Work properly under UTF-8 LC_CTYPE locales

[perl5.git] / locale.c

/*    locale.c
 *
 *    Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
 *    2002, 2003, 2005, 2006, 2007, 2008 by Larry Wall and others
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 */

/*
 *      A Elbereth Gilthoniel,
 *      silivren penna míriel
 *      o menel aglar elenath!
 *      Na-chaered palan-díriel
 *      o galadhremmin ennorath,
 *      Fanuilos, le linnathon
 *      nef aear, si nef aearon!
 *
 *     [p.238 of _The Lord of the Rings_, II/i: "Many Meetings"]
 */

/* utility functions for handling locale-specific stuff like what
 * character represents the decimal point.
 *
 * All C programs have an underlying locale.  Perl generally doesn't pay any
 * attention to it except within the scope of a 'use locale'.  For most
 * categories, it accomplishes this by just using different operations if it is
 * in such scope than if not.  However, various libc functions called by Perl
 * are affected by the LC_NUMERIC category, so there are macros in perl.h that
 * are used to toggle between the current locale and the C locale depending on
 * the desired behavior of those functions at the moment.
 */

#include "EXTERN.h"
#define PERL_IN_LOCALE_C
#include "perl.h"

#ifdef I_LANGINFO
#   include <langinfo.h>
#endif

#include "reentr.h"

#ifdef USE_LOCALE

/*
 * Standardize the locale name from a string returned by 'setlocale', possibly
 * modifying that string.
 *
 * The typical return value of setlocale() is either
 * (1) "xx_YY" if the first argument of setlocale() is not LC_ALL
 * (2) "xa_YY xb_YY ..." if the first argument of setlocale() is LC_ALL
 *     (the space-separated values represent the various sublocales,
 *      in some unspecified order).  This is not handled by this function.
 *
 * In some platforms it has a form like "LC_SOMETHING=Lang_Country.866\n",
 * which is harmful for further use of the string in setlocale().  This
 * function removes the trailing new line and everything up through the '='
 *
 */
STATIC char *
S_stdize_locale(pTHX_ char *locs)
{
    const char * const s = strchr(locs, '=');
    bool okay = TRUE;

    PERL_ARGS_ASSERT_STDIZE_LOCALE;

    if (s) {
	const char * const t = strchr(s, '.');
	okay = FALSE;
	if (t) {
	    const char * const u = strchr(t, '\n');
	    if (u && (u[1] == 0)) {
		const STRLEN len = u - s;
		Move(s + 1, locs, len, char);
		locs[len] = 0;
		okay = TRUE;
	    }
	}
    }

    if (!okay)
	Perl_croak(aTHX_ "Can't fix broken locale name \"%s\"", locs);

    return locs;
}

#endif

void
Perl_set_numeric_radix(pTHX)
{
#ifdef USE_LOCALE_NUMERIC
    dVAR;
# ifdef HAS_LOCALECONV
    const struct lconv* const lc = localeconv();

    if (lc && lc->decimal_point) {
	if (lc->decimal_point[0] == '.' && lc->decimal_point[1] == 0) {
	    SvREFCNT_dec(PL_numeric_radix_sv);
	    PL_numeric_radix_sv = NULL;
	}
	else {
	    if (PL_numeric_radix_sv)
		sv_setpv(PL_numeric_radix_sv, lc->decimal_point);
	    else
		PL_numeric_radix_sv = newSVpv(lc->decimal_point, 0);
            if (! is_ascii_string((U8 *) lc->decimal_point, 0)
                && is_utf8_string((U8 *) lc->decimal_point, 0)
                && is_cur_LC_category_utf8(LC_NUMERIC))
            {
		SvUTF8_on(PL_numeric_radix_sv);
            }
	}
    }
    else
	PL_numeric_radix_sv = NULL;
# endif /* HAS_LOCALECONV */
#endif /* USE_LOCALE_NUMERIC */
}

void
Perl_new_numeric(pTHX_ const char *newnum)
{
#ifdef USE_LOCALE_NUMERIC

    /* Called after all libc setlocale() calls affecting LC_NUMERIC, to tell
     * core Perl this and that 'newnum' is the name of the new locale.
     * It installs this locale as the current underlying default.
     *
     * The default locale and the C locale can be toggled between by use of the
     * set_numeric_local() and set_numeric_standard() functions, which should
     * probably not be called directly, but only via macros like
     * SET_NUMERIC_STANDARD() in perl.h.
     *
     * The toggling is necessary mainly so that a non-dot radix decimal point
     * character can be output, while allowing internal calculations to use a
     * dot.
     *
     * This sets several interpreter-level variables:
     * PL_numeric_name  The default locale's name: a copy of 'newnum'
     * PL_numeric_local A boolean indicating if the toggled state is such
     *                  that the current locale is the default locale
     * PL_numeric_standard A boolean indicating if the toggled state is such
     *                  that the current locale is the C locale
     * Note that both of the last two variables can be true at the same time,
     * if the underlying locale is C.  (Toggling is a no-op under these
     * circumstances.)
     *
     * Any code changing the locale (outside this file) should use
     * POSIX::setlocale, which calls this function.  Therefore this function
     * should be called directly only from this file and from
     * POSIX::setlocale() */

    char *save_newnum;
    dVAR;

    if (! newnum) {
	Safefree(PL_numeric_name);
	PL_numeric_name = NULL;
	PL_numeric_standard = TRUE;
	PL_numeric_local = TRUE;
	return;
    }

    save_newnum = stdize_locale(savepv(newnum));
    if (! PL_numeric_name || strNE(PL_numeric_name, save_newnum)) {
	Safefree(PL_numeric_name);
	PL_numeric_name = save_newnum;
    }

    PL_numeric_standard = ((*save_newnum == 'C' && save_newnum[1] == '\0')
                            || strEQ(save_newnum, "POSIX"));
    PL_numeric_local = TRUE;
    set_numeric_radix();

#endif /* USE_LOCALE_NUMERIC */
}

void
Perl_set_numeric_standard(pTHX)
{
#ifdef USE_LOCALE_NUMERIC
    dVAR;

    /* Toggle the LC_NUMERIC locale to C, if not already there.  Probably
     * should use the macros like SET_NUMERIC_STANDARD() in perl.h instead of
     * calling this directly. */

    if (! PL_numeric_standard) {
	setlocale(LC_NUMERIC, "C");
	PL_numeric_standard = TRUE;
	PL_numeric_local = FALSE;
	set_numeric_radix();
    }

#endif /* USE_LOCALE_NUMERIC */
}

void
Perl_set_numeric_local(pTHX)
{
#ifdef USE_LOCALE_NUMERIC
    dVAR;

    /* Toggle the LC_NUMERIC locale to the current underlying default, if not
     * already there.  Probably should use the macros like SET_NUMERIC_LOCAL()
     * in perl.h instead of calling this directly. */

    if (! PL_numeric_local) {
	setlocale(LC_NUMERIC, PL_numeric_name);
	PL_numeric_standard = FALSE;
	PL_numeric_local = TRUE;
	set_numeric_radix();
    }

#endif /* USE_LOCALE_NUMERIC */
}

/*
 * Set up for a new ctype locale.
 */
void
Perl_new_ctype(pTHX_ const char *newctype)
{
#ifdef USE_LOCALE_CTYPE

    /* Called after all libc setlocale() calls affecting LC_CTYPE, to tell
     * core Perl this and that 'newctype' is the name of the new locale.
     *
     * This function sets up the folding arrays for all 256 bytes, assuming
     * that tofold() is tolc() since fold case is not a concept in POSIX,
     *
     * Any code changing the locale (outside this file) should use
     * POSIX::setlocale, which calls this function.  Therefore this function
     * should be called directly only from this file and from
     * POSIX::setlocale() */

    dVAR;
    UV i;

    PERL_ARGS_ASSERT_NEW_CTYPE;

    PL_in_utf8_CTYPE_locale = is_cur_LC_category_utf8(LC_CTYPE);

    /* A UTF-8 locale gets standard rules.  But note that code still has to
     * handle this specially because of the three problematic code points */
    if (PL_in_utf8_CTYPE_locale) {
        Copy(PL_fold_latin1, PL_fold_locale, 256, U8);
    }
    else {

    for (i = 0; i < 256; i++) {
	if (isUPPER_LC((U8) i))
	    PL_fold_locale[i] = (U8) toLOWER_LC((U8) i);
	else if (isLOWER_LC((U8) i))
	    PL_fold_locale[i] = (U8) toUPPER_LC((U8) i);
	else
	    PL_fold_locale[i] = (U8) i;
    }
    }

#endif /* USE_LOCALE_CTYPE */
    PERL_ARGS_ASSERT_NEW_CTYPE;
    PERL_UNUSED_ARG(newctype);
    PERL_UNUSED_CONTEXT;
}

void
Perl_new_collate(pTHX_ const char *newcoll)
{
#ifdef USE_LOCALE_COLLATE

    /* Called after all libc setlocale() calls affecting LC_COLLATE, to tell
     * core Perl this and that 'newcoll' is the name of the new locale.
     *
     * Any code changing the locale (outside this file) should use
     * POSIX::setlocale, which calls this function.  Therefore this function
     * should be called directly only from this file and from
     * POSIX::setlocale() */

    dVAR;

    if (! newcoll) {
	if (PL_collation_name) {
	    ++PL_collation_ix;
	    Safefree(PL_collation_name);
	    PL_collation_name = NULL;
	}
	PL_collation_standard = TRUE;
	PL_collxfrm_base = 0;
	PL_collxfrm_mult = 2;
	return;
    }

    if (! PL_collation_name || strNE(PL_collation_name, newcoll)) {
	++PL_collation_ix;
	Safefree(PL_collation_name);
	PL_collation_name = stdize_locale(savepv(newcoll));
	PL_collation_standard = ((*newcoll == 'C' && newcoll[1] == '\0')
				 || strEQ(newcoll, "POSIX"));

	{
	  /*  2: at most so many chars ('a', 'b'). */
	  /* 50: surely no system expands a char more. */
#define XFRMBUFSIZE  (2 * 50)
	  char xbuf[XFRMBUFSIZE];
	  const Size_t fa = strxfrm(xbuf, "a",  XFRMBUFSIZE);
	  const Size_t fb = strxfrm(xbuf, "ab", XFRMBUFSIZE);
	  const SSize_t mult = fb - fa;
	  if (mult < 1 && !(fa == 0 && fb == 0))
	      Perl_croak(aTHX_ "panic: strxfrm() gets absurd - a => %"UVuf", ab => %"UVuf,
			 (UV) fa, (UV) fb);
	  PL_collxfrm_base = (fa > (Size_t)mult) ? (fa - mult) : 0;
	  PL_collxfrm_mult = mult;
	}
    }

#endif /* USE_LOCALE_COLLATE */
}

/*
 * Initialize locale awareness.
 */
int
Perl_init_i18nl10n(pTHX_ int printwarn)
{
    int ok = 1;
    /* returns
     *    1 = set ok or not applicable,
     *    0 = fallback to C locale,
     *   -1 = fallback to C locale failed
     */

#if defined(USE_LOCALE)
    dVAR;

#ifdef USE_LOCALE_CTYPE
    char *curctype   = NULL;
#endif /* USE_LOCALE_CTYPE */
#ifdef USE_LOCALE_COLLATE
    char *curcoll    = NULL;
#endif /* USE_LOCALE_COLLATE */
#ifdef USE_LOCALE_NUMERIC
    char *curnum     = NULL;
#endif /* USE_LOCALE_NUMERIC */
#ifdef __GLIBC__
    char * const language   = PerlEnv_getenv("LANGUAGE");
#endif
    /* NULL uses the existing already set up locale */
    const char * const setlocale_init = (PerlEnv_getenv("PERL_SKIP_LOCALE_INIT"))
                                        ? NULL
                                        : "";
    char * const lc_all     = PerlEnv_getenv("LC_ALL");
    char * const lang       = PerlEnv_getenv("LANG");
    bool setlocale_failure = FALSE;

#ifdef LOCALE_ENVIRON_REQUIRED

    /*
     * Ultrix setlocale(..., "") fails if there are no environment
     * variables from which to get a locale name.
     */

    bool done = FALSE;

#   ifdef LC_ALL
    if (lang) {
	if (setlocale(LC_ALL, setlocale_init))
	    done = TRUE;
	else
	    setlocale_failure = TRUE;
    }
    if (!setlocale_failure) {
#       ifdef USE_LOCALE_CTYPE
	Safefree(curctype);
	if (! (curctype =
	       setlocale(LC_CTYPE,
			 (!done && (lang || PerlEnv_getenv("LC_CTYPE")))
				    ? setlocale_init : NULL)))
	    setlocale_failure = TRUE;
	else
	    curctype = savepv(curctype);
#       endif /* USE_LOCALE_CTYPE */
#       ifdef USE_LOCALE_COLLATE
	Safefree(curcoll);
	if (! (curcoll =
	       setlocale(LC_COLLATE,
			 (!done && (lang || PerlEnv_getenv("LC_COLLATE")))
				   ? setlocale_init : NULL)))
	    setlocale_failure = TRUE;
	else
	    curcoll = savepv(curcoll);
#       endif /* USE_LOCALE_COLLATE */
#       ifdef USE_LOCALE_NUMERIC
	Safefree(curnum);
	if (! (curnum =
	       setlocale(LC_NUMERIC,
			 (!done && (lang || PerlEnv_getenv("LC_NUMERIC")))
				  ? setlocale_init : NULL)))
	    setlocale_failure = TRUE;
	else
	    curnum = savepv(curnum);
#       endif /* USE_LOCALE_NUMERIC */
    }

#   endif /* LC_ALL */

#endif /* !LOCALE_ENVIRON_REQUIRED */

#ifdef LC_ALL
    if (! setlocale(LC_ALL, setlocale_init))
	setlocale_failure = TRUE;
#endif /* LC_ALL */

    if (!setlocale_failure) {
#ifdef USE_LOCALE_CTYPE
	Safefree(curctype);
	if (! (curctype = setlocale(LC_CTYPE, setlocale_init)))
	    setlocale_failure = TRUE;
	else
	    curctype = savepv(curctype);
#endif /* USE_LOCALE_CTYPE */
#ifdef USE_LOCALE_COLLATE
	Safefree(curcoll);
	if (! (curcoll = setlocale(LC_COLLATE, setlocale_init)))
	    setlocale_failure = TRUE;
	else
	    curcoll = savepv(curcoll);
#endif /* USE_LOCALE_COLLATE */
#ifdef USE_LOCALE_NUMERIC
	Safefree(curnum);
	if (! (curnum = setlocale(LC_NUMERIC, setlocale_init)))
	    setlocale_failure = TRUE;
	else
	    curnum = savepv(curnum);
#endif /* USE_LOCALE_NUMERIC */
    }

    if (setlocale_failure) {
	char *p;
	const bool locwarn = (printwarn > 1 ||
			(printwarn &&
			 (!(p = PerlEnv_getenv("PERL_BADLANG")) || atoi(p))));

	if (locwarn) {
#ifdef LC_ALL

	    PerlIO_printf(Perl_error_log,
	       "perl: warning: Setting locale failed.\n");

#else /* !LC_ALL */

	    PerlIO_printf(Perl_error_log,
	       "perl: warning: Setting locale failed for the categories:\n\t");
#ifdef USE_LOCALE_CTYPE
	    if (! curctype)
		PerlIO_printf(Perl_error_log, "LC_CTYPE ");
#endif /* USE_LOCALE_CTYPE */
#ifdef USE_LOCALE_COLLATE
	    if (! curcoll)
		PerlIO_printf(Perl_error_log, "LC_COLLATE ");
#endif /* USE_LOCALE_COLLATE */
#ifdef USE_LOCALE_NUMERIC
	    if (! curnum)
		PerlIO_printf(Perl_error_log, "LC_NUMERIC ");
#endif /* USE_LOCALE_NUMERIC */
	    PerlIO_printf(Perl_error_log, "\n");

#endif /* LC_ALL */

	    PerlIO_printf(Perl_error_log,
		"perl: warning: Please check that your locale settings:\n");

#ifdef __GLIBC__
	    PerlIO_printf(Perl_error_log,
			  "\tLANGUAGE = %c%s%c,\n",
			  language ? '"' : '(',
			  language ? language : "unset",
			  language ? '"' : ')');
#endif

	    PerlIO_printf(Perl_error_log,
			  "\tLC_ALL = %c%s%c,\n",
			  lc_all ? '"' : '(',
			  lc_all ? lc_all : "unset",
			  lc_all ? '"' : ')');

#if defined(USE_ENVIRON_ARRAY)
	    {
	      char **e;
	      for (e = environ; *e; e++) {
		  if (strnEQ(*e, "LC_", 3)
			&& strnNE(*e, "LC_ALL=", 7)
			&& (p = strchr(*e, '=')))
		      PerlIO_printf(Perl_error_log, "\t%.*s = \"%s\",\n",
				    (int)(p - *e), *e, p + 1);
	      }
	    }
#else
	    PerlIO_printf(Perl_error_log,
			  "\t(possibly more locale environment variables)\n");
#endif

	    PerlIO_printf(Perl_error_log,
			  "\tLANG = %c%s%c\n",
			  lang ? '"' : '(',
			  lang ? lang : "unset",
			  lang ? '"' : ')');

	    PerlIO_printf(Perl_error_log,
			  "    are supported and installed on your system.\n");
	}

#ifdef LC_ALL

	if (setlocale(LC_ALL, "C")) {
	    if (locwarn)
		PerlIO_printf(Perl_error_log,
      "perl: warning: Falling back to the standard locale (\"C\").\n");
	    ok = 0;
	}
	else {
	    if (locwarn)
		PerlIO_printf(Perl_error_log,
      "perl: warning: Failed to fall back to the standard locale (\"C\").\n");
	    ok = -1;
	}

#else /* ! LC_ALL */

	if (0
#ifdef USE_LOCALE_CTYPE
	    || !(curctype || setlocale(LC_CTYPE, "C"))
#endif /* USE_LOCALE_CTYPE */
#ifdef USE_LOCALE_COLLATE
	    || !(curcoll || setlocale(LC_COLLATE, "C"))
#endif /* USE_LOCALE_COLLATE */
#ifdef USE_LOCALE_NUMERIC
	    || !(curnum || setlocale(LC_NUMERIC, "C"))
#endif /* USE_LOCALE_NUMERIC */
	    )
	{
	    if (locwarn)
		PerlIO_printf(Perl_error_log,
      "perl: warning: Cannot fall back to the standard locale (\"C\").\n");
	    ok = -1;
	}

#endif /* ! LC_ALL */

#ifdef USE_LOCALE_CTYPE
	Safefree(curctype);
	curctype = savepv(setlocale(LC_CTYPE, NULL));
#endif /* USE_LOCALE_CTYPE */
#ifdef USE_LOCALE_COLLATE
	Safefree(curcoll);
	curcoll = savepv(setlocale(LC_COLLATE, NULL));
#endif /* USE_LOCALE_COLLATE */
#ifdef USE_LOCALE_NUMERIC
	Safefree(curnum);
	curnum = savepv(setlocale(LC_NUMERIC, NULL));
#endif /* USE_LOCALE_NUMERIC */
    }
    else {

#ifdef USE_LOCALE_CTYPE
    new_ctype(curctype);
#endif /* USE_LOCALE_CTYPE */

#ifdef USE_LOCALE_COLLATE
    new_collate(curcoll);
#endif /* USE_LOCALE_COLLATE */

#ifdef USE_LOCALE_NUMERIC
    new_numeric(curnum);
#endif /* USE_LOCALE_NUMERIC */

    }

#if defined(USE_PERLIO) && defined(USE_LOCALE_CTYPE)
    {
      /* Set PL_utf8locale to TRUE if using PerlIO _and_
         the current LC_CTYPE locale is UTF-8.
	 If PL_utf8locale and PL_unicode (set by -C or by $ENV{PERL_UNICODE})
         are true, perl.c:S_parse_body() will turn on the PerlIO :utf8 layer
	 on STDIN, STDOUT, STDERR, _and_ the default open discipline.
      */
        PL_utf8locale = is_cur_LC_category_utf8(LC_CTYPE);
    }
    /* Set PL_unicode to $ENV{PERL_UNICODE} if using PerlIO.
       This is an alternative to using the -C command line switch
       (the -C if present will override this). */
    {
	 const char *p = PerlEnv_getenv("PERL_UNICODE");
	 PL_unicode = p ? parse_unicode_opts(&p) : 0;
	 if (PL_unicode & PERL_UNICODE_UTF8CACHEASSERT_FLAG)
	     PL_utf8cache = -1;
    }
#endif

#ifdef USE_LOCALE_CTYPE
    Safefree(curctype);
#endif /* USE_LOCALE_CTYPE */
#ifdef USE_LOCALE_COLLATE
    Safefree(curcoll);
#endif /* USE_LOCALE_COLLATE */
#ifdef USE_LOCALE_NUMERIC
    Safefree(curnum);
#endif /* USE_LOCALE_NUMERIC */

#endif /* USE_LOCALE */

    return ok;
}

#ifdef USE_LOCALE_COLLATE

/*
 * mem_collxfrm() is a bit like strxfrm() but with two important
 * differences. First, it handles embedded NULs. Second, it allocates
 * a bit more memory than needed for the transformed data itself.
 * The real transformed data begins at offset sizeof(collationix).
 * Please see sv_collxfrm() to see how this is used.
 */

char *
Perl_mem_collxfrm(pTHX_ const char *s, STRLEN len, STRLEN *xlen)
{
    dVAR;
    char *xbuf;
    STRLEN xAlloc, xin, xout; /* xalloc is a reserved word in VC */

    PERL_ARGS_ASSERT_MEM_COLLXFRM;

    /* the first sizeof(collationix) bytes are used by sv_collxfrm(). */
    /* the +1 is for the terminating NUL. */

    xAlloc = sizeof(PL_collation_ix) + PL_collxfrm_base + (PL_collxfrm_mult * len) + 1;
    Newx(xbuf, xAlloc, char);
    if (! xbuf)
	goto bad;

    *(U32*)xbuf = PL_collation_ix;
    xout = sizeof(PL_collation_ix);
    for (xin = 0; xin < len; ) {
	Size_t xused;

	for (;;) {
	    xused = strxfrm(xbuf + xout, s + xin, xAlloc - xout);
	    if (xused >= PERL_INT_MAX)
		goto bad;
	    if ((STRLEN)xused < xAlloc - xout)
		break;
	    xAlloc = (2 * xAlloc) + 1;
	    Renew(xbuf, xAlloc, char);
	    if (! xbuf)
		goto bad;
	}

	xin += strlen(s + xin) + 1;
	xout += xused;

	/* Embedded NULs are understood but silently skipped
	 * because they make no sense in locale collation. */
    }

    xbuf[xout] = '\0';
    *xlen = xout - sizeof(PL_collation_ix);
    return xbuf;

  bad:
    Safefree(xbuf);
    *xlen = 0;
    return NULL;
}

#endif /* USE_LOCALE_COLLATE */

#ifdef USE_LOCALE

STATIC bool
S_is_cur_LC_category_utf8(pTHX_ int category)
{
    /* Returns TRUE if the current locale for 'category' is UTF-8; FALSE
     * otherwise. 'category' may not be LC_ALL.  If the platform doesn't have
     * nl_langinfo(), nor MB_CUR_MAX, this employs a heuristic, which hence
     * could give the wrong result.  It errs on the side of not being a UTF-8
     * locale. */

    char *save_input_locale = NULL;
    STRLEN final_pos;

#ifdef LC_ALL
    assert(category != LC_ALL);
#endif

    /* First dispose of the trivial cases */
    save_input_locale = setlocale(category, NULL);
    if (! save_input_locale) {
        return FALSE;   /* XXX maybe should croak */
    }
    save_input_locale = stdize_locale(savepv(save_input_locale));
    if ((*save_input_locale == 'C' && save_input_locale[1] == '\0')
        || strEQ(save_input_locale, "POSIX"))
    {
        Safefree(save_input_locale);
        return FALSE;
    }

#if defined(USE_LOCALE_CTYPE) && (defined(MB_CUR_MAX) || defined(HAS_NL_LANGINFO) && defined(CODESET))

    { /* Next try MB_CUR_MAX or nl_langinfo if available */

        char *save_ctype_locale = NULL;
        bool is_utf8;

        if (category != LC_CTYPE) { /* These work only on LC_CTYPE */

            /* Get the current LC_CTYPE locale */
            save_ctype_locale = stdize_locale(savepv(setlocale(LC_CTYPE, NULL)));
            if (! save_ctype_locale) {
                goto cant_use_nllanginfo;
            }

            /* If LC_CTYPE and the desired category use the same locale, this
             * means that finding the value for LC_CTYPE is the same as finding
             * the value for the desired category.  Otherwise, switch LC_CTYPE
             * to the desired category's locale */
            if (strEQ(save_ctype_locale, save_input_locale)) {
                Safefree(save_ctype_locale);
                save_ctype_locale = NULL;
            }
            else if (! setlocale(LC_CTYPE, save_input_locale)) {
                Safefree(save_ctype_locale);
                goto cant_use_nllanginfo;
            }
        }

        /* Here the current LC_CTYPE is set to the locale of the category whose
         * information is desired.  This means that MB_CUR_MAX and
         * nl_langinfo() should give the correct results */

#   ifdef MB_CUR_MAX

        /* If we switched LC_CTYPE, switch back */
        if (save_ctype_locale) {
            setlocale(LC_CTYPE, save_ctype_locale);
            Safefree(save_ctype_locale);
        }

        /* Standard UTF-8 needs at least 4 bytes to represent the maximum
         * Unicode code point.  Since UTF-8 is the only non-single byte
         * encoding we handle, we just say any such encoding is UTF-8, and if
         * turns out to be wrong, other things will fail */
        is_utf8 = MB_CUR_MAX >= 4;

        Safefree(save_input_locale);

#       ifdef HAS_MBTOWC

        /* ... But, most system that have MB_CUR_MAX will also have mbtowc(),
         * since they are both in the C99 standard.  We can feed a known byte
         * string to the latter function, and check that it gives the expected
         * result */
        if (is_utf8) {
            wchar_t wc;
            if (mbtowc(&wc, HYPHEN_UTF8, strlen(HYPHEN_UTF8))
                                                        != strlen(HYPHEN_UTF8)
                || wc != (wchar_t) 0x2010)
            {
                is_utf8 = FALSE;
            }
        }

#       endif

        return is_utf8;
#else
#   if defined(HAS_NL_LANGINFO) && defined(CODESET)
        {
            char *codeset = savepv(nl_langinfo(CODESET));
            if (codeset) {

                /* If we switched LC_CTYPE, switch back */
                if (save_ctype_locale) {
                    setlocale(LC_CTYPE, save_ctype_locale);
                    Safefree(save_ctype_locale);
                }

                is_utf8 = foldEQ(codeset, STR_WITH_LEN("UTF-8"))
                        || foldEQ(codeset, STR_WITH_LEN("UTF8"));

                Safefree(codeset);
                Safefree(save_input_locale);
                return is_utf8;
            }
        }

#   endif
#   endif
    }

  cant_use_nllanginfo:

#endif /* HAS_NL_LANGINFO etc */

    /* nl_langinfo not available or failed somehow.  Look at the locale name to
     * see if it matches qr/UTF -? 8 /ix  */

    final_pos = strlen(save_input_locale) - 1;
    if (final_pos >= 3) {
        char *name = save_input_locale;

        /* Find next 'U' or 'u' and look from there */
        while ((name += strcspn(name, "Uu") + 1)
                                            <= save_input_locale + final_pos - 2)
        {
            if (toFOLD(*(name)) != 't'
                || toFOLD(*(name + 1)) != 'f')
            {
                continue;
            }
            name += 2;
            if (*(name) == '-') {
                if ((name > save_input_locale + final_pos - 1)) {
                    break;
                }
                name++;
            }
            if (*(name) == '8') {
                Safefree(save_input_locale);
                return TRUE;
            }
        }
    }

#ifdef WIN32
    /* http://msdn.microsoft.com/en-us/library/windows/desktop/dd317756.aspx */
    if (final_pos >= 4
        && *(save_input_locale + final_pos - 0) == '1'
        && *(save_input_locale + final_pos - 1) == '0'
        && *(save_input_locale + final_pos - 2) == '0'
        && *(save_input_locale + final_pos - 3) == '5'
        && *(save_input_locale + final_pos - 4) == '6')
    {
        Safefree(save_input_locale);
        return TRUE;
    }
#endif

    /* Other common encodings are the ISO 8859 series, which aren't UTF-8 */
    if (instr(save_input_locale, "8859")) {
        Safefree(save_input_locale);
        return FALSE;
    }

#ifdef HAS_LOCALECONV

#   ifdef USE_LOCALE_MONETARY

    /* Here, there is nothing in the locale name to indicate whether the locale
     * is UTF-8 or not.  This "name", the return of setlocale(), is actually
     * defined to be opaque, so we can't really rely on the absence of various
     * substrings in the name to indicate its UTF-8ness.  Look at the locale's
     * currency symbol.  Often that will be in the native script, and if the
     * symbol isn't in UTF-8, we know that the locale isn't.  If it is
     * non-ASCII UTF-8, we infer that the locale is too.
     * To do this, like above for LC_CTYPE, we first set LC_MONETARY to the
     * locale of the desired category, if it isn't that locale already */

    {
        char *save_monetary_locale = NULL;
        bool illegal_utf8 = FALSE;
        bool only_ascii = FALSE;
        const struct lconv* const lc = localeconv();

        if (category != LC_MONETARY) {

            save_monetary_locale = stdize_locale(savepv(setlocale(LC_MONETARY,
                                                                  NULL)));
            if (! save_monetary_locale) {
                goto cