pg_locale_libc.c

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/*-----------------------------------------------------------------------
 *
 * PostgreSQL locale utilities for libc
 *
 * Portions Copyright (c) 2002-2025, PostgreSQL Global Development Group
 *
 * src/backend/utils/adt/pg_locale_libc.c
 *
 *-----------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include <limits.h>
#include <wctype.h>
 
#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"
 
#ifdef __GLIBC__
#include <gnu/libc-version.h>
#endif
 
#ifdef WIN32
#include <shlwapi.h>
#endif
 
/*
 * 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_libc(Oid collid, MemoryContext context);
 
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);
 
static int  strncoll_libc(const char *arg1, ssize_t len1,
                          const char *arg2, ssize_t len2,
                          pg_locale_t locale);
static size_t strnxfrm_libc(char *dest, size_t destsize,
                            const char *src, ssize_t srclen,
                            pg_locale_t locale);
extern char *get_collation_actual_version_libc(const char *collcollate);
static locale_t make_libc_collator(const char *collate,
                                   const char *ctype);
static void report_newlocale_failure(const char *localename);
 
#ifdef WIN32
static int  strncoll_libc_win32_utf8(const char *arg1, ssize_t len1,
                                     const char *arg2, ssize_t len2,
                                     pg_locale_t locale);
#endif
 
static size_t strlower_libc_sb(char *dest, size_t destsize,
                               const char *src, ssize_t srclen,
                               pg_locale_t locale);
static size_t strlower_libc_mb(char *dest, size_t destsize,
                               const char *src, ssize_t srclen,
                               pg_locale_t locale);
static size_t strtitle_libc_sb(char *dest, size_t destsize,
                               const char *src, ssize_t srclen,
                               pg_locale_t locale);
static size_t strtitle_libc_mb(char *dest, size_t destsize,
                               const char *src, ssize_t srclen,
                               pg_locale_t locale);
static size_t strupper_libc_sb(char *dest, size_t destsize,
                               const char *src, ssize_t srclen,
                               pg_locale_t locale);
static size_t strupper_libc_mb(char *dest, size_t destsize,
                               const char *src, ssize_t srclen,
                               pg_locale_t locale);
 
static const struct collate_methods collate_methods_libc = {
    .strncoll = strncoll_libc,
    .strnxfrm = strnxfrm_libc,
    .strnxfrm_prefix = NULL,
 
    /*
     * Unfortunately, it seems that strxfrm() for non-C collations is broken
     * on many common platforms; testing of multiple versions of glibc reveals
     * that, for many locales, strcoll() and strxfrm() do not return
     * consistent results. While no other libc other than Cygwin has so far
     * been shown to have a problem, we take the conservative course of action
     * for right now and disable this categorically.  (Users who are certain
     * this isn't a problem on their system can define TRUST_STRXFRM.)
     */
#ifdef TRUST_STRXFRM
    .strxfrm_is_safe = true,
#else
    .strxfrm_is_safe = false,
#endif
};
 
#ifdef WIN32
static const struct collate_methods collate_methods_libc_win32_utf8 = {
    .strncoll = strncoll_libc_win32_utf8,
    .strnxfrm = strnxfrm_libc,
    .strnxfrm_prefix = NULL,
#ifdef TRUST_STRXFRM
    .strxfrm_is_safe = true,
#else
    .strxfrm_is_safe = false,
#endif
};
#endif
 
size_t
strlower_libc(char *dst, size_t dstsize, const char *src,
              ssize_t srclen, pg_locale_t locale)
{
    if (pg_database_encoding_max_length() > 1)
        return strlower_libc_mb(dst, dstsize, src, srclen, locale);
    else
        return strlower_libc_sb(dst, dstsize, src, srclen, locale);
}
 
size_t
strtitle_libc(char *dst, size_t dstsize, const char *src,
              ssize_t srclen, pg_locale_t locale)
{
    if (pg_database_encoding_max_length() > 1)
        return strtitle_libc_mb(dst, dstsize, src, srclen, locale);
    else
        return strtitle_libc_sb(dst, dstsize, src, srclen, locale);
}
 
