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coll.h (60928B)


      1 // © 2016 and later: Unicode, Inc. and others.
      2 // License & terms of use: http://www.unicode.org/copyright.html
      3 /*
      4 ******************************************************************************
      5 *   Copyright (C) 1996-2016, International Business Machines
      6 *   Corporation and others.  All Rights Reserved.
      7 ******************************************************************************
      8 */
      9 
     10 /**
     11 * \file
     12 * \brief C++ API: Collation Service.
     13 */
     14 
     15 /**
     16 * File coll.h
     17 *
     18 * Created by: Helena Shih
     19 *
     20 * Modification History:
     21 *
     22 *  Date        Name        Description
     23 * 02/5/97      aliu        Modified createDefault to load collation data from
     24 *                          binary files when possible.  Added related methods
     25 *                          createCollationFromFile, chopLocale, createPathName.
     26 * 02/11/97     aliu        Added members addToCache, findInCache, and fgCache.
     27 * 02/12/97     aliu        Modified to create objects from RuleBasedCollator cache.
     28 *                          Moved cache out of Collation class.
     29 * 02/13/97     aliu        Moved several methods out of this class and into
     30 *                          RuleBasedCollator, with modifications.  Modified
     31 *                          createDefault() to call new RuleBasedCollator(Locale&)
     32 *                          constructor.  General clean up and documentation.
     33 * 02/20/97     helena      Added clone, operator==, operator!=, operator=, copy
     34 *                          constructor and getDynamicClassID.
     35 * 03/25/97     helena      Updated with platform independent data types.
     36 * 05/06/97     helena      Added memory allocation error detection.
     37 * 06/20/97     helena      Java class name change.
     38 * 09/03/97     helena      Added createCollationKeyValues().
     39 * 02/10/98     damiba      Added compare() with length as parameter.
     40 * 04/23/99     stephen     Removed EDecompositionMode, merged with
     41 *                          Normalizer::EMode.
     42 * 11/02/99     helena      Collator performance enhancements.  Eliminates the
     43 *                          UnicodeString construction and special case for NO_OP.
     44 * 11/23/99     srl         More performance enhancements. Inlining of
     45 *                          critical accessors.
     46 * 05/15/00     helena      Added version information API.
     47 * 01/29/01     synwee      Modified into a C++ wrapper which calls C apis
     48 *                          (ucol.h).
     49 * 2012-2014    markus      Rewritten in C++ again.
     50 */
     51 
     52 #ifndef COLL_H
     53 #define COLL_H
     54 
     55 #include "unicode/utypes.h"
     56 
     57 #if U_SHOW_CPLUSPLUS_API
     58 
     59 #if !UCONFIG_NO_COLLATION
     60 
     61 #include <functional>
     62 #include <string_view>
     63 #include <type_traits>
     64 
     65 #include "unicode/char16ptr.h"
     66 #include "unicode/uobject.h"
     67 #include "unicode/ucol.h"
     68 #include "unicode/unorm.h"
     69 #include "unicode/locid.h"
     70 #include "unicode/uniset.h"
     71 #include "unicode/umisc.h"
     72 #include "unicode/unistr.h"
     73 #include "unicode/uiter.h"
     74 #include "unicode/stringpiece.h"
     75 
     76 U_NAMESPACE_BEGIN
     77 
     78 class StringEnumeration;
     79 
     80 #if !UCONFIG_NO_SERVICE
     81 /**
     82 * @stable ICU 2.6
     83 */
     84 class CollatorFactory;
     85 #endif
     86 
     87 /**
     88 * @stable ICU 2.0
     89 */
     90 class CollationKey;
     91 
     92 /**
     93 * The <code>Collator</code> class performs locale-sensitive string
     94 * comparison.<br>
     95 * You use this class to build searching and sorting routines for natural
     96 * language text.
     97 * <p>
     98 * <code>Collator</code> is an abstract base class. Subclasses implement
     99 * specific collation strategies. One subclass,
    100 * <code>RuleBasedCollator</code>, is currently provided and is applicable
    101 * to a wide set of languages. Other subclasses may be created to handle more
    102 * specialized needs.
    103 * <p>
    104 * Like other locale-sensitive classes, you can use the static factory method,
    105 * <code>createInstance</code>, to obtain the appropriate
    106 * <code>Collator</code> object for a given locale. You will only need to
    107 * look at the subclasses of <code>Collator</code> if you need to
    108 * understand the details of a particular collation strategy or if you need to
    109 * modify that strategy.
    110 * <p>
    111 * The following example shows how to compare two strings using the
    112 * <code>Collator</code> for the default locale.
    113 * \htmlonly<blockquote>\endhtmlonly
    114 * <pre>
    115 * \code
    116 * // Compare two strings in the default locale
    117 * UErrorCode success = U_ZERO_ERROR;
    118 * Collator* myCollator = Collator::createInstance(success);
    119 * if (myCollator->compare("abc", "ABC") < 0)
    120 *   cout << "abc is less than ABC" << endl;
    121 * else
    122 *   cout << "abc is greater than or equal to ABC" << endl;
    123 * \endcode
    124 * </pre>
    125 * \htmlonly</blockquote>\endhtmlonly
    126 * <p>
    127 * You can set a <code>Collator</code>'s <em>strength</em> attribute to
    128 * determine the level of difference considered significant in comparisons.
    129 * Five strengths are provided: <code>PRIMARY</code>, <code>SECONDARY</code>,
    130 * <code>TERTIARY</code>, <code>QUATERNARY</code> and <code>IDENTICAL</code>.
    131 * The exact assignment of strengths to language features is locale dependent.
    132 * For example, in Czech, "e" and "f" are considered primary differences,
    133 * while "e" and "\u00EA" are secondary differences, "e" and "E" are tertiary
    134 * differences and "e" and "e" are identical. The following shows how both case
    135 * and accents could be ignored for US English.
    136 * \htmlonly<blockquote>\endhtmlonly
    137 * <pre>
    138 * \code
    139 * //Get the Collator for US English and set its strength to PRIMARY
    140 * UErrorCode success = U_ZERO_ERROR;
    141 * Collator* usCollator = Collator::createInstance(Locale::getUS(), success);
    142 * usCollator->setStrength(Collator::PRIMARY);
    143 * if (usCollator->compare("abc", "ABC") == 0)
    144 *     cout << "'abc' and 'ABC' strings are equivalent with strength PRIMARY" << endl;
    145 * \endcode
    146 * </pre>
    147 * \htmlonly</blockquote>\endhtmlonly
    148 *
    149 * The <code>getSortKey</code> methods
    150 * convert a string to a series of bytes that can be compared bitwise against
    151 * other sort keys using <code>strcmp()</code>. Sort keys are written as
    152 * zero-terminated byte strings.
    153 *
    154 * Another set of APIs returns a <code>CollationKey</code> object that wraps
    155 * the sort key bytes instead of returning the bytes themselves.
    156 * </p>
    157 * <p>
    158 * <strong>Note:</strong> <code>Collator</code>s with different Locale,
    159 * and CollationStrength settings will return different sort
    160 * orders for the same set of strings. Locales have specific collation rules,
    161 * and the way in which secondary and tertiary differences are taken into
    162 * account, for example, will result in a different sorting order for same
    163 * strings.
    164 * </p>
    165 * @see         RuleBasedCollator
    166 * @see         CollationKey
    167 * @see         CollationElementIterator
    168 * @see         Locale
    169 * @see         Normalizer2
    170 * @version     2.0 11/15/01
    171 */
    172 
    173 class U_I18N_API Collator : public UObject {
    174 public:
    175 
    176    // Collator public enums -----------------------------------------------
    177 
    178    /**
    179     * Base letter represents a primary difference. Set comparison level to
    180     * PRIMARY to ignore secondary and tertiary differences.<br>
    181     * Use this to set the strength of a Collator object.<br>
    182     * Example of primary difference, "abc" &lt; "abd"
    183     *
    184     * Diacritical differences on the same base letter represent a secondary
    185     * difference. Set comparison level to SECONDARY to ignore tertiary
    186     * differences. Use this to set the strength of a Collator object.<br>
    187     * Example of secondary difference, "&auml;" >> "a".
    188     *
    189     * Uppercase and lowercase versions of the same character represents a
    190     * tertiary difference.  Set comparison level to TERTIARY to include all
    191     * comparison differences. Use this to set the strength of a Collator
    192     * object.<br>
    193     * Example of tertiary difference, "abc" &lt;&lt;&lt; "ABC".
    194     *
    195     * Two characters are considered "identical" when they have the same unicode
    196     * spellings.<br>
    197     * For example, "&auml;" == "&auml;".
    198     *
    199     * UCollationStrength is also used to determine the strength of sort keys
    200     * generated from Collator objects.
    201     * @stable ICU 2.0
    202     */
    203    enum ECollationStrength
    204    {
    205        PRIMARY    = UCOL_PRIMARY,  // 0
    206        SECONDARY  = UCOL_SECONDARY,  // 1
    207        TERTIARY   = UCOL_TERTIARY,  // 2
    208        QUATERNARY = UCOL_QUATERNARY,  // 3
    209        IDENTICAL  = UCOL_IDENTICAL  // 15
    210    };
    211 
    212 
    213    // Cannot use #ifndef U_HIDE_DEPRECATED_API for the following, it is
    214    // used by virtual methods that cannot have that conditional.
    215 #ifndef U_FORCE_HIDE_DEPRECATED_API
    216    /**
    217     * LESS is returned if source string is compared to be less than target
    218     * string in the compare() method.
    219     * EQUAL is returned if source string is compared to be equal to target
    220     * string in the compare() method.
    221     * GREATER is returned if source string is compared to be greater than
    222     * target string in the compare() method.
    223     * @see Collator#compare
    224     * @deprecated ICU 2.6. Use C enum UCollationResult defined in ucol.h
    225     */
    226    enum EComparisonResult
    227    {
    228        LESS = UCOL_LESS,  // -1
    229        EQUAL = UCOL_EQUAL,  // 0
    230        GREATER = UCOL_GREATER  // 1
    231    };
    232 #endif  // U_FORCE_HIDE_DEPRECATED_API
    233 
    234    // Collator public destructor -----------------------------------------
    235 
    236    /**
    237     * Destructor
    238     * @stable ICU 2.0
    239     */
    240    virtual ~Collator();
    241 
    242    // Collator public methods --------------------------------------------
    243 
    244    /**
    245     * Returns true if "other" is the same as "this".
    246     *
    247     * The base class implementation returns true if "other" has the same type/class as "this":
    248     * `typeid(*this) == typeid(other)`.
    249     *
    250     * Subclass implementations should do something like the following:
    251     *
    252     *     if (this == &other) { return true; }
    253     *     if (!Collator::operator==(other)) { return false; }  // not the same class
    254     *
    255     *     const MyCollator &o = (const MyCollator&)other;
    256     *     (compare this vs. o's subclass fields)
    257     *
    258     * @param other Collator object to be compared
    259     * @return true if other is the same as this.
    260     * @stable ICU 2.0
    261     */
    262    virtual bool operator==(const Collator& other) const;
    263 
    264    /**
    265     * Returns true if "other" is not the same as "this".
    266     * Calls ! operator==(const Collator&) const which works for all subclasses.
    267     * @param other Collator object to be compared
    268     * @return true if other is not the same as this.
    269     * @stable ICU 2.0
    270     */
    271    virtual bool operator!=(const Collator& other) const;
    272 
    273    /**
    274     * Makes a copy of this object.
    275     * @return a copy of this object, owned by the caller
    276     * @stable ICU 2.0
    277     */
    278    virtual Collator* clone() const = 0;
    279 
    280    /**
    281     * Creates the Collator object for the current default locale.
    282     * The default locale is determined by Locale::getDefault.
    283     * The UErrorCode& err parameter is used to return status information to the user.
    284     * To check whether the construction succeeded or not, you should check the
    285     * value of U_SUCCESS(err).  If you wish more detailed information, you can
    286     * check for informational error results which still indicate success.
    287     * U_USING_FALLBACK_ERROR indicates that a fall back locale was used. For
    288     * example, 'de_CH' was requested, but nothing was found there, so 'de' was
    289     * used. U_USING_DEFAULT_ERROR indicates that the default locale data was
    290     * used; neither the requested locale nor any of its fall back locales
    291     * could be found.
    292     * The caller owns the returned object and is responsible for deleting it.
    293     *
    294     * @param err    the error code status.
    295     * @return       the collation object of the default locale.(for example, en_US)
    296     * @see Locale#getDefault
    297     * @stable ICU 2.0
    298     */
    299    static Collator* U_EXPORT2 createInstance(UErrorCode&  err);
    300 
    301    /**
    302     * Gets the collation object for the desired locale. The
    303     * resource of the desired locale will be loaded.
    304     *
    305     * Locale::getRoot() is the base collation table and all other languages are
    306     * built on top of it with additional language-specific modifications.
    307     *
    308     * For some languages, multiple collation types are available;
    309     * for example, "de@collation=phonebook".
    310     * Starting with ICU 54, collation attributes can be specified via locale keywords as well,
    311     * in the old locale extension syntax ("el@colCaseFirst=upper")
    312     * or in language tag syntax ("el-u-kf-upper").
    313     * See <a href="https://unicode-org.github.io/icu/userguide/collation/api">User Guide: Collation API</a>.
    314     *
    315     * The UErrorCode& err parameter is used to return status information to the user.
    316     * To check whether the construction succeeded or not, you should check
    317     * the value of U_SUCCESS(err).  If you wish more detailed information, you
    318     * can check for informational error results which still indicate success.
    319     * U_USING_FALLBACK_ERROR indicates that a fall back locale was used.  For
    320     * example, 'de_CH' was requested, but nothing was found there, so 'de' was
    321     * used.  U_USING_DEFAULT_ERROR indicates that the default locale data was
    322     * used; neither the requested locale nor any of its fall back locales
    323     * could be found.
    324     *
    325     * The caller owns the returned object and is responsible for deleting it.
    326     * @param loc    The locale ID for which to open a collator.
    327     * @param err    the error code status.
    328     * @return       the created table-based collation object based on the desired
    329     *               locale.
    330     * @see Locale
    331     * @see ResourceLoader
    332     * @stable ICU 2.2
    333     */
    334    static Collator* U_EXPORT2 createInstance(const Locale& loc, UErrorCode& err);
    335 
    336 #ifndef U_FORCE_HIDE_DEPRECATED_API
    337    /**
    338     * The comparison function compares the character data stored in two
    339     * different strings. Returns information about whether a string is less
    340     * than, greater than or equal to another string.
    341     * @param source the source string to be compared with.
    342     * @param target the string that is to be compared with the source string.
    343     * @return Returns a byte value. GREATER if source is greater
    344     * than target; EQUAL if source is equal to target; LESS if source is less
    345     * than target
    346     * @deprecated ICU 2.6 use the overload with UErrorCode &
    347     */
    348    virtual EComparisonResult compare(const UnicodeString& source,
    349                                      const UnicodeString& target) const;
    350 #endif  // U_FORCE_HIDE_DEPRECATED_API
    351 
    352    /**
    353     * The comparison function compares the character data stored in two
    354     * different strings. Returns information about whether a string is less
    355     * than, greater than or equal to another string.
    356     * @param source the source string to be compared with.
    357     * @param target the string that is to be compared with the source string.
    358     * @param status possible error code
    359     * @return Returns an enum value. UCOL_GREATER if source is greater
    360     * than target; UCOL_EQUAL if source is equal to target; UCOL_LESS if source is less
    361     * than target
    362     * @stable ICU 2.6
    363     */
    364    virtual UCollationResult compare(const UnicodeString& source,
    365                                      const UnicodeString& target,
    366                                      UErrorCode &status) const = 0;
    367 
    368 #ifndef U_FORCE_HIDE_DEPRECATED_API
    369    /**
    370     * Does the same thing as compare but limits the comparison to a specified
    371     * length
    372     * @param source the source string to be compared with.
    373     * @param target the string that is to be compared with the source string.
    374     * @param length the length the comparison is limited to
    375     * @return Returns a byte value. GREATER if source (up to the specified
    376     *         length) is greater than target; EQUAL if source (up to specified
    377     *         length) is equal to target; LESS if source (up to the specified
    378     *         length) is less  than target.
    379     * @deprecated ICU 2.6 use the overload with UErrorCode &
    380     */
    381    virtual EComparisonResult compare(const UnicodeString& source,
    382                                      const UnicodeString& target,
    383                                      int32_t length) const;
    384 #endif  // U_FORCE_HIDE_DEPRECATED_API
    385 
    386    /**
    387     * Does the same thing as compare but limits the comparison to a specified
    388     * length
    389     * @param source the source string to be compared with.
    390     * @param target the string that is to be compared with the source string.
    391     * @param length the length the comparison is limited to
    392     * @param status possible error code
    393     * @return Returns an enum value. UCOL_GREATER if source (up to the specified
    394     *         length) is greater than target; UCOL_EQUAL if source (up to specified
    395     *         length) is equal to target; UCOL_LESS if source (up to the specified
    396     *         length) is less  than target.
    397     * @stable ICU 2.6
    398     */
    399    virtual UCollationResult compare(const UnicodeString& source,
    400                                      const UnicodeString& target,
    401                                      int32_t length,
    402                                      UErrorCode &status) const = 0;
    403 
    404 #ifndef U_FORCE_HIDE_DEPRECATED_API
    405    /**
    406     * The comparison function compares the character data stored in two
    407     * different string arrays. Returns information about whether a string array
    408     * is less than, greater than or equal to another string array.
    409     * <p>Example of use:
    410     * <pre>
    411     * .       char16_t ABC[] = {0x41, 0x42, 0x43, 0};  // = "ABC"
    412     * .       char16_t abc[] = {0x61, 0x62, 0x63, 0};  // = "abc"
    413     * .       UErrorCode status = U_ZERO_ERROR;
    414     * .       Collator *myCollation =
    415     * .                         Collator::createInstance(Locale::getUS(), status);
    416     * .       if (U_FAILURE(status)) return;
    417     * .       myCollation->setStrength(Collator::PRIMARY);
    418     * .       // result would be Collator::EQUAL ("abc" == "ABC")
    419     * .       // (no primary difference between "abc" and "ABC")
    420     * .       Collator::EComparisonResult result =
    421     * .                             myCollation->compare(abc, 3, ABC, 3);
    422     * .       myCollation->setStrength(Collator::TERTIARY);
    423     * .       // result would be Collator::LESS ("abc" &lt;&lt;&lt; "ABC")
    424     * .       // (with tertiary difference between "abc" and "ABC")
    425     * .       result = myCollation->compare(abc, 3, ABC, 3);
    426     * </pre>
    427     * @param source the source string array to be compared with.
    428     * @param sourceLength the length of the source string array.  If this value
    429     *        is equal to -1, the string array is null-terminated.
    430     * @param target the string that is to be compared with the source string.
    431     * @param targetLength the length of the target string array.  If this value
    432     *        is equal to -1, the string array is null-terminated.
    433     * @return Returns a byte value. GREATER if source is greater than target;
    434     *         EQUAL if source is equal to target; LESS if source is less than
    435     *         target
    436     * @deprecated ICU 2.6 use the overload with UErrorCode &
    437     */
    438    virtual EComparisonResult compare(const char16_t* source, int32_t sourceLength,
    439                                      const char16_t* target, int32_t targetLength)
    440                                      const;
    441 #endif  // U_FORCE_HIDE_DEPRECATED_API
    442 
    443    /**
    444     * The comparison function compares the character data stored in two
    445     * different string arrays. Returns information about whether a string array
    446     * is less than, greater than or equal to another string array.
    447     * @param source the source string array to be compared with.
    448     * @param sourceLength the length of the source string array.  If this value
    449     *        is equal to -1, the string array is null-terminated.
    450     * @param target the string that is to be compared with the source string.
    451     * @param targetLength the length of the target string array.  If this value
    452     *        is equal to -1, the string array is null-terminated.
    453     * @param status possible error code
    454     * @return Returns an enum value. UCOL_GREATER if source is greater
    455     * than target; UCOL_EQUAL if source is equal to target; UCOL_LESS if source is less
    456     * than target
    457     * @stable ICU 2.6
    458     */
    459    virtual UCollationResult compare(const char16_t* source, int32_t sourceLength,
    460                                      const char16_t* target, int32_t targetLength,
    461                                      UErrorCode &status) const = 0;
    462 
    463    /**
    464     * Compares two strings using the Collator.
    465     * Returns whether the first one compares less than/equal to/greater than
    466     * the second one.
    467     * This version takes UCharIterator input.
    468     * @param sIter the first ("source") string iterator
    469     * @param tIter the second ("target") string iterator
    470     * @param status ICU status
    471     * @return UCOL_LESS, UCOL_EQUAL or UCOL_GREATER
    472     * @stable ICU 4.2
    473     */
    474    virtual UCollationResult compare(UCharIterator &sIter,
    475                                     UCharIterator &tIter,
    476                                     UErrorCode &status) const;
    477 
    478    /**
    479     * Compares two UTF-8 strings using the Collator.
    480     * Returns whether the first one compares less than/equal to/greater than
    481     * the second one.
    482     * This version takes UTF-8 input.
    483     * Note that a StringPiece can be implicitly constructed
    484     * from a std::string or a NUL-terminated const char * string.
    485     * @param source the first UTF-8 string
    486     * @param target the second UTF-8 string
    487     * @param status ICU status
    488     * @return UCOL_LESS, UCOL_EQUAL or UCOL_GREATER
    489     * @stable ICU 4.2
    490     */
    491    virtual UCollationResult compareUTF8(const StringPiece &source,
    492                                         const StringPiece &target,
    493                                         UErrorCode &status) const;
    494 
    495    /**
    496     * Transforms the string into a series of characters that can be compared
    497     * with CollationKey::compareTo. It is not possible to restore the original
    498     * string from the chars in the sort key.
    499     * <p>Use CollationKey::equals or CollationKey::compare to compare the
    500     * generated sort keys.
    501     * If the source string is null, a null collation key will be returned.
    502     *
    503     * Note that sort keys are often less efficient than simply doing comparison.
    504     * For more details, see the ICU User Guide.
    505     *
    506     * @param source the source string to be transformed into a sort key.
    507     * @param key the collation key to be filled in
    508     * @param status the error code status.
    509     * @return the collation key of the string based on the collation rules.
    510     * @see CollationKey#compare
    511     * @stable ICU 2.0
    512     */
    513    virtual CollationKey& getCollationKey(const UnicodeString&  source,
    514                                          CollationKey& key,
    515                                          UErrorCode& status) const = 0;
    516 
    517    /**
    518     * Transforms the string into a series of characters that can be compared
    519     * with CollationKey::compareTo. It is not possible to restore the original
    520     * string from the chars in the sort key.
    521     * <p>Use CollationKey::equals or CollationKey::compare to compare the
    522     * generated sort keys.
    523     * <p>If the source string is null, a null collation key will be returned.
    524     *
    525     * Note that sort keys are often less efficient than simply doing comparison.
    526     * For more details, see the ICU User Guide.
    527     *
    528     * @param source the source string to be transformed into a sort key.
    529     * @param sourceLength length of the collation key
    530     * @param key the collation key to be filled in
    531     * @param status the error code status.
    532     * @return the collation key of the string based on the collation rules.
    533     * @see CollationKey#compare
    534     * @stable ICU 2.0
    535     */
    536    virtual CollationKey& getCollationKey(const char16_t*source,
    537                                          int32_t sourceLength,
    538                                          CollationKey& key,
    539                                          UErrorCode& status) const = 0;
    540    /**
    541     * Generates the hash code for the collation object
    542     * @stable ICU 2.0
    543     */
    544    virtual int32_t hashCode() const = 0;
    545 
    546 #ifndef U_FORCE_HIDE_DEPRECATED_API
    547    /**
    548     * Gets the locale of the Collator
    549     *
    550     * @param type can be either requested, valid or actual locale. For more
    551     *             information see the definition of ULocDataLocaleType in
    552     *             uloc.h
    553     * @param status the error code status.
    554     * @return locale where the collation data lives. If the collator
    555     *         was instantiated from rules, locale is empty.
    556     * @deprecated ICU 2.8 This API is under consideration for revision
    557     * in ICU 3.0.
    558     */
    559    virtual Locale getLocale(ULocDataLocaleType type, UErrorCode& status) const = 0;
    560 #endif  // U_FORCE_HIDE_DEPRECATED_API
    561 
    562    /**
    563     * Convenience method for comparing two strings based on the collation rules.
    564     * @param source the source string to be compared with.
    565     * @param target the target string to be compared with.
    566     * @return true if the first string is greater than the second one,
    567     *         according to the collation rules. false, otherwise.
    568     * @see Collator#compare
    569     * @stable ICU 2.0
    570     */
    571    UBool greater(const UnicodeString& source, const UnicodeString& target)
    572                  const;
    573 
    574    /**
    575     * Convenience method for comparing two strings based on the collation rules.
    576     * @param source the source string to be compared with.
    577     * @param target the target string to be compared with.
    578     * @return true if the first string is greater than or equal to the second
    579     *         one, according to the collation rules. false, otherwise.
    580     * @see Collator#compare
    581     * @stable ICU 2.0
    582     */
    583    UBool greaterOrEqual(const UnicodeString& source,
    584                         const UnicodeString& target) const;
    585 
    586    /**
    587     * Convenience method for comparing two strings based on the collation rules.
    588     * @param source the source string to be compared with.
    589     * @param target the target string to be compared with.
    590     * @return true if the strings are equal according to the collation rules.
    591     *         false, otherwise.
    592     * @see Collator#compare
    593     * @stable ICU 2.0
    594     */
    595    UBool equals(const UnicodeString& source, const UnicodeString& target) const;
    596 
    597    /**
    598     * Creates a comparison function object that uses this collator.
    599     * Like <code>std::equal_to</code> but uses the collator instead of <code>operator==</code>.
    600     * @stable ICU 76
    601     */
    602    inline auto equal_to() const { return Predicate<std::equal_to, UCOL_EQUAL>(*this); }
    603 
    604    /**
    605     * Creates a comparison function object that uses this collator.
    606     * Like <code>std::greater</code> but uses the collator instead of <code>operator&gt;</code>.
    607     * @stable ICU 76
    608     */
    609    inline auto greater() const { return Predicate<std::equal_to, UCOL_GREATER>(*this); }
    610 
    611    /**
    612     * Creates a comparison function object that uses this collator.
    613     * Like <code>std::less</code> but uses the collator instead of <code>operator&lt;</code>.
    614     * @stable ICU 76
    615     */
    616    inline auto less() const { return Predicate<std::equal_to, UCOL_LESS>(*this); }
    617 
    618    /**
    619     * Creates a comparison function object that uses this collator.
    620     * Like <code>std::not_equal_to</code> but uses the collator instead of <code>operator!=</code>.
    621     * @stable ICU 76
    622     */
    623    inline auto not_equal_to() const { return Predicate<std::not_equal_to, UCOL_EQUAL>(*this); }
    624 
    625    /**
    626     * Creates a comparison function object that uses this collator.
    627     * Like <code>std::greater_equal</code> but uses the collator instead of <code>operator&gt;=</code>.
    628     * @stable ICU 76
    629     */
    630    inline auto greater_equal() const { return Predicate<std::not_equal_to, UCOL_LESS>(*this); }
    631 
    632    /**
    633     * Creates a comparison function object that uses this collator.
    634     * Like <code>std::less_equal</code> but uses the collator instead of <code>operator&lt;=</code>.
    635     * @stable ICU 76
    636     */
    637    inline auto less_equal() const { return Predicate<std::not_equal_to, UCOL_GREATER>(*this); }
    638 
    639 #ifndef U_FORCE_HIDE_DEPRECATED_API
    640    /**
    641     * Determines the minimum strength that will be used in comparison or
    642     * transformation.
    643     * <p>E.g. with strength == SECONDARY, the tertiary difference is ignored
    644     * <p>E.g. with strength == PRIMARY, the secondary and tertiary difference
    645     * are ignored.
    646     * @return the current comparison level.
    647     * @see Collator#setStrength
    648     * @deprecated ICU 2.6 Use getAttribute(UCOL_STRENGTH...) instead
    649     */
    650    virtual ECollationStrength getStrength() const;
    651 
    652    /**
    653     * Sets the minimum strength to be used in comparison or transformation.
    654     * <p>Example of use:
    655     * <pre>
    656     *  \code
    657     *  UErrorCode status = U_ZERO_ERROR;
    658     *  Collator*myCollation = Collator::createInstance(Locale::getUS(), status);
    659     *  if (U_FAILURE(status)) return;
    660     *  myCollation->setStrength(Collator::PRIMARY);
    661     *  // result will be "abc" == "ABC"
    662     *  // tertiary differences will be ignored
    663     *  Collator::ComparisonResult result = myCollation->compare("abc", "ABC");
    664     * \endcode
    665     * </pre>
    666     * @see Collator#getStrength
    667     * @param newStrength the new comparison level.
    668     * @deprecated ICU 2.6 Use setAttribute(UCOL_STRENGTH...) instead
    669     */
    670    virtual void setStrength(ECollationStrength newStrength);
    671 #endif  // U_FORCE_HIDE_DEPRECATED_API
    672 
    673    /**
    674     * Retrieves the reordering codes for this collator.
    675     * @param dest The array to fill with the script ordering.
    676     * @param destCapacity The length of dest. If it is 0, then dest may be nullptr and the function
    677     *  will only return the length of the result without writing any codes (pre-flighting).
    678     * @param status A reference to an error code value, which must not indicate
    679     * a failure before the function call.
    680     * @return The length of the script ordering array.
    681     * @see ucol_setReorderCodes
    682     * @see Collator#getEquivalentReorderCodes
    683     * @see Collator#setReorderCodes
    684     * @see UScriptCode
    685     * @see UColReorderCode
    686     * @stable ICU 4.8
    687     */
    688     virtual int32_t getReorderCodes(int32_t *dest,
    689                                     int32_t destCapacity,
    690                                     UErrorCode& status) const;
    691 
    692    /**
    693     * Sets the ordering of scripts for this collator.
    694     *
    695     * <p>The reordering codes are a combination of script codes and reorder codes.
    696     * @param reorderCodes An array of script codes in the new order. This can be nullptr if the
    697     * length is also set to 0. An empty array will clear any reordering codes on the collator.
    698     * @param reorderCodesLength The length of reorderCodes.
    699     * @param status error code
    700     * @see ucol_setReorderCodes
    701     * @see Collator#getReorderCodes
    702     * @see Collator#getEquivalentReorderCodes
    703     * @see UScriptCode
    704     * @see UColReorderCode
    705     * @stable ICU 4.8
    706     */
    707     virtual void setReorderCodes(const int32_t* reorderCodes,
    708                                  int32_t reorderCodesLength,
    709                                  UErrorCode& status) ;
    710 
    711    /**
    712     * Retrieves the reorder codes that are grouped with the given reorder code. Some reorder
    713     * codes will be grouped and must reorder together.
    714     * Beginning with ICU 55, scripts only reorder together if they are primary-equal,
    715     * for example Hiragana and Katakana.
    716     *
    717     * @param reorderCode The reorder code to determine equivalence for.
    718     * @param dest The array to fill with the script equivalence reordering codes.
    719     * @param destCapacity The length of dest. If it is 0, then dest may be nullptr and the
    720     * function will only return the length of the result without writing any codes (pre-flighting).
    721     * @param status A reference to an error code value, which must not indicate
    722     * a failure before the function call.
    723     * @return The length of the of the reordering code equivalence array.
    724     * @see ucol_setReorderCodes
    725     * @see Collator#getReorderCodes
    726     * @see Collator#setReorderCodes
    727     * @see UScriptCode
    728     * @see UColReorderCode
    729     * @stable ICU 4.8
    730     */
    731    static int32_t U_EXPORT2 getEquivalentReorderCodes(int32_t reorderCode,
    732                                int32_t* dest,
    733                                int32_t destCapacity,
    734                                UErrorCode& status);
    735 
    736    /**
    737     * Get name of the object for the desired Locale, in the desired language
    738     * @param objectLocale must be from getAvailableLocales
    739     * @param displayLocale specifies the desired locale for output
    740     * @param name the fill-in parameter of the return value
    741     * @return display-able name of the object for the object locale in the
    742     *         desired language
    743     * @stable ICU 2.0
    744     */
    745    static UnicodeString& U_EXPORT2 getDisplayName(const Locale& objectLocale,
    746                                         const Locale& displayLocale,
    747                                         UnicodeString& name);
    748 
    749    /**
    750    * Get name of the object for the desired Locale, in the language of the
    751    * default locale.
    752    * @param objectLocale must be from getAvailableLocales
    753    * @param name the fill-in parameter of the return value
    754    * @return name of the object for the desired locale in the default language
    755    * @stable ICU 2.0
    756    */
    757    static UnicodeString& U_EXPORT2 getDisplayName(const Locale& objectLocale,
    758                                         UnicodeString& name);
    759 
    760    /**
    761     * Get the set of Locales for which Collations are installed.
    762     *
    763     * <p>Note this does not include locales supported by registered collators.
    764     * If collators might have been registered, use the overload of getAvailableLocales
    765     * that returns a StringEnumeration.</p>
    766     *
    767     * @param count the output parameter of number of elements in the locale list
    768     * @return the list of available locales for which collations are installed
    769     * @stable ICU 2.0
    770     */
    771    static const Locale* U_EXPORT2 getAvailableLocales(int32_t& count);
    772 
    773    /**
    774     * Return a StringEnumeration over the locales available at the time of the call,
    775     * including registered locales.  If a severe error occurs (such as out of memory
    776     * condition) this will return null. If there is no locale data, an empty enumeration
    777     * will be returned.
    778     * @return a StringEnumeration over the locales available at the time of the call
    779     * @stable ICU 2.6
    780     */
    781    static StringEnumeration* U_EXPORT2 getAvailableLocales();
    782 
    783    /**
    784     * Create a string enumerator of all possible keywords that are relevant to
    785     * collation. At this point, the only recognized keyword for this
    786     * service is "collation".
    787     * @param status input-output error code
    788     * @return a string enumeration over locale strings. The caller is
    789     * responsible for closing the result.
    790     * @stable ICU 3.0
    791     */
    792    static StringEnumeration* U_EXPORT2 getKeywords(UErrorCode& status);
    793 
    794    /**
    795     * Given a keyword, create a string enumeration of all values
    796     * for that keyword that are currently in use.
    797     * @param keyword a particular keyword as enumerated by
    798     * ucol_getKeywords. If any other keyword is passed in, status is set
    799     * to U_ILLEGAL_ARGUMENT_ERROR.
    800     * @param status input-output error code
    801     * @return a string enumeration over collation keyword values, or nullptr
    802     * upon error. The caller is responsible for deleting the result.
    803     * @stable ICU 3.0
    804     */
    805    static StringEnumeration* U_EXPORT2 getKeywordValues(const char *keyword, UErrorCode& status);
    806 
    807    /**
    808     * Given a key and a locale, returns an array of string values in a preferred
    809     * order that would make a difference. These are all and only those values where
    810     * the open (creation) of the service with the locale formed from the input locale
    811     * plus input keyword and that value has different behavior than creation with the
    812     * input locale alone.
    813     * @param keyword        one of the keys supported by this service.  For now, only
    814     *                      "collation" is supported.
    815     * @param locale        the locale
    816     * @param commonlyUsed  if set to true it will return only commonly used values
    817     *                      with the given locale in preferred order.  Otherwise,
    818     *                      it will return all the available values for the locale.
    819     * @param status ICU status
    820     * @return a string enumeration over keyword values for the given key and the locale.
    821     * @stable ICU 4.2
    822     */
    823    static StringEnumeration* U_EXPORT2 getKeywordValuesForLocale(const char* keyword, const Locale& locale,
    824                                                                    UBool commonlyUsed, UErrorCode& status);
    825 
    826    /**
    827     * Return the functionally equivalent locale for the given
    828     * requested locale, with respect to given keyword, for the
    829     * collation service.  If two locales return the same result, then
    830     * collators instantiated for these locales will behave
    831     * equivalently.  The converse is not always true; two collators
    832     * may in fact be equivalent, but return different results, due to
    833     * internal details.  The return result has no other meaning than
    834     * that stated above, and implies nothing as to the relationship
    835     * between the two locales.  This is intended for use by
    836     * applications who wish to cache collators, or otherwise reuse
    837     * collators when possible.  The functional equivalent may change
    838     * over time.  For more information, please see the <a
    839     * href="https://unicode-org.github.io/icu/userguide/locale#locales-and-services">
    840     * Locales and Services</a> section of the ICU User Guide.
    841     * @param keyword a particular keyword as enumerated by
    842     * ucol_getKeywords.
    843     * @param locale the requested locale
    844     * @param isAvailable reference to a fillin parameter that
    845     * indicates whether the requested locale was 'available' to the
    846     * collation service. A locale is defined as 'available' if it
    847     * physically exists within the collation locale data.
    848     * @param status reference to input-output error code
    849     * @return the functionally equivalent collation locale, or the root
    850     * locale upon error.
    851     * @stable ICU 3.0
    852     */
    853    static Locale U_EXPORT2 getFunctionalEquivalent(const char* keyword, const Locale& locale,
    854                                          UBool& isAvailable, UErrorCode& status);
    855 
    856 #if !UCONFIG_NO_SERVICE
    857    /**
    858     * Register a new Collator.  The collator will be adopted.
    859     * Because ICU may choose to cache collators internally, this must be
    860     * called at application startup, prior to any calls to
    861     * Collator::createInstance to avoid undefined behavior.
    862     * @param toAdopt the Collator instance to be adopted
    863     * @param locale the locale with which the collator will be associated
    864     * @param status the in/out status code, no special meanings are assigned
    865     * @return a registry key that can be used to unregister this collator
    866     * @stable ICU 2.6
    867     */
    868    static URegistryKey U_EXPORT2 registerInstance(Collator* toAdopt, const Locale& locale, UErrorCode& status);
    869 
    870    /**
    871     * Register a new CollatorFactory.  The factory will be adopted.
    872     * Because ICU may choose to cache collators internally, this must be
    873     * called at application startup, prior to any calls to
    874     * Collator::createInstance to avoid undefined behavior.
    875     * @param toAdopt the CollatorFactory instance to be adopted
    876     * @param status the in/out status code, no special meanings are assigned
    877     * @return a registry key that can be used to unregister this collator
    878     * @stable ICU 2.6
    879     */
    880    static URegistryKey U_EXPORT2 registerFactory(CollatorFactory* toAdopt, UErrorCode& status);
    881 
    882    /**
    883     * Unregister a previously-registered Collator or CollatorFactory
    884     * using the key returned from the register call.  Key becomes
    885     * invalid after a successful call and should not be used again.
    886     * The object corresponding to the key will be deleted.
    887     * Because ICU may choose to cache collators internally, this should
    888     * be called during application shutdown, after all calls to
    889     * Collator::createInstance to avoid undefined behavior.
    890     * @param key the registry key returned by a previous call to registerInstance
    891     * @param status the in/out status code, no special meanings are assigned
    892     * @return true if the collator for the key was successfully unregistered
    893     * @stable ICU 2.6
    894     */
    895    static UBool U_EXPORT2 unregister(URegistryKey key, UErrorCode& status);
    896 #endif /* UCONFIG_NO_SERVICE */
    897 
    898    /**
    899     * Gets the version information for a Collator.
    900     * @param info the version # information, the result will be filled in
    901     * @stable ICU 2.0
    902     */
    903    virtual void getVersion(UVersionInfo info) const = 0;
    904 
    905    /**
    906     * Returns a unique class ID POLYMORPHICALLY. Pure virtual method.
    907     * This method is to implement a simple version of RTTI, since not all C++
    908     * compilers support genuine RTTI. Polymorphic operator==() and clone()
    909     * methods call this method.
    910     * @return The class ID for this object. All objects of a given class have
    911     *         the same class ID.  Objects of other classes have different class
    912     *         IDs.
    913     * @stable ICU 2.0
    914     */
    915    virtual UClassID getDynamicClassID() const override = 0;
    916 
    917    /**
    918     * Universal attribute setter
    919     * @param attr attribute type
    920     * @param value attribute value
    921     * @param status to indicate whether the operation went on smoothly or
    922     *        there were errors
    923     * @stable ICU 2.2
    924     */
    925    virtual void setAttribute(UColAttribute attr, UColAttributeValue value,
    926                              UErrorCode &status) = 0;
    927 
    928    /**
    929     * Universal attribute getter
    930     * @param attr attribute type
    931     * @param status to indicate whether the operation went on smoothly or
    932     *        there were errors
    933     * @return attribute value
    934     * @stable ICU 2.2
    935     */
    936    virtual UColAttributeValue getAttribute(UColAttribute attr,
    937                                            UErrorCode &status) const = 0;
    938 
    939    /**
    940     * Sets the variable top to the top of the specified reordering group.
    941     * The variable top determines the highest-sorting character
    942     * which is affected by UCOL_ALTERNATE_HANDLING.
    943     * If that attribute is set to UCOL_NON_IGNORABLE, then the variable top has no effect.
    944     *
    945     * The base class implementation sets U_UNSUPPORTED_ERROR.
    946     * @param group one of UCOL_REORDER_CODE_SPACE, UCOL_REORDER_CODE_PUNCTUATION,
    947     *              UCOL_REORDER_CODE_SYMBOL, UCOL_REORDER_CODE_CURRENCY;
    948     *              or UCOL_REORDER_CODE_DEFAULT to restore the default max variable group
    949     * @param errorCode Standard ICU error code. Its input value must
    950     *                  pass the U_SUCCESS() test, or else the function returns
    951     *                  immediately. Check for U_FAILURE() on output or use with
    952     *                  function chaining. (See User Guide for details.)
    953     * @return *this
    954     * @see getMaxVariable
    955     * @stable ICU 53
    956     */
    957    virtual Collator &setMaxVariable(UColReorderCode group, UErrorCode &errorCode);
    958 
    959    /**
    960     * Returns the maximum reordering group whose characters are affected by UCOL_ALTERNATE_HANDLING.
    961     *
    962     * The base class implementation returns UCOL_REORDER_CODE_PUNCTUATION.
    963     * @return the maximum variable reordering group.
    964     * @see setMaxVariable
    965     * @stable ICU 53
    966     */
    967    virtual UColReorderCode getMaxVariable() const;
    968 
    969 #ifndef U_FORCE_HIDE_DEPRECATED_API
    970    /**
    971     * Sets the variable top to the primary weight of the specified string.
    972     *
    973     * Beginning with ICU 53, the variable top is pinned to
    974     * the top of one of the supported reordering groups,
    975     * and it must not be beyond the last of those groups.
    976     * See setMaxVariable().
    977     * @param varTop one or more (if contraction) char16_ts to which the variable top should be set
    978     * @param len length of variable top string. If -1 it is considered to be zero terminated.
    979     * @param status error code. If error code is set, the return value is undefined. Errors set by this function are: <br>
    980     *    U_CE_NOT_FOUND_ERROR if more than one character was passed and there is no such contraction<br>
    981     *    U_ILLEGAL_ARGUMENT_ERROR if the variable top is beyond
    982     *    the last reordering group supported by setMaxVariable()
    983     * @return variable top primary weight
    984     * @deprecated ICU 53 Call setMaxVariable() instead.
    985     */
    986    virtual uint32_t setVariableTop(const char16_t *varTop, int32_t len, UErrorCode &status) = 0;
    987 
    988    /**
    989     * Sets the variable top to the primary weight of the specified string.
    990     *
    991     * Beginning with ICU 53, the variable top is pinned to
    992     * the top of one of the supported reordering groups,
    993     * and it must not be beyond the last of those groups.
    994     * See setMaxVariable().
    995     * @param varTop a UnicodeString size 1 or more (if contraction) of char16_ts to which the variable top should be set
    996     * @param status error code. If error code is set, the return value is undefined. Errors set by this function are: <br>
    997     *    U_CE_NOT_FOUND_ERROR if more than one character was passed and there is no such contraction<br>
    998     *    U_ILLEGAL_ARGUMENT_ERROR if the variable top is beyond
    999     *    the last reordering group supported by setMaxVariable()
   1000     * @return variable top primary weight
   1001     * @deprecated ICU 53 Call setMaxVariable() instead.
   1002     */
   1003    virtual uint32_t setVariableTop(const UnicodeString &varTop, UErrorCode &status) = 0;
   1004 
   1005    /**
   1006     * Sets the variable top to the specified primary weight.
   1007     *
   1008     * Beginning with ICU 53, the variable top is pinned to
   1009     * the top of one of the supported reordering groups,
   1010     * and it must not be beyond the last of those groups.
   1011     * See setMaxVariable().
   1012     * @param varTop primary weight, as returned by setVariableTop or ucol_getVariableTop
   1013     * @param status error code
   1014     * @deprecated ICU 53 Call setMaxVariable() instead.
   1015     */
   1016    virtual void setVariableTop(uint32_t varTop, UErrorCode &status) = 0;
   1017 #endif  // U_FORCE_HIDE_DEPRECATED_API
   1018 
   1019    /**
   1020     * Gets the variable top value of a Collator.
   1021     * @param status error code (not changed by function). If error code is set, the return value is undefined.
   1022     * @return the variable top primary weight
   1023     * @see getMaxVariable
   1024     * @stable ICU 2.0
   1025     */
   1026    virtual uint32_t getVariableTop(UErrorCode &status) const = 0;
   1027 
   1028    /**
   1029     * Get a UnicodeSet that contains all the characters and sequences
   1030     * tailored in this collator.
   1031     * @param status      error code of the operation
   1032     * @return a pointer to a UnicodeSet object containing all the
   1033     *         code points and sequences that may sort differently than
   1034     *         in the root collator. The object must be disposed of by using delete
   1035     * @stable ICU 2.4
   1036     */
   1037    virtual UnicodeSet *getTailoredSet(UErrorCode &status) const;
   1038 
   1039 #ifndef U_FORCE_HIDE_DEPRECATED_API
   1040    /**
   1041     * Same as clone().
   1042     * The base class implementation simply calls clone().
   1043     * @return a copy of this object, owned by the caller
   1044     * @see clone()
   1045     * @deprecated ICU 50 no need to have two methods for cloning
   1046     */
   1047    virtual Collator* safeClone() const;
   1048 #endif  // U_FORCE_HIDE_DEPRECATED_API
   1049 
   1050    /**
   1051     * Get the sort key as an array of bytes from a UnicodeString.
   1052     * Sort key byte arrays are zero-terminated and can be compared using
   1053     * strcmp().
   1054     *
   1055     * Note that sort keys are often less efficient than simply doing comparison.
   1056     * For more details, see the ICU User Guide.
   1057     *
   1058     * @param source string to be processed.
   1059     * @param result buffer to store result in. If nullptr, number of bytes needed
   1060     *        will be returned.
   1061     * @param resultLength length of the result buffer. If if not enough the
   1062     *        buffer will be filled to capacity.
   1063     * @return Number of bytes needed for storing the sort key
   1064     * @stable ICU 2.2
   1065     */
   1066    virtual int32_t getSortKey(const UnicodeString& source,
   1067                              uint8_t* result,
   1068                              int32_t resultLength) const = 0;
   1069 
   1070    /**
   1071     * Get the sort key as an array of bytes from a char16_t buffer.
   1072     * Sort key byte arrays are zero-terminated and can be compared using
   1073     * strcmp().
   1074     *
   1075     * Note that sort keys are often less efficient than simply doing comparison.
   1076     * For more details, see the ICU User Guide.
   1077     *
   1078     * @param source string to be processed.
   1079     * @param sourceLength length of string to be processed.
   1080     *        If -1, the string is 0 terminated and length will be decided by the
   1081     *        function.
   1082     * @param result buffer to store result in. If nullptr, number of bytes needed
   1083     *        will be returned.
   1084     * @param resultLength length of the result buffer. If if not enough the
   1085     *        buffer will be filled to capacity.
   1086     * @return Number of bytes needed for storing the sort key
   1087     * @stable ICU 2.2
   1088     */
   1089    virtual int32_t getSortKey(const char16_t*source, int32_t sourceLength,
   1090                               uint8_t*result, int32_t resultLength) const = 0;
   1091 
   1092    /**
   1093     * Produce a bound for a given sortkey and a number of levels.
   1094     * Return value is always the number of bytes needed, regardless of
   1095     * whether the result buffer was big enough or even valid.<br>
   1096     * Resulting bounds can be used to produce a range of strings that are
   1097     * between upper and lower bounds. For example, if bounds are produced
   1098     * for a sortkey of string "smith", strings between upper and lower
   1099     * bounds with one level would include "Smith", "SMITH", "sMiTh".<br>
   1100     * There are two upper bounds that can be produced. If UCOL_BOUND_UPPER
   1101     * is produced, strings matched would be as above. However, if bound
   1102     * produced using UCOL_BOUND_UPPER_LONG is used, the above example will
   1103     * also match "Smithsonian" and similar.<br>
   1104     * For more on usage, see example in cintltst/capitst.c in procedure
   1105     * TestBounds.
   1106     * Sort keys may be compared using <TT>strcmp</TT>.
   1107     * @param source The source sortkey.
   1108     * @param sourceLength The length of source, or -1 if null-terminated.
   1109     *                     (If an unmodified sortkey is passed, it is always null
   1110     *                      terminated).
   1111     * @param boundType Type of bound required. It can be UCOL_BOUND_LOWER, which
   1112     *                  produces a lower inclusive bound, UCOL_BOUND_UPPER, that
   1113     *                  produces upper bound that matches strings of the same length
   1114     *                  or UCOL_BOUND_UPPER_LONG that matches strings that have the
   1115     *                  same starting substring as the source string.
   1116     * @param noOfLevels  Number of levels required in the resulting bound (for most
   1117     *                    uses, the recommended value is 1). See users guide for
   1118     *                    explanation on number of levels a sortkey can have.
   1119     * @param result A pointer to a buffer to receive the resulting sortkey.
   1120     * @param resultLength The maximum size of result.
   1121     * @param status Used for returning error code if something went wrong. If the
   1122     *               number of levels requested is higher than the number of levels
   1123     *               in the source key, a warning (U_SORT_KEY_TOO_SHORT_WARNING) is
   1124     *               issued.
   1125     * @return The size needed to fully store the bound.
   1126     * @see ucol_keyHashCode
   1127     * @stable ICU 2.1
   1128     */
   1129    static int32_t U_EXPORT2 getBound(const uint8_t       *source,
   1130            int32_t             sourceLength,
   1131            UColBoundMode       boundType,
   1132            uint32_t            noOfLevels,
   1133            uint8_t             *result,
   1134            int32_t             resultLength,
   1135            UErrorCode          &status);
   1136 
   1137 
   1138 protected:
   1139 
   1140    // Collator protected constructors -------------------------------------
   1141 
   1142    /**
   1143    * Default constructor.
   1144    * Constructor is different from the old default Collator constructor.
   1145    * The task for determining the default collation strength and normalization
   1146    * mode is left to the child class.
   1147    * @stable ICU 2.0
   1148    */
   1149    Collator();
   1150 
   1151 #ifndef U_HIDE_DEPRECATED_API
   1152    /**
   1153    * Constructor.
   1154    * Empty constructor, does not handle the arguments.
   1155    * This constructor is done for backward compatibility with 1.7 and 1.8.
   1156    * The task for handling the argument collation strength and normalization
   1157    * mode is left to the child class.
   1158    * @param collationStrength collation strength
   1159    * @param decompositionMode
   1160    * @deprecated ICU 2.4. Subclasses should use the default constructor
   1161    * instead and handle the strength and normalization mode themselves.
   1162    */
   1163    Collator(UCollationStrength collationStrength,
   1164             UNormalizationMode decompositionMode);
   1165 #endif  /* U_HIDE_DEPRECATED_API */
   1166 
   1167    /**
   1168    * Copy constructor.
   1169    * @param other Collator object to be copied from
   1170    * @stable ICU 2.0
   1171    */
   1172    Collator(const Collator& other);
   1173 
   1174 public:
   1175   /**
   1176    * Used internally by registration to define the requested and valid locales.
   1177    * @param requestedLocale the requested locale
   1178    * @param validLocale the valid locale
   1179    * @param actualLocale the actual locale
   1180    * @internal
   1181    */
   1182    virtual void setLocales(const Locale& requestedLocale, const Locale& validLocale, const Locale& actualLocale);
   1183 
   1184    /** Get the short definition string for a collator. This internal API harvests the collator's
   1185     *  locale and the attribute set and produces a string that can be used for opening
   1186     *  a collator with the same attributes using the ucol_openFromShortString API.
   1187     *  This string will be normalized.
   1188     *  The structure and the syntax of the string is defined in the "Naming collators"
   1189     *  section of the users guide:
   1190     *  https://unicode-org.github.io/icu/userguide/collation/concepts#collator-naming-scheme
   1191     *  This function supports preflighting.
   1192     *
   1193     *  This is internal, and intended to be used with delegate converters.
   1194     *
   1195     *  @param locale a locale that will appear as a collators locale in the resulting
   1196     *                short string definition. If nullptr, the locale will be harvested
   1197     *                from the collator.
   1198     *  @param buffer space to hold the resulting string
   1199     *  @param capacity capacity of the buffer
   1200     *  @param status for returning errors. All the preflighting errors are featured
   1201     *  @return length of the resulting string
   1202     *  @see ucol_openFromShortString
   1203     *  @see ucol_normalizeShortDefinitionString
   1204     *  @see ucol_getShortDefinitionString
   1205     *  @internal
   1206     */
   1207    virtual int32_t internalGetShortDefinitionString(const char *locale,
   1208                                                     char *buffer,
   1209                                                     int32_t capacity,
   1210                                                     UErrorCode &status) const;
   1211 
   1212    /**
   1213     * Implements ucol_strcollUTF8().
   1214     * @internal
   1215     */
   1216    virtual UCollationResult internalCompareUTF8(
   1217            const char *left, int32_t leftLength,
   1218            const char *right, int32_t rightLength,
   1219            UErrorCode &errorCode) const;
   1220 
   1221    /**
   1222     * Implements ucol_nextSortKeyPart().
   1223     * @internal
   1224     */
   1225    virtual int32_t
   1226    internalNextSortKeyPart(
   1227            UCharIterator *iter, uint32_t state[2],
   1228            uint8_t *dest, int32_t count, UErrorCode &errorCode) const;
   1229 
   1230 #ifndef U_HIDE_INTERNAL_API
   1231    /** @internal */
   1232    static inline Collator *fromUCollator(UCollator *uc) {
   1233        return reinterpret_cast<Collator *>(uc);
   1234    }
   1235    /** @internal */
   1236    static inline const Collator *fromUCollator(const UCollator *uc) {
   1237        return reinterpret_cast<const Collator *>(uc);
   1238    }
   1239    /** @internal */
   1240    inline UCollator *toUCollator() {
   1241        return reinterpret_cast<UCollator *>(this);
   1242    }
   1243    /** @internal */
   1244    inline const UCollator *toUCollator() const {
   1245        return reinterpret_cast<const UCollator *>(this);
   1246    }
   1247 #endif  // U_HIDE_INTERNAL_API
   1248 
   1249 private:
   1250    /**
   1251     * Assignment operator. Private for now.
   1252     */
   1253    Collator& operator=(const Collator& other) = delete;
   1254 
   1255    friend class CFactory;
   1256    friend class SimpleCFactory;
   1257    friend class ICUCollatorFactory;
   1258    friend class ICUCollatorService;
   1259    static Collator* makeInstance(const Locale& desiredLocale,
   1260                                  UErrorCode& status);
   1261 
   1262    /**
   1263     * Function object for performing comparisons using a Collator.
   1264     * @internal
   1265     */
   1266    template <template <typename...> typename Compare, UCollationResult result>
   1267    class Predicate {
   1268      public:
   1269        explicit Predicate(const Collator& parent) : collator(parent) {}
   1270 
   1271        template <
   1272            typename T, typename U,
   1273            typename = std::enable_if_t<ConvertibleToU16StringView<T> && ConvertibleToU16StringView<U>>>
   1274        bool operator()(const T& lhs, const U& rhs) const {
   1275            UErrorCode status = U_ZERO_ERROR;
   1276            return compare(
   1277                collator.compare(
   1278                    UnicodeString::readOnlyAlias(lhs),
   1279                    UnicodeString::readOnlyAlias(rhs),
   1280                    status),
   1281                result);
   1282        }
   1283 
   1284        bool operator()(std::string_view lhs, std::string_view rhs) const {
   1285            UErrorCode status = U_ZERO_ERROR;
   1286            return compare(collator.compareUTF8(lhs, rhs, status), result);
   1287        }
   1288 
   1289 #if defined(__cpp_char8_t)
   1290        bool operator()(std::u8string_view lhs, std::u8string_view rhs) const {
   1291            UErrorCode status = U_ZERO_ERROR;
   1292            return compare(collator.compareUTF8(lhs, rhs, status), result);
   1293        }
   1294 #endif
   1295 
   1296      private:
   1297        const Collator& collator;
   1298        static constexpr Compare<UCollationResult> compare{};
   1299    };
   1300 };
   1301 
   1302 #if !UCONFIG_NO_SERVICE
   1303 /**
   1304 * A factory, used with registerFactory, the creates multiple collators and provides
   1305 * display names for them.  A factory supports some number of locales-- these are the
   1306 * locales for which it can create collators.  The factory can be visible, in which
   1307 * case the supported locales will be enumerated by getAvailableLocales, or invisible,
   1308 * in which they are not.  Invisible locales are still supported, they are just not
   1309 * listed by getAvailableLocales.
   1310 * <p>
   1311 * If standard locale display names are sufficient, Collator instances can
   1312 * be registered using registerInstance instead.</p>
   1313 * <p>
   1314 * Note: if the collators are to be used from C APIs, they must be instances
   1315 * of RuleBasedCollator.</p>
   1316 *
   1317 * @stable ICU 2.6
   1318 */
   1319 class U_I18N_API CollatorFactory : public UObject {
   1320 public:
   1321 
   1322    /**
   1323     * Destructor
   1324     * @stable ICU 3.0
   1325     */
   1326    virtual ~CollatorFactory();
   1327 
   1328    /**
   1329     * Return true if this factory is visible.  Default is true.
   1330     * If not visible, the locales supported by this factory will not
   1331     * be listed by getAvailableLocales.
   1332     * @return true if the factory is visible.
   1333     * @stable ICU 2.6
   1334     */
   1335    virtual UBool visible() const;
   1336 
   1337    /**
   1338     * Return a collator for the provided locale.  If the locale
   1339     * is not supported, return nullptr.
   1340     * @param loc the locale identifying the collator to be created.
   1341     * @return a new collator if the locale is supported, otherwise nullptr.
   1342     * @stable ICU 2.6
   1343     */
   1344    virtual Collator* createCollator(const Locale& loc) = 0;
   1345 
   1346    /**
   1347     * Return the name of the collator for the objectLocale, localized for the displayLocale.
   1348     * If objectLocale is not supported, or the factory is not visible, set the result string
   1349     * to bogus.
   1350     * @param objectLocale the locale identifying the collator
   1351     * @param displayLocale the locale for which the display name of the collator should be localized
   1352     * @param result an output parameter for the display name, set to bogus if not supported.
   1353     * @return the display name
   1354     * @stable ICU 2.6
   1355     */
   1356    virtual  UnicodeString& getDisplayName(const Locale& objectLocale,
   1357                                           const Locale& displayLocale,
   1358                                           UnicodeString& result);
   1359 
   1360    /**
   1361     * Return an array of all the locale names directly supported by this factory.
   1362     * The number of names is returned in count.  This array is owned by the factory.
   1363     * Its contents must never change.
   1364     * @param count output parameter for the number of locales supported by the factory
   1365     * @param status the in/out error code
   1366     * @return a pointer to an array of count UnicodeStrings.
   1367     * @stable ICU 2.6
   1368     */
   1369    virtual const UnicodeString * getSupportedIDs(int32_t &count, UErrorCode& status) = 0;
   1370 };
   1371 #endif /* UCONFIG_NO_SERVICE */
   1372 
   1373 // Collator inline methods -----------------------------------------------
   1374 
   1375 U_NAMESPACE_END
   1376 
   1377 #endif /* #if !UCONFIG_NO_COLLATION */
   1378 
   1379 #endif /* U_SHOW_CPLUSPLUS_API */
   1380 
   1381 #endif