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diff --git a/intl/icu/source/i18n/units_router.h b/intl/icu/source/i18n/units_router.h
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+// © 2020 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+
+#include "unicode/utypes.h"
+
+#if !UCONFIG_NO_FORMATTING
+#ifndef __UNITS_ROUTER_H__
+#define __UNITS_ROUTER_H__
+
+#include <limits>
+
+#include "cmemory.h"
+#include "measunit_impl.h"
+#include "unicode/locid.h"
+#include "unicode/measunit.h"
+#include "unicode/stringpiece.h"
+#include "unicode/uobject.h"
+#include "units_complexconverter.h"
+#include "units_data.h"
+
+U_NAMESPACE_BEGIN
+
+// Forward declarations
+class Measure;
+namespace number {
+class Precision;
+}
+
+namespace units {
+
+struct RouteResult : UMemory {
+    // A list of measures: a single measure for single units, multiple measures
+    // for mixed units.
+    MaybeStackVector<Measure> measures;
+
+    // The output unit for this RouteResult. This may be a MIXED unit - for
+    // example: "yard-and-foot-and-inch", for which `measures` will have three
+    // elements.
+    MeasureUnitImpl outputUnit;
+
+    RouteResult(MaybeStackVector<Measure> measures, MeasureUnitImpl outputUnit)
+        : measures(std::move(measures)), outputUnit(std::move(outputUnit)) {}
+};
+
+/**
+ * Contains the complex unit converter and the limit which representing the smallest value that the
+ * converter should accept. For example, if the converter is converting to `foot+inch` and the limit
+ * equals 3.0, thus means the converter should not convert to a value less than `3.0 feet`.
+ *
+ * NOTE:
+ *    if the limit doest not has a value `i.e. (std::numeric_limits<double>::lowest())`, this mean there
+ *    is no limit for the converter.
+ */
+struct ConverterPreference : UMemory {
+    ComplexUnitsConverter converter;
+    double limit;
+    UnicodeString precision;
+
+    // The output unit for this ConverterPreference. This may be a MIXED unit -
+    // for example: "yard-and-foot-and-inch".
+    MeasureUnitImpl targetUnit;
+
+    // In case there is no limit, the limit will be -inf.
+    ConverterPreference(const MeasureUnitImpl &source, const MeasureUnitImpl &complexTarget,
+                        UnicodeString precision, const ConversionRates &ratesInfo, UErrorCode &status)
+        : ConverterPreference(source, complexTarget, std::numeric_limits<double>::lowest(), precision,
+                              ratesInfo, status) {}
+
+    ConverterPreference(const MeasureUnitImpl &source, const MeasureUnitImpl &complexTarget,
+                        double limit, UnicodeString precision, const ConversionRates &ratesInfo,
+                        UErrorCode &status)
+        : converter(source, complexTarget, ratesInfo, status), limit(limit),
+          precision(std::move(precision)), targetUnit(complexTarget.copy(status)) {}
+};
+
+} // namespace units
+
+// Export explicit template instantiations of MaybeStackArray, MemoryPool and
+// MaybeStackVector. This is required when building DLLs for Windows. (See
+// datefmt.h, collationiterator.h, erarules.h and others for similar examples.)
+//
+// Note: These need to be outside of the units namespace, or Clang will generate
+// a compile error.
+#if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN
+template class U_I18N_API MaybeStackArray<units::ConverterPreference*, 8>;
+template class U_I18N_API MemoryPool<units::ConverterPreference, 8>;
+template class U_I18N_API MaybeStackVector<units::ConverterPreference, 8>;
+#endif
+
+namespace units {
+
+/**
+ * `UnitsRouter` responsible for converting from a single unit (such as `meter` or `meter-per-second`) to
+ * one of the complex units based on the limits.
+ * For example:
+ *    if the input is `meter` and the output as following
+ *    {`foot+inch`, limit: 3.0}
+ *    {`inch`     , limit: no value (-inf)}
+ *    Thus means if the input in `meter` is greater than or equal to `3.0 feet`, the output will be in
+ *    `foot+inch`, otherwise, the output will be in `inch`.
+ *
+ * NOTE:
+ *    the output units and the their limits MUST BE in order, for example, if the output units, from the
+ *    previous example, are the following:
+ *        {`inch`     , limit: no value (-inf)}
+ *        {`foot+inch`, limit: 3.0}
+ *     IN THIS CASE THE OUTPUT WILL BE ALWAYS IN `inch`.
+ *
+ * NOTE:
+ *    the output units  and their limits will be extracted from the units preferences database by knowing
+ *    the following:
+ *        - input unit
+ *        - locale
+ *        - usage
+ *
+ * DESIGN:
+ *    `UnitRouter` uses internally `ComplexUnitConverter` in order to convert the input units to the
+ *    desired complex units and to check the limit too.
+ */
+class U_I18N_API UnitsRouter {
+  public:
+    UnitsRouter(StringPiece inputUnitIdentifier, const Locale &locale, StringPiece usage,
+                UErrorCode &status);
+    UnitsRouter(const MeasureUnit &inputUnit, const Locale &locale, StringPiece usage,
+                UErrorCode &status);
+
+    /**
+     * Performs locale and usage sensitive unit conversion.
+     * @param quantity The quantity to convert, expressed in terms of inputUnit.
+     * @param rounder If not null, this RoundingImpl will be used to do rounding
+     *     on the converted value. If the rounder lacks an fPrecision, the
+     *     rounder will be modified to use the preferred precision for the usage
+     *     and locale preference, alternatively with the default precision.
+     * @param status Receives status.
+     */
+    RouteResult route(double quantity, icu::number::impl::RoundingImpl *rounder, UErrorCode &status) const;
+
+    /**
+     * Returns the list of possible output units, i.e. the full set of
+     * preferences, for the localized, usage-specific unit preferences.
+     *
+     * The returned pointer should be valid for the lifetime of the
+     * UnitsRouter instance.
+     */
+    const MaybeStackVector<MeasureUnit> *getOutputUnits() const;
+
+  private:
+    // List of possible output units. TODO: converterPreferences_ now also has
+    // this data available. Maybe drop outputUnits_ and have getOutputUnits
+    // construct a the list from data in converterPreferences_ instead?
+    MaybeStackVector<MeasureUnit> outputUnits_;
+
+    MaybeStackVector<ConverterPreference> converterPreferences_;
+
+    static number::Precision parseSkeletonToPrecision(icu::UnicodeString precisionSkeleton,
+                                                      UErrorCode &status);
+
+    void init(const MeasureUnit &inputUnit, const Locale &locale, StringPiece usage, UErrorCode &status);
+};
+
+} // namespace units
+U_NAMESPACE_END
+
+#endif //__UNITS_ROUTER_H__
+
+#endif /* #if !UCONFIG_NO_FORMATTING */