pg_locale.c

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/*-----------------------------------------------------------------------
 *
 * PostgreSQL locale utilities
 *
 * Portions Copyright (c) 2002-2025, PostgreSQL Global Development Group
 *
 * src/backend/utils/adt/pg_locale.c
 *
 *-----------------------------------------------------------------------
 */
 
/*----------
 * Here is how the locale stuff is handled: LC_COLLATE and LC_CTYPE
 * are fixed at CREATE DATABASE time, stored in pg_database, and cannot
 * be changed. Thus, the effects of strcoll(), strxfrm(), isupper(),
 * toupper(), etc. are always in the same fixed locale.
 *
 * LC_MESSAGES is settable at run time and will take effect
 * immediately.
 *
 * The other categories, LC_MONETARY, LC_NUMERIC, and LC_TIME are also
 * settable at run-time.  However, we don't actually set those locale
 * categories permanently.  This would have bizarre effects like no
 * longer accepting standard floating-point literals in some locales.
 * Instead, we only set these locale categories briefly when needed,
 * cache the required information obtained from localeconv() or
 * strftime(), and then set the locale categories back to "C".
 * The cached information is only used by the formatting functions
 * (to_char, etc.) and the money type.  For the user, this should all be
 * transparent.
 *
 * !!! NOW HEAR THIS !!!
 *
 * We've been bitten repeatedly by this bug, so let's try to keep it in
 * mind in future: on some platforms, the locale functions return pointers
 * to static data that will be overwritten by any later locale function.
 * Thus, for example, the obvious-looking sequence
 *          save = setlocale(category, NULL);
 *          if (!setlocale(category, value))
 *              fail = true;
 *          setlocale(category, save);
 * DOES NOT WORK RELIABLY: on some platforms the second setlocale() call
 * will change the memory save is pointing at.  To do this sort of thing
 * safely, you *must* pstrdup what setlocale returns the first time.
 *
 * The POSIX locale standard is available here:
 *
 *  http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap07.html
 *----------
 */
 
 
#include "postgres.h"
 
#include <time.h>
 
#include "access/htup_details.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_database.h"
#include "common/hashfn.h"
#include "common/string.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/formatting.h"
#include "utils/guc_hooks.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/pg_locale.h"
#include "utils/syscache.h"
 
#ifdef WIN32
#include <shlwapi.h>
#endif
 
/* Error triggered for locale-sensitive subroutines */
#define     PGLOCALE_SUPPORT_ERROR(provider) \
    elog(ERROR, "unsupported collprovider for %s: %c", __func__, provider)
 
/*
 * 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
 
#define     MAX_L10N_DATA       80
 
/* pg_locale_builtin.c */
extern pg_locale_t create_pg_locale_builtin(Oid collid, MemoryContext context);
extern char *get_collation_actual_version_builtin(const char *collcollate);
 
/* pg_locale_icu.c */
#ifdef USE_ICU
extern UCollator *pg_ucol_open(const char *loc_str);
extern char *get_collation_actual_version_icu(const char *collcollate);
#endif
extern pg_locale_t create_pg_locale_icu(Oid collid, MemoryContext context);
 
/* pg_locale_libc.c */
extern pg_locale_t create_pg_locale_libc(Oid collid, MemoryContext context);
extern char *get_collation_actual_version_libc(const char *collcollate);
 
extern size_t strlower_builtin(char *dst, size_t dstsize, const char *src,
                               ssize_t srclen, pg_locale_t locale);
extern size_t strtitle_builtin(char *dst, size_t dstsize, const char *src,
                               ssize_t srclen, pg_locale_t locale);
extern size_t strupper_builtin(char *dst, size_t dstsize, const char *src,
                               ssize_t srclen, pg_locale_t locale);
 
extern size_t strlower_icu(char *dst, size_t dstsize, const char *src,
                           ssize_t srclen, pg_locale_t locale);
extern size_t strtitle_icu(char *dst, size_t dstsize, const char *src,
                           ssize_t srclen, pg_locale_t locale);
extern size_t strupper_icu(char *dst, size_t dstsize, const char *src,
                           ssize_t srclen, pg_locale_t locale);
 
extern size_t strlower_libc(char *dst, size_t dstsize, const char *src,
                            ssize_t srclen, pg_locale_t locale);
extern size_t strtitle_libc(char *dst, size_t dstsize, const char *src,
                            ssize_t srclen, pg_locale_t locale);
extern size_t strupper_libc(char *dst, size_t dstsize, const char *src,
                            ssize_t srclen, pg_locale_t locale);
 
/* GUC settings */
char       *locale_messages;
char       *locale_monetary;
char       *locale_numeric;
char       *locale_time;
 
int         icu_validation_level = WARNING;
 
/*
 * lc_time localization cache.
 *
 * We use only the first 7 or 12 entries of these arrays.  The last array
 * element is left as NULL for the convenience of outside code that wants
 * to sequentially scan these arrays.
 */
char       *localized_abbrev_days[7 + 1];
char       *localized_full_days[7 + 1];
char       *localized_abbrev_months[12 + 1];
char       *localized_full_months[12 + 1];
 
/* is the databases's LC_CTYPE the C locale? */
bool        database_ctype_is_c = false;
 
static pg_locale_t default_locale = NULL;
 
/* indicates whether locale information cache is valid */
static bool CurrentLocaleConvValid = false;
static bool CurrentLCTimeValid = false;
 
/* Cache for collation-related knowledge */
 
typedef struct
{
    Oid         collid;         /* hash key: pg_collation OID */
    pg_locale_t locale;         /* locale_t struct, or 0 if not valid */
 
    /* needed for simplehash */
    uint32      hash;
    char        status;
} collation_cache_entry;
 
#define SH_PREFIX       collation_cache
#define SH_ELEMENT_TYPE collation_cache_entry
#define SH_KEY_TYPE     Oid
#define SH_KEY          collid
#define SH_HASH_KEY(tb, key)    murmurhash32((uint32) key)
#define SH_EQUAL(tb, a, b)      (a == b)
#define SH_GET_HASH(tb, a)      a->hash
#define SH_SCOPE        static inline
#define SH_STORE_HASH
#define SH_DECLARE
#define SH_DEFINE
#include "lib/simplehash.h"
 
static MemoryContext CollationCacheContext = NULL;
static collation_cache_hash *CollationCache = NULL;
 
/*
 * The collation cache is often accessed repeatedly for the same collation, so
 * remember the last one used.
 */
static Oid  last_collation_cache_oid = InvalidOid;
static pg_locale_t last_collation_cache_locale = NULL;
 
#if defined(WIN32) && defined(LC_MESSAGES)
static char *IsoLocaleName(const char *);
#endif
 
/*
 * pg_perm_setlocale
 *
 * This wraps the libc function setlocale(), with two additions.  First, when
 * changing LC_CTYPE, update gettext's encoding for the current message
 * domain.  GNU gettext automatically tracks LC_CTYPE on most platforms, but
 * not on Windows.  Second, if the operation is successful, the corresponding
 * LC_XXX environment variable is set to match.  By setting the environment
 * variable, we ensure that any subsequent use of setlocale(..., "") will
 * preserve the settings made through this routine.  Of course, LC_ALL must
 * also be unset to fully ensure that, but that has to be done elsewhere after
 * all the individual LC_XXX variables have been set correctly.  (Thank you
 * Perl for making this kluge necessary.)
 */
char *
pg_perm_setlocale(int category, const char *locale)
{
    char       *result;
    const char *envvar;
 
#ifndef WIN32
    result = setlocale(category, locale);
#else
 
    /*
     * On Windows, setlocale(LC_MESSAGES) does not work, so just assume that
     * the given value is good and set it in the environment variables. We
     * must ignore attempts to set to "", which means "keep using the old
     * environment value".
     */
#ifdef LC_MESSAGES
    if (category == LC_MESSAGES)
    {
        result = (char *) locale;
        if (locale == NULL || locale[0] == '\0')
            return result;
    }
    else
#endif
        result = setlocale(category, locale);
#endif                          /* WIN32 */
 
    if (result == NULL)
        return result;          /* fall out immediately on failure */
 
    /*
     * Use the right encoding in translated messages.  Under ENABLE_NLS, let
     * pg_bind_textdomain_codeset() figure it out.  Under !ENABLE_NLS, message
     * format strings are ASCII, but database-encoding strings may enter the
     * message via %s.  This makes the overall message encoding equal to the
     * database encoding.
     */
    if (category == LC_CTYPE)
    {
        static char save_lc_ctype[LOCALE_NAME_BUFLEN];
 
        /* copy setlocale() return value before callee invokes it again */
        strlcpy(save_lc_ctype, result, sizeof(save_lc_ctype));
        result = save_lc_ctype;
 
#ifdef ENABLE_NLS
        SetMessageEncoding(pg_bind_textdomain_codeset(textdomain(NULL)));
#else
        SetMessageEncoding(GetDatabaseEncoding());
#endif
    }
 
    switch (category)
    {
        case LC_COLLATE:
            envvar = "LC_COLLATE";
            break;
        case LC_CTYPE:
            envvar = "LC_CTYPE";
            break;
#ifdef LC_MESSAGES
        case LC_MESSAGES:
            envvar = "LC_MESSAGES";
#ifdef WIN32
            result = IsoLocaleName(locale);
            if (result == NULL)
                result = (char *) locale;
            elog(DEBUG3, "IsoLocaleName() executed; locale: \"%s\"", result);
#endif                          /* WIN32 */
            break;
#endif                          /* LC_MESSAGES */
        case LC_MONETARY:
            envvar = "LC_MONETARY";
            break;
        case LC_NUMERIC:
            envvar = "LC_NUMERIC";
            break;
        case LC_TIME:
            envvar = "LC_TIME";
            break;
        default:
            elog(FATAL, "unrecognized LC category: %d", category);
            return NULL;        /* keep compiler quiet */
    }
 
    if (setenv(envvar, result, 1) != 0)
        return NULL;
 
    return result;
}
 
 
/*
 * Is the locale name valid for the locale category?
 *
 * If successful, and canonname isn't NULL, a palloc'd copy of the locale's
 * canonical name is stored there.  This is especially useful for figuring out
 * what locale name "" means (ie, the server environment value).  (Actually,
 * it seems that on most implementations that's the only thing it's good for;
 * we could wish that setlocale gave back a canonically spelled version of
 * the locale name, but typically it doesn't.)
 */
bool
check_locale(int category, const char *locale, char **canonname)
{
    char       *save;
    char       *res;
 
    /* Don't let Windows' non-ASCII locale names in. */
    if (!pg_is_ascii(locale))
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("locale name \"%s\" contains non-ASCII characters",
                        locale)));
        return false;
    }
 
    if (canonname)
        *canonname = NULL;      /* in case of failure */
 
    save = setlocale(category, NULL);
    if (!save)
        return false;           /* won't happen, we hope */
 
    /* save may be pointing at a modifiable scratch variable, see above. */
    save = pstrdup(save);
 
    /* set the locale with setlocale, to see if it accepts it. */
    res = setlocale(category, locale);
 
    /* save canonical name if requested. */
    if (res && canonname)
        *canonname = pstrdup(res);
 
    /* restore old value. */
    if (!setlocale(category, save))
        elog(WARNING, "failed to restore old locale \"%s\"", save);
    pfree(save);
 
    /* Don't let Windows' non-ASCII locale names out. */
    if (canonname && *canonname && !pg_is_ascii(*canonname))
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("locale name \"%s\" contains non-ASCII characters",
                        *canonname)));
        pfree(*canonname);
        *canonname = NULL;
        return false;
    }
 
    return (res != NULL);
}
 
 
/*
 * GUC check/assign hooks
 *
 * For most locale categories, the assign hook doesn't actually set the locale
 * permanently, just reset flags so that the next use will cache the
 * appropriate values.  (See explanation at the top of this file.)
 *
 * Note: we accept value = "" as selecting the postmaster's environment
 * value, whatever it was (so long as the environment setting is legal).
 * This will have been locked down by an earlier call to pg_perm_setlocale.
 */
bool
check_locale_monetary(char **newval, void **extra, GucSource source)
{
    return check_locale(LC_MONETARY, *newval, NULL);
}
 
void
assign_locale_monetary(const char *newval, void *extra)
{
    CurrentLocaleConvValid = false;
}
 
bool
check_locale_numeric(char **newval, void **extra, GucSource source)
{
    return check_locale(LC_NUMERIC, *newval, NULL);
}
 
void
assign_locale_numeric(const char *newval, void *extra)
{
    CurrentLocaleConvValid = false;
}
 
bool
check_locale_time(char **newval, void **extra, GucSource source)
{
    return check_locale(LC_TIME, *newval, NULL);
}
 
void
assign_locale_time(const char *newval, void *extra)
{
    CurrentLCTimeValid = false;
}
 
/*
 * We allow LC_MESSAGES to actually be set globally.
 *
 * Note: we normally disallow value = "" because it wouldn't have consistent
 * semantics (it'd effectively just use the previous value).  However, this
 * is the value passed for PGC_S_DEFAULT, so don't complain in that case,
 * not even if the attempted setting fails due to invalid environment value.
 * The idea there is just to accept the environment setting *if possible*
 * during startup, until we can read the proper value from postgresql.conf.
 */
bool
check_locale_messages(char **newval, void **extra, GucSource source)
{
    if (**newval == '\0')
    {
        if (source == PGC_S_DEFAULT)
            return true;
        else
            return false;
    }
 
    /*
     * LC_MESSAGES category does not exist everywhere, but accept it anyway
     *
     * On Windows, we can't even check the value, so accept blindly
     */
#if defined(LC_MESSAGES) && !defined(WIN32)
    return check_locale(LC_MESSAGES, *newval, NULL);
#else
    return true;
#endif
}
 
void
assign_locale_messages(const char *newval, void *extra)
{
    /*
     * LC_MESSAGES category does not exist everywhere, but accept it anyway.
     * We ignore failure, as per comment above.
     */
#ifdef LC_MESSAGES
    (void) pg_perm_setlocale(LC_MESSAGES, newval);
#endif
}
 
 
/*
 * Frees the malloced content of a struct lconv.  (But not the struct
 * itself.)  It's important that this not throw elog(ERROR).
 */
static void
free_struct_lconv(struct lconv *s)
{
    free(s->decimal_point);
    free(s->thousands_sep);
    free(s->grouping);
    free(s->int_curr_symbol);
    free(s->currency_symbol);
    free(s->mon_decimal_point);
    free(s->mon_thousands_sep);
    free(s->mon_grouping);
    free(s->positive_sign);
    free(s->negative_sign);
}
 
/*
 * Check that all fields of a struct lconv (or at least, the ones we care
 * about) are non-NULL.  The field list must match free_struct_lconv().
 */
static bool
struct_lconv_is_valid(struct lconv *s)
{
    if (s->decimal_point == NULL)
        return false;
    if (s->thousands_sep == NULL)
        return false;
    if (s->grouping == NULL)
        return false;
    if (s->int_curr_symbol == NULL)
        return false;
    if (s->currency_symbol == NULL)
        return false;
    if (s->mon_decimal_point == NULL)
        return false;
    if (s->mon_thousands_sep == NULL)
        return false;
    if (s->mon_grouping == NULL)
        return false;
    if (s->positive_sign == NULL)
        return false;
    if (s->negative_sign == NULL)
        return false;
    return true;
}
 
 
/*
 * Convert the strdup'd string at *str from the specified encoding to the
 * database encoding.
 */
static void
db_encoding_convert(int encoding, char **str)
{
    char       *pstr;
    char       *mstr;
 
    /* convert the string to the database encoding */
    pstr = pg_any_to_server(*str, strlen(*str), encoding);
    if (pstr == *str)
        return;                 /* no conversion happened */
 
    /* need it malloc'd not palloc'd */
    mstr = strdup(pstr);
    if (mstr == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));
 
    /* replace old string */
    free(*str);
    *str = mstr;
 
    pfree(pstr);
}
 
 
/*
 * Return the POSIX lconv struct (contains number/money formatting
 * information) with locale information for all categories.
 */
struct lconv *
PGLC_localeconv(void)
{
    static struct lconv CurrentLocaleConv;
    static bool CurrentLocaleConvAllocated = false;
    struct lconv *extlconv;
    struct lconv worklconv;
    char       *save_lc_monetary;
    char       *save_lc_numeric;
#ifdef WIN32
    char       *save_lc_ctype;
#endif
 
    /* Did we do it already? */
    if (CurrentLocaleConvValid)
        return &CurrentLocaleConv;
 
    /* Free any already-allocated storage */
    if (CurrentLocaleConvAllocated)
    {
        free_struct_lconv(&CurrentLocaleConv);
        CurrentLocaleConvAllocated = false;
    }
 
    /*
     * This is tricky because we really don't want to risk throwing error
     * while the locale is set to other than our usual settings.  Therefore,
     * the process is: collect the usual settings, set locale to special
     * setting, copy relevant data into worklconv using strdup(), restore
     * normal settings, convert data to desired encoding, and finally stash
     * the collected data in CurrentLocaleConv.  This makes it safe if we
     * throw an error during encoding conversion or run out of memory anywhere
     * in the process.  All data pointed to by struct lconv members is
     * allocated with strdup, to avoid premature elog(ERROR) and to allow
     * using a single cleanup routine.
     */
    memset(&worklconv, 0, sizeof(worklconv));
 
    /* Save prevailing values of monetary and numeric locales */
    save_lc_monetary = setlocale(LC_MONETARY, NULL);
    if (!save_lc_monetary)
        elog(ERROR, "setlocale(NULL) failed");
    save_lc_monetary = pstrdup(save_lc_monetary);
 
    save_lc_numeric = setlocale(LC_NUMERIC, NULL);
    if (!save_lc_numeric)
        elog(ERROR, "setlocale(NULL) failed");
    save_lc_numeric = pstrdup(save_lc_numeric);
 
#ifdef WIN32
 
    /*
     * The POSIX standard explicitly says that it is undefined what happens if
     * LC_MONETARY or LC_NUMERIC imply an encoding (codeset) different from
     * that implied by LC_CTYPE.  In practice, all Unix-ish platforms seem to
     * believe that localeconv() should return strings that are encoded in the
     * codeset implied by the LC_MONETARY or LC_NUMERIC locale name.  Hence,
     * once we have successfully collected the localeconv() results, we will
     * convert them from that codeset to the desired server encoding.
     *
     * Windows, of course, resolutely does things its own way; on that
     * platform LC_CTYPE has to match LC_MONETARY/LC_NUMERIC to get sane
     * results.  Hence, we must temporarily set that category as well.
     */
 
    /* Save prevailing value of ctype locale */
    save_lc_ctype = setlocale(LC_CTYPE, NULL);
    if (!save_lc_ctype)
        elog(ERROR, "setlocale(NULL) failed");
    save_lc_ctype = pstrdup(save_lc_ctype);
 
    /* Here begins the critical section where we must not throw error */
 
    /* use numeric to set the ctype */
    setlocale(LC_CTYPE, locale_numeric);
#endif
 
    /* Get formatting information for numeric */
    setlocale(LC_NUMERIC, locale_numeric);
    extlconv = localeconv();
 
    /* Must copy data now in case setlocale() overwrites it */
    worklconv.decimal_point = strdup(extlconv->decimal_point);
    worklconv.thousands_sep = strdup(extlconv->thousands_sep);
    worklconv.grouping = strdup(extlconv->grouping);
 
#ifdef WIN32
    /* use monetary to set the ctype */
    setlocale(LC_CTYPE, locale_monetary);
#endif
 
    /* Get formatting information for monetary */
    setlocale(LC_MONETARY, locale_monetary);
    extlconv = localeconv();
 
    /* Must copy data now in case setlocale() overwrites it */
    worklconv.int_curr_symbol = strdup(extlconv->int_curr_symbol);
    worklconv.currency_symbol = strdup(extlconv->currency_symbol);
    worklconv.mon_decimal_point = strdup(extlconv->mon_decimal_point);
    worklconv.mon_thousands_sep = strdup(extlconv->mon_thousands_sep);
    worklconv.mon_grouping = strdup(extlconv->mon_grouping);
    worklconv.positive_sign = strdup(extlconv->positive_sign);
    worklconv.negative_sign = strdup(extlconv->negative_sign);
    /* Copy scalar fields as well */
    worklconv.int_frac_digits = extlconv->int_frac_digits;
    worklconv.frac_digits = extlconv->frac_digits;
    worklconv.p_cs_precedes = extlconv->p_cs_precedes;
    worklconv.p_sep_by_space = extlconv->p_sep_by_space;
    worklconv.n_cs_precedes = extlconv->n_cs_precedes;
    worklconv.n_sep_by_space = extlconv->n_sep_by_space;
    worklconv.p_sign_posn = extlconv->p_sign_posn;
    worklconv.n_sign_posn = extlconv->n_sign_posn;
 
    /*
     * Restore the prevailing locale settings; failure to do so is fatal.
     * Possibly we could limp along with nondefault LC_MONETARY or LC_NUMERIC,
     * but proceeding with the wrong value of LC_CTYPE would certainly be bad
     * news; and considering that the prevailing LC_MONETARY and LC_NUMERIC
     * are almost certainly "C", there's really no reason that restoring those
     * should fail.
     */
#ifdef WIN32
    if (!setlocale(LC_CTYPE, save_lc_ctype))
        elog(FATAL, "failed to restore LC_CTYPE to \"%s\"", save_lc_ctype);
#endif
    if (!setlocale(LC_MONETARY, save_lc_monetary))
        elog(FATAL, "failed to restore LC_MONETARY to \"%s\"", save_lc_monetary);
    if (!setlocale(LC_NUMERIC, save_lc_numeric))
        elog(FATAL, "failed to restore LC_NUMERIC to \"%s\"", save_lc_numeric);
 
    /*
     * At this point we've done our best to clean up, and can call functions
     * that might possibly throw errors with a clean conscience.  But let's
     * make sure we don't leak any already-strdup'd fields in worklconv.
     */
    PG_TRY();
    {
        int         encoding;
 
        /* Release the pstrdup'd locale names */
        pfree(save_lc_monetary);
        pfree(save_lc_numeric);
#ifdef WIN32
        pfree(save_lc_ctype);
#endif
 
        /* If any of the preceding strdup calls failed, complain now. */
        if (!struct_lconv_is_valid(&worklconv))
            ereport(ERROR,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of memory")));
 
        /*
         * Now we must perform encoding conversion from whatever's associated
         * with the locales into the database encoding.  If we can't identify
         * the encoding implied by LC_NUMERIC or LC_MONETARY (ie we get -1),
         * use PG_SQL_ASCII, which will result in just validating that the
         * strings are OK in the database encoding.
         */
        encoding = pg_get_encoding_from_locale(locale_numeric, true);
        if (encoding < 0)
            encoding = PG_SQL_ASCII;
 
        db_encoding_convert(encoding, &worklconv.decimal_point);
        db_encoding_convert(encoding, &worklconv.thousands_sep);
        /* grouping is not text and does not require conversion */
 
        encoding = pg_get_encoding_from_locale(locale_monetary, true);
        if (encoding < 0)
            encoding = PG_SQL_ASCII;
 
        db_encoding_convert(encoding, &worklconv.int_curr_symbol);
        db_encoding_convert(encoding, &worklconv.currency_symbol);
        db_encoding_convert(encoding, &worklconv.mon_decimal_point);
        db_encoding_convert(encoding, &worklconv.mon_thousands_sep);
        /* mon_grouping is not text and does not require conversion */
        db_encoding_convert(encoding, &worklconv.positive_sign);
        db_encoding_convert(encoding, &worklconv.negative_sign);
    }
    PG_CATCH();
    {
        free_struct_lconv(&worklconv);
        PG_RE_THROW();
    }
    PG_END_TRY();
 
    /*
     * Everything is good, so save the results.
     */
    CurrentLocaleConv = worklconv;
    CurrentLocaleConvAllocated = true;
    CurrentLocaleConvValid = true;
    return &CurrentLocaleConv;
}
 
#ifdef WIN32
/*
 * On Windows, strftime() returns its output in encoding CP_ACP (the default
 * operating system codepage for the computer), which is likely different
 * from SERVER_ENCODING.  This is especially important in Japanese versions
 * of Windows which will use SJIS encoding, which we don't support as a
 * server encoding.
 *
 * So, instead of using strftime(), use wcsftime() to return the value in
 * wide characters (internally UTF16) and then convert to UTF8, which we
 * know how to handle directly.
 *
 * Note that this only affects the calls to strftime() in this file, which are
 * used to get the locale-aware strings. Other parts of the backend use
 * pg_strftime(), which isn't locale-aware and does not need to be replaced.
 */
static size_t
strftime_win32(char *dst, size_t dstlen,
               const char *format, const struct tm *tm)
{
    size_t      len;
    wchar_t     wformat[8];     /* formats used below need 3 chars */
    wchar_t     wbuf[MAX_L10N_DATA];
 
    /*
     * Get a wchar_t version of the format string.  We only actually use
     * plain-ASCII formats in this file, so we can say that they're UTF8.
     */
    len = MultiByteToWideChar(CP_UTF8, 0, format, -1,
                              wformat, lengthof(wformat));
    if (len == 0)
        elog(ERROR, "could not convert format string from UTF-8: error code %lu",
             GetLastError());
 
    len = wcsftime(wbuf, MAX_L10N_DATA, wformat, tm);
    if (len == 0)
    {
        /*
         * wcsftime failed, possibly because the result would not fit in
         * MAX_L10N_DATA.  Return 0 with the contents of dst unspecified.
         */
        return 0;
    }
 
    len = WideCharToMultiByte(CP_UTF8, 0, wbuf, len, dst, dstlen - 1,
                              NULL, NULL);
    if (len == 0)
        elog(ERROR, "could not convert string to UTF-8: error code %lu",
             GetLastError());
 
    dst[len] = '\0';
 
    return len;
}
 
/* redefine strftime() */
#define strftime(a,b,c,d) strftime_win32(a,b,c,d)
#endif                          /* WIN32 */
 
/*
 * Subroutine for cache_locale_time().
 * Convert the given string from encoding "encoding" to the database
 * encoding, and store the result at *dst, replacing any previous value.
 */
static void
cache_single_string(char **dst, const char *src, int encoding)
{
    char       *ptr;
    char       *olddst;
 
    /* Convert the string to the database encoding, or validate it's OK */
    ptr = pg_any_to_server(src, strlen(src), encoding);
 
    /* Store the string in long-lived storage, replacing any previous value */
    olddst = *dst;
    *dst = MemoryContextStrdup(TopMemoryContext, ptr);
    if (olddst)
        pfree(olddst);
 
    /* Might as well clean up any palloc'd conversion result, too */
    if (ptr != src)
        pfree(ptr);
}
 
/*
 * Update the lc_time localization cache variables if needed.
 */
void
cache_locale_time(void)
{
    char        buf[(2 * 7 + 2 * 12) * MAX_L10N_DATA];
    char       *bufptr;
    time_t      timenow;
    struct tm  *timeinfo;
    struct tm   timeinfobuf;
    bool        strftimefail = false;
    int         encoding;
    int         i;
    char       *save_lc_time;
#ifdef WIN32
    char       *save_lc_ctype;
#endif
 
    /* did we do this already? */
    if (CurrentLCTimeValid)
        return;
 
    elog(DEBUG3, "cache_locale_time() executed; locale: \"%s\"", locale_time);
 
    /*
     * As in PGLC_localeconv(), it's critical that we not throw error while
     * libc's locale settings have nondefault values.  Hence, we just call
     * strftime() within the critical section, and then convert and save its
     * results afterwards.
     */
 
    /* Save prevailing value of time locale */
    save_lc_time = setlocale(LC_TIME, NULL);
    if (!save_lc_time)
        elog(ERROR, "setlocale(NULL) failed");
    save_lc_time = pstrdup(save_lc_time);
 
#ifdef WIN32
 
    /*
     * On Windows, it appears that wcsftime() internally uses LC_CTYPE, so we
     * must set it here.  This code looks the same as what PGLC_localeconv()
     * does, but the underlying reason is different: this does NOT determine
     * the encoding we'll get back from strftime_win32().
     */
 
    /* Save prevailing value of ctype locale */
    save_lc_ctype = setlocale(LC_CTYPE, NULL);
    if (!save_lc_ctype)
        elog(ERROR, "setlocale(NULL) failed");
    save_lc_ctype = pstrdup(save_lc_ctype);
 
    /* use lc_time to set the ctype */
    setlocale(LC_CTYPE, locale_time);
#endif
 
    setlocale(LC_TIME, locale_time);
 
    /* We use times close to current time as data for strftime(). */
    timenow = time(NULL);
    timeinfo = gmtime_r(&timenow, &timeinfobuf);
 
    /* Store the strftime results in MAX_L10N_DATA-sized portions of buf[] */
    bufptr = buf;
 
    /*
     * MAX_L10N_DATA is sufficient buffer space for every known locale, and
     * POSIX defines no strftime() errors.  (Buffer space exhaustion is not an
     * error.)  An implementation might report errors (e.g. ENOMEM) by
     * returning 0 (or, less plausibly, a negative value) and setting errno.
     * Report errno just in case the implementation did that, but clear it in
     * advance of the calls so we don't emit a stale, unrelated errno.
     */
    errno = 0;
 
    /* localized days */
    for (i = 0; i < 7; i++)
    {
        timeinfo->tm_wday = i;
        if (strftime(bufptr, MAX_L10N_DATA, "%a", timeinfo) <= 0)
            strftimefail = true;
        bufptr += MAX_L10N_DATA;
        if (strftime(bufptr, MAX_L10N_DATA, "%A", timeinfo) <= 0)
            strftimefail = true;
        bufptr += MAX_L10N_DATA;
    }
 
    /* localized months */
    for (i = 0; i < 12; i++)
    {
        timeinfo->tm_mon = i;
        timeinfo->tm_mday = 1;  /* make sure we don't have invalid date */
        if (strftime(bufptr, MAX_L10N_DATA, "%b", timeinfo) <= 0)
            strftimefail = true;
        bufptr += MAX_L10N_DATA;
        if (strftime(bufptr, MAX_L10N_DATA, "%B", timeinfo) <= 0)
            strftimefail = true;
        bufptr += MAX_L10N_DATA;
    }
 
    /*
     * Restore the prevailing locale settings; as in PGLC_localeconv(),
     * failure to do so is fatal.
     */
#ifdef WIN32
    if (!setlocale(LC_CTYPE, save_lc_ctype))
        elog(FATAL, "failed to restore LC_CTYPE to \"%s\"", save_lc_ctype);
#endif
    if (!setlocale(LC_TIME, save_lc_time))
        elog(FATAL, "failed to restore LC_TIME to \"%s\"", save_lc_time);
 
    /*
     * At this point we've done our best to clean up, and can throw errors, or
     * call functions that might throw errors, with a clean conscience.
     */
    if (strftimefail)
        elog(ERROR, "strftime() failed: %m");
 
    /* Release the pstrdup'd locale names */
    pfree(save_lc_time);
#ifdef WIN32
    pfree(save_lc_ctype);
#endif
 
#ifndef WIN32
 
    /*
     * As in PGLC_localeconv(), we must convert strftime()'s output from the
     * encoding implied by LC_TIME to the database encoding.  If we can't
     * identify the LC_TIME encoding, just perform encoding validation.
     */
    encoding = pg_get_encoding_from_locale(locale_time, true);
    if (encoding < 0)
        encoding = PG_SQL_ASCII;
 
#else
 
    /*
     * On Windows, strftime_win32() always returns UTF8 data, so convert from
     * that if necessary.
     */
    encoding = PG_UTF8;
 
#endif                          /* WIN32 */
 
    bufptr = buf;
 
    /* localized days */
    for (i = 0; i < 7; i++)
    {
        cache_single_string(&localized_abbrev_days[i], bufptr, encoding);
        bufptr += MAX_L10N_DATA;
        cache_single_string(&localized_full_days[i], bufptr, encoding);
        bufptr += MAX_L10N_DATA;
    }
    localized_abbrev_days[7] = NULL;
    localized_full_days[7] = NULL;
 
    /* localized months */
    for (i = 0; i < 12; i++)
    {
        cache_single_string(&localized_abbrev_months[i], bufptr, encoding);
        bufptr += MAX_L10N_DATA;
        cache_single_string(&localized_full_months[i], bufptr, encoding);
        bufptr += MAX_L10N_DATA;
    }
    localized_abbrev_months[12] = NULL;
    localized_full_months[12] = NULL;
 
    CurrentLCTimeValid = true;
}
 
 
#if defined(WIN32) && defined(LC_MESSAGES)
/*
 * Convert a Windows setlocale() argument to a Unix-style one.
 *
 * Regardless of platform, we install message catalogs under a Unix-style
 * LL[_CC][.ENCODING][@VARIANT] naming convention.  Only LC_MESSAGES settings
 * following that style will elicit localized interface strings.
 *
 * Before Visual Studio 2012 (msvcr110.dll), Windows setlocale() accepted "C"
 * (but not "c") and strings of the form <Language>[_<Country>][.<CodePage>],
 * case-insensitive.  setlocale() returns the fully-qualified form; for
 * example, setlocale("thaI") returns "Thai_Thailand.874".  Internally,
 * setlocale() and _create_locale() select a "locale identifier"[1] and store
 * it in an undocumented _locale_t field.  From that LCID, we can retrieve the
 * ISO 639 language and the ISO 3166 country.  Character encoding does not
 * matter, because the server and client encodings govern that.
 *
 * Windows Vista introduced the "locale name" concept[2], closely following
 * RFC 4646.  Locale identifiers are now deprecated.  Starting with Visual
 * Studio 2012, setlocale() accepts locale names in addition to the strings it
 * accepted historically.  It does not standardize them; setlocale("Th-tH")
 * returns "Th-tH".  setlocale(category, "") still returns a traditional
 * string.  Furthermore, msvcr110.dll changed the undocumented _locale_t
 * content to carry locale names instead of locale identifiers.
 *
 * Visual Studio 2015 should still be able to do the same as Visual Studio
 * 2012, but the declaration of locale_name is missing in _locale_t, causing
 * this code compilation to fail, hence this falls back instead on to
 * enumerating all system locales by using EnumSystemLocalesEx to find the
 * required locale name.  If the input argument is in Unix-style then we can
 * get ISO Locale name directly by using GetLocaleInfoEx() with LCType as
 * LOCALE_SNAME.
 *
 * This function returns a pointer to a static buffer bearing the converted
 * name or NULL if conversion fails.
 *
 * [1] https://docs.microsoft.com/en-us/windows/win32/intl/locale-identifiers
 * [2] https://docs.microsoft.com/en-us/windows/win32/intl/locale-names
 */
 
/*
 * Callback function for EnumSystemLocalesEx() in get_iso_localename().
 *
 * This function enumerates all system locales, searching for one that matches
 * an input with the format: <Language>[_<Country>], e.g.
 * English[_United States]
 *
 * The input is a three wchar_t array as an LPARAM. The first element is the
 * locale_name we want to match, the second element is an allocated buffer
 * where the Unix-style locale is copied if a match is found, and the third
 * element is the search status, 1 if a match was found, 0 otherwise.
 */
static BOOL CALLBACK
search_locale_enum(LPWSTR pStr, DWORD dwFlags, LPARAM lparam)
{
    wchar_t     test_locale[LOCALE_NAME_MAX_LENGTH];
    wchar_t   **argv;
 
    (void) (dwFlags);
 
    argv = (wchar_t **) lparam;
    *argv[2] = (wchar_t) 0;
 
    memset(test_locale, 0, sizeof(test_locale));
 
    /* Get the name of the <Language> in English */
    if (GetLocaleInfoEx(pStr, LOCALE_SENGLISHLANGUAGENAME,
                        test_locale, LOCALE_NAME_MAX_LENGTH))
    {
        /*
         * If the enumerated locale does not have a hyphen ("en") OR the
         * locale_name input does not have an underscore ("English"), we only
         * need to compare the <Language> tags.
         */
        if (wcsrchr(pStr, '-') == NULL || wcsrchr(argv[0], '_') == NULL)
        {
            if (_wcsicmp(argv[0], test_locale) == 0)
            {
                wcscpy(argv[1], pStr);
                *argv[2] = (wchar_t) 1;
                return FALSE;
            }
        }
 
        /*
         * We have to compare a full <Language>_<Country> tag, so we append
         * the underscore and name of the country/region in English, e.g.
         * "English_United States".
         */
        else
        {
            size_t      len;
 
            wcscat(test_locale, L"_");
            len = wcslen(test_locale);
            if (GetLocaleInfoEx(pStr, LOCALE_SENGLISHCOUNTRYNAME,
                                test_locale + len,
                                LOCALE_NAME_MAX_LENGTH - len))
            {
                if (_wcsicmp(argv[0], test_locale) == 0)
                {
                    wcscpy(argv[1], pStr);
                    *argv[2] = (wchar_t) 1;
                    return FALSE;
                }
            }
        }
    }
 
    return TRUE;
}
 
/*
 * This function converts a Windows locale name to an ISO formatted version
 * for Visual Studio 2015 or greater.
 *
 * Returns NULL, if no valid conversion was found.
 */
static char *
get_iso_localename(const char *winlocname)
{
    wchar_t     wc_locale_name[LOCALE_NAME_MAX_LENGTH];
    wchar_t     buffer[LOCALE_NAME_MAX_LENGTH];
    static char iso_lc_messages[LOCALE_NAME_MAX_LENGTH];
    char       *period;
    int         len;
    int         ret_val;
 
    /*
     * Valid locales have the following syntax:
     * <Language>[_<Country>[.<CodePage>]]
     *
     * GetLocaleInfoEx can only take locale name without code-page and for the
     * purpose of this API the code-page doesn't matter.
     */
    period = strchr(winlocname, '.');
    if (period != NULL)
        len = period - winlocname;
    else
        len = pg_mbstrlen(winlocname);
 
    memset(wc_locale_name, 0, sizeof(wc_locale_name));
    memset(buffer, 0, sizeof(buffer));
    MultiByteToWideChar(CP_ACP, 0, winlocname, len, wc_locale_name,
                        LOCALE_NAME_MAX_LENGTH);
 
    /*
     * If the lc_messages is already a Unix-style string, we have a direct
     * match with LOCALE_SNAME, e.g. en-US, en_US.
     */
    ret_val = GetLocaleInfoEx(wc_locale_name, LOCALE_SNAME, (LPWSTR) &buffer,
                              LOCALE_NAME_MAX_LENGTH);
    if (!ret_val)
    {
        /*
         * Search for a locale in the system that matches language and country
         * name.
         */
        wchar_t    *argv[3];
 
        argv[0] = wc_locale_name;
        argv[1] = buffer;
        argv[2] = (wchar_t *) &ret_val;
        EnumSystemLocalesEx(search_locale_enum, LOCALE_WINDOWS, (LPARAM) argv,
                            NULL);
    }
 
    if (ret_val)
    {
        size_t      rc;
        char       *hyphen;
 
        /* Locale names use only ASCII, any conversion locale suffices. */
        rc = wchar2char(iso_lc_messages, buffer, sizeof(iso_lc_messages), NULL);
        if (rc == -1 || rc == sizeof(iso_lc_messages))
            return NULL;
 
        /*
         * Since the message catalogs sit on a case-insensitive filesystem, we
         * need not standardize letter case here.  So long as we do not ship
         * message catalogs for which it would matter, we also need not
         * translate the script/variant portion, e.g.  uz-Cyrl-UZ to
         * uz_UZ@cyrillic.  Simply replace the hyphen with an underscore.
         */
        hyphen = strchr(iso_lc_messages, '-');
        if (hyphen)
            *hyphen = '_';
        return iso_lc_messages;
    }
 
    return NULL;
}
 
static char *
IsoLocaleName(const char *winlocname)
{
    static char iso_lc_messages[LOCALE_NAME_MAX_LENGTH];
 
    if (pg_strcasecmp("c", winlocname) == 0 ||
        pg_strcasecmp("posix", winlocname) == 0)
    {
        strcpy(iso_lc_messages, "C");
        return iso_lc_messages;
    }
    else
        return get_iso_localename(winlocname);
}
 
#endif                          /* WIN32 && LC_MESSAGES */
 
/*
 * Create a new pg_locale_t struct for the given collation oid.
 */
static pg_locale_t
create_pg_locale(Oid collid, MemoryContext context)
{
    HeapTuple   tp;
    Form_pg_collation collform;
    pg_locale_t result;
    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);
 
    if (collform->collprovider == COLLPROVIDER_BUILTIN)
        result = create_pg_locale_builtin(collid, context);
    else if (collform->collprovider == COLLPROVIDER_ICU)
        result = create_pg_locale_icu(collid, context);
    else if (collform->collprovider == COLLPROVIDER_LIBC)
        result = create_pg_locale_libc(collid, context);
    else
        /* shouldn't happen */
        PGLOCALE_SUPPORT_ERROR(collform->collprovider);
 
    result->is_default = false;
 
    Assert((result->collate_is_c && result->collate == NULL) ||
           (!result->collate_is_c && result->collate != NULL));
 
    datum = SysCacheGetAttr(COLLOID, tp, Anum_pg_collation_collversion,
                            &isnull);
    if (!isnull)
    {
        char       *actual_versionstr;
        char       *collversionstr;
 
        collversionstr = TextDatumGetCString(datum);
 
        if (collform->collprovider == COLLPROVIDER_LIBC)
            datum = SysCacheGetAttrNotNull(COLLOID, tp, Anum_pg_collation_collcollate);
        else
            datum = SysCacheGetAttrNotNull(COLLOID, tp, Anum_pg_collation_colllocale);
 
        actual_versionstr = get_collation_actual_version(collform->collprovider,
                                                         TextDatumGetCString(datum));
        if (!actual_versionstr)
        {
            /*
             * This could happen when specifying a version in CREATE COLLATION
             * but the provider does not support versioning, or manually
             * creating a mess in the catalogs.
             */
            ereport(ERROR,
                    (errmsg("collation \"%s\" has no actual version, but a version was recorded",
                            NameStr(collform->collname))));
        }
 
        if (strcmp(actual_versionstr, collversionstr) != 0)
            ereport(WARNING,
                    (errmsg("collation \"%s\" has version mismatch",
                            NameStr(collform->collname)),
                     errdetail("The collation in the database was created using version %s, "
                               "but the operating system provides version %s.",
                               collversionstr, actual_versionstr),
                     errhint("Rebuild all objects affected by this collation and run "
                             "ALTER COLLATION %s REFRESH VERSION, "
                             "or build PostgreSQL with the right library version.",
                             quote_qualified_identifier(get_namespace_name(collform->collnamespace),
                                                        NameStr(collform->collname)))));
    }
 
    ReleaseSysCache(tp);
 
    return result;
}
 
/*
 * Initialize default_locale with database locale settings.
 */
void
init_database_collation(void)
{
    HeapTuple   tup;
    Form_pg_database dbform;
    pg_locale_t result;
 
    Assert(default_locale == NULL);
 
    /* Fetch our pg_database row normally, via syscache */
    tup = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(MyDatabaseId));
    if (!HeapTupleIsValid(tup))
        elog(ERROR, "cache lookup failed for database %u", MyDatabaseId);
    dbform = (Form_pg_database) GETSTRUCT(tup);
 
    if (dbform->datlocprovider == COLLPROVIDER_BUILTIN)
        result = create_pg_locale_builtin(DEFAULT_COLLATION_OID,
                                          TopMemoryContext);
    else if (dbform->datlocprovider == COLLPROVIDER_ICU)
        result = create_pg_locale_icu(DEFAULT_COLLATION_OID,
                                      TopMemoryContext);
    else if (dbform->datlocprovider == COLLPROVIDER_LIBC)
        result = create_pg_locale_libc(DEFAULT_COLLATION_OID,
                                       TopMemoryContext);
    else
        /* shouldn't happen */
        PGLOCALE_SUPPORT_ERROR(dbform->datlocprovider);
 
    result->is_default = true;
    ReleaseSysCache(tup);
 
    default_locale = result;
}
 
/*
 * Create a pg_locale_t from a collation OID.  Results are cached for the
 * lifetime of the backend.  Thus, do not free the result with freelocale().
 *
 * For simplicity, we always generate COLLATE + CTYPE even though we
 * might only need one of them.  Since this is called only once per session,
 * it shouldn't cost much.
 */
pg_locale_t
pg_newlocale_from_collation(Oid collid)
{
    collation_cache_entry *cache_entry;
    bool        found;
 
    if (collid == DEFAULT_COLLATION_OID)
        return default_locale;
 
    if (!OidIsValid(collid))
        elog(ERROR, "cache lookup failed for collation %u", collid);
 
    if (last_collation_cache_oid == collid)
        return last_collation_cache_locale;
 
    if (CollationCache == NULL)
    {
        CollationCacheContext = AllocSetContextCreate(TopMemoryContext,
                                                      "collation cache",
                                                      ALLOCSET_DEFAULT_SIZES);
        CollationCache = collation_cache_create(CollationCacheContext,
                                                16, NULL);
    }
 
    cache_entry = collation_cache_insert(CollationCache, collid, &found);
    if (!found)
    {
        /*
         * Make sure cache entry is marked invalid, in case we fail before
         * setting things.
         */
        cache_entry->locale = 0;
    }
 
    if (cache_entry->locale == 0)
    {
        cache_entry->locale = create_pg_locale(collid, CollationCacheContext);
    }
 
    last_collation_cache_oid = collid;
    last_collation_cache_locale = cache_entry->locale;
 
    return cache_entry->locale;
}
 
/*
 * Get provider-specific collation version string for the given collation from
 * the operating system/library.
 */
char *
get_collation_actual_version(char collprovider, const char *collcollate)
{
    char       *collversion = NULL;
 
    if (collprovider == COLLPROVIDER_BUILTIN)
        collversion = get_collation_actual_version_builtin(collcollate);
#ifdef USE_ICU
    else if (collprovider == COLLPROVIDER_ICU)
        collversion = get_collation_actual_version_icu(collcollate);
#endif
    else if (collprovider == COLLPROVIDER_LIBC)
        collversion = get_collation_actual_version_libc(collcollate);
 
    return collversion;
}
 
size_t
pg_strlower(char *dst, size_t dstsize, const char *src, ssize_t srclen,
            pg_locale_t locale)
{
    if (locale->provider == COLLPROVIDER_BUILTIN)
        return strlower_builtin(dst, dstsize, src, srclen, locale);
#ifdef USE_ICU
    else if (locale->provider == COLLPROVIDER_ICU)
        return strlower_icu(dst, dstsize, src, srclen, locale);
#endif
    else if (locale->provider == COLLPROVIDER_LIBC)
        return strlower_libc(dst, dstsize, src, srclen, locale);
    else
        /* shouldn't happen */
        PGLOCALE_SUPPORT_ERROR(locale->provider);
 
    return 0;                   /* keep compiler quiet */
}
 
size_t
pg_strtitle(char *dst, size_t dstsize, const char *src, ssize_t srclen,
            pg_locale_t locale)
{
    if (locale->provider == COLLPROVIDER_BUILTIN)
        return strtitle_builtin(dst, dstsize, src, srclen, locale);
#ifdef USE_ICU
    else if (locale->provider == COLLPROVIDER_ICU)
        return strtitle_icu(dst, dstsize, src, srclen, locale);
#endif
    else if (locale->provider == COLLPROVIDER_LIBC)
        return strtitle_libc(dst, dstsize, src, srclen, locale);
    else
        /* shouldn't happen */
        PGLOCALE_SUPPORT_ERROR(locale->provider);
 
    return 0;                   /* keep compiler quiet */
}
 
size_t
pg_strupper(char *dst, size_t dstsize, const char *src, ssize_t srclen,
            pg_locale_t locale)
{
    if (locale->provider == COLLPROVIDER_BUILTIN)
        return strupper_builtin(dst, dstsize, src, srclen, locale);
#ifdef USE_ICU
    else if (locale->provider == COLLPROVIDER_ICU)
        return strupper_icu(dst, dstsize, src, srclen, locale);
#endif
    else if (locale->provider == COLLPROVIDER_LIBC)
        return strupper_libc(dst, dstsize, src, srclen, locale);
    else
        /* shouldn't happen */
        PGLOCALE_SUPPORT_ERROR(locale->provider);
 
    return 0;                   /* keep compiler quiet */
}
 
/*
 * pg_strcoll
 *
 * Like pg_strncoll for NUL-terminated input strings.
 */
int
pg_strcoll(const char *arg1, const char *arg2, pg_locale_t locale)
{
    return locale->collate->strncoll(arg1, -1, arg2, -1, locale);
}
 
/*
 * pg_strncoll
 *
 * Call ucol_strcollUTF8(), ucol_strcoll(), strcoll_l() or wcscoll_l() as
 * appropriate for the given locale, platform, and database encoding. If the
 * locale is not specified, use the database collation.
 *
 * The input strings must be encoded in the database encoding. If an input
 * string is NUL-terminated, its length may be specified as -1.
 *
 * The caller is responsible for breaking ties if the collation is
 * deterministic; this maintains consistency with pg_strnxfrm(), which cannot
 * easily account for deterministic collations.
 */
int
pg_strncoll(const char *arg1, ssize_t len1, const char *arg2, ssize_t len2,
            pg_locale_t locale)
{
    return locale->collate->strncoll(arg1, len1, arg2, len2, locale);
}
 
/*
 * Return true if the collation provider supports pg_strxfrm() and
 * pg_strnxfrm(); otherwise false.
 *
 *
 * No similar problem is known for the ICU provider.
 */
bool
pg_strxfrm_enabled(pg_locale_t locale)
{
    /*
     * locale->collate->strnxfrm is still a required method, even if it may
     * have the wrong behavior, because the planner uses it for estimates in
     * some cases.
     */
    return locale->collate->strxfrm_is_safe;
}
 
/*
 * pg_strxfrm
 *
 * Like pg_strnxfrm for a NUL-terminated input string.
 */
size_t
pg_strxfrm(char *dest, const char *src, size_t destsize, pg_locale_t locale)
{
    return locale->collate->strnxfrm(dest, destsize, src, -1, locale);
}
 
/*
 * pg_strnxfrm
 *
 * Transforms 'src' to a nul-terminated string stored in 'dest' such that
 * ordinary strcmp() on transformed strings is equivalent to pg_strcoll() on
 * untransformed strings.
 *
 * The input string must be encoded in the database encoding. If the input
 * string is NUL-terminated, its length may be specified as -1. If 'destsize'
 * is zero, 'dest' may be NULL.
 *
 * Not all providers support pg_strnxfrm() safely. The caller should check
 * pg_strxfrm_enabled() first, otherwise this function may return wrong
 * results or an error.
 *
 * Returns the number of bytes needed (or more) to store the transformed
 * string, excluding the terminating nul byte. If the value returned is
 * 'destsize' or greater, the resulting contents of 'dest' are undefined.
 */
size_t
pg_strnxfrm(char *dest, size_t destsize, const char *src, ssize_t srclen,
            pg_locale_t locale)
{
    return locale->collate->strnxfrm(dest, destsize, src, srclen, locale);
}
 
/*
 * Return true if the collation provider supports pg_strxfrm_prefix() and
 * pg_strnxfrm_prefix(); otherwise false.
 */
bool
pg_strxfrm_prefix_enabled(pg_locale_t locale)
{
    return (locale->collate->strnxfrm_prefix != NULL);
}
 
/*
 * pg_strxfrm_prefix
 *
 * Like pg_strnxfrm_prefix for a NUL-terminated input string.
 */
size_t
pg_strxfrm_prefix(char *dest, const char *src, size_t destsize,
                  pg_locale_t locale)
{
    return locale->collate->strnxfrm_prefix(dest, destsize, src, -1, locale);
}
 
/*
 * pg_strnxfrm_prefix
 *
 * Transforms 'src' to a byte sequence stored in 'dest' such that ordinary
 * memcmp() on the byte sequence is equivalent to pg_strncoll() on
 * untransformed strings. The result is not nul-terminated.
 *
 * The input string must be encoded in the database encoding. If the input
 * string is NUL-terminated, its length may be specified as -1.
 *
 * Not all providers support pg_strnxfrm_prefix() safely. The caller should
 * check pg_strxfrm_prefix_enabled() first, otherwise this function may return
 * wrong results or an error.
 *
 * If destsize is not large enough to hold the resulting byte sequence, stores
 * only the first destsize bytes in 'dest'. Returns the number of bytes
 * actually copied to 'dest'.
 */
size_t
pg_strnxfrm_prefix(char *dest, size_t destsize, const char *src,
                   ssize_t srclen, pg_locale_t locale)
{
    return locale->collate->strnxfrm_prefix(dest, destsize, src, srclen, locale);
}
 
/*
 * Return required encoding ID for the given locale, or -1 if any encoding is
 * valid for the locale.
 */
int
builtin_locale_encoding(const char *locale)
{
    if (strcmp(locale, "C") == 0)
        return -1;
    else if (strcmp(locale, "C.UTF-8") == 0)
        return PG_UTF8;
    else if (strcmp(locale, "PG_UNICODE_FAST") == 0)
        return PG_UTF8;
 
 
    ereport(ERROR,
            (errcode(ERRCODE_WRONG_OBJECT_TYPE),
             errmsg("invalid locale name \"%s\" for builtin provider",
                    locale)));
 
    return 0;                   /* keep compiler quiet */
}
 
 
/*
 * Validate the locale and encoding combination, and return the canonical form
 * of the locale name.
 */
const char *
builtin_validate_locale(int encoding, const char *locale)
{
    const char *canonical_name = NULL;
    int         required_encoding;
 
    if (strcmp(locale, "C") == 0)
        canonical_name = "C";
    else if (strcmp(locale, "C.UTF-8") == 0 || strcmp(locale, "C.UTF8") == 0)
        canonical_name = "C.UTF-8";
    else if (strcmp(locale, "PG_UNICODE_FAST") == 0)
        canonical_name = "PG_UNICODE_FAST";
 
    if (!canonical_name)
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("invalid locale name \"%s\" for builtin provider",
                        locale)));
 
    required_encoding = builtin_locale_encoding(canonical_name);
    if (required_encoding >= 0 && encoding != required_encoding)
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("encoding \"%s\" does not match locale \"%s\"",
                        pg_encoding_to_char(encoding), locale)));
 
    return canonical_name;
}
 
 
 
/*
 * Return the BCP47 language tag representation of the requested locale.
 *
 * This function should be called before passing the string to ucol_open(),
 * because conversion to a language tag also performs "level 2
 * canonicalization". In addition to producing a consistent format, level 2
 * canonicalization is able to more accurately interpret different input
 * locale string formats, such as POSIX and .NET IDs.
 */
char *
icu_language_tag(const char *loc_str, int elevel)
{
#ifdef USE_ICU
    UErrorCode  status;
    char       *langtag;
    size_t      buflen = 32;    /* arbitrary starting buffer size */
    const bool  strict = true;
 
    /*
     * A BCP47 language tag doesn't have a clearly-defined upper limit (cf.
     * RFC5646 section 4.4). Additionally, in older ICU versions,
     * uloc_toLanguageTag() doesn't always return the ultimate length on the
     * first call, necessitating a loop.
     */
    langtag = palloc(buflen);
    while (true)
    {
        status = U_ZERO_ERROR;
        uloc_toLanguageTag(loc_str, langtag, buflen, strict, &status);
 
        /* try again if the buffer is not large enough */
        if ((status == U_BUFFER_OVERFLOW_ERROR ||
             status == U_STRING_NOT_TERMINATED_WARNING) &&
            buflen < MaxAllocSize)
        {
            buflen = Min(buflen * 2, MaxAllocSize);
            langtag = repalloc(langtag, buflen);
            continue;
        }
 
        break;
    }
 
    if (U_FAILURE(status))
    {
        pfree(langtag);
 
        if (elevel > 0)
            ereport(elevel,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("could not convert locale name \"%s\" to language tag: %s",
                            loc_str, u_errorName(status))));
        return NULL;
    }
 
    return langtag;
#else                           /* not USE_ICU */
    ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("ICU is not supported in this build")));
    return NULL;                /* keep compiler quiet */
#endif                          /* not USE_ICU */
}
 
/*
 * Perform best-effort check that the locale is a valid one.
 */
void
icu_validate_locale(const char *loc_str)
{
#ifdef USE_ICU
    UCollator  *collator;
    UErrorCode  status;
    char        lang[ULOC_LANG_CAPACITY];
    bool        found = false;
    int         elevel = icu_validation_level;
 
    /* no validation */
    if (elevel < 0)
        return;
 
    /* downgrade to WARNING during pg_upgrade */
    if (IsBinaryUpgrade && elevel > WARNING)
        elevel = WARNING;
 
    /* validate that we can extract the language */
    status = U_ZERO_ERROR;
    uloc_getLanguage(loc_str, lang, ULOC_LANG_CAPACITY, &status);
    if (U_FAILURE(status) || status == U_STRING_NOT_TERMINATED_WARNING)
    {
        ereport(elevel,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("could not get language from ICU locale \"%s\": %s",
                        loc_str, u_errorName(status)),
                 errhint("To disable ICU locale validation, set the parameter \"%s\" to \"%s\".",
                         "icu_validation_level", "disabled")));
        return;
    }
 
    /* check for special language name */
    if (strcmp(lang, "") == 0 ||
        strcmp(lang, "root") == 0 || strcmp(lang, "und") == 0)
        found = true;
 
    /* search for matching language within ICU */
    for (int32_t i = 0; !found && i < uloc_countAvailable(); i++)
    {
        const char *otherloc = uloc_getAvailable(i);
        char        otherlang[ULOC_LANG_CAPACITY];
 
        status = U_ZERO_ERROR;
        uloc_getLanguage(otherloc, otherlang, ULOC_LANG_CAPACITY, &status);
        if (U_FAILURE(status) || status == U_STRING_NOT_TERMINATED_WARNING)
            continue;
 
        if (strcmp(lang, otherlang) == 0)
            found = true;
    }
 
    if (!found)
        ereport(elevel,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("ICU locale \"%s\" has unknown language \"%s\"",
                        loc_str, lang),
                 errhint("To disable ICU locale validation, set the parameter \"%s\" to \"%s\".",
                         "icu_validation_level", "disabled")));
 
    /* check that it can be opened */
    collator = pg_ucol_open(loc_str);
    ucol_close(collator);
#else                           /* not USE_ICU */
    /* 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")));
#endif                          /* not USE_ICU */
}