size_t
strupper_libc(char *dst, size_t dstsize, const char *src,
              ssize_t srclen, pg_locale_t locale)
{
    if (pg_database_encoding_max_length() > 1)
        return strupper_libc_mb(dst, dstsize, src, srclen, locale);
    else
        return strupper_libc_sb(dst, dstsize, src, srclen, locale);
}
 
static size_t
strlower_libc_sb(char *dest, size_t destsize, const char *src, ssize_t srclen,
                 pg_locale_t locale)
{
    if (srclen < 0)
        srclen = strlen(src);
 
    if (srclen + 1 <= destsize)
    {
        locale_t    loc = locale->info.lt;
        char       *p;
 
        if (srclen + 1 > destsize)
            return srclen;
 
        memcpy(dest, src, srclen);
        dest[srclen] = '\0';
 
        /*
         * Note: we assume that tolower_l() will not be so broken as to need
         * an isupper_l() guard test.  When using the default collation, we
         * apply the traditional Postgres behavior that forces ASCII-style
         * treatment of I/i, but in non-default collations you get exactly
         * what the collation says.
         */
        for (p = dest; *p; p++)
        {
            if (locale->is_default)
                *p = pg_tolower((unsigned char) *p);
            else
                *p = tolower_l((unsigned char) *p, loc);
        }
    }
 
    return srclen;
}
 
static size_t
strlower_libc_mb(char *dest, size_t destsize, const char *src, ssize_t srclen,
                 pg_locale_t locale)
{
    locale_t    loc = locale->info.lt;
    size_t      result_size;
    wchar_t    *workspace;
    char       *result;
    size_t      curr_char;
    size_t      max_size;
 
    if (srclen < 0)
        srclen = strlen(src);
 
    /* Overflow paranoia */
    if ((srclen + 1) > (INT_MAX / sizeof(wchar_t)))
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));
 
    /* Output workspace cannot have more codes than input bytes */
    workspace = (wchar_t *) palloc((srclen + 1) * sizeof(wchar_t));
 
    char2wchar(workspace, srclen + 1, src, srclen, locale);
 
    for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
        workspace[curr_char] = towlower_l(workspace[curr_char], loc);
 
    /*
     * Make result large enough; case change might change number of bytes
     */
    max_size = curr_char * pg_database_encoding_max_length();
    result = palloc(max_size + 1);
 
    result_size = wchar2char(result, workspace, max_size + 1, locale);
 
    if (result_size + 1 > destsize)
        return result_size;
 
    memcpy(dest, result, result_size);
    dest[result_size] = '\0';
 
    pfree(workspace);
    pfree(result);
 
    return result_size;
}
 
static size_t
strtitle_libc_sb(char *dest, size_t destsize, const char *src, ssize_t srclen,
                 pg_locale_t locale)
{
    if (srclen < 0)
        srclen = strlen(src);
 
    if (srclen + 1 <= destsize)
    {
        locale_t    loc = locale->info.lt;
        int         wasalnum = false;
        char       *p;
 
        memcpy(dest, src, srclen);
        dest[srclen] = '\0';
 
        /*
         * Note: we assume that toupper_l()/tolower_l() will not be so broken
         * as to need guard tests.  When using the default collation, we apply
         * the traditional Postgres behavior that forces ASCII-style treatment
         * of I/i, but in non-default collations you get exactly what the
         * collation says.
         */
        for (p = dest; *p; p++)
        {
            if (locale->is_default)
            {
                if (wasalnum)
                    *p = pg_tolower((unsigned char) *p);
                else
                    *p = pg_toupper((unsigned char) *p);
            }
            else
            {
                if (wasalnum)
                    *p = tolower_l((unsigned char) *p, loc);
                else
                    *p = toupper_l((unsigned char) *p, loc);
            }
            wasalnum = isalnum_l((unsigned char) *p, loc);
        }
    }
 
    return srclen;
}
 
static size_t
strtitle_libc_mb(char *dest, size_t destsize, const char *src, ssize_t srclen,
                 pg_locale_t locale)
{
    locale_t    loc = locale->info.lt;
    int         wasalnum = false;
    size_t      result_size;
    wchar_t    *workspace;
    char       *result;
    size_t      curr_char;
    size_t      max_size;
 
    if (srclen < 0)
        srclen = strlen(src);
 
    /* Overflow paranoia */
    if ((srclen + 1) > (INT_MAX / sizeof(wchar_t)))
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));
 
    /* Output workspace cannot have more codes than input bytes */
    workspace = (wchar_t *) palloc((srclen + 1) * sizeof(wchar_t));
 
    char2wchar(workspace, srclen + 1, src, srclen, locale);
 
    for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
    {
        if (wasalnum)
            workspace[curr_char] = towlower_l(workspace[curr_char], loc);
        else
            workspace[curr_char] = towupper_l(workspace[curr_char], loc);
        wasalnum = iswalnum_l(workspace[curr_char], loc);
    }
 
    /*
     * Make result large enough; case change might change number of bytes
     */
    max_size = curr_char * pg_database_encoding_max_length();
    result = palloc(max_size + 1);
 
    result_size = wchar2char(result, workspace, max_size + 1, locale);
 
    if (result_size + 1 > destsize)
        return result_size;
 
    memcpy(dest, result, result_size);
    dest[result_size] = '\0';
 
    pfree(workspace);
    pfree(result);
 
    return result_size;
}
 
static size_t
strupper_libc_sb(char *dest, size_t destsize, const char *src, ssize_t srclen,
                 pg_locale_t locale)
{
    if (srclen < 0)
        srclen = strlen(src);
 
    if (srclen + 1 <= destsize)
    {
        locale_t    loc = locale->info.lt;
        char       *p;
 
        memcpy(dest, src, srclen);
        dest[srclen] = '\0';
 
        /*
         * Note: we assume that toupper_l() will not be so broken as to need
         * an islower_l() guard test.  When using the default collation, we
         * apply the traditional Postgres behavior that forces ASCII-style
         * treatment of I/i, but in non-default collations you get exactly
         * what the collation says.
         */
        for (p = dest; *p; p++)
        {
            if (locale->is_default)
                *p = pg_toupper((unsigned char) *p);
            else
                *p = toupper_l((unsigned char) *p, loc);
        }
    }
 
    return srclen;
}
 
static size_t
strupper_libc_mb(char *dest, size_t destsize, const char *src, ssize_t srclen,
                 pg_locale_t locale)
{
    locale_t    loc = locale->info.lt;
    size_t      result_size;
    wchar_t    *workspace;
    char       *result;
    size_t      curr_char;
    size_t      max_size;
 
    if (srclen < 0)
        srclen = strlen(src);
 
    /* Overflow paranoia */
    if ((srclen + 1) > (INT_MAX / sizeof(wchar_t)))
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));
 
    /* Output workspace cannot have more codes than input bytes */
    workspace = (wchar_t *) palloc((srclen + 1) * sizeof(wchar_t));
 
    char2wchar(workspace, srclen + 1, src, srclen, locale);
 
    for (curr_char = 0; workspace[curr_char] != 0; curr_char++)
        workspace[curr_char] = towupper_l(workspace[curr_char], loc);
 
    /*
     * Make result large enough; case change might change number of bytes
     */
    max_size = curr_char * pg_database_encoding_max_length();
    result = palloc(max_size + 1);
 
    result_size = wchar2char(result, workspace, max_size + 1, locale);
 
    if (result_size + 1 > destsize)
        return result_size;
 
    memcpy(dest, result, result_size);
    dest[result_size] = '\0';
 
    pfree(workspace);
    pfree(result);
 
    return result_size;
}
 
pg_locale_t
create_pg_locale_libc(Oid collid, MemoryContext context)
{
    const char *collate;
    const char *ctype;
    locale_t    loc;
    pg_locale_t result;
 
    if (collid == DEFAULT_COLLATION_OID)
    {
        HeapTuple   tp;
        Datum       datum;
 
        tp = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(MyDatabaseId));
        if (!HeapTupleIsValid(tp))
            elog(ERROR, "cache lookup failed for database %u", MyDatabaseId);
        datum = SysCacheGetAttrNotNull(DATABASEOID, tp,
                                       Anum_pg_database_datcollate);
        collate = TextDatumGetCString(datum);
        datum = SysCacheGetAttrNotNull(DATABASEOID, tp,
                                       Anum_pg_database_datctype);
        ctype = TextDatumGetCString(datum);
 
        ReleaseSysCache(tp);
    }
    else
    {
        HeapTuple   tp;
        Datum       datum;
 
        tp = SearchSysCache1(COLLOID, ObjectIdGetDatum(collid));
        if (!HeapTupleIsValid(tp))
            elog(ERROR, "cache lookup failed for collation %u", collid);
 
        datum = SysCacheGetAttrNotNull(COLLOID, tp,
                                       Anum_pg_collation_collcollate);
        collate = TextDatumGetCString(datum);
        datum = SysCacheGetAttrNotNull(COLLOID, tp,
                                       Anum_pg_collation_collctype);
        ctype = TextDatumGetCString(datum);
 
        ReleaseSysCache(tp);
    }
 
 
    loc = make_libc_collator(collate, ctype);
 
    result = MemoryContextAllocZero(context, sizeof(struct pg_locale_struct));
    result->provider = COLLPROVIDER_LIBC;
    result->deterministic = true;
    result->collate_is_c = (strcmp(collate, "C") == 0) ||
        (strcmp(collate, "POSIX") == 0);
    result->ctype_is_c = (strcmp(ctype, "C") == 0) ||
        (strcmp(ctype, "POSIX") == 0);
    result->info.lt = loc;
    if (!result->collate_is_c)
    {
#ifdef WIN32
        if (GetDatabaseEncoding() == PG_UTF8)
            result->collate = &collate_methods_libc_win32_utf8;
        else
#endif
            result->collate = &collate_methods_libc;
    }
 
    return result;
}
 
/*
 * Create a locale_t with the given collation and ctype.
 *
 * The "C" and "POSIX" locales are not actually handled by libc, so return
 * NULL.
 *
 * Ensure that no path leaks a locale_t.
 */
static locale_t
make_libc_collator(const char *collate, const char *ctype)
{
    locale_t    loc = 0;
 
    if (strcmp(collate, ctype) == 0)
    {
        if (strcmp(ctype, "C") != 0 && strcmp(ctype, "POSIX") != 0)
        {
            /* Normal case where they're the same */
            errno = 0;
#ifndef WIN32
            loc = newlocale(LC_COLLATE_MASK | LC_CTYPE_MASK, collate,
                            NULL);
#else
            loc = _create_locale(LC_ALL, collate);
#endif
            if (!loc)
                report_newlocale_failure(collate);
        }
    }
    else
    {
#ifndef WIN32
        /* We need two newlocale() steps */
        locale_t    loc1 = 0;
 
        if (strcmp(collate, "C") != 0 && strcmp(collate, "POSIX") != 0)
        {
            errno = 0;
            loc1 = newlocale(LC_COLLATE_MASK, collate, NULL);
            if (!loc1)
                report_newlocale_failure(collate);
        }
 
        if (strcmp(ctype, "C") != 0 && strcmp(ctype, "POSIX") != 0)
        {
            errno = 0;
            loc = newlocale(LC_CTYPE_MASK, ctype, loc1);
            if (!loc)
            {
                if (loc1)
                    freelocale(loc1);
                report_newlocale_failure(ctype);
            }
        }
        else
            loc = loc1;
#else
 
        /*
         * XXX The _create_locale() API doesn't appear to support this. Could
         * perhaps be worked around by changing pg_locale_t to contain two
         * separate fields.
         */
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("collations with different collate and ctype values are not supported on this platform")));
#endif
    }
 
    return loc;
}
 
/*
 * strncoll_libc
 *
 * NUL-terminate arguments, if necessary, and pass to strcoll_l().
 *
 * An input string length of -1 means that it's already NUL-terminated.
 */
int
strncoll_libc(const char *arg1, ssize_t len1, const char *arg2, ssize_t len2,
              pg_locale_t locale)
{
    char        sbuf[TEXTBUFLEN];
    char       *buf = sbuf;
    size_t      bufsize1 = (len1 == -1) ? 0 : len1 + 1;
    size_t      bufsize2 = (len2 == -1) ? 0 : len2 + 1;
    const char *arg1n;
    const char *arg2n;
    int         result;
 
    Assert(locale->provider == COLLPROVIDER_LIBC);
 
    if (bufsize1 + bufsize2 > TEXTBUFLEN)
        buf = palloc(bufsize1 + bufsize2);
 
    /* nul-terminate arguments if necessary */
    if (len1 == -1)
    {
        arg1n = arg1;
    }
    else
    {
        char       *buf1 = buf;
 
        memcpy(buf1, arg1, len1);
        buf1[len1] = '\0';
        arg1n = buf1;
    }
 
    if (len2 == -1)
    {
        arg2n = arg2;
    }
    else
    {
        char       *buf2 = buf + bufsize1;
 
        memcpy(buf2, arg2, len2);
        buf2[len2] = '\0';
        arg2n = buf2;
    }
 
    result = strcoll_l(arg1n, arg2n, locale->info.lt);
 
    if (buf != sbuf)
        pfree(buf);
 
    return result;
}
 
/*
 * strnxfrm_libc
 *
 * NUL-terminate src, if necessary, and pass to strxfrm_l().
 *
 * A source length of -1 means that it's already NUL-terminated.
 */
size_t
strnxfrm_libc(char *dest, size_t destsize, const char *src, ssize_t srclen,
              pg_locale_t locale)
{
    char        sbuf[TEXTBUFLEN];
    char       *buf = sbuf;
    size_t      bufsize = srclen + 1;
    size_t      result;
 
    Assert(locale->provider == COLLPROVIDER_LIBC);
 
    if (srclen == -1)
        return strxfrm_l(dest, src, destsize, locale->info.lt);
 
    if (bufsize > TEXTBUFLEN)
        buf = palloc(bufsize);
 
    /* nul-terminate argument */
    memcpy(buf, src, srclen);
    buf[srclen] = '\0';
 
    result = strxfrm_l(dest, buf, destsize, locale->info.lt);
 
    if (buf != sbuf)
        pfree(buf);
 
    /* if dest is defined, it should be nul-terminated */
    Assert(result >= destsize || dest[result] == '\0');
 
    return result;
}
 
char *
get_collation_actual_version_libc(const char *collcollate)
{
    char       *collversion = NULL;
 
    if (pg_strcasecmp("C", collcollate) != 0 &&
        pg_strncasecmp("C.", collcollate, 2) != 0 &&
        pg_strcasecmp("POSIX", collcollate) != 0)
    {
#if defined(__GLIBC__)
        /* Use the glibc version because we don't have anything better. */
        collversion = pstrdup(gnu_get_libc_version());
#elif defined(LC_VERSION_MASK)
        locale_t    loc;
 
        /* Look up FreeBSD collation version. */
        loc = newlocale(LC_COLLATE_MASK, collcollate, NULL);
        if (loc)
        {
            collversion =
                pstrdup(querylocale(LC_COLLATE_MASK | LC_VERSION_MASK, loc));
            freelocale(loc);
        }
        else
            ereport(ERROR,
                    (errmsg("could not load locale \"%s\"", collcollate)));
#elif defined(WIN32)
        /*
         * If we are targeting Windows Vista and above, we can ask for a name
         * given a collation name (earlier versions required a location code
         * that we don't have).
         */
        NLSVERSIONINFOEX version = {sizeof(NLSVERSIONINFOEX)};
        WCHAR       wide_collcollate[LOCALE_NAME_MAX_LENGTH];
 
        MultiByteToWideChar(CP_ACP, 0, collcollate, -1, wide_collcollate,
                            LOCALE_NAME_MAX_LENGTH);
        if (!GetNLSVersionEx(COMPARE_STRING, wide_collcollate, &version))
        {
            /*
             * GetNLSVersionEx() wants a language tag such as "en-US", not a
             * locale name like "English_United States.1252".  Until those
             * values can be prevented from entering the system, or 100%
             * reliably converted to the more useful tag format, tolerate the
             * resulting error and report that we have no version data.
             */
            if (GetLastError() == ERROR_INVALID_PARAMETER)
                return NULL;
 
            ereport(ERROR,
                    (errmsg("could not get collation version for locale \"%s\": error code %lu",
                            collcollate,
                            GetLastError())));
        }
        collversion = psprintf("%lu.%lu,%lu.%lu",
                               (version.dwNLSVersion >> 8) & 0xFFFF,
                               version.dwNLSVersion & 0xFF,
                               (version.dwDefinedVersion >> 8) & 0xFFFF,
                               version.dwDefinedVersion & 0xFF);
#endif
    }
 
    return collversion;
}
 
/*
 * strncoll_libc_win32_utf8
 *
 * Win32 does not have UTF-8. Convert UTF8 arguments to wide characters and
 * invoke wcscoll_l().
 *
 * An input string length of -1 means that it's NUL-terminated.
 */
#ifdef WIN32
static int
strncoll_libc_win32_utf8(const char *arg1, ssize_t len1, const char *arg2,
                         ssize_t len2, pg_locale_t locale)
{
    char        sbuf[TEXTBUFLEN];
    char       *buf = sbuf;
    char       *a1p,
               *a2p;
    int         a1len;
    int         a2len;
    int         r;
    int         result;
 
    Assert(locale->provider == COLLPROVIDER_LIBC);
    Assert(GetDatabaseEncoding() == PG_UTF8);
 
    if (len1 == -1)
        len1 = strlen(arg1);
    if (len2 == -1)
        len2 = strlen(arg2);
 
    a1len = len1 * 2 + 2;
    a2len = len2 * 2 + 2;
 
    if (a1len + a2len > TEXTBUFLEN)
        buf = palloc(a1len + a2len);
 
    a1p = buf;
    a2p = buf + a1len;
 
    /* API does not work for zero-length input */
    if (len1 == 0)
        r = 0;
    else
    {
        r = MultiByteToWideChar(CP_UTF8, 0, arg1, len1,
                                (LPWSTR) a1p, a1len / 2);
        if (!r)
            ereport(ERROR,
                    (errmsg("could not convert string to UTF-16: error code %lu",
                            GetLastError())));
    }
    ((LPWSTR) a1p)[r] = 0;
 
    if (len2 == 0)
        r = 0;
    else
    {
        r = MultiByteToWideChar(CP_UTF8, 0, arg2, len2,
                                (LPWSTR) a2p, a2len / 2);
        if (!r)
            ereport(ERROR,
                    (errmsg("could not convert string to UTF-16: error code %lu",
                            GetLastError())));
    }
    ((LPWSTR) a2p)[r] = 0;
 
    errno = 0;
    result = wcscoll_l((LPWSTR) a1p, (LPWSTR) a2p, locale->info.lt);
    if (result == 2147483647)   /* _NLSCMPERROR; missing from mingw headers */
        ereport(ERROR,
                (errmsg("could not compare Unicode strings: %m")));
 
    if (buf != sbuf)
        pfree(buf);
 
    return result;
}
#endif                          /* WIN32 */
 
/* simple subroutine for reporting errors from newlocale() */
static void
report_newlocale_failure(const char *localename)
{
    int         save_errno;
 
    /*
     * Windows doesn't provide any useful error indication from
     * _create_locale(), and BSD-derived platforms don't seem to feel they
     * need to set errno either (even though POSIX is pretty clear that
     * newlocale should do so).  So, if errno hasn't been set, assume ENOENT
     * is what to report.
     */
    if (errno == 0)
        errno = ENOENT;
 
    /*
     * ENOENT means "no such locale", not "no such file", so clarify that
     * errno with an errdetail message.
     */
    save_errno = errno;         /* auxiliary funcs might change errno */
    ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
             errmsg("could not create locale \"%s\": %m",
                    localename),
             (save_errno == ENOENT ?
              errdetail("The operating system could not find any locale data for the locale name \"%s\".",
                        localename) : 0)));
}
 
/*
 * POSIX doesn't define _l-variants of these functions, but several systems
 * have them.  We provide our own replacements here.
 */
#ifndef HAVE_MBSTOWCS_L
static size_t
mbstowcs_l(wchar_t *dest, const char *src, size_t n, locale_t loc)
{
#ifdef WIN32
    return _mbstowcs_l(dest, src, n, loc);
#else
    size_t      result;
    locale_t    save_locale = uselocale(loc);
 
    result = mbstowcs(dest, src, n);
    uselocale(save_locale);
    return result;
#endif
}
#endif
#ifndef HAVE_WCSTOMBS_L
static size_t
wcstombs_l(char *dest, const wchar_t *src, size_t n, locale_t loc)
{
#ifdef WIN32
    return _wcstombs_l(dest, src, n, loc);
#else
    size_t      result;
    locale_t    save_locale = uselocale(loc);
 
    result = wcstombs(dest, src, n);
    uselocale(save_locale);
    return result;
#endif
}
#endif
 
/*
 * These functions convert from/to libc's wchar_t, *not* pg_wchar_t.
 * Therefore we keep them here rather than with the mbutils code.
 */
 
/*
 * wchar2char --- convert wide characters to multibyte format
 *
 * This has the same API as the standard wcstombs_l() function; in particular,
 * tolen is the maximum number of bytes to store at *to, and *from must be
 * zero-terminated.  The output will be zero-terminated iff there is room.
 */
size_t
wchar2char(char *to, const wchar_t *from, size_t tolen, pg_locale_t locale)
{
    size_t      result;
 
    if (tolen == 0)
        return 0;
 
#ifdef WIN32
 
    /*
     * On Windows, the "Unicode" locales assume UTF16 not UTF8 encoding, and
     * for some reason mbstowcs and wcstombs won't do this for us, so we use
     * MultiByteToWideChar().
     */
    if (GetDatabaseEncoding() == PG_UTF8)
    {
        result = WideCharToMultiByte(CP_UTF8, 0, from, -1, to, tolen,
                                     NULL, NULL);
        /* A zero return is failure */
        if (result <= 0)
            result = -1;
        else
        {
            Assert(result <= tolen);
            /* Microsoft counts the zero terminator in the result */
            result--;
        }
    }
    else
#endif                          /* WIN32 */
    if (locale == (pg_locale_t) 0)
    {
        /* Use wcstombs directly for the default locale */
        result = wcstombs(to, from, tolen);
    }
    else
    {
        /* Use wcstombs_l for nondefault locales */
        result = wcstombs_l(to, from, tolen, locale->info.lt);
    }
 
    return result;
}
 
/*
 * char2wchar --- convert multibyte characters to wide characters
 *
 * This has almost the API of mbstowcs_l(), except that *from need not be
 * null-terminated; instead, the number of input bytes is specified as
 * fromlen.  Also, we ereport() rather than returning -1 for invalid
 * input encoding.  tolen is the maximum number of wchar_t's to store at *to.
 * The output will be zero-terminated iff there is room.
 */
size_t
char2wchar(wchar_t *to, size_t tolen, const char *from, size_t fromlen,
           pg_locale_t locale)
{
    size_t      result;
 
    if (tolen == 0)
        return 0;
 
#ifdef WIN32
    /* See WIN32 "Unicode" comment above */
    if (GetDatabaseEncoding() == PG_UTF8)
    {
        /* Win32 API does not work for zero-length input */
        if (fromlen == 0)
            result = 0;
        else
        {
            result = MultiByteToWideChar(CP_UTF8, 0, from, fromlen, to, tolen - 1);
            /* A zero return is failure */
            if (result == 0)
                result = -1;
        }
 
        if (result != -1)
        {
            Assert(result < tolen);
            /* Append trailing null wchar (MultiByteToWideChar() does not) */
            to[result] = 0;
        }
    }
    else
#endif                          /* WIN32 */
    {
        /* mbstowcs requires ending '\0' */
        char       *str = pnstrdup(from, fromlen);
 
        if (locale == (pg_locale_t) 0)
        {
            /* Use mbstowcs directly for the default locale */
            result = mbstowcs(to, str, tolen);
        }
        else
        {
            /* Use mbstowcs_l for nondefault locales */
            result = mbstowcs_l(to, str, tolen, locale->info.lt);
        }
 
        pfree(str);
    }
 
    if (result == -1)
    {
        /*
         * Invalid multibyte character encountered.  We try to give a useful
         * error message by letting pg_verifymbstr check the string.  But it's
         * possible that the string is OK to us, and not OK to mbstowcs ---
         * this suggests that the LC_CTYPE locale is different from the
         * database encoding.  Give a generic error message if pg_verifymbstr
         * can't find anything wrong.
         */
        pg_verifymbstr(from, fromlen, false);   /* might not return */
        /* but if it does ... */
        ereport(ERROR,
                (errcode(ERRCODE_CHARACTER_NOT_IN_REPERTOIRE),
                 errmsg("invalid multibyte character for locale"),
                 errhint("The server's LC_CTYPE locale is probably incompatible with the database encoding.")));
    }
 
    return result;
}