chromium/third_party/icu/source/i18n/units_router.h

// © 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 { … };

/**
 * 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 { … };

} // 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 { … };

} // namespace units
U_NAMESPACE_END

#endif //__UNITS_ROUTER_H__

#endif /* #if !UCONFIG_NO_FORMATTING */