YQL-13710 try to switch to new shiny PG

ref:2bed0445c8e8bd6c575883632adf19445f0a72a7

1 files changed, 1879 insertions, 0 deletions

diff --git a/contrib/libs/icu/i18n/decimfmt.cpp b/contrib/libs/icu/i18n/decimfmt.cpp
new file mode 100644
index 0000000000..daa1129a6a
--- /dev/null
+++ b/contrib/libs/icu/i18n/decimfmt.cpp
@@ -0,0 +1,1879 @@
+// © 2018 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+
+#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 <cmath>
+#include <cstdlib>
+#include <stdlib.h>
+#include "unicode/errorcode.h"
+#include "unicode/decimfmt.h"
+#include "number_decimalquantity.h"
+#include "number_types.h"
+#include "numparse_impl.h"
+#include "number_mapper.h"
+#include "number_patternstring.h"
+#include "putilimp.h"
+#include "number_utils.h"
+#include "number_utypes.h"
+
+using namespace icu;
+using namespace icu::number;
+using namespace icu::number::impl;
+using namespace icu::numparse;
+using namespace icu::numparse::impl;
+using ERoundingMode = icu::DecimalFormat::ERoundingMode;
+using EPadPosition = icu::DecimalFormat::EPadPosition;
+
+// MSVC VS2015 warns C4805 when comparing bool with UBool, VS2017 no longer emits this warning.
+// TODO: Move this macro into a better place?
+#if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN
+#define UBOOL_TO_BOOL(b) static_cast<bool>(b)
+#else
+#define UBOOL_TO_BOOL(b) b
+#endif
+
+
+UOBJECT_DEFINE_RTTI_IMPLEMENTATION(DecimalFormat)
+
+
+DecimalFormat::DecimalFormat(UErrorCode& status)
+        : DecimalFormat(nullptr, status) {
+    if (U_FAILURE(status)) { return; }
+    // Use the default locale and decimal pattern.
+    const char* localeName = Locale::getDefault().getName();
+    LocalPointer<NumberingSystem> ns(NumberingSystem::createInstance(status));
+    UnicodeString patternString = utils::getPatternForStyle(
+            localeName,
+            ns->getName(),
+            CLDR_PATTERN_STYLE_DECIMAL,
+            status);
+    setPropertiesFromPattern(patternString, IGNORE_ROUNDING_IF_CURRENCY, status);
+    touch(status);
+}
+
+DecimalFormat::DecimalFormat(const UnicodeString& pattern, UErrorCode& status)
+        : DecimalFormat(nullptr, status) {
+    if (U_FAILURE(status)) { return; }
+    setPropertiesFromPattern(pattern, IGNORE_ROUNDING_IF_CURRENCY, status);
+    touch(status);
+}
+
+DecimalFormat::DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt,
+                             UErrorCode& status)
+        : DecimalFormat(symbolsToAdopt, status) {
+    if (U_FAILURE(status)) { return; }
+    setPropertiesFromPattern(pattern, IGNORE_ROUNDING_IF_CURRENCY, status);
+    touch(status);
+}
+
+DecimalFormat::DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt,
+                             UNumberFormatStyle style, UErrorCode& status)
+        : DecimalFormat(symbolsToAdopt, status) {
+    if (U_FAILURE(status)) { return; }
+    // If choice is a currency type, ignore the rounding information.
+    if (style == UNumberFormatStyle::UNUM_CURRENCY ||
+        style == UNumberFormatStyle::UNUM_CURRENCY_ISO ||
+        style == UNumberFormatStyle::UNUM_CURRENCY_ACCOUNTING ||
+        style == UNumberFormatStyle::UNUM_CASH_CURRENCY ||
+        style == UNumberFormatStyle::UNUM_CURRENCY_STANDARD ||
+        style == UNumberFormatStyle::UNUM_CURRENCY_PLURAL) {
+        setPropertiesFromPattern(pattern, IGNORE_ROUNDING_ALWAYS, status);
+    } else {
+        setPropertiesFromPattern(pattern, IGNORE_ROUNDING_IF_CURRENCY, status);
+    }
+    // Note: in Java, CurrencyPluralInfo is set in NumberFormat.java, but in C++, it is not set there,
+    // so we have to set it here.
+    if (style == UNumberFormatStyle::UNUM_CURRENCY_PLURAL) {
+        LocalPointer<CurrencyPluralInfo> cpi(
+                new CurrencyPluralInfo(fields->symbols->getLocale(), status),
+                status);
+        if (U_FAILURE(status)) { return; }
+        fields->properties.currencyPluralInfo.fPtr.adoptInstead(cpi.orphan());
+    }
+    touch(status);
+}
+
+DecimalFormat::DecimalFormat(const DecimalFormatSymbols* symbolsToAdopt, UErrorCode& status) {
+    // we must take ownership of symbolsToAdopt, even in a failure case.
+    LocalPointer<const DecimalFormatSymbols> adoptedSymbols(symbolsToAdopt);
+    if (U_FAILURE(status)) {
+        return;
+    }
+    fields = new DecimalFormatFields();
+    if (fields == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    if (adoptedSymbols.isNull()) {
+        fields->symbols.adoptInsteadAndCheckErrorCode(new DecimalFormatSymbols(status), status);
+    } else {
+        fields->symbols.adoptInsteadAndCheckErrorCode(adoptedSymbols.orphan(), status);
+    }
+    if (U_FAILURE(status)) {
+        delete fields;
+        fields = nullptr;
+    }
+}
+
+#if UCONFIG_HAVE_PARSEALLINPUT
+
+void DecimalFormat::setParseAllInput(UNumberFormatAttributeValue value) {
+    if (fields == nullptr) { return; }
+    if (value == fields->properties.parseAllInput) { return; }
+    fields->properties.parseAllInput = value;
+}
+
+#endif
+
+DecimalFormat&
+DecimalFormat::setAttribute(UNumberFormatAttribute attr, int32_t newValue, UErrorCode& status) {
+    if (U_FAILURE(status)) { return *this; }
+
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return *this;
+    }
+
+    switch (attr) {
+        case UNUM_LENIENT_PARSE:
+            setLenient(newValue != 0);
+            break;
+
+        case UNUM_PARSE_INT_ONLY:
+            setParseIntegerOnly(newValue != 0);
+            break;
+
+        case UNUM_GROUPING_USED:
+            setGroupingUsed(newValue != 0);
+            break;
+
+        case UNUM_DECIMAL_ALWAYS_SHOWN:
+            setDecimalSeparatorAlwaysShown(newValue != 0);
+            break;
+
+        case UNUM_MAX_INTEGER_DIGITS:
+            setMaximumIntegerDigits(newValue);
+            break;
+
+        case UNUM_MIN_INTEGER_DIGITS:
+            setMinimumIntegerDigits(newValue);
+            break;
+
+        case UNUM_INTEGER_DIGITS:
+            setMinimumIntegerDigits(newValue);
+            setMaximumIntegerDigits(newValue);
+            break;
+
+        case UNUM_MAX_FRACTION_DIGITS:
+            setMaximumFractionDigits(newValue);
+            break;
+
+        case UNUM_MIN_FRACTION_DIGITS:
+            setMinimumFractionDigits(newValue);
+            break;
+
+        case UNUM_FRACTION_DIGITS:
+            setMinimumFractionDigits(newValue);
+            setMaximumFractionDigits(newValue);
+            break;
+
+        case UNUM_SIGNIFICANT_DIGITS_USED:
+            setSignificantDigitsUsed(newValue != 0);
+            break;
+
+        case UNUM_MAX_SIGNIFICANT_DIGITS:
+            setMaximumSignificantDigits(newValue);
+            break;
+
+        case UNUM_MIN_SIGNIFICANT_DIGITS:
+            setMinimumSignificantDigits(newValue);
+            break;
+
+        case UNUM_MULTIPLIER:
+            setMultiplier(newValue);
+            break;
+
+        case UNUM_SCALE:
+            setMultiplierScale(newValue);
+            break;
+
+        case UNUM_GROUPING_SIZE:
+            setGroupingSize(newValue);
+            break;
+
+        case UNUM_ROUNDING_MODE:
+            setRoundingMode((DecimalFormat::ERoundingMode) newValue);
+            break;
+
+        case UNUM_FORMAT_WIDTH:
+            setFormatWidth(newValue);
+            break;
+
+        case UNUM_PADDING_POSITION:
+            /** The position at which padding will take place. */
+            setPadPosition((DecimalFormat::EPadPosition) newValue);
+            break;
+
+        case UNUM_SECONDARY_GROUPING_SIZE:
+            setSecondaryGroupingSize(newValue);
+            break;
+
+#if UCONFIG_HAVE_PARSEALLINPUT
+        case UNUM_PARSE_ALL_INPUT:
+            setParseAllInput((UNumberFormatAttributeValue) newValue);
+            break;
+#endif
+
+        case UNUM_PARSE_NO_EXPONENT:
+            setParseNoExponent((UBool) newValue);
+            break;
+
+        case UNUM_PARSE_DECIMAL_MARK_REQUIRED:
+            setDecimalPatternMatchRequired((UBool) newValue);
+            break;
+
+        case UNUM_CURRENCY_USAGE:
+            setCurrencyUsage((UCurrencyUsage) newValue, &status);
+            break;
+
+        case UNUM_MINIMUM_GROUPING_DIGITS:
+            setMinimumGroupingDigits(newValue);
+            break;
+
+        case UNUM_PARSE_CASE_SENSITIVE:
+            setParseCaseSensitive(static_cast<UBool>(newValue));
+            break;
+
+        case UNUM_SIGN_ALWAYS_SHOWN:
+            setSignAlwaysShown(static_cast<UBool>(newValue));
+            break;
+
+        case UNUM_FORMAT_FAIL_IF_MORE_THAN_MAX_DIGITS:
+            setFormatFailIfMoreThanMaxDigits(static_cast<UBool>(newValue));
+            break;
+
+        default:
+            status = U_UNSUPPORTED_ERROR;
+            break;
+    }
+    return *this;
+}
+
+int32_t DecimalFormat::getAttribute(UNumberFormatAttribute attr, UErrorCode& status) const {
+    if (U_FAILURE(status)) { return -1; }
+    
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return -1;
+    }
+
+    switch (attr) {
+        case UNUM_LENIENT_PARSE:
+            return isLenient();
+
+        case UNUM_PARSE_INT_ONLY:
+            return isParseIntegerOnly();
+
+        case UNUM_GROUPING_USED:
+            return isGroupingUsed();
+
+        case UNUM_DECIMAL_ALWAYS_SHOWN:
+            return isDecimalSeparatorAlwaysShown();
+
+        case UNUM_MAX_INTEGER_DIGITS:
+            return getMaximumIntegerDigits();
+
+        case UNUM_MIN_INTEGER_DIGITS:
+            return getMinimumIntegerDigits();
+
+        case UNUM_INTEGER_DIGITS:
+            // TBD: what should this return?
+            return getMinimumIntegerDigits();
+
+        case UNUM_MAX_FRACTION_DIGITS:
+            return getMaximumFractionDigits();
+
+        case UNUM_MIN_FRACTION_DIGITS:
+            return getMinimumFractionDigits();
+
+        case UNUM_FRACTION_DIGITS:
+            // TBD: what should this return?
+            return getMinimumFractionDigits();
+
+        case UNUM_SIGNIFICANT_DIGITS_USED:
+            return areSignificantDigitsUsed();
+
+        case UNUM_MAX_SIGNIFICANT_DIGITS:
+            return getMaximumSignificantDigits();
+
+        case UNUM_MIN_SIGNIFICANT_DIGITS:
+            return getMinimumSignificantDigits();
+
+        case UNUM_MULTIPLIER:
+            return getMultiplier();
+
+        case UNUM_SCALE:
+            return getMultiplierScale();
+
+        case UNUM_GROUPING_SIZE:
+            return getGroupingSize();
+
+        case UNUM_ROUNDING_MODE:
+            return getRoundingMode();
+
+        case UNUM_FORMAT_WIDTH:
+            return getFormatWidth();
+
+        case UNUM_PADDING_POSITION:
+            return getPadPosition();
+
+        case UNUM_SECONDARY_GROUPING_SIZE:
+            return getSecondaryGroupingSize();
+
+        case UNUM_PARSE_NO_EXPONENT:
+            return isParseNoExponent();
+
+        case UNUM_PARSE_DECIMAL_MARK_REQUIRED:
+            return isDecimalPatternMatchRequired();
+
+        case UNUM_CURRENCY_USAGE:
+            return getCurrencyUsage();
+
+        case UNUM_MINIMUM_GROUPING_DIGITS:
+            return getMinimumGroupingDigits();
+
+        case UNUM_PARSE_CASE_SENSITIVE:
+            return isParseCaseSensitive();
+
+        case UNUM_SIGN_ALWAYS_SHOWN:
+            return isSignAlwaysShown();
+
+        case UNUM_FORMAT_FAIL_IF_MORE_THAN_MAX_DIGITS:
+            return isFormatFailIfMoreThanMaxDigits();
+
+        default:
+            status = U_UNSUPPORTED_ERROR;
+            break;
+    }
+
+    return -1; /* undefined */
+}
+
+void DecimalFormat::setGroupingUsed(UBool enabled) {
+    if (fields == nullptr) {
+        return;
+    }
+    if (UBOOL_TO_BOOL(enabled) == fields->properties.groupingUsed) { return; }
+    NumberFormat::setGroupingUsed(enabled); // to set field for compatibility
+    fields->properties.groupingUsed = enabled;
+    touchNoError();
+}
+
+void DecimalFormat::setParseIntegerOnly(UBool value) {
+    if (fields == nullptr) {
+        return;
+    }
+    if (UBOOL_TO_BOOL(value) == fields->properties.parseIntegerOnly) { return; }
+    NumberFormat::setParseIntegerOnly(value); // to set field for compatibility
+    fields->properties.parseIntegerOnly = value;
+    touchNoError();
+}
+
+void DecimalFormat::setLenient(UBool enable) {
+    if (fields == nullptr) {
+        return;
+    }
+    ParseMode mode = enable ? PARSE_MODE_LENIENT : PARSE_MODE_STRICT;
+    if (!fields->properties.parseMode.isNull() && mode == fields->properties.parseMode.getNoError()) { return; }
+    NumberFormat::setLenient(enable); // to set field for compatibility
+    fields->properties.parseMode = mode;
+    touchNoError();
+}
+
+DecimalFormat::DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt,
+                             UParseError&, UErrorCode& status)
+        : DecimalFormat(symbolsToAdopt, status) {
+    if (U_FAILURE(status)) { return; }
+    // TODO: What is parseError for?
+    setPropertiesFromPattern(pattern, IGNORE_ROUNDING_IF_CURRENCY, status);
+    touch(status);
+}
+
+DecimalFormat::DecimalFormat(const UnicodeString& pattern, const DecimalFormatSymbols& symbols,
+                             UErrorCode& status)
+        : DecimalFormat(nullptr, status) {
+    if (U_FAILURE(status)) { return; }
+    LocalPointer<DecimalFormatSymbols> dfs(new DecimalFormatSymbols(symbols), status);
+    if (U_FAILURE(status)) {
+        // If we failed to allocate DecimalFormatSymbols, then release fields and its members.
+        // We must have a fully complete fields object, we cannot have partially populated members.
+        delete fields;
+        fields = nullptr;
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    fields->symbols.adoptInstead(dfs.orphan());
+    setPropertiesFromPattern(pattern, IGNORE_ROUNDING_IF_CURRENCY, status);
+    touch(status);
+}
+
+DecimalFormat::DecimalFormat(const DecimalFormat& source) : NumberFormat(source) {
+    // If the object that we are copying from is invalid, no point in going further.
+    if (source.fields == nullptr) {
+        return;
+    }
+    // Note: it is not safe to copy fields->formatter or fWarehouse directly because fields->formatter might have
+    // dangling pointers to fields inside fWarehouse. The safe thing is to re-construct fields->formatter from
+    // the property bag, despite being somewhat slower.
+    fields = new DecimalFormatFields(source.fields->properties);
+    if (fields == nullptr) {
+        return; // no way to report an error.
+    }
+    UErrorCode status = U_ZERO_ERROR;
+    fields->symbols.adoptInsteadAndCheckErrorCode(new DecimalFormatSymbols(*source.fields->symbols), status);
+    // In order to simplify error handling logic in the various getters/setters/etc, we do not allow
+    // any partially populated DecimalFormatFields object. We must have a fully complete fields object
+    // or else we set it to nullptr.
+    if (U_FAILURE(status)) {
+        delete fields;
+        fields = nullptr;
+        return;
+    }
+    touch(status);
+}
+
+DecimalFormat& DecimalFormat::operator=(const DecimalFormat& rhs) {
+    // guard against self-assignment
+    if (this == &rhs) {
+        return *this;
+    }
+    // Make sure both objects are valid.
+    if (fields == nullptr || rhs.fields == nullptr) {
+        return *this; // unfortunately, no way to report an error.
+    }
+    fields->properties = rhs.fields->properties;
+    fields->exportedProperties.clear();
+    UErrorCode status = U_ZERO_ERROR;
+    LocalPointer<DecimalFormatSymbols> dfs(new DecimalFormatSymbols(*rhs.fields->symbols), status);
+    if (U_FAILURE(status)) {
+        // We failed to allocate DecimalFormatSymbols, release fields and its members.
+        // We must have a fully complete fields object, we cannot have partially populated members.
+        delete fields;
+        fields = nullptr;
+        return *this;
+    }
+    fields->symbols.adoptInstead(dfs.orphan());
+    touch(status);
+
+    return *this;
+}
+
+DecimalFormat::~DecimalFormat() {
+    if (fields == nullptr) { return; }
+
+    delete fields->atomicParser.exchange(nullptr);
+    delete fields->atomicCurrencyParser.exchange(nullptr);
+    delete fields;
+}
+
+DecimalFormat* DecimalFormat::clone() const {
+    // can only clone valid objects.
+    if (fields == nullptr) {
+        return nullptr;
+    }
+    LocalPointer<DecimalFormat> df(new DecimalFormat(*this));
+    if (df.isValid() && df->fields != nullptr) {
+        return df.orphan();
+    }
+    return nullptr;
+}
+
+UBool DecimalFormat::operator==(const Format& other) const {
+    auto* otherDF = dynamic_cast<const DecimalFormat*>(&other);
+    if (otherDF == nullptr) {
+        return false;
+    }
+    // If either object is in an invalid state, prevent dereferencing nullptr below.
+    // Additionally, invalid objects should not be considered equal to anything.
+    if (fields == nullptr || otherDF->fields == nullptr) {
+        return false;
+    }
+    return fields->properties == otherDF->fields->properties && *fields->symbols == *otherDF->fields->symbols;
+}
+
+UnicodeString& DecimalFormat::format(double number, UnicodeString& appendTo, FieldPosition& pos) const {
+    if (fields == nullptr) {
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    if (pos.getField() == FieldPosition::DONT_CARE && fastFormatDouble(number, appendTo)) {
+        return appendTo;
+    }
+    UErrorCode localStatus = U_ZERO_ERROR;
+    UFormattedNumberData output;
+    output.quantity.setToDouble(number);
+    fields->formatter.formatImpl(&output, localStatus);
+    fieldPositionHelper(output, pos, appendTo.length(), localStatus);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, localStatus);
+    return appendTo;
+}
+
+UnicodeString& DecimalFormat::format(double number, UnicodeString& appendTo, FieldPosition& pos,
+                                     UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return appendTo; // don't overwrite status if it's already a failure.
+    }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    if (pos.getField() == FieldPosition::DONT_CARE && fastFormatDouble(number, appendTo)) {
+        return appendTo;
+    }
+    UFormattedNumberData output;
+    output.quantity.setToDouble(number);
+    fields->formatter.formatImpl(&output, status);
+    fieldPositionHelper(output, pos, appendTo.length(), status);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, status);
+    return appendTo;
+}
+
+UnicodeString&
+DecimalFormat::format(double number, UnicodeString& appendTo, FieldPositionIterator* posIter,
+                      UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return appendTo; // don't overwrite status if it's already a failure.
+    }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    if (posIter == nullptr && fastFormatDouble(number, appendTo)) {
+        return appendTo;
+    }
+    UFormattedNumberData output;
+    output.quantity.setToDouble(number);
+    fields->formatter.formatImpl(&output, status);
+    fieldPositionIteratorHelper(output, posIter, appendTo.length(), status);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, status);
+    return appendTo;
+}
+
+UnicodeString& DecimalFormat::format(int32_t number, UnicodeString& appendTo, FieldPosition& pos) const {
+    return format(static_cast<int64_t> (number), appendTo, pos);
+}
+
+UnicodeString& DecimalFormat::format(int32_t number, UnicodeString& appendTo, FieldPosition& pos,
+                                     UErrorCode& status) const {
+    return format(static_cast<int64_t> (number), appendTo, pos, status);
+}
+
+UnicodeString&
+DecimalFormat::format(int32_t number, UnicodeString& appendTo, FieldPositionIterator* posIter,
+                      UErrorCode& status) const {
+    return format(static_cast<int64_t> (number), appendTo, posIter, status);
+}
+
+UnicodeString& DecimalFormat::format(int64_t number, UnicodeString& appendTo, FieldPosition& pos) const {
+    if (fields == nullptr) {
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    if (pos.getField() == FieldPosition::DONT_CARE && fastFormatInt64(number, appendTo)) {
+        return appendTo;
+    }
+    UErrorCode localStatus = U_ZERO_ERROR;
+    UFormattedNumberData output;
+    output.quantity.setToLong(number);
+    fields->formatter.formatImpl(&output, localStatus);
+    fieldPositionHelper(output, pos, appendTo.length(), localStatus);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, localStatus);
+    return appendTo;
+}
+
+UnicodeString& DecimalFormat::format(int64_t number, UnicodeString& appendTo, FieldPosition& pos,
+                                     UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return appendTo; // don't overwrite status if it's already a failure.
+    }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    if (pos.getField() == FieldPosition::DONT_CARE && fastFormatInt64(number, appendTo)) {
+        return appendTo;
+    }
+    UFormattedNumberData output;
+    output.quantity.setToLong(number);
+    fields->formatter.formatImpl(&output, status);
+    fieldPositionHelper(output, pos, appendTo.length(), status);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, status);
+    return appendTo;
+}
+
+UnicodeString&
+DecimalFormat::format(int64_t number, UnicodeString& appendTo, FieldPositionIterator* posIter,
+                      UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return appendTo; // don't overwrite status if it's already a failure.
+    }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    if (posIter == nullptr && fastFormatInt64(number, appendTo)) {
+        return appendTo;
+    }
+    UFormattedNumberData output;
+    output.quantity.setToLong(number);
+    fields->formatter.formatImpl(&output, status);
+    fieldPositionIteratorHelper(output, posIter, appendTo.length(), status);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, status);
+    return appendTo;
+}
+
+UnicodeString&
+DecimalFormat::format(StringPiece number, UnicodeString& appendTo, FieldPositionIterator* posIter,
+                      UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return appendTo; // don't overwrite status if it's already a failure.
+    }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    UFormattedNumberData output;
+    output.quantity.setToDecNumber(number, status);
+    fields->formatter.formatImpl(&output, status);
+    fieldPositionIteratorHelper(output, posIter, appendTo.length(), status);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, status);
+    return appendTo;
+}
+
+UnicodeString& DecimalFormat::format(const DecimalQuantity& number, UnicodeString& appendTo,
+                                     FieldPositionIterator* posIter, UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return appendTo; // don't overwrite status if it's already a failure.
+    }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    UFormattedNumberData output;
+    output.quantity = number;
+    fields->formatter.formatImpl(&output, status);
+    fieldPositionIteratorHelper(output, posIter, appendTo.length(), status);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, status);
+    return appendTo;
+}
+
+UnicodeString&
+DecimalFormat::format(const DecimalQuantity& number, UnicodeString& appendTo, FieldPosition& pos,
+                      UErrorCode& status) const {
+    if (U_FAILURE(status)) {
+        return appendTo; // don't overwrite status if it's already a failure.
+    }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        appendTo.setToBogus();
+        return appendTo;
+    }
+    UFormattedNumberData output;
+    output.quantity = number;
+    fields->formatter.formatImpl(&output, status);
+    fieldPositionHelper(output, pos, appendTo.length(), status);
+    auto appendable = UnicodeStringAppendable(appendTo);
+    output.appendTo(appendable, status);
+    return appendTo;
+}
+
+void DecimalFormat::parse(const UnicodeString& text, Formattable& output,
+                          ParsePosition& parsePosition) const {
+    if (fields == nullptr) {
+        return;
+    }
+    if (parsePosition.getIndex() < 0 || parsePosition.getIndex() >= text.length()) {
+        if (parsePosition.getIndex() == text.length()) {
+            // If there is nothing to parse, it is an error
+            parsePosition.setErrorIndex(parsePosition.getIndex());
+        }
+        return;
+    }
+
+    ErrorCode status;
+    ParsedNumber result;
+    // Note: if this is a currency instance, currencies will be matched despite the fact that we are not in the
+    // parseCurrency method (backwards compatibility)
+    int32_t startIndex = parsePosition.getIndex();
+    const NumberParserImpl* parser = getParser(status);
+    if (U_FAILURE(status)) {
+        return; // unfortunately no way to report back the error.
+    }
+    parser->parse(text, startIndex, true, result, status);
+    if (U_FAILURE(status)) {
+        return; // unfortunately no way to report back the error.
+    }
+    // TODO: Do we need to check for fImpl->properties->parseAllInput (UCONFIG_HAVE_PARSEALLINPUT) here?
+    if (result.success()) {
+        parsePosition.setIndex(result.charEnd);
+        result.populateFormattable(output, parser->getParseFlags());
+    } else {
+        parsePosition.setErrorIndex(startIndex + result.charEnd);
+    }
+}
+
+CurrencyAmount* DecimalFormat::parseCurrency(const UnicodeString& text, ParsePosition& parsePosition) const {
+    if (fields == nullptr) {
+        return nullptr;
+    }
+    if (parsePosition.getIndex() < 0 || parsePosition.getIndex() >= text.length()) {
+        return nullptr;
+    }
+
+    ErrorCode status;
+    ParsedNumber result;
+    // Note: if this is a currency instance, currencies will be matched despite the fact that we are not in the
+    // parseCurrency method (backwards compatibility)
+    int32_t startIndex = parsePosition.getIndex();
+    const NumberParserImpl* parser = getCurrencyParser(status);
+    if (U_FAILURE(status)) {
+        return nullptr;
+    }
+    parser->parse(text, startIndex, true, result, status);
+    if (U_FAILURE(status)) {
+        return nullptr;
+    }
+    // TODO: Do we need to check for fImpl->properties->parseAllInput (UCONFIG_HAVE_PARSEALLINPUT) here?
+    if (result.success()) {
+        parsePosition.setIndex(result.charEnd);
+        Formattable formattable;
+        result.populateFormattable(formattable, parser->getParseFlags());
+        LocalPointer<CurrencyAmount> currencyAmount(
+            new CurrencyAmount(formattable, result.currencyCode, status), status);
+        if (U_FAILURE(status)) {
+            return nullptr;
+        }
+        return currencyAmount.orphan();
+    } else {
+        parsePosition.setErrorIndex(startIndex + result.charEnd);
+        return nullptr;
+    }
+}
+
+const DecimalFormatSymbols* DecimalFormat::getDecimalFormatSymbols(void) const {
+    if (fields == nullptr) {
+        return nullptr;
+    }
+    return fields->symbols.getAlias();
+}
+
+void DecimalFormat::adoptDecimalFormatSymbols(DecimalFormatSymbols* symbolsToAdopt) {
+    if (symbolsToAdopt == nullptr) {
+        return; // do not allow caller to set fields->symbols to NULL
+    }
+    // we must take ownership of symbolsToAdopt, even in a failure case.
+    LocalPointer<DecimalFormatSymbols> dfs(symbolsToAdopt);
+    if (fields == nullptr) {
+        return;
+    }
+    fields->symbols.adoptInstead(dfs.orphan());
+    touchNoError();
+}
+
+void DecimalFormat::setDecimalFormatSymbols(const DecimalFormatSymbols& symbols) {
+    if (fields == nullptr) {
+        return;
+    }
+    UErrorCode status = U_ZERO_ERROR;
+    LocalPointer<DecimalFormatSymbols> dfs(new DecimalFormatSymbols(symbols), status);
+    if (U_FAILURE(status)) {
+        // We failed to allocate DecimalFormatSymbols, release fields and its members.
+        // We must have a fully complete fields object, we cannot have partially populated members.
+        delete fields;
+        fields = nullptr;
+        return;
+    }
+    fields->symbols.adoptInstead(dfs.orphan());
+    touchNoError();
+}
+
+const CurrencyPluralInfo* DecimalFormat::getCurrencyPluralInfo(void) const {
+    if (fields == nullptr) {
+        return nullptr;
+    }
+    return fields->properties.currencyPluralInfo.fPtr.getAlias();
+}
+
+void DecimalFormat::adoptCurrencyPluralInfo(CurrencyPluralInfo* toAdopt) {
+    // TODO: should we guard against nullptr input, like in adoptDecimalFormatSymbols?
+    // we must take ownership of toAdopt, even in a failure case.
+    LocalPointer<CurrencyPluralInfo> cpi(toAdopt);
+    if (fields == nullptr) {
+        return;
+    }
+    fields->properties.currencyPluralInfo.fPtr.adoptInstead(cpi.orphan());
+    touchNoError();
+}
+
+void DecimalFormat::setCurrencyPluralInfo(const CurrencyPluralInfo& info) {
+    if (fields == nullptr) {
+        return;
+    }
+    if (fields->properties.currencyPluralInfo.fPtr.isNull()) {
+        // Note: clone() can fail with OOM error, but we have no way to report it. :(
+        fields->properties.currencyPluralInfo.fPtr.adoptInstead(info.clone());
+    } else {
+        *fields->properties.currencyPluralInfo.fPtr = info; // copy-assignment operator
+    }
+    touchNoError();
+}
+
+UnicodeString& DecimalFormat::getPositivePrefix(UnicodeString& result) const {
+    if (fields == nullptr) {
+        result.setToBogus();
+        return result;
+    }
+    UErrorCode status = U_ZERO_ERROR;
+    fields->formatter.getAffixImpl(true, false, result, status);
+    if (U_FAILURE(status)) { result.setToBogus(); }
+    return result;
+}
+
+void DecimalFormat::setPositivePrefix(const UnicodeString& newValue) {
+    if (fields == nullptr) {
+        return;
+    }
+    if (newValue == fields->properties.positivePrefix) { return; }
+    fields->properties.positivePrefix = newValue;
+    touchNoError();
+}
+
+UnicodeString& DecimalFormat::getNegativePrefix(UnicodeString& result) const {
+    if (fields == nullptr) {
+        result.setToBogus();
+        return result;
+    }
+    UErrorCode status = U_ZERO_ERROR;
+    fields->formatter.getAffixImpl(true, true, result, status);
+    if (U_FAILURE(status)) { result.setToBogus(); }
+    return result;
+}
+
+void DecimalFormat::setNegativePrefix(const UnicodeString& newValue) {
+    if (fields == nullptr) {
+        return;
+    }
+    if (newValue == fields->properties.negativePrefix) { return; }
+    fields->properties.negativePrefix = newValue;
+    touchNoError();
+}
+
+UnicodeString& DecimalFormat::getPositiveSuffix(UnicodeString& result) const {
+    if (fields == nullptr) {
+        result.setToBogus();
+        return result;
+    }
+    UErrorCode status = U_ZERO_ERROR;
+    fields->formatter.getAffixImpl(false, false, result, status);
+    if (U_FAILURE(status)) { result.setToBogus(); }
+    return result;
+}
+
+void DecimalFormat::setPositiveSuffix(const UnicodeString& newValue) {
+    if (fields == nullptr) {
+        return;
+    }
+    if (newValue == fields->properties.positiveSuffix) { return; }
+    fields->properties.positiveSuffix = newValue;
+    touchNoError();
+}
+
+UnicodeString& DecimalFormat::getNegativeSuffix(UnicodeString& result) const {
+    if (fields == nullptr) {
+        result.setToBogus();
+        return result;
+    }
+    UErrorCode status = U_ZERO_ERROR;
+    fields->formatter.getAffixImpl(false, true, result, status);
+    if (U_FAILURE(status)) { result.setToBogus(); }
+    return result;
+}
+
+void DecimalFormat::setNegativeSuffix(const UnicodeString& newValue) {
+    if (fields == nullptr) {
+        return;
+    }
+    if (newValue == fields->properties.negativeSuffix) { return; }
+    fields->properties.negativeSuffix = newValue;
+    touchNoError();
+}
+
+UBool DecimalFormat::isSignAlwaysShown() const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        return DecimalFormatProperties::getDefault().signAlwaysShown;
+    }
+    return fields->properties.signAlwaysShown;
+}
+
+void DecimalFormat::setSignAlwaysShown(UBool value) {
+    if (fields == nullptr) { return; }
+    if (UBOOL_TO_BOOL(value) == fields->properties.signAlwaysShown) { return; }
+    fields->properties.signAlwaysShown = value;
+    touchNoError();
+}
+
+int32_t DecimalFormat::getMultiplier(void) const {
+    const DecimalFormatProperties *dfp;
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        dfp = &(DecimalFormatProperties::getDefault());
+    } else {
+        dfp = &fields->properties;
+    }
+    if (dfp->multiplier != 1) {
+        return dfp->multiplier;
+    } else if (dfp->magnitudeMultiplier != 0) {
+        return static_cast<int32_t>(uprv_pow10(dfp->magnitudeMultiplier));
+    } else {
+        return 1;
+    }
+}
+
+void DecimalFormat::setMultiplier(int32_t multiplier) {
+    if (fields == nullptr) {
+         return;
+    }
+    if (multiplier == 0) {
+        multiplier = 1;     // one being the benign default value for a multiplier.
+    }
+
+    // Try to convert to a magnitude multiplier first
+    int delta = 0;
+    int value = multiplier;
+    while (value != 1) {
+        delta++;
+        int temp = value / 10;
+        if (temp * 10 != value) {
+            delta = -1;
+            break;
+        }
+        value = temp;
+    }
+    if (delta != -1) {
+        fields->properties.magnitudeMultiplier = delta;
+        fields->properties.multiplier = 1;
+    } else {
+        fields->properties.magnitudeMultiplier = 0;
+        fields->properties.multiplier = multiplier;
+    }
+    touchNoError();
+}
+
+int32_t DecimalFormat::getMultiplierScale() const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().multiplierScale;
+    }
+    return fields->properties.multiplierScale;
+}
+
+void DecimalFormat::setMultiplierScale(int32_t newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.multiplierScale) { return; }
+    fields->properties.multiplierScale = newValue;
+    touchNoError();
+}
+
+double DecimalFormat::getRoundingIncrement(void) const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().roundingIncrement;
+    }
+    return fields->exportedProperties.roundingIncrement;
+}
+
+void DecimalFormat::setRoundingIncrement(double newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.roundingIncrement) { return; }
+    fields->properties.roundingIncrement = newValue;
+    touchNoError();
+}
+
+ERoundingMode DecimalFormat::getRoundingMode(void) const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return static_cast<ERoundingMode>(DecimalFormatProperties::getDefault().roundingMode.getNoError());
+    }
+    // UNumberFormatRoundingMode and ERoundingMode have the same values.
+    return static_cast<ERoundingMode>(fields->exportedProperties.roundingMode.getNoError());
+}
+
+void DecimalFormat::setRoundingMode(ERoundingMode roundingMode) {
+    if (fields == nullptr) { return; }
+    auto uRoundingMode = static_cast<UNumberFormatRoundingMode>(roundingMode);
+    if (!fields->properties.roundingMode.isNull() && uRoundingMode == fields->properties.roundingMode.getNoError()) {
+        return;
+    }
+    NumberFormat::setMaximumIntegerDigits(roundingMode); // to set field for compatibility
+    fields->properties.roundingMode = uRoundingMode;
+    touchNoError();
+}
+
+int32_t DecimalFormat::getFormatWidth(void) const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().formatWidth;
+    }
+    return fields->properties.formatWidth;
+}
+
+void DecimalFormat::setFormatWidth(int32_t width) {
+    if (fields == nullptr) { return; }
+    if (width == fields->properties.formatWidth) { return; }
+    fields->properties.formatWidth = width;
+    touchNoError();
+}
+
+UnicodeString DecimalFormat::getPadCharacterString() const {
+    if (fields == nullptr || fields->properties.padString.isBogus()) {
+        // Readonly-alias the static string kFallbackPaddingString
+        return {TRUE, kFallbackPaddingString, -1};
+    } else {
+        return fields->properties.padString;
+    }
+}
+
+void DecimalFormat::setPadCharacter(const UnicodeString& padChar) {
+    if (fields == nullptr) { return; }
+    if (padChar == fields->properties.padString) { return; }
+    if (padChar.length() > 0) {
+        fields->properties.padString = UnicodeString(padChar.char32At(0));
+    } else {
+        fields->properties.padString.setToBogus();
+    }
+    touchNoError();
+}
+
+EPadPosition DecimalFormat::getPadPosition(void) const {
+    if (fields == nullptr || fields->properties.padPosition.isNull()) {
+        return EPadPosition::kPadBeforePrefix;
+    } else {
+        // UNumberFormatPadPosition and EPadPosition have the same values.
+        return static_cast<EPadPosition>(fields->properties.padPosition.getNoError());
+    }
+}
+
+void DecimalFormat::setPadPosition(EPadPosition padPos) {
+    if (fields == nullptr) { return; }
+    auto uPadPos = static_cast<UNumberFormatPadPosition>(padPos);
+    if (!fields->properties.padPosition.isNull() && uPadPos == fields->properties.padPosition.getNoError()) {
+        return;
+    }
+    fields->properties.padPosition = uPadPos;
+    touchNoError();
+}
+
+UBool DecimalFormat::isScientificNotation(void) const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return (DecimalFormatProperties::getDefault().minimumExponentDigits != -1);
+    }
+    return (fields->properties.minimumExponentDigits != -1);
+}
+
+void DecimalFormat::setScientificNotation(UBool useScientific) {
+    if (fields == nullptr) { return; }
+    int32_t minExp = useScientific ? 1 : -1;
+    if (fields->properties.minimumExponentDigits == minExp) { return; }
+    if (useScientific) {
+        fields->properties.minimumExponentDigits = 1;
+    } else {
+        fields->properties.minimumExponentDigits = -1;
+    }
+    touchNoError();
+}
+
+int8_t DecimalFormat::getMinimumExponentDigits(void) const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return static_cast<int8_t>(DecimalFormatProperties::getDefault().minimumExponentDigits);
+    }
+    return static_cast<int8_t>(fields->properties.minimumExponentDigits);
+}
+
+void DecimalFormat::setMinimumExponentDigits(int8_t minExpDig) {
+    if (fields == nullptr) { return; }
+    if (minExpDig == fields->properties.minimumExponentDigits) { return; }
+    fields->properties.minimumExponentDigits = minExpDig;
+    touchNoError();
+}
+
+UBool DecimalFormat::isExponentSignAlwaysShown(void) const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().exponentSignAlwaysShown;
+    }
+    return fields->properties.exponentSignAlwaysShown;
+}
+
+void DecimalFormat::setExponentSignAlwaysShown(UBool expSignAlways) {
+    if (fields == nullptr) { return; }
+    if (UBOOL_TO_BOOL(expSignAlways) == fields->properties.exponentSignAlwaysShown) { return; }
+    fields->properties.exponentSignAlwaysShown = expSignAlways;
+    touchNoError();
+}
+
+int32_t DecimalFormat::getGroupingSize(void) const {
+    int32_t groupingSize;
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        groupingSize = DecimalFormatProperties::getDefault().groupingSize;
+    } else {
+        groupingSize = fields->properties.groupingSize;
+    }
+    if (groupingSize < 0) {
+        return 0;
+    }
+    return groupingSize;
+}
+
+void DecimalFormat::setGroupingSize(int32_t newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.groupingSize) { return; }
+    fields->properties.groupingSize = newValue;
+    touchNoError();
+}
+
+int32_t DecimalFormat::getSecondaryGroupingSize(void) const {
+    int32_t grouping2;
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        grouping2 = DecimalFormatProperties::getDefault().secondaryGroupingSize;
+    } else {
+        grouping2 = fields->properties.secondaryGroupingSize;
+    }
+    if (grouping2 < 0) {
+        return 0;
+    }
+    return grouping2;
+}
+
+void DecimalFormat::setSecondaryGroupingSize(int32_t newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.secondaryGroupingSize) { return; }
+    fields->properties.secondaryGroupingSize = newValue;
+    touchNoError();
+}
+
+int32_t DecimalFormat::getMinimumGroupingDigits() const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().minimumGroupingDigits;
+    }
+    return fields->properties.minimumGroupingDigits;
+}
+
+void DecimalFormat::setMinimumGroupingDigits(int32_t newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.minimumGroupingDigits) { return; }
+    fields->properties.minimumGroupingDigits = newValue;
+    touchNoError();
+}
+
+UBool DecimalFormat::isDecimalSeparatorAlwaysShown(void) const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().decimalSeparatorAlwaysShown;
+    }
+    return fields->properties.decimalSeparatorAlwaysShown;
+}
+
+void DecimalFormat::setDecimalSeparatorAlwaysShown(UBool newValue) {
+    if (fields == nullptr) { return; }
+    if (UBOOL_TO_BOOL(newValue) == fields->properties.decimalSeparatorAlwaysShown) { return; }
+    fields->properties.decimalSeparatorAlwaysShown = newValue;
+    touchNoError();
+}
+
+UBool DecimalFormat::isDecimalPatternMatchRequired(void) const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().decimalPatternMatchRequired;
+    }
+    return fields->properties.decimalPatternMatchRequired;
+}
+
+void DecimalFormat::setDecimalPatternMatchRequired(UBool newValue) {
+    if (fields == nullptr) { return; }
+    if (UBOOL_TO_BOOL(newValue) == fields->properties.decimalPatternMatchRequired) { return; }
+    fields->properties.decimalPatternMatchRequired = newValue;
+    touchNoError();
+}
+
+UBool DecimalFormat::isParseNoExponent() const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().parseNoExponent;
+    }
+    return fields->properties.parseNoExponent;
+}
+
+void DecimalFormat::setParseNoExponent(UBool value) {
+    if (fields == nullptr) { return; }
+    if (UBOOL_TO_BOOL(value) == fields->properties.parseNoExponent) { return; }
+    fields->properties.parseNoExponent = value;
+    touchNoError();
+}
+
+UBool DecimalFormat::isParseCaseSensitive() const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().parseCaseSensitive;
+    }
+    return fields->properties.parseCaseSensitive;
+}
+
+void DecimalFormat::setParseCaseSensitive(UBool value) {
+    if (fields == nullptr) { return; }
+    if (UBOOL_TO_BOOL(value) == fields->properties.parseCaseSensitive) { return; }
+    fields->properties.parseCaseSensitive = value;
+    touchNoError();
+}
+
+UBool DecimalFormat::isFormatFailIfMoreThanMaxDigits() const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().formatFailIfMoreThanMaxDigits;
+    }
+    return fields->properties.formatFailIfMoreThanMaxDigits;
+}
+
+void DecimalFormat::setFormatFailIfMoreThanMaxDigits(UBool value) {
+    if (fields == nullptr) { return; }
+    if (UBOOL_TO_BOOL(value) == fields->properties.formatFailIfMoreThanMaxDigits) { return; }
+    fields->properties.formatFailIfMoreThanMaxDigits = value;
+    touchNoError();
+}
+
+UnicodeString& DecimalFormat::toPattern(UnicodeString& result) const {
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        result.setToBogus();
+        return result;
+    }
+    // Pull some properties from exportedProperties and others from properties
+    // to keep affix patterns intact.  In particular, pull rounding properties
+    // so that CurrencyUsage is reflected properly.
+    // TODO: Consider putting this logic in number_patternstring.cpp instead.
+    ErrorCode localStatus;
+    DecimalFormatProperties tprops(fields->properties);
+    bool useCurrency = (
+        !tprops.currency.isNull() ||
+        !tprops.currencyPluralInfo.fPtr.isNull() ||
+        !tprops.currencyUsage.isNull() ||
+        AffixUtils::hasCurrencySymbols(tprops.positivePrefixPattern, localStatus) ||
+        AffixUtils::hasCurrencySymbols(tprops.positiveSuffixPattern, localStatus) ||
+        AffixUtils::hasCurrencySymbols(tprops.negativePrefixPattern, localStatus) ||
+        AffixUtils::hasCurrencySymbols(tprops.negativeSuffixPattern, localStatus));
+    if (useCurrency) {
+        tprops.minimumFractionDigits = fields->exportedProperties.minimumFractionDigits;
+        tprops.maximumFractionDigits = fields->exportedProperties.maximumFractionDigits;
+        tprops.roundingIncrement = fields->exportedProperties.roundingIncrement;
+    }
+    result = PatternStringUtils::propertiesToPatternString(tprops, localStatus);
+    return result;
+}
+
+UnicodeString& DecimalFormat::toLocalizedPattern(UnicodeString& result) const {
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        result.setToBogus();
+        return result;
+    }
+    ErrorCode localStatus;
+    result = toPattern(result);
+    result = PatternStringUtils::convertLocalized(result, *fields->symbols, true, localStatus);
+    return result;
+}
+
+void DecimalFormat::applyPattern(const UnicodeString& pattern, UParseError&, UErrorCode& status) {
+    // TODO: What is parseError for?
+    applyPattern(pattern, status);
+}
+
+void DecimalFormat::applyPattern(const UnicodeString& pattern, UErrorCode& status) {
+    // don't overwrite status if it's already a failure.
+    if (U_FAILURE(status)) { return; }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    setPropertiesFromPattern(pattern, IGNORE_ROUNDING_NEVER, status);
+    touch(status);
+}
+
+void DecimalFormat::applyLocalizedPattern(const UnicodeString& localizedPattern, UParseError&,
+                                          UErrorCode& status) {
+    // TODO: What is parseError for?
+    applyLocalizedPattern(localizedPattern, status);
+}
+
+void DecimalFormat::applyLocalizedPattern(const UnicodeString& localizedPattern, UErrorCode& status) {
+    // don't overwrite status if it's already a failure.
+    if (U_FAILURE(status)) { return; }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    UnicodeString pattern = PatternStringUtils::convertLocalized(
+            localizedPattern, *fields->symbols, false, status);
+    applyPattern(pattern, status);
+}
+
+void DecimalFormat::setMaximumIntegerDigits(int32_t newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.maximumIntegerDigits) { return; }
+    // For backwards compatibility, conflicting min/max need to keep the most recent setting.
+    int32_t min = fields->properties.minimumIntegerDigits;
+    if (min >= 0 && min > newValue) {
+        fields->properties.minimumIntegerDigits = newValue;
+    }
+    fields->properties.maximumIntegerDigits = newValue;
+    touchNoError();
+}
+
+void DecimalFormat::setMinimumIntegerDigits(int32_t newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.minimumIntegerDigits) { return; }
+    // For backwards compatibility, conflicting min/max need to keep the most recent setting.
+    int32_t max = fields->properties.maximumIntegerDigits;
+    if (max >= 0 && max < newValue) {
+        fields->properties.maximumIntegerDigits = newValue;
+    }
+    fields->properties.minimumIntegerDigits = newValue;
+    touchNoError();
+}
+
+void DecimalFormat::setMaximumFractionDigits(int32_t newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.maximumFractionDigits) { return; }
+    // cap for backward compatibility, formerly 340, now 999
+    if (newValue > kMaxIntFracSig) {
+        newValue = kMaxIntFracSig;
+    }
+    // For backwards compatibility, conflicting min/max need to keep the most recent setting.
+    int32_t min = fields->properties.minimumFractionDigits;
+    if (min >= 0 && min > newValue) {
+        fields->properties.minimumFractionDigits = newValue;
+    }
+    fields->properties.maximumFractionDigits = newValue;
+    touchNoError();
+}
+
+void DecimalFormat::setMinimumFractionDigits(int32_t newValue) {
+    if (fields == nullptr) { return; }
+    if (newValue == fields->properties.minimumFractionDigits) { return; }
+    // For backwards compatibility, conflicting min/max need to keep the most recent setting.
+    int32_t max = fields->properties.maximumFractionDigits;
+    if (max >= 0 && max < newValue) {
+        fields->properties.maximumFractionDigits = newValue;
+    }
+    fields->properties.minimumFractionDigits = newValue;
+    touchNoError();
+}
+
+int32_t DecimalFormat::getMinimumSignificantDigits() const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().minimumSignificantDigits;
+    }
+    return fields->exportedProperties.minimumSignificantDigits;
+}
+
+int32_t DecimalFormat::getMaximumSignificantDigits() const {
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        return DecimalFormatProperties::getDefault().maximumSignificantDigits;
+    }
+    return fields->exportedProperties.maximumSignificantDigits;
+}
+
+void DecimalFormat::setMinimumSignificantDigits(int32_t value) {
+    if (fields == nullptr) { return; }
+    if (value == fields->properties.minimumSignificantDigits) { return; }
+    int32_t max = fields->properties.maximumSignificantDigits;
+    if (max >= 0 && max < value) {
+        fields->properties.maximumSignificantDigits = value;
+    }
+    fields->properties.minimumSignificantDigits = value;
+    touchNoError();
+}
+
+void DecimalFormat::setMaximumSignificantDigits(int32_t value) {
+    if (fields == nullptr) { return; }
+    if (value == fields->properties.maximumSignificantDigits) { return; }
+    int32_t min = fields->properties.minimumSignificantDigits;
+    if (min >= 0 && min > value) {
+        fields->properties.minimumSignificantDigits = value;
+    }
+    fields->properties.maximumSignificantDigits = value;
+    touchNoError();
+}
+
+UBool DecimalFormat::areSignificantDigitsUsed() const {
+    const DecimalFormatProperties* dfp;
+    // Not much we can do to report an error.
+    if (fields == nullptr) {
+        // Fallback to using the default instance of DecimalFormatProperties.
+        dfp = &(DecimalFormatProperties::getDefault());
+    } else {
+        dfp = &fields->properties;
+    }
+    return dfp->minimumSignificantDigits != -1 || dfp->maximumSignificantDigits != -1;    
+}
+
+void DecimalFormat::setSignificantDigitsUsed(UBool useSignificantDigits) {
+    if (fields == nullptr) { return; }
+    
+    // These are the default values from the old implementation.
+    if (useSignificantDigits) {
+        if (fields->properties.minimumSignificantDigits != -1 ||
+            fields->properties.maximumSignificantDigits != -1) {
+            return;
+        }
+    } else {
+        if (fields->properties.minimumSignificantDigits == -1 &&
+            fields->properties.maximumSignificantDigits == -1) {
+            return;
+        }
+    }
+    int32_t minSig = useSignificantDigits ? 1 : -1;
+    int32_t maxSig = useSignificantDigits ? 6 : -1;
+    fields->properties.minimumSignificantDigits = minSig;
+    fields->properties.maximumSignificantDigits = maxSig;
+    touchNoError();
+}
+
+void DecimalFormat::setCurrency(const char16_t* theCurrency, UErrorCode& ec) {
+    // don't overwrite ec if it's already a failure.
+    if (U_FAILURE(ec)) { return; }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        ec = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    CurrencyUnit currencyUnit(theCurrency, ec);
+    if (U_FAILURE(ec)) { return; }
+    if (!fields->properties.currency.isNull() && fields->properties.currency.getNoError() == currencyUnit) {
+        return;
+    }
+    NumberFormat::setCurrency(theCurrency, ec); // to set field for compatibility
+    fields->properties.currency = currencyUnit;
+    // In Java, the DecimalFormatSymbols is mutable. Why not in C++?
+    LocalPointer<DecimalFormatSymbols> newSymbols(new DecimalFormatSymbols(*fields->symbols), ec);
+    newSymbols->setCurrency(currencyUnit.getISOCurrency(), ec);
+    fields->symbols.adoptInsteadAndCheckErrorCode(newSymbols.orphan(), ec);
+    touch(ec);
+}
+
+void DecimalFormat::setCurrency(const char16_t* theCurrency) {
+    ErrorCode localStatus;
+    setCurrency(theCurrency, localStatus);
+}
+
+void DecimalFormat::setCurrencyUsage(UCurrencyUsage newUsage, UErrorCode* ec) {
+    // don't overwrite ec if it's already a failure.
+    if (U_FAILURE(*ec)) { return; }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        *ec = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    if (!fields->properties.currencyUsage.isNull() && newUsage == fields->properties.currencyUsage.getNoError()) {
+        return;
+    }
+    fields->properties.currencyUsage = newUsage;
+    touch(*ec);
+}
+
+UCurrencyUsage DecimalFormat::getCurrencyUsage() const {
+    // CurrencyUsage is not exported, so we have to get it from the input property bag.
+    // TODO: Should we export CurrencyUsage instead?
+    if (fields == nullptr || fields->properties.currencyUsage.isNull()) {
+        return UCURR_USAGE_STANDARD;
+    }
+    return fields->properties.currencyUsage.getNoError();
+}
+
+void
+DecimalFormat::formatToDecimalQuantity(double number, DecimalQuantity& output, UErrorCode& status) const {
+    // don't overwrite status if it's already a failure.
+    if (U_FAILURE(status)) { return; }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    fields->formatter.formatDouble(number, status).getDecimalQuantity(output, status);
+}
+
+void DecimalFormat::formatToDecimalQuantity(const Formattable& number, DecimalQuantity& output,
+                                            UErrorCode& status) const {
+    // don't overwrite status if it's already a failure.
+    if (U_FAILURE(status)) { return; }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    UFormattedNumberData obj;
+    number.populateDecimalQuantity(obj.quantity, status);
+    fields->formatter.formatImpl(&obj, status);
+    output = std::move(obj.quantity);
+}
+
+const number::LocalizedNumberFormatter* DecimalFormat::toNumberFormatter(UErrorCode& status) const {
+    // We sometimes need to return nullptr here (see ICU-20380)
+    if (U_FAILURE(status)) { return nullptr; }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return nullptr;
+    }
+    return &fields->formatter;
+}
+
+/** Rebuilds the formatter object from the property bag. */
+void DecimalFormat::touch(UErrorCode& status) {
+    if (U_FAILURE(status)) {
+        return;
+    }
+    if (fields == nullptr) {
+        // We only get here if an OOM error happend during construction, copy construction, assignment, or modification.
+        // For regular construction, the caller should have checked the status variable for errors.
+        // For copy construction, there is unfortunately nothing to report the error, so we need to guard against
+        // this possible bad state here and set the status to an error.
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+
+    // In C++, fields->symbols is the source of truth for the locale.
+    Locale locale = fields->symbols->getLocale();
+
+    // Note: The formatter is relatively cheap to create, and we need it to populate fields->exportedProperties,
+    // so automatically recompute it here. The parser is a bit more expensive and is not needed until the
+    // parse method is called, so defer that until needed.
+    // TODO: Only update the pieces that changed instead of re-computing the whole formatter?
+ 
+    // Since memory has already been allocated for the formatter, we can move assign a stack-allocated object
+    // and don't need to call new. (Which is slower and could possibly fail).
+    fields->formatter = NumberPropertyMapper::create(
+        fields->properties, *fields->symbols, fields->warehouse, fields->exportedProperties, status
+    ).locale(locale);
+
+    // Do this after fields->exportedProperties are set up
+    setupFastFormat();
+
+    // Delete the parsers if they were made previously
+    delete fields->atomicParser.exchange(nullptr);
+    delete fields->atomicCurrencyParser.exchange(nullptr);
+
+    // In order for the getters to work, we need to populate some fields in NumberFormat.
+    NumberFormat::setCurrency(fields->exportedProperties.currency.get(status).getISOCurrency(), status);
+    NumberFormat::setMaximumIntegerDigits(fields->exportedProperties.maximumIntegerDigits);
+    NumberFormat::setMinimumIntegerDigits(fields->exportedProperties.minimumIntegerDigits);
+    NumberFormat::setMaximumFractionDigits(fields->exportedProperties.maximumFractionDigits);
+    NumberFormat::setMinimumFractionDigits(fields->exportedProperties.minimumFractionDigits);
+    // fImpl->properties, not fields->exportedProperties, since this information comes from the pattern:
+    NumberFormat::setGroupingUsed(fields->properties.groupingUsed);
+}
+
+void DecimalFormat::touchNoError() {
+    UErrorCode localStatus = U_ZERO_ERROR;
+    touch(localStatus);
+}
+
+void DecimalFormat::setPropertiesFromPattern(const UnicodeString& pattern, int32_t ignoreRounding,
+                                             UErrorCode& status) {
+    if (U_SUCCESS(status)) {
+        // Cast workaround to get around putting the enum in the public header file
+        auto actualIgnoreRounding = static_cast<IgnoreRounding>(ignoreRounding);
+        PatternParser::parseToExistingProperties(pattern, fields->properties,  actualIgnoreRounding, status);
+    }
+}
+
+const numparse::impl::NumberParserImpl* DecimalFormat::getParser(UErrorCode& status) const {
+    // TODO: Move this into umutex.h? (similar logic also in numrange_fluent.cpp)
+    // See ICU-20146
+
+    if (U_FAILURE(status)) {
+        return nullptr;
+    }
+
+    // First try to get the pre-computed parser
+    auto* ptr = fields->atomicParser.load();
+    if (ptr != nullptr) {
+        return ptr;
+    }
+
+    // Try computing the parser on our own
+    auto* temp = NumberParserImpl::createParserFromProperties(fields->properties, *fields->symbols, false, status);
+    if (U_FAILURE(status)) {
+        return nullptr;
+    }
+    if (temp == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return nullptr;
+    }
+
+    // Note: ptr starts as nullptr; during compare_exchange,
+    // it is set to what is actually stored in the atomic
+    // if another thread beat us to computing the parser object.
+    auto* nonConstThis = const_cast<DecimalFormat*>(this);
+    if (!nonConstThis->fields->atomicParser.compare_exchange_strong(ptr, temp)) {
+        // Another thread beat us to computing the parser
+        delete temp;
+        return ptr;
+    } else {
+        // Our copy of the parser got stored in the atomic
+        return temp;
+    }
+}
+
+const numparse::impl::NumberParserImpl* DecimalFormat::getCurrencyParser(UErrorCode& status) const {
+    if (U_FAILURE(status)) { return nullptr; }
+
+    // First try to get the pre-computed parser
+    auto* ptr = fields->atomicCurrencyParser.load();
+    if (ptr != nullptr) {
+        return ptr;
+    }
+
+    // Try computing the parser on our own
+    auto* temp = NumberParserImpl::createParserFromProperties(fields->properties, *fields->symbols, true, status);
+    if (temp == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        // although we may still dereference, call sites should be guarded
+    }
+
+    // Note: ptr starts as nullptr; during compare_exchange, it is set to what is actually stored in the
+    // atomic if another thread beat us to computing the parser object.
+    auto* nonConstThis = const_cast<DecimalFormat*>(this);
+    if (!nonConstThis->fields->atomicCurrencyParser.compare_exchange_strong(ptr, temp)) {
+        // Another thread beat us to computing the parser
+        delete temp;
+        return ptr;
+    } else {
+        // Our copy of the parser got stored in the atomic
+        return temp;
+    }
+}
+
+void
+DecimalFormat::fieldPositionHelper(
+        const UFormattedNumberData& formatted,
+        FieldPosition& fieldPosition,
+        int32_t offset,
+        UErrorCode& status) {
+    if (U_FAILURE(status)) { return; }
+    // always return first occurrence:
+    fieldPosition.setBeginIndex(0);
+    fieldPosition.setEndIndex(0);
+    bool found = formatted.nextFieldPosition(fieldPosition, status);
+    if (found && offset != 0) {
+        FieldPositionOnlyHandler fpoh(fieldPosition);
+        fpoh.shiftLast(offset);
+    }
+}
+
+void
+DecimalFormat::fieldPositionIteratorHelper(
+        const UFormattedNumberData& formatted,
+        FieldPositionIterator* fpi,
+        int32_t offset,
+        UErrorCode& status) {
+    if (U_SUCCESS(status) && (fpi != nullptr)) {
+        FieldPositionIteratorHandler fpih(fpi, status);
+        fpih.setShift(offset);
+        formatted.getAllFieldPositions(fpih, status);
+    }
+}
+
+// To debug fast-format, change void(x) to printf(x)
+#define trace(x) void(x)
+
+void DecimalFormat::setupFastFormat() {
+    // Check the majority of properties:
+    if (!fields->properties.equalsDefaultExceptFastFormat()) {
+        trace("no fast format: equality\n");
+        fields->canUseFastFormat = false;
+        return;
+    }
+
+    // Now check the remaining properties.
+    // Nontrivial affixes:
+    UBool trivialPP = fields->properties.positivePrefixPattern.isEmpty();
+    UBool trivialPS = fields->properties.positiveSuffixPattern.isEmpty();
+    UBool trivialNP = fields->properties.negativePrefixPattern.isBogus() || (
+            fields->properties.negativePrefixPattern.length() == 1 &&
+            fields->properties.negativePrefixPattern.charAt(0) == u'-');
+    UBool trivialNS = fields->properties.negativeSuffixPattern.isEmpty();
+    if (!trivialPP || !trivialPS || !trivialNP || !trivialNS) {
+        trace("no fast format: affixes\n");
+        fields->canUseFastFormat = false;
+        return;
+    }
+
+    // Grouping (secondary grouping is forbidden in equalsDefaultExceptFastFormat):
+    bool groupingUsed = fields->properties.groupingUsed;
+    int32_t groupingSize = fields->properties.groupingSize;
+    bool unusualGroupingSize = groupingSize > 0 && groupingSize != 3;
+    const UnicodeString& groupingString = fields->symbols->getConstSymbol(DecimalFormatSymbols::kGroupingSeparatorSymbol);
+    if (groupingUsed && (unusualGroupingSize || groupingString.length() != 1)) {
+        trace("no fast format: grouping\n");
+        fields->canUseFastFormat = false;
+        return;
+    }
+
+    // Integer length:
+    int32_t minInt = fields->exportedProperties.minimumIntegerDigits;
+    int32_t maxInt = fields->exportedProperties.maximumIntegerDigits;
+    // Fastpath supports up to only 10 digits (length of INT32_MIN)
+    if (minInt > 10) {
+        trace("no fast format: integer\n");
+        fields->canUseFastFormat = false;
+        return;
+    }
+
+    // Fraction length (no fraction part allowed in fast path):
+    int32_t minFrac = fields->exportedProperties.minimumFractionDigits;
+    if (minFrac > 0) {
+        trace("no fast format: fraction\n");
+        fields->canUseFastFormat = false;
+        return;
+    }
+
+    // Other symbols:
+    const UnicodeString& minusSignString = fields->symbols->getConstSymbol(DecimalFormatSymbols::kMinusSignSymbol);
+    UChar32 codePointZero = fields->symbols->getCodePointZero();
+    if (minusSignString.length() != 1 || U16_LENGTH(codePointZero) != 1) {
+        trace("no fast format: symbols\n");
+        fields->canUseFastFormat = false;
+        return;
+    }
+
+    // Good to go!
+    trace("can use fast format!\n");
+    fields->canUseFastFormat = true;
+    fields->fastData.cpZero = static_cast<char16_t>(codePointZero);
+    fields->fastData.cpGroupingSeparator = groupingUsed && groupingSize == 3 ? groupingString.charAt(0) : 0;
+    fields->fastData.cpMinusSign = minusSignString.charAt(0);
+    fields->fastData.minInt = (minInt < 0 || minInt > 127) ? 0 : static_cast<int8_t>(minInt);
+    fields->fastData.maxInt = (maxInt < 0 || maxInt > 127) ? 127 : static_cast<int8_t>(maxInt);
+}
+
+bool DecimalFormat::fastFormatDouble(double input, UnicodeString& output) const {
+    if (!fields->canUseFastFormat) {
+        return false;
+    }
+    if (std::isnan(input)
+            || uprv_trunc(input) != input
+            || input <= INT32_MIN
+            || input > INT32_MAX) {
+        return false;
+    }
+    doFastFormatInt32(static_cast<int32_t>(input), std::signbit(input), output);
+    return true;
+}
+
+bool DecimalFormat::fastFormatInt64(int64_t input, UnicodeString& output) const {
+    if (!fields->canUseFastFormat) {
+        return false;
+    }
+    if (input <= INT32_MIN || input > INT32_MAX) {
+        return false;
+    }
+    doFastFormatInt32(static_cast<int32_t>(input), input < 0, output);
+    return true;
+}
+
+void DecimalFormat::doFastFormatInt32(int32_t input, bool isNegative, UnicodeString& output) const {
+    U_ASSERT(fields->canUseFastFormat);
+    if (isNegative) {
+        output.append(fields->fastData.cpMinusSign);
+        U_ASSERT(input != INT32_MIN);  // handled by callers
+        input = -input;
+    }
+    // Cap at int32_t to make the buffer small and operations fast.
+    // Longest string: "2,147,483,648" (13 chars in length)
+    static constexpr int32_t localCapacity = 13;
+    char16_t localBuffer[localCapacity];
+    char16_t* ptr = localBuffer + localCapacity;
+    int8_t group = 0;
+    int8_t minInt = (fields->fastData.minInt < 1)? 1: fields->fastData.minInt;
+    for (int8_t i = 0; i < fields->fastData.maxInt && (input != 0 || i < minInt); i++) {
+        if (group++ == 3 && fields->fastData.cpGroupingSeparator != 0) {
+            *(--ptr) = fields->fastData.cpGroupingSeparator;
+            group = 1;
+        }
+        std::div_t res = std::div(input, 10);
+        *(--ptr) = static_cast<char16_t>(fields->fastData.cpZero + res.rem);
+        input = res.quot;
+    }
+    int32_t len = localCapacity - static_cast<int32_t>(ptr - localBuffer);
+    output.append(ptr, len);
+}
+
+
+#endif /* #if !UCONFIG_NO_FORMATTING */