pg_locale_icu.c

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/*-----------------------------------------------------------------------
 *
 * PostgreSQL locale utilities for ICU
 *
 * Portions Copyright (c) 2002-2025, PostgreSQL Global Development Group
 *
 * src/backend/utils/adt/pg_locale_icu.c
 *
 *-----------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#ifdef USE_ICU
#include <unicode/ucnv.h>
#include <unicode/ustring.h>
 
/*
 * ucol_strcollUTF8() was introduced in ICU 50, but it is buggy before ICU 53.
 * (see
 * <https://www.postgresql.org/message-id/flat/f1438ec6-22aa-4029-9a3b-26f79d330e72%40manitou-mail.org>)
 */
#if U_ICU_VERSION_MAJOR_NUM >= 53
#define HAVE_UCOL_STRCOLLUTF8 1
#else
#undef HAVE_UCOL_STRCOLLUTF8
#endif
 
#endif
 
#include "access/htup_details.h"
#include "catalog/pg_database.h"
#include "catalog/pg_collation.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/formatting.h"
#include "utils/memutils.h"
#include "utils/pg_locale.h"
#include "utils/syscache.h"
 
/*
 * Size of stack buffer to use for string transformations, used to avoid heap
 * allocations in typical cases. This should be large enough that most strings
 * will fit, but small enough that we feel comfortable putting it on the
 * stack.
 */
#define     TEXTBUFLEN          1024
 
extern pg_locale_t create_pg_locale_icu(Oid collid, MemoryContext context);
extern size_t strlower_icu(char *dest, size_t destsize, const char *src,
                           ssize_t srclen, pg_locale_t locale);
extern size_t strtitle_icu(char *dest, size_t destsize, const char *src,
                           ssize_t srclen, pg_locale_t locale);
extern size_t strupper_icu(char *dest, size_t destsize, const char *src,
                           ssize_t srclen, pg_locale_t locale);
extern size_t strfold_icu(char *dest, size_t destsize, const char *src,
                          ssize_t srclen, pg_locale_t locale);
 
#ifdef USE_ICU
 
extern UCollator *pg_ucol_open(const char *loc_str);
 
static size_t strnxfrm_icu(char *dest, size_t destsize,
                           const char *src, ssize_t srclen,
                           pg_locale_t locale);
extern char *get_collation_actual_version_icu(const char *collcollate);
 
typedef int32_t (*ICU_Convert_Func) (UChar *dest, int32_t destCapacity,
                                     const UChar *src, int32_t srcLength,
                                     const char *locale,
                                     UErrorCode *pErrorCode);
 
/*
 * Converter object for converting between ICU's UChar strings and C strings
 * in database encoding.  Since the database encoding doesn't change, we only
 * need one of these per session.
 */
static UConverter *icu_converter = NULL;
 
static UCollator *make_icu_collator(const char *iculocstr,
                                    const char *icurules);
static int  strncoll_icu(const char *arg1, ssize_t len1,
                         const char *arg2, ssize_t len2,
                         pg_locale_t locale);
static size_t strnxfrm_prefix_icu(char *dest, size_t destsize,
                                  const char *src, ssize_t srclen,
                                  pg_locale_t locale);
#ifdef HAVE_UCOL_STRCOLLUTF8
static int  strncoll_icu_utf8(const char *arg1, ssize_t len1,
                              const char *arg2, ssize_t len2,
                              pg_locale_t locale);
#endif
static size_t strnxfrm_prefix_icu_utf8(char *dest, size_t destsize,
                                       const char *src, ssize_t srclen,
                                       pg_locale_t locale);
static void init_icu_converter(void);
static size_t uchar_length(UConverter *converter,
                           const char *str, int32_t len);
static int32_t uchar_convert(UConverter *converter,
                             UChar *dest, int32_t destlen,
                             const char *src, int32_t srclen);
static int32_t icu_to_uchar(UChar **buff_uchar, const char *buff,
                            size_t nbytes);
static size_t icu_from_uchar(char *dest, size_t destsize,
                             const UChar *buff_uchar, int32_t len_uchar);
static void icu_set_collation_attributes(UCollator *collator, const char *loc,
                                         UErrorCode *status);
static int32_t icu_convert_case(ICU_Convert_Func func, pg_locale_t mylocale,
                                UChar **buff_dest, UChar *buff_source,
                                int32_t len_source);
static int32_t u_strToTitle_default_BI(UChar *dest, int32_t destCapacity,
                                       const UChar *src, int32_t srcLength,
                                       const char *locale,
                                       UErrorCode *pErrorCode);
static int32_t u_strFoldCase_default(UChar *dest, int32_t destCapacity,
                                     const UChar *src, int32_t srcLength,
                                     const char *locale,
                                     UErrorCode *pErrorCode);
 
static const struct collate_methods collate_methods_icu = {
    .strncoll = strncoll_icu,
    .strnxfrm = strnxfrm_icu,
    .strnxfrm_prefix = strnxfrm_prefix_icu,
    .strxfrm_is_safe = true,
};
 
static const struct collate_methods collate_methods_icu_utf8 = {
#ifdef HAVE_UCOL_STRCOLLUTF8
    .strncoll = strncoll_icu_utf8,
#else
    .strncoll = strncoll_icu,
#endif
    .strnxfrm = strnxfrm_icu,
    .strnxfrm_prefix = strnxfrm_prefix_icu_utf8,
    .strxfrm_is_safe = true,
};
 
#endif
 
pg_locale_t
create_pg_locale_icu(Oid collid, MemoryContext context)
{
#ifdef USE_ICU
    bool        deterministic;
    const char *iculocstr;
    const char *icurules = NULL;
    UCollator  *collator;
    pg_locale_t result;
 
    if (collid == DEFAULT_COLLATION_OID)
    {
        HeapTuple   tp;
        Datum       datum;
        bool        isnull;
 
        tp = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(MyDatabaseId));
        if (!HeapTupleIsValid(tp))
            elog(ERROR, "cache lookup failed for database %u", MyDatabaseId);
 
        /* default database collation is always deterministic */
        deterministic = true;
        datum = SysCacheGetAttrNotNull(DATABASEOID, tp,
                                       Anum_pg_database_datlocale);
        iculocstr = TextDatumGetCString(datum);
        datum = SysCacheGetAttr(DATABASEOID, tp,
                                Anum_pg_database_daticurules, &isnull);
        if (!isnull)
            icurules = TextDatumGetCString(datum);
 
        ReleaseSysCache(tp);
    }
    else
    {
        Form_pg_collation collform;
        HeapTuple   tp;
        Datum       datum;
        bool        isnull;
 
        tp = SearchSysCache1(COLLOID, ObjectIdGetDatum(collid));
        if (!HeapTupleIsValid(tp))
            elog(ERROR, "cache lookup failed for collation %u", collid);
        collform = (Form_pg_collation) GETSTRUCT(tp);
        deterministic = collform->collisdeterministic;
        datum = SysCacheGetAttrNotNull(COLLOID, tp,
                                       Anum_pg_collation_colllocale);
        iculocstr = TextDatumGetCString(datum);
        datum = SysCacheGetAttr(COLLOID, tp,
                                Anum_pg_collation_collicurules, &isnull);
        if (!isnull)
            icurules = TextDatumGetCString(datum);
 
        ReleaseSysCache(tp);
    }
 
    collator = make_icu_collator(iculocstr, icurules);
 
    result = MemoryContextAllocZero(context, sizeof(struct pg_locale_struct));
    result->info.icu.locale = MemoryContextStrdup(context, iculocstr);
    result->info.icu.ucol = collator;
    result->provider = COLLPROVIDER_ICU;
    result->deterministic = deterministic;
    result->collate_is_c = false;
    result->ctype_is_c = false;
    if (GetDatabaseEncoding() == PG_UTF8)
        result->collate = &collate_methods_icu_utf8;
    else
        result->collate = &collate_methods_icu;
 
    return result;
#else
    /* could get here if a collation was created by a build with ICU */
    ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("ICU is not supported in this build")));
 
    return NULL;
#endif
}
 
#ifdef USE_ICU
 
/*
 * Wrapper around ucol_open() to handle API differences for older ICU
 * versions.
 *
 * Ensure that no path leaks a UCollator.
 */
UCollator *
pg_ucol_open(const char *loc_str)
{
    UCollator  *collator;
    UErrorCode  status;
    const char *orig_str = loc_str;
    char       *fixed_str = NULL;
 
    /*
     * Must never open default collator, because it depends on the environment
     * and may change at any time. Should not happen, but check here to catch
     * bugs that might be hard to catch otherwise.
     *
     * NB: the default collator is not the same as the collator for the root
     * locale. The root locale may be specified as the empty string, "und", or
     * "root". The default collator is opened by passing NULL to ucol_open().
     */
    if (loc_str == NULL)
        elog(ERROR, "opening default collator is not supported");
 
    /*
     * In ICU versions 54 and earlier, "und" is not a recognized spelling of
     * the root locale. If the first component of the locale is "und", replace
     * with "root" before opening.
     */
    if (U_ICU_VERSION_MAJOR_NUM < 55)
    {
        char        lang[ULOC_LANG_CAPACITY];
 
        status = U_ZERO_ERROR;
        uloc_getLanguage(loc_str, lang, ULOC_LANG_CAPACITY, &status);
        if (U_FAILURE(status) || status == U_STRING_NOT_TERMINATED_WARNING)
        {
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("could not get language from locale \"%s\": %s",
                            loc_str, u_errorName(status))));
        }
 
        if (strcmp(lang, "und") == 0)
        {
            const char *remainder = loc_str + strlen("und");
 
            fixed_str = palloc(strlen("root") + strlen(remainder) + 1);
            strcpy(fixed_str, "root");
            strcat(fixed_str, remainder);
 
            loc_str = fixed_str;
        }
    }
 
    status = U_ZERO_ERROR;
    collator = ucol_open(loc_str, &status);
    if (U_FAILURE(status))
        ereport(ERROR,
        /* use original string for error report */
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("could not open collator for locale \"%s\": %s",
                        orig_str, u_errorName(status))));
 
    if (U_ICU_VERSION_MAJOR_NUM < 54)
    {
        status = U_ZERO_ERROR;
        icu_set_collation_attributes(collator, loc_str, &status);
 
        /*
         * Pretend the error came from ucol_open(), for consistent error
         * message across ICU versions.
         */
        if (U_FAILURE(status) || status == U_STRING_NOT_TERMINATED_WARNING)
        {
            ucol_close(collator);
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("could not open collator for locale \"%s\": %s",
                            orig_str, u_errorName(status))));
        }
    }
 
    if (fixed_str != NULL)
        pfree(fixed_str);
 
    return collator;
}
 
/*
 * Create a UCollator with the given locale string and rules.
 *
 * Ensure that no path leaks a UCollator.
 */
static UCollator *
make_icu_collator(const char *iculocstr, const char *icurules)
{
    if (!icurules)
    {
        /* simple case without rules */
        return pg_ucol_open(iculocstr);
    }
    else
    {
        UCollator  *collator_std_rules;
        UCollator  *collator_all_rules;
        const UChar *std_rules;
        UChar      *my_rules;
        UChar      *all_rules;
        int32_t     length;
        int32_t     total;
        UErrorCode  status;
 
        /*
         * If rules are specified, we extract the rules of the standard
         * collation, add our own rules, and make a new collator with the
         * combined rules.
         */
        icu_to_uchar(&my_rules, icurules, strlen(icurules));
 
        collator_std_rules = pg_ucol_open(iculocstr);
 
        std_rules = ucol_getRules(collator_std_rules, &length);
 
        total = u_strlen(std_rules) + u_strlen(my_rules) + 1;
 
        /* avoid leaking collator on OOM */
        all_rules = palloc_extended(sizeof(UChar) * total, MCXT_ALLOC_NO_OOM);
        if (!all_rules)
        {
            ucol_close(collator_std_rules);
            ereport(ERROR,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of memory")));
        }
 
        u_strcpy(all_rules, std_rules);
        u_strcat(all_rules, my_rules);
 
        ucol_close(collator_std_rules);
 
        status = U_ZERO_ERROR;
        collator_all_rules = ucol_openRules(all_rules, u_strlen(all_rules),
                                            UCOL_DEFAULT, UCOL_DEFAULT_STRENGTH,
                                            NULL, &status);
        if (U_FAILURE(status))
        {
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("could not open collator for locale \"%s\" with rules \"%s\": %s",
                            iculocstr, icurules, u_errorName(status))));
        }
 
        return collator_all_rules;
    }
}
 
size_t
strlower_icu(char *dest, size_t destsize, const char *src, ssize_t srclen,
             pg_locale_t locale)
{
    int32_t     len_uchar;
    int32_t     len_conv;
    UChar      *buff_uchar;
    UChar      *buff_conv;
    size_t      result_len;
 
    len_uchar = icu_to_uchar(&buff_uchar, src, srclen);
    len_conv = icu_convert_case(u_strToLower, locale,
                                &buff_conv, buff_uchar, len_uchar);
    result_len = icu_from_uchar(dest, destsize, buff_conv, len_conv);
    pfree(buff_uchar);
    pfree(buff_conv);
 
    return result_len;
}
 
size_t
strtitle_icu(char *dest, size_t destsize, const char *src, ssize_t srclen,
             pg_locale_t locale)
{
    int32_t     len_uchar;
    int32_t     len_conv;
    UChar      *buff_uchar;
    UChar      *buff_conv;
    size_t      result_len;
 
    len_uchar = icu_to_uchar(&buff_uchar, src, srclen);
    len_conv = icu_convert_case(u_strToTitle_default_BI, locale,
                                &buff_conv, buff_uchar, len_uchar);
    result_len = icu_from_uchar(dest, destsize, buff_conv, len_conv);
    pfree(buff_uchar);
    pfree(buff_conv);
 
    return result_len;
}
 
size_t
strupper_icu(char *dest, size_t destsize, const char *src, ssize_t srclen,
             pg_locale_t locale)
{
    int32_t     len_uchar;
    int32_t     len_conv;
    UChar      *buff_uchar;
    UChar      *buff_conv;
    size_t      result_len;
 
    len_uchar = icu_to_uchar(&buff_uchar, src, srclen);
    len_conv = icu_convert_case(u_strToUpper, locale,
                                &buff_conv, buff_uchar, len_uchar);
    result_len = icu_from_uchar(dest, destsize, buff_conv, len_conv);
    pfree(buff_uchar);
    pfree(buff_conv);
 
    return result_len;
}
 
size_t
strfold_icu(char *dest, size_t destsize, const char *src, ssize_t srclen,
            pg_locale_t locale)
{
    int32_t     len_uchar;
    int32_t     len_conv;
    UChar      *buff_uchar;
    UChar      *buff_conv;
    size_t      result_len;
 
    len_uchar = icu_to_uchar(&buff_uchar, src, srclen);
    len_conv = icu_convert_case(u_strFoldCase_default, locale,
                                &buff_conv, buff_uchar, len_uchar);
    result_len = icu_from_uchar(dest, destsize, buff_conv, len_conv);
    pfree(buff_uchar);
    pfree(buff_conv);
 
    return result_len;
}
 
/*
 * strncoll_icu_utf8
 *
 * Call ucol_strcollUTF8() or ucol_strcoll() as appropriate for the given
 * database encoding. An argument length of -1 means the string is
 * NUL-terminated.
 */
#ifdef HAVE_UCOL_STRCOLLUTF8
int
strncoll_icu_utf8(const char *arg1, ssize_t len1, const char *arg2, ssize_t len2,
                  pg_locale_t locale)
{
    int         result;
    UErrorCode  status;
 
    Assert(locale->provider == COLLPROVIDER_ICU);
 
    Assert(GetDatabaseEncoding() == PG_UTF8);
 
    status = U_ZERO_ERROR;
    result = ucol_strcollUTF8(locale->info.icu.ucol,
                              arg1, len1,
                              arg2, len2,
                              &status);
    if (U_FAILURE(status))
        ereport(ERROR,
                (errmsg("collation failed: %s", u_errorName(status))));
 
    return result;
}
#endif
 
/* 'srclen' of -1 means the strings are NUL-terminated */
size_t
strnxfrm_icu(char *dest, size_t destsize, const char *src, ssize_t srclen,
             pg_locale_t locale)
{
    char        sbuf[TEXTBUFLEN];
    char       *buf = sbuf;
    UChar      *uchar;
    int32_t     ulen;
    size_t      uchar_bsize;
    Size        result_bsize;
 
    Assert(locale->provider == COLLPROVIDER_ICU);
 
    init_icu_converter();
 
    ulen = uchar_length(icu_converter, src, srclen);
 
    uchar_bsize = (ulen + 1) * sizeof(UChar);
 
    if (uchar_bsize > TEXTBUFLEN)
        buf = palloc(uchar_bsize);
 
    uchar = (UChar *) buf;
 
    ulen = uchar_convert(icu_converter, uchar, ulen + 1, src, srclen);
 
    result_bsize = ucol_getSortKey(locale->info.icu.ucol,
                                   uchar, ulen,
                                   (uint8_t *) dest, destsize);
 
    /*
     * ucol_getSortKey() counts the nul-terminator in the result length, but
     * this function should not.
     */
    Assert(result_bsize > 0);
    result_bsize--;
 
    if (buf != sbuf)
        pfree(buf);
 
    /* if dest is defined, it should be nul-terminated */
    Assert(result_bsize >= destsize || dest[result_bsize] == '\0');
 
    return result_bsize;
}
 
/* 'srclen' of -1 means the strings are NUL-terminated */
size_t
strnxfrm_prefix_icu_utf8(char *dest, size_t destsize,
                         const char *src, ssize_t srclen,
                         pg_locale_t locale)
{
    size_t      result;
    UCharIterator iter;
    uint32_t    state[2];
    UErrorCode  status;
 
    Assert(locale->provider == COLLPROVIDER_ICU);
 
    Assert(GetDatabaseEncoding() == PG_UTF8);
 
    uiter_setUTF8(&iter, src, srclen);
    state[0] = state[1] = 0;    /* won't need that again */
    status = U_ZERO_ERROR;
    result = ucol_nextSortKeyPart(locale->info.icu.ucol,
                                  &iter,
                                  state,
                                  (uint8_t *) dest,
                                  destsize,
                                  &status);
    if (U_FAILURE(status))
        ereport(ERROR,
                (errmsg("sort key generation failed: %s",
                        u_errorName(status))));
 
    return result;
}
 
char *
get_collation_actual_version_icu(const char *collcollate)
{
    UCollator  *collator;
    UVersionInfo versioninfo;
    char        buf[U_MAX_VERSION_STRING_LENGTH];
 
    collator = pg_ucol_open(collcollate);
 
    ucol_getVersion(collator, versioninfo);
    ucol_close(collator);
 
    u_versionToString(versioninfo, buf);
    return pstrdup(buf);
}
 
/*
 * Convert a string in the database encoding into a string of UChars.
 *
 * The source string at buff is of length nbytes
 * (it needn't be nul-terminated)
 *
 * *buff_uchar receives a pointer to the palloc'd result string, and
 * the function's result is the number of UChars generated.
 *
 * The result string is nul-terminated, though most callers rely on the
 * result length instead.
 */
static int32_t
icu_to_uchar(UChar **buff_uchar, const char *buff, size_t nbytes)
{
    int32_t     len_uchar;
 
    init_icu_converter();
 
    len_uchar = uchar_length(icu_converter, buff, nbytes);
 
    *buff_uchar = palloc((len_uchar + 1) * sizeof(**buff_uchar));
    len_uchar = uchar_convert(icu_converter,
                              *buff_uchar, len_uchar + 1, buff, nbytes);
 
    return len_uchar;
}
 
/*
 * Convert a string of UChars into the database encoding.
 *
 * The source string at buff_uchar is of length len_uchar
 * (it needn't be nul-terminated)
 *
 * *result receives a pointer to the palloc'd result string, and the
 * function's result is the number of bytes generated (not counting nul).
 *
 * The result string is nul-terminated.
 */
static size_t
icu_from_uchar(char *dest, size_t destsize, const UChar *buff_uchar, int32_t len_uchar)
{
    UErrorCode  status;
    int32_t     len_result;
 
    init_icu_converter();
 
    status = U_ZERO_ERROR;
    len_result = ucnv_fromUChars(icu_converter, NULL, 0,
                                 buff_uchar, len_uchar, &status);
    if (U_FAILURE(status) && status != U_BUFFER_OVERFLOW_ERROR)
        ereport(ERROR,
                (errmsg("%s failed: %s", "ucnv_fromUChars",
                        u_errorName(status))));
 
    if (len_result + 1 > destsize)
        return len_result;
 
    status = U_ZERO_ERROR;
    len_result = ucnv_fromUChars(icu_converter, dest, len_result + 1,
                                 buff_uchar, len_uchar, &status);
    if (U_FAILURE(status) ||
        status == U_STRING_NOT_TERMINATED_WARNING)
        ereport(ERROR,
                (errmsg("%s failed: %s", "ucnv_fromUChars",
                        u_errorName(status))));
 
    return len_result;
}
 
static int32_t
icu_convert_case(ICU_Convert_Func func, pg_locale_t mylocale,
                 UChar **buff_dest, UChar *buff_source, int32_t len_source)
{
    UErrorCode  status;
    int32_t     len_dest;
 
    len_dest = len_source;      /* try first with same length */
    *buff_dest = palloc(len_dest * sizeof(**buff_dest));
    status = U_ZERO_ERROR;
    len_dest = func(*buff_dest, len_dest, buff_source, len_source,
                    mylocale->info.icu.locale, &status);
    if (status == U_BUFFER_OVERFLOW_ERROR)
    {
        /* try again with adjusted length */
        pfree(*buff_dest);
        *buff_dest = palloc(len_dest * sizeof(**buff_dest));
        status = U_ZERO_ERROR;
        len_dest = func(*buff_dest, len_dest, buff_source, len_source,
                        mylocale->info.icu.locale, &status);
    }
    if (U_FAILURE(status))
        ereport(ERROR,
                (errmsg("case conversion failed: %s", u_errorName(status))));
    return len_dest;
}
 
static int32_t
u_strToTitle_default_BI(UChar *dest, int32_t destCapacity,
                        const UChar *src, int32_t srcLength,
                        const char *locale,
                        UErrorCode *pErrorCode)
{
    return u_strToTitle(dest, destCapacity, src, srcLength,
                        NULL, locale, pErrorCode);
}
 
static int32_t
u_strFoldCase_default(UChar *dest, int32_t destCapacity,
                      const UChar *src, int32_t srcLength,
                      const char *locale,
                      UErrorCode *pErrorCode)
{
    uint32      options = U_FOLD_CASE_DEFAULT;
    char        lang[3];
    UErrorCode  status;
 
    /*
     * Unlike the ICU APIs for lowercasing, titlecasing, and uppercasing, case
     * folding does not accept a locale. Instead it just supports a single
     * option relevant to Turkic languages 'az' and 'tr'; check for those
     * languages to enable the option.
     */
    status = U_ZERO_ERROR;
    uloc_getLanguage(locale, lang, 3, &status);
    if (U_SUCCESS(status))
    {
        /*
         * The option name is confusing, but it causes u_strFoldCase to use
         * the 'T' mappings, which are ignored for U_FOLD_CASE_DEFAULT.
         */
        if (strcmp(lang, "tr") == 0 || strcmp(lang, "az") == 0)
            options = U_FOLD_CASE_EXCLUDE_SPECIAL_I;
    }
 
    return u_strFoldCase(dest, destCapacity, src, srcLength,
                         options, pErrorCode);
}
 
/*
 * strncoll_icu
 *
 * Convert the arguments from the database encoding to UChar strings, then
 * call ucol_strcoll(). An argument length of -1 means that the string is
 * NUL-terminated.
 *
 * When the database encoding is UTF-8, and ICU supports ucol_strcollUTF8(),
 * caller should call that instead.
 */
static int
strncoll_icu(const char *arg1, ssize_t len1,
             const char *arg2, ssize_t len2, pg_locale_t locale)
{
    char        sbuf[TEXTBUFLEN];
    char       *buf = sbuf;
    int32_t     ulen1;
    int32_t     ulen2;
    size_t      bufsize1;
    size_t      bufsize2;
    UChar      *uchar1,
               *uchar2;
    int         result;
 
    Assert(locale->provider == COLLPROVIDER_ICU);
 
    /* if encoding is UTF8, use more efficient strncoll_icu_utf8 */
#ifdef HAVE_UCOL_STRCOLLUTF8
    Assert(GetDatabaseEncoding() != PG_UTF8);
#endif
 
    init_icu_converter();
 
    ulen1 = uchar_length(icu_converter, arg1, len1);
    ulen2 = uchar_length(icu_converter, arg2, len2);
 
    bufsize1 = (ulen1 + 1) * sizeof(UChar);
    bufsize2 = (ulen2 + 1) * sizeof(UChar);
 
    if (bufsize1 + bufsize2 > TEXTBUFLEN)
        buf = palloc(bufsize1 + bufsize2);
 
    uchar1 = (UChar *) buf;
    uchar2 = (UChar *) (buf + bufsize1);
 
    ulen1 = uchar_convert(icu_converter, uchar1, ulen1 + 1, arg1, len1);
    ulen2 = uchar_convert(icu_converter, uchar2, ulen2 + 1, arg2, len2);
 
    result = ucol_strcoll(locale->info.icu.ucol,
                          uchar1, ulen1,
                          uchar2, ulen2);
 
    if (buf != sbuf)
        pfree(buf);
 
    return result;
}
 
/* 'srclen' of -1 means the strings are NUL-terminated */
static size_t
strnxfrm_prefix_icu(char *dest, size_t destsize,
                    const char *src, ssize_t srclen,
                    pg_locale_t locale)
{
    char        sbuf[TEXTBUFLEN];
    char       *buf = sbuf;
    UCharIterator iter;
    uint32_t    state[2];
    UErrorCode  status;
    int32_t     ulen = -1;
    UChar      *uchar = NULL;
    size_t      uchar_bsize;
    Size        result_bsize;
 
    Assert(locale->provider == COLLPROVIDER_ICU);
 
    /* if encoding is UTF8, use more efficient strnxfrm_prefix_icu_utf8 */
    Assert(GetDatabaseEncoding() != PG_UTF8);
 
    init_icu_converter();
 
    ulen = uchar_length(icu_converter, src, srclen);
 
    uchar_bsize = (ulen + 1) * sizeof(UChar);
 
    if (uchar_bsize > TEXTBUFLEN)
        buf = palloc(uchar_bsize);
 
    uchar = (UChar *) buf;
 
    ulen = uchar_convert(icu_converter, uchar, ulen + 1, src, srclen);
 
    uiter_setString(&iter, uchar, ulen);
    state[0] = state[1] = 0;    /* won't need that again */
    status = U_ZERO_ERROR;
    result_bsize = ucol_nextSortKeyPart(locale->info.icu.ucol,
                                        &iter,
                                        state,
                                        (uint8_t *) dest,
                                        destsize,
                                        &status);
    if (U_FAILURE(status))
        ereport(ERROR,
                (errmsg("sort key generation failed: %s",
                        u_errorName(status))));
 
    return result_bsize;
}
 
static void
init_icu_converter(void)
{
    const char *icu_encoding_name;
    UErrorCode  status;
    UConverter *conv;
 
    if (icu_converter)
        return;                 /* already done */
 
    icu_encoding_name = get_encoding_name_for_icu(GetDatabaseEncoding());
    if (!icu_encoding_name)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("encoding \"%s\" not supported by ICU",
                        pg_encoding_to_char(GetDatabaseEncoding()))));
 
    status = U_ZERO_ERROR;
    conv = ucnv_open(icu_encoding_name, &status);
    if (U_FAILURE(status))
        ereport(ERROR,
                (errmsg("could not open ICU converter for encoding \"%s\": %s",
                        icu_encoding_name, u_errorName(status))));
 
    icu_converter = conv;
}
 
/*
 * Find length, in UChars, of given string if converted to UChar string.
 *
 * A length of -1 indicates that the input string is NUL-terminated.
 */
static size_t
uchar_length(UConverter *converter, const char *str, int32_t len)
{
    UErrorCode  status = U_ZERO_ERROR;
    int32_t     ulen;
 
    ulen = ucnv_toUChars(converter, NULL, 0, str, len, &status);
    if (U_FAILURE(status) && status != U_BUFFER_OVERFLOW_ERROR)
        ereport(ERROR,
                (errmsg("%s failed: %s", "ucnv_toUChars", u_errorName(status))));
    return ulen;
}
 
/*
 * Convert the given source string into a UChar string, stored in dest, and
 * return the length (in UChars).
 *
 * A srclen of -1 indicates that the input string is NUL-terminated.
 */
static int32_t
uchar_convert(UConverter *converter, UChar *dest, int32_t destlen,
              const char *src, int32_t srclen)
{
    UErrorCode  status = U_ZERO_ERROR;
    int32_t     ulen;
 
    status = U_ZERO_ERROR;
    ulen = ucnv_toUChars(converter, dest, destlen, src, srclen, &status);
    if (U_FAILURE(status))
        ereport(ERROR,
                (errmsg("%s failed: %s", "ucnv_toUChars", u_errorName(status))));
    return ulen;
}
 
/*
 * Parse collation attributes from the given locale string and apply them to
 * the open collator.
 *
 * First, the locale string is canonicalized to an ICU format locale ID such
 * as "und@colStrength=primary;colCaseLevel=yes". Then, it parses and applies
 * the key-value arguments.
 *
 * Starting with ICU version 54, the attributes are processed automatically by
 * ucol_open(), so this is only necessary for emulating this behavior on older
 * versions.
 */
pg_attribute_unused()
static void
icu_set_collation_attributes(UCollator *collator, const char *loc,
                             UErrorCode *status)
{
    int32_t     len;
    char       *icu_locale_id;
    char       *lower_str;
    char       *str;
    char       *token;
 
    /*
     * The input locale may be a BCP 47 language tag, e.g.
     * "und-u-kc-ks-level1", which expresses the same attributes in a
     * different form. It will be converted to the equivalent ICU format
     * locale ID, e.g. "und@colcaselevel=yes;colstrength=primary", by
     * uloc_canonicalize().
     */
    *status = U_ZERO_ERROR;
    len = uloc_canonicalize(loc, NULL, 0, status);
    icu_locale_id = palloc(len + 1);
    *status = U_ZERO_ERROR;
    len = uloc_canonicalize(loc, icu_locale_id, len + 1, status);
    if (U_FAILURE(*status) || *status == U_STRING_NOT_TERMINATED_WARNING)
        return;
 
    lower_str = asc_tolower(icu_locale_id, strlen(icu_locale_id));
 
    pfree(icu_locale_id);
 
    str = strchr(lower_str, '@');
    if (!str)
        return;
    str++;
 
    while ((token = strsep(&str, ";")))
    {
        char       *e = strchr(token, '=');
 
        if (e)
        {
            char       *name;
            char       *value;
            UColAttribute uattr;
            UColAttributeValue uvalue;
 
            *status = U_ZERO_ERROR;
 
            *e = '\0';
            name = token;
            value = e + 1;
 
            /*
             * See attribute name and value lists in ICU i18n/coll.cpp
             */
            if (strcmp(name, "colstrength") == 0)
                uattr = UCOL_STRENGTH;
            else if (strcmp(name, "colbackwards") == 0)
                uattr = UCOL_FRENCH_COLLATION;
            else if (strcmp(name, "colcaselevel") == 0)
                uattr = UCOL_CASE_LEVEL;
            else if (strcmp(name, "colcasefirst") == 0)
                uattr = UCOL_CASE_FIRST;
            else if (strcmp(name, "colalternate") == 0)
                uattr = UCOL_ALTERNATE_HANDLING;
            else if (strcmp(name, "colnormalization") == 0)
                uattr = UCOL_NORMALIZATION_MODE;
            else if (strcmp(name, "colnumeric") == 0)
                uattr = UCOL_NUMERIC_COLLATION;
            else
                /* ignore if unknown */
                continue;
 
            if (strcmp(value, "primary") == 0)
                uvalue = UCOL_PRIMARY;
            else if (strcmp(value, "secondary") == 0)
                uvalue = UCOL_SECONDARY;
            else if (strcmp(value, "tertiary") == 0)
                uvalue = UCOL_TERTIARY;
            else if (strcmp(value, "quaternary") == 0)
                uvalue = UCOL_QUATERNARY;
            else if (strcmp(value, "identical") == 0)
                uvalue = UCOL_IDENTICAL;
            else if (strcmp(value, "no") == 0)
                uvalue = UCOL_OFF;
            else if (strcmp(value, "yes") == 0)
                uvalue = UCOL_ON;
            else if (strcmp(value, "shifted") == 0)
                uvalue = UCOL_SHIFTED;
            else if (strcmp(value, "non-ignorable") == 0)
                uvalue = UCOL_NON_IGNORABLE;
            else if (strcmp(value, "lower") == 0)
                uvalue = UCOL_LOWER_FIRST;
            else if (strcmp(value, "upper") == 0)
                uvalue = UCOL_UPPER_FIRST;
            else
            {
                *status = U_ILLEGAL_ARGUMENT_ERROR;
                break;
            }
 
            ucol_setAttribute(collator, uattr, uvalue, status);
        }
    }
 
    pfree(lower_str);
}
 
#endif                          /* USE_ICU */