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// © 2019 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
// localematcher.h
// created: 2019may08 Markus W. Scherer
#ifndef __LOCALEMATCHER_H__
#define __LOCALEMATCHER_H__
#include "unicode/utypes.h"
#if U_SHOW_CPLUSPLUS_API
#include "unicode/locid.h"
#include "unicode/stringpiece.h"
#include "unicode/uobject.h"
/**
* \file
* \brief C++ API: Locale matcher: User's desired locales vs. application's supported locales.
*/
/**
* Builder option for whether the language subtag or the script subtag is most important.
*
* @see LocaleMatcher::Builder#setFavorSubtag(ULocMatchFavorSubtag)
* @stable ICU 65
*/
enum ULocMatchFavorSubtag {
/**
* Language differences are most important, then script differences, then region differences.
* (This is the default behavior.)
*
* @stable ICU 65
*/
ULOCMATCH_FAVOR_LANGUAGE,
/**
* Makes script differences matter relatively more than language differences.
*
* @stable ICU 65
*/
ULOCMATCH_FAVOR_SCRIPT
};
#ifndef U_IN_DOXYGEN
typedef enum ULocMatchFavorSubtag ULocMatchFavorSubtag;
#endif
/**
* Builder option for whether all desired locales are treated equally or
* earlier ones are preferred.
*
* @see LocaleMatcher::Builder#setDemotionPerDesiredLocale(ULocMatchDemotion)
* @stable ICU 65
*/
enum ULocMatchDemotion {
/**
* All desired locales are treated equally.
*
* @stable ICU 65
*/
ULOCMATCH_DEMOTION_NONE,
/**
* Earlier desired locales are preferred.
*
* <p>From each desired locale to the next,
* the distance to any supported locale is increased by an additional amount
* which is at least as large as most region mismatches.
* A later desired locale has to have a better match with some supported locale
* due to more than merely having the same region subtag.
*
* <p>For example: <code>Supported={en, sv} desired=[en-GB, sv]</code>
* yields <code>Result(en-GB, en)</code> because
* with the demotion of sv its perfect match is no better than
* the region distance between the earlier desired locale en-GB and en=en-US.
*
* <p>Notes:
* <ul>
* <li>In some cases, language and/or script differences can be as small as
* the typical region difference. (Example: sr-Latn vs. sr-Cyrl)
* <li>It is possible for certain region differences to be larger than usual,
* and larger than the demotion.
* (As of CLDR 35 there is no such case, but
* this is possible in future versions of the data.)
* </ul>
*
* @stable ICU 65
*/
ULOCMATCH_DEMOTION_REGION
};
#ifndef U_IN_DOXYGEN
typedef enum ULocMatchDemotion ULocMatchDemotion;
#endif
/**
* Builder option for whether to include or ignore one-way (fallback) match data.
* The LocaleMatcher uses CLDR languageMatch data which includes fallback (oneway=true) entries.
* Sometimes it is desirable to ignore those.
*
* <p>For example, consider a web application with the UI in a given language,
* with a link to another, related web app.
* The link should include the UI language, and the target server may also use
* the client’s Accept-Language header data.
* The target server has its own list of supported languages.
* One may want to favor UI language consistency, that is,
* if there is a decent match for the original UI language, we want to use it,
* but not if it is merely a fallback.
*
* @see LocaleMatcher::Builder#setDirection(ULocMatchDirection)
* @stable ICU 67
*/
enum ULocMatchDirection {
/**
* Locale matching includes one-way matches such as Breton→French. (default)
*
* @stable ICU 67
*/
ULOCMATCH_DIRECTION_WITH_ONE_WAY,
/**
* Locale matching limited to two-way matches including e.g. Danish↔Norwegian
* but ignoring one-way matches.
*
* @stable ICU 67
*/
ULOCMATCH_DIRECTION_ONLY_TWO_WAY
};
#ifndef U_IN_DOXYGEN
typedef enum ULocMatchDirection ULocMatchDirection;
#endif
struct UHashtable;
U_NAMESPACE_BEGIN
struct LSR;
class LocaleDistance;
class LocaleLsrIterator;
class UVector;
class XLikelySubtags;
/**
* Immutable class that picks the best match between a user's desired locales and
* an application's supported locales.
* Movable but not copyable.
*
* <p>Example:
* <pre>
* UErrorCode errorCode = U_ZERO_ERROR;
* LocaleMatcher matcher = LocaleMatcher::Builder().setSupportedLocales("fr, en-GB, en").build(errorCode);
* Locale *bestSupported = matcher.getBestLocale(Locale.US, errorCode); // "en"
* </pre>
*
* <p>A matcher takes into account when languages are close to one another,
* such as Danish and Norwegian,
* and when regional variants are close, like en-GB and en-AU as opposed to en-US.
*
* <p>If there are multiple supported locales with the same (language, script, region)
* likely subtags, then the current implementation returns the first of those locales.
* It ignores variant subtags (except for pseudolocale variants) and extensions.
* This may change in future versions.
*
* <p>For example, the current implementation does not distinguish between
* de, de-DE, de-Latn, de-1901, de-u-co-phonebk.
*
* <p>If you prefer one equivalent locale over another, then provide only the preferred one,
* or place it earlier in the list of supported locales.
*
* <p>Otherwise, the order of supported locales may have no effect on the best-match results.
* The current implementation compares each desired locale with supported locales
* in the following order:
* 1. Default locale, if supported;
* 2. CLDR "paradigm locales" like en-GB and es-419;
* 3. other supported locales.
* This may change in future versions.
*
* <p>Often a product will just need one matcher instance, built with the languages
* that it supports. However, it may want multiple instances with different
* default languages based on additional information, such as the domain.
*
* <p>This class is not intended for public subclassing.
*
* @stable ICU 65
*/
class U_COMMON_API LocaleMatcher : public UMemory {
public:
/**
* Data for the best-matching pair of a desired and a supported locale.
* Movable but not copyable.
*
* @stable ICU 65
*/
class U_COMMON_API Result : public UMemory {
public:
/**
* Move constructor; might modify the source.
* This object will have the same contents that the source object had.
*
* @param src Result to move contents from.
* @stable ICU 65
*/
Result(Result &&src) noexcept;
/**
* Destructor.
*
* @stable ICU 65
*/
~Result();
/**
* Move assignment; might modify the source.
* This object will have the same contents that the source object had.
*
* @param src Result to move contents from.
* @stable ICU 65
*/
Result &operator=(Result &&src) noexcept;
/**
* Returns the best-matching desired locale.
* nullptr if the list of desired locales is empty or if none matched well enough.
*
* @return the best-matching desired locale, or nullptr.
* @stable ICU 65
*/
inline const Locale *getDesiredLocale() const { return desiredLocale; }
/**
* Returns the best-matching supported locale.
* If none matched well enough, this is the default locale.
* The default locale is nullptr if Builder::setNoDefaultLocale() was called,
* or if the list of supported locales is empty and no explicit default locale is set.
*
* @return the best-matching supported locale, or nullptr.
* @stable ICU 65
*/
inline const Locale *getSupportedLocale() const { return supportedLocale; }
/**
* Returns the index of the best-matching desired locale in the input Iterable order.
* -1 if the list of desired locales is empty or if none matched well enough.
*
* @return the index of the best-matching desired locale, or -1.
* @stable ICU 65
*/
inline int32_t getDesiredIndex() const { return desiredIndex; }
/**
* Returns the index of the best-matching supported locale in the
* constructor’s or builder’s input order (“set” Collection plus “added” locales).
* If the matcher was built from a locale list string, then the iteration order is that
* of a LocalePriorityList built from the same string.
* -1 if the list of supported locales is empty or if none matched well enough.
*
* @return the index of the best-matching supported locale, or -1.
* @stable ICU 65
*/
inline int32_t getSupportedIndex() const { return supportedIndex; }
/**
* Takes the best-matching supported locale and adds relevant fields of the
* best-matching desired locale, such as the -t- and -u- extensions.
* May replace some fields of the supported locale.
* The result is the locale that should be used for date and number formatting, collation, etc.
* Returns the root locale if getSupportedLocale() returns nullptr.
*
* <p>Example: desired=ar-SA-u-nu-latn, supported=ar-EG, resolved locale=ar-SA-u-nu-latn
*
* @return a locale combining the best-matching desired and supported locales.
* @stable ICU 65
*/
Locale makeResolvedLocale(UErrorCode &errorCode) const;
private:
Result(const Locale *desired, const Locale *supported,
int32_t desIndex, int32_t suppIndex, UBool owned) :
desiredLocale(desired), supportedLocale(supported),
desiredIndex(desIndex), supportedIndex(suppIndex),
desiredIsOwned(owned) {}
Result(const Result &other) = delete;
Result &operator=(const Result &other) = delete;
const Locale *desiredLocale;
const Locale *supportedLocale;
int32_t desiredIndex;
int32_t supportedIndex;
UBool desiredIsOwned;
friend class LocaleMatcher;
};
/**
* LocaleMatcher builder.
* Movable but not copyable.
*
* @stable ICU 65
*/
class U_COMMON_API Builder : public UMemory {
public:
/**
* Constructs a builder used in chaining parameters for building a LocaleMatcher.
*
* @return a new Builder object
* @stable ICU 65
*/
Builder() {}
/**
* Move constructor; might modify the source.
* This builder will have the same contents that the source builder had.
*
* @param src Builder to move contents from.
* @stable ICU 65
*/
Builder(Builder &&src) noexcept;
/**
* Destructor.
*
* @stable ICU 65
*/
~Builder();
/**
* Move assignment; might modify the source.
* This builder will have the same contents that the source builder had.
*
* @param src Builder to move contents from.
* @stable ICU 65
*/
Builder &operator=(Builder &&src) noexcept;
/**
* Parses an Accept-Language string
* (<a href="https://tools.ietf.org/html/rfc2616#section-14.4">RFC 2616 Section 14.4</a>),
* such as "af, en, fr;q=0.9", and sets the supported locales accordingly.
* Allows whitespace in more places but does not allow "*".
* Clears any previously set/added supported locales first.
*
* @param locales the Accept-Language string of locales to set
* @return this Builder object
* @stable ICU 65
*/
Builder &setSupportedLocalesFromListString(StringPiece locales);
/**
* Copies the supported locales, preserving iteration order.
* Clears any previously set/added supported locales first.
* Duplicates are allowed, and are not removed.
*
* @param locales the list of locale
* @return this Builder object
* @stable ICU 65
*/
Builder &setSupportedLocales(Locale::Iterator &locales);
/**
* Copies the supported locales from the begin/end range, preserving iteration order.
* Clears any previously set/added supported locales first.
* Duplicates are allowed, and are not removed.
*
* Each of the iterator parameter values must be an
* input iterator whose value is convertible to const Locale &.
*
* @param begin Start of range.
* @param end Exclusive end of range.
* @return this Builder object
* @stable ICU 65
*/
template<typename Iter>
Builder &setSupportedLocales(Iter begin, Iter end) {
if (U_FAILURE(errorCode_)) { return *this; }
clearSupportedLocales();
while (begin != end) {
addSupportedLocale(*begin++);
}
return *this;
}
/**
* Copies the supported locales from the begin/end range, preserving iteration order.
* Calls the converter to convert each *begin to a Locale or const Locale &.
* Clears any previously set/added supported locales first.
* Duplicates are allowed, and are not removed.
*
* Each of the iterator parameter values must be an
* input iterator whose value is convertible to const Locale &.
*
* @param begin Start of range.
* @param end Exclusive end of range.
* @param converter Converter from *begin to const Locale & or compatible.
* @return this Builder object
* @stable ICU 65
*/
template<typename Iter, typename Conv>
Builder &setSupportedLocalesViaConverter(Iter begin, Iter end, Conv converter) {
if (U_FAILURE(errorCode_)) { return *this; }
clearSupportedLocales();
while (begin != end) {
addSupportedLocale(converter(*begin++));
}
return *this;
}
/**
* Adds another supported locale.
* Duplicates are allowed, and are not removed.
*
* @param locale another locale
* @return this Builder object
* @stable ICU 65
*/
Builder &addSupportedLocale(const Locale &locale);
/**
* Sets no default locale.
* There will be no explicit or implicit default locale.
* If there is no good match, then the matcher will return nullptr for the
* best supported locale.
*
* @stable ICU 68
*/
Builder &setNoDefaultLocale();
/**
* Sets the default locale; if nullptr, or if it is not set explicitly,
* then the first supported locale is used as the default locale.
* There is no default locale at all (nullptr will be returned instead)
* if setNoDefaultLocale() is called.
*
* @param defaultLocale the default locale (will be copied)
* @return this Builder object
* @stable ICU 65
*/
Builder &setDefaultLocale(const Locale *defaultLocale);
/**
* If ULOCMATCH_FAVOR_SCRIPT, then the language differences are smaller than script
* differences.
* This is used in situations (such as maps) where
* it is better to fall back to the same script than a similar language.
*
* @param subtag the subtag to favor
* @return this Builder object
* @stable ICU 65
*/
Builder &setFavorSubtag(ULocMatchFavorSubtag subtag);
/**
* Option for whether all desired locales are treated equally or
* earlier ones are preferred (this is the default).
*
* @param demotion the demotion per desired locale to set.
* @return this Builder object
* @stable ICU 65
*/
Builder &setDemotionPerDesiredLocale(ULocMatchDemotion demotion);
/**
* Option for whether to include or ignore one-way (fallback) match data.
* By default, they are included.
*
* @param matchDirection the match direction to set.
* @return this Builder object
* @stable ICU 67
*/
Builder &setDirection(ULocMatchDirection matchDirection) {
if (U_SUCCESS(errorCode_)) {
direction_ = matchDirection;
}
return *this;
}
/**
* Sets the maximum distance for an acceptable match.
* The matcher will return a match for a pair of locales only if
* they match at least as well as the pair given here.
*
* For example, setMaxDistance(en-US, en-GB) limits matches to ones where the
* (desired, support) locales have a distance no greater than a region subtag difference.
* This is much stricter than the CLDR default.
*
* The details of locale matching are subject to changes in
* CLDR data and in the algorithm.
* Specifying a maximum distance in relative terms via a sample pair of locales
* insulates from changes that affect all distance metrics similarly,
* but some changes will necessarily affect relative distances between
* different pairs of locales.
*
* @param desired the desired locale for distance comparison.
* @param supported the supported locale for distance comparison.
* @return this Builder object
* @stable ICU 68
*/
Builder &setMaxDistance(const Locale &desired, const Locale &supported);
/**
* Sets the UErrorCode if an error occurred while setting parameters.
* Preserves older error codes in the outErrorCode.
*
* @param outErrorCode Set to an error code if it does not contain one already
* and an error occurred while setting parameters.
* Otherwise unchanged.
* @return true if U_FAILURE(outErrorCode)
* @stable ICU 65
*/
UBool copyErrorTo(UErrorCode &outErrorCode) const;
/**
* Builds and returns a new locale matcher.
* This builder can continue to be used.
*
* @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
* or else the function returns immediately. Check for U_FAILURE()
* on output or use with function chaining. (See User Guide for details.)
* @return LocaleMatcher
* @stable ICU 65
*/
LocaleMatcher build(UErrorCode &errorCode) const;
private:
friend class LocaleMatcher;
Builder(const Builder &other) = delete;
Builder &operator=(const Builder &other) = delete;
void clearSupportedLocales();
bool ensureSupportedLocaleVector();
UErrorCode errorCode_ = U_ZERO_ERROR;
UVector *supportedLocales_ = nullptr;
int32_t thresholdDistance_ = -1;
ULocMatchDemotion demotion_ = ULOCMATCH_DEMOTION_REGION;
Locale *defaultLocale_ = nullptr;
bool withDefault_ = true;
ULocMatchFavorSubtag favor_ = ULOCMATCH_FAVOR_LANGUAGE;
ULocMatchDirection direction_ = ULOCMATCH_DIRECTION_WITH_ONE_WAY;
Locale *maxDistanceDesired_ = nullptr;
Locale *maxDistanceSupported_ = nullptr;
};
// FYI No public LocaleMatcher constructors in C++; use the Builder.
/**
* Move copy constructor; might modify the source.
* This matcher will have the same settings that the source matcher had.
* @param src source matcher
* @stable ICU 65
*/
LocaleMatcher(LocaleMatcher &&src) noexcept;
/**
* Destructor.
* @stable ICU 65
*/
~LocaleMatcher();
/**
* Move assignment operator; might modify the source.
* This matcher will have the same settings that the source matcher had.
* The behavior is undefined if *this and src are the same object.
* @param src source matcher
* @return *this
* @stable ICU 65
*/
LocaleMatcher &operator=(LocaleMatcher &&src) noexcept;
/**
* Returns the supported locale which best matches the desired locale.
*
* @param desiredLocale Typically a user's language.
* @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
* or else the function returns immediately. Check for U_FAILURE()
* on output or use with function chaining. (See User Guide for details.)
* @return the best-matching supported locale.
* @stable ICU 65
*/
const Locale *getBestMatch(const Locale &desiredLocale, UErrorCode &errorCode) const;
/**
* Returns the supported locale which best matches one of the desired locales.
*
* @param desiredLocales Typically a user's languages, in order of preference (descending).
* @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
* or else the function returns immediately. Check for U_FAILURE()
* on output or use with function chaining. (See User Guide for details.)
* @return the best-matching supported locale.
* @stable ICU 65
*/
const Locale *getBestMatch(Locale::Iterator &desiredLocales, UErrorCode &errorCode) const;
/**
* Parses an Accept-Language string
* (<a href="https://tools.ietf.org/html/rfc2616#section-14.4">RFC 2616 Section 14.4</a>),
* such as "af, en, fr;q=0.9",
* and returns the supported locale which best matches one of the desired locales.
* Allows whitespace in more places but does not allow "*".
*
* @param desiredLocaleList Typically a user's languages, as an Accept-Language string.
* @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
* or else the function returns immediately. Check for U_FAILURE()
* on output or use with function chaining. (See User Guide for details.)
* @return the best-matching supported locale.
* @stable ICU 65
*/
const Locale *getBestMatchForListString(StringPiece desiredLocaleList, UErrorCode &errorCode) const;
/**
* Returns the best match between the desired locale and the supported locales.
* If the result's desired locale is not nullptr, then it is the address of the input locale.
* It has not been cloned.
*
* @param desiredLocale Typically a user's language.
* @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
* or else the function returns immediately. Check for U_FAILURE()
* on output or use with function chaining. (See User Guide for details.)
* @return the best-matching pair of the desired and a supported locale.
* @stable ICU 65
*/
Result getBestMatchResult(const Locale &desiredLocale, UErrorCode &errorCode) const;
/**
* Returns the best match between the desired and supported locales.
* If the result's desired locale is not nullptr, then it is a clone of
* the best-matching desired locale. The Result object owns the clone.
*
* @param desiredLocales Typically a user's languages, in order of preference (descending).
* @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
* or else the function returns immediately. Check for U_FAILURE()
* on output or use with function chaining. (See User Guide for details.)
* @return the best-matching pair of a desired and a supported locale.
* @stable ICU 65
*/
Result getBestMatchResult(Locale::Iterator &desiredLocales, UErrorCode &errorCode) const;
/**
* Returns true if the pair of locales matches acceptably.
* This is influenced by Builder options such as setDirection(), setFavorSubtag(),
* and setMaxDistance().
*
* @param desired The desired locale.
* @param supported The supported locale.
* @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
* or else the function returns immediately. Check for U_FAILURE()
* on output or use with function chaining. (See User Guide for details.)
* @return true if the pair of locales matches acceptably.
* @stable ICU 68
*/
UBool isMatch(const Locale &desired, const Locale &supported, UErrorCode &errorCode) const;
#ifndef U_HIDE_INTERNAL_API
/**
* Returns a fraction between 0 and 1, where 1 means that the languages are a
* perfect match, and 0 means that they are completely different.
*
* <p>This is mostly an implementation detail, and the precise values may change over time.
* The implementation may use either the maximized forms or the others ones, or both.
* The implementation may or may not rely on the forms to be consistent with each other.
*
* <p>Callers should construct and use a matcher rather than match pairs of locales directly.
*
* @param desired Desired locale.
* @param supported Supported locale.
* @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
* or else the function returns immediately. Check for U_FAILURE()
* on output or use with function chaining. (See User Guide for details.)
* @return value between 0 and 1, inclusive.
* @internal (has a known user)
*/
double internalMatch(const Locale &desired, const Locale &supported, UErrorCode &errorCode) const;
#endif // U_HIDE_INTERNAL_API
private:
LocaleMatcher(const Builder &builder, UErrorCode &errorCode);
LocaleMatcher(const LocaleMatcher &other) = delete;
LocaleMatcher &operator=(const LocaleMatcher &other) = delete;
int32_t putIfAbsent(const LSR &lsr, int32_t i, int32_t suppLength, UErrorCode &errorCode);
int32_t getBestSuppIndex(LSR desiredLSR, LocaleLsrIterator *remainingIter, UErrorCode &errorCode) const;
const XLikelySubtags &likelySubtags;
const LocaleDistance &localeDistance;
int32_t thresholdDistance;
int32_t demotionPerDesiredLocale;
ULocMatchFavorSubtag favorSubtag;
ULocMatchDirection direction;
// These are in input order.
const Locale ** supportedLocales;
LSR *lsrs;
int32_t supportedLocalesLength;
// These are in preference order: 1. Default locale 2. paradigm locales 3. others.
UHashtable *supportedLsrToIndex; // Map<LSR, Integer>
// Array versions of the supportedLsrToIndex keys and values.
// The distance lookup loops over the supportedLSRs and returns the index of the best match.
const LSR **supportedLSRs;
int32_t *supportedIndexes;
int32_t supportedLSRsLength;
Locale *ownedDefaultLocale;
const Locale *defaultLocale;
};
U_NAMESPACE_END
#endif // U_SHOW_CPLUSPLUS_API
#endif // __LOCALEMATCHER_H__