // TODO(icu-units#28): the MeasureUnitImpl::build() method uses
+    // findBySubtype, which is relatively slow.
+    // - At the time of loading the simple unit IDs, we could also save a
+    //   mapping to the builtin MeasureUnit type and subtype they correspond to.
+    // - This method could then check dimensionality and index, and if both are
+    //   1, directly return MeasureUnit instances very quickly.
+    return std::move(temp).build(status);
+}
+
+const char *SingleUnitImpl::getSimpleUnitID() const {
+    return gSimpleUnits[index];
+}
+
+void SingleUnitImpl::appendNeutralIdentifier(CharString &result, UErrorCode &status) const UPRV_NO_SANITIZE_UNDEFINED {
+    int32_t absPower = std::abs(this->dimensionality);
+
+    U_ASSERT(absPower > 0); // "this function does not support the dimensionless single units";
+    
+    if (absPower == 1) {
+        // no-op
+    } else if (absPower == 2) {
+        result.append(StringPiece("square-"), status);
+    } else if (absPower == 3) {
+        result.append(StringPiece("cubic-"), status);
+    } else if (absPower <= 15) {
+        result.append(StringPiece("pow"), status);
+        result.appendNumber(absPower, status);
+        result.append(StringPiece("-"), status);
+    } else {
+        status = U_ILLEGAL_ARGUMENT_ERROR; // Unit Identifier Syntax Error
+        return;
+    }
+
+    if (U_FAILURE(status)) {
+        return;
+    }
+
+    if (this->unitPrefix != UMEASURE_PREFIX_ONE) {
+        bool found = false;
+        for (const auto &unitPrefixInfo : gUnitPrefixStrings) {
+            // TODO: consider using binary search? If we do this, add a unit
+            // test to ensure gUnitPrefixStrings is sorted?
+            if (unitPrefixInfo.value == this->unitPrefix) {
+                result.append(unitPrefixInfo.string, status);
+                found = true;
+                break;
+            }
+        }
+        if (!found) {
+            status = U_UNSUPPORTED_ERROR;
+            return;
+        }
+    }
+
+    result.append(StringPiece(this->getSimpleUnitID()), status);
+}
+
+int32_t SingleUnitImpl::getUnitCategoryIndex() const {
+    return gSimpleUnitCategories[index];
+}
+
+MeasureUnitImpl::MeasureUnitImpl(const SingleUnitImpl &singleUnit, UErrorCode &status) {
+    this->appendSingleUnit(singleUnit, status);
+}
+
+MeasureUnitImpl MeasureUnitImpl::forIdentifier(StringPiece identifier, UErrorCode& status) {
+    return Parser::from(identifier, status).parse(status);
+}
+
+const MeasureUnitImpl& MeasureUnitImpl::forMeasureUnit(
+        const MeasureUnit& measureUnit, MeasureUnitImpl& memory, UErrorCode& status) {
+    if (measureUnit.fImpl) {
+        return *measureUnit.fImpl;
+    } else {
+        memory = Parser::from(measureUnit.getIdentifier(), status).parse(status);
+        return memory;
+    }
+}
+
+MeasureUnitImpl MeasureUnitImpl::forMeasureUnitMaybeCopy(
+        const MeasureUnit& measureUnit, UErrorCode& status) {
+    if (measureUnit.fImpl) {
+        return measureUnit.fImpl->copy(status);
+    } else {
+        return Parser::from(measureUnit.getIdentifier(), status).parse(status);
+    }
+}
+
+void MeasureUnitImpl::takeReciprocal(UErrorCode& /*status*/) {
+    identifier.clear();
+    for (int32_t i = 0; i < singleUnits.length(); i++) {
+        singleUnits[i]->dimensionality *= -1;
+    }
+}
+
+MeasureUnitImpl MeasureUnitImpl::copyAndSimplify(UErrorCode &status) const {
+    MeasureUnitImpl result;
+    for (int32_t i = 0; i < singleUnits.length(); i++) {
+        const SingleUnitImpl &singleUnit = *this->singleUnits[i];
+        
+        // The following `for` loop will cause time complexity to be O(n^2).
+        // However, n is very small (number of units, generally, at maximum equal to 10)
+        bool unitExist = false;
+        for (int32_t j = 0; j < result.singleUnits.length(); j++) {
+            if (uprv_strcmp(result.singleUnits[j]->getSimpleUnitID(), singleUnit.getSimpleUnitID()) ==
+                    0 &&
+                result.singleUnits[j]->unitPrefix == singleUnit.unitPrefix) {
+                unitExist = true;
+                result.singleUnits[j]->dimensionality =
+                    result.singleUnits[j]->dimensionality + singleUnit.dimensionality;
+                break;
+            }
+        }
+
+        if (!unitExist) {
+            result.appendSingleUnit(singleUnit, status);
+        }
+    }
+
+    return result;
+}
+
+bool MeasureUnitImpl::appendSingleUnit(const SingleUnitImpl &singleUnit, UErrorCode &status) {
+    identifier.clear();
+
+    if (singleUnit.isDimensionless()) {
+        // Do not append dimensionless units.
+        return false;
+    }
+
+    // Find a similar unit that already exists, to attempt to coalesce
+    SingleUnitImpl *oldUnit = nullptr;
+    for (int32_t i = 0; i < this->singleUnits.length(); i++) {
+        auto *candidate = this->singleUnits[i];
+        if (candidate->isCompatibleWith(singleUnit)) {
+            oldUnit = candidate;
+        }
+    }
+
+    if (oldUnit) {
+        // Both dimensionalities will be positive, or both will be negative, by
+        // virtue of isCompatibleWith().
+        oldUnit->dimensionality += singleUnit.dimensionality;
+
+        return false;
+    }
+
+    // Add a copy of singleUnit
+    // NOTE: MaybeStackVector::emplaceBackAndCheckErrorCode creates new copy of  singleUnit.
+    this->singleUnits.emplaceBackAndCheckErrorCode(status, singleUnit);
+    if (U_FAILURE(status)) {
+        return false;
+    }
+
+    // If the MeasureUnitImpl is `UMEASURE_UNIT_SINGLE` and after the appending a unit, the `singleUnits`
+    // contains more than one. thus means the complexity should be `UMEASURE_UNIT_COMPOUND`
+    if (this->singleUnits.length() > 1 &&
+        this->complexity == UMeasureUnitComplexity::UMEASURE_UNIT_SINGLE) {
+        this->complexity = UMeasureUnitComplexity::UMEASURE_UNIT_COMPOUND;
+    }
+
+    return true;
+}
+
+MaybeStackVector<MeasureUnitImplWithIndex>
+MeasureUnitImpl::extractIndividualUnitsWithIndices(UErrorCode &status) const {
+    MaybeStackVector<MeasureUnitImplWithIndex> result;
+
+    if (this->complexity != UMeasureUnitComplexity::UMEASURE_UNIT_MIXED) {
+        result.emplaceBackAndCheckErrorCode(status, 0, *this, status);
+        return result;
+    }
+
+    for (int32_t i = 0; i < singleUnits.length(); ++i) {
+        result.emplaceBackAndCheckErrorCode(status, i, *singleUnits[i], status);
+        if (U_FAILURE(status)) {
+            return result;
+        }
+    }
+
+    return result;
+}
+
+/**
+ * Normalize a MeasureUnitImpl and generate the identifier string in place.
+ */
+void MeasureUnitImpl::serialize(UErrorCode &status) {
+    if (U_FAILURE(status)) {
+        return;
+    }
+
+    if (this->singleUnits.length() == 0) {
+        // Dimensionless, constructed by the default constructor.
+        return;
+    }
+
+    if (this->complexity == UMEASURE_UNIT_COMPOUND) {
+        // Note: don't sort a MIXED unit
+        uprv_sortArray(this->singleUnits.getAlias(), this->singleUnits.length(),
+                       sizeof(this->singleUnits[0]), compareSingleUnits, nullptr, false, &status);
+        if (U_FAILURE(status)) {
+            return;
+        }
+    }
+
+    CharString result;
+    bool beforePer = true;
+    bool firstTimeNegativeDimension = false;
+    for (int32_t i = 0; i < this->singleUnits.length(); i++) {
+        if (beforePer && (*this->singleUnits[i]).dimensionality < 0) {
+            beforePer = false;
+            firstTimeNegativeDimension = true;
+        } else if ((*this->singleUnits[i]).dimensionality < 0) {
+            firstTimeNegativeDimension = false;
+        }
+
+        if (U_FAILURE(status)) {
+            return;
+        }
+
+        if (this->complexity == UMeasureUnitComplexity::UMEASURE_UNIT_MIXED) {
+            if (result.length() != 0) {
+                result.append(StringPiece("-and-"), status);
+            }
+        } else {
+            if (firstTimeNegativeDimension) {
+                if (result.length() == 0) {
+                    result.append(StringPiece("per-"), status);
+                } else {
+                    result.append(StringPiece("-per-"), status);
+                }
+            } else {
+                if (result.length() != 0) {
+                    result.append(StringPiece("-"), status);
+                }
+            }
+        }
+
+        this->singleUnits[i]->appendNeutralIdentifier(result, status);
+    }
+
+    this->identifier = CharString(result, status);
+}
+
+MeasureUnit MeasureUnitImpl::build(UErrorCode& status) && {
+    this->serialize(status);
+    return MeasureUnit(std::move(*this));
+}
+
+MeasureUnit MeasureUnit::forIdentifier(StringPiece identifier, UErrorCode& status) {
+    return Parser::from(identifier, status).parse(status).build(status);
+}
+
+UMeasureUnitComplexity MeasureUnit::getComplexity(UErrorCode& status) const {
+    MeasureUnitImpl temp;
+    return MeasureUnitImpl::forMeasureUnit(*this, temp, status).complexity;
+}
+
+UMeasurePrefix MeasureUnit::getPrefix(UErrorCode& status) const {
+    return SingleUnitImpl::forMeasureUnit(*this, status).unitPrefix;
+}
+
+MeasureUnit MeasureUnit::withPrefix(UMeasurePrefix prefix, UErrorCode& status) const UPRV_NO_SANITIZE_UNDEFINED {
+    SingleUnitImpl singleUnit = SingleUnitImpl::forMeasureUnit(*this, status);
+    singleUnit.unitPrefix = prefix;
+    return singleUnit.build(status);
+}
+
+int32_t MeasureUnit::getDimensionality(UErrorCode& status) const {
+    SingleUnitImpl singleUnit = SingleUnitImpl::forMeasureUnit(*this, status);
+    if (U_FAILURE(status)) { return 0; }
+    if (singleUnit.isDimensionless()) {
+        return 0;
+    }
+    return singleUnit.dimensionality;
+}
+
+MeasureUnit MeasureUnit::withDimensionality(int32_t dimensionality, UErrorCode& status) const {
+    SingleUnitImpl singleUnit = SingleUnitImpl::forMeasureUnit(*this, status);
+    singleUnit.dimensionality = dimensionality;
+    return singleUnit.build(status);
+}
+
+MeasureUnit MeasureUnit::reciprocal(UErrorCode& status) const {
+    MeasureUnitImpl impl = MeasureUnitImpl::forMeasureUnitMaybeCopy(*this, status);
+    impl.takeReciprocal(status);
+    return std::move(impl).build(status);
+}
+
+MeasureUnit MeasureUnit::product(const MeasureUnit& other, UErrorCode& status) const {
+    MeasureUnitImpl impl = MeasureUnitImpl::forMeasureUnitMaybeCopy(*this, status);
+    MeasureUnitImpl temp;
+    const MeasureUnitImpl& otherImpl = MeasureUnitImpl::forMeasureUnit(other, temp, status);
+    if (impl.complexity == UMEASURE_UNIT_MIXED || otherImpl.complexity == UMEASURE_UNIT_MIXED) {
+        status = U_ILLEGAL_ARGUMENT_ERROR;
+        return {};
+    }
+    for (int32_t i = 0; i < otherImpl.singleUnits.length(); i++) {
+        impl.appendSingleUnit(*otherImpl.singleUnits[i], status);
+    }
+    if (impl.singleUnits.length() > 1) {
+        impl.complexity = UMEASURE_UNIT_COMPOUND;
+    }
+    return std::move(impl).build(status);
+}
+
+LocalArray<MeasureUnit> MeasureUnit::splitToSingleUnitsImpl(int32_t& outCount, UErrorCode& status) const {
+    MeasureUnitImpl temp;
+    const MeasureUnitImpl& impl = MeasureUnitImpl::forMeasureUnit(*this, temp, status);
+    outCount = impl.singleUnits.length();
+    MeasureUnit* arr = new MeasureUnit[outCount];
+    if (arr == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return LocalArray<MeasureUnit>();
+    }
+    for (int32_t i = 0; i < outCount; i++) {
+        arr[i] = impl.singleUnits[i]->build(status);
+    }
+    return LocalArray<MeasureUnit>(arr, status);
+}
+
+
+U_NAMESPACE_END
+
+#endif /* !UNCONFIG_NO_FORMATTING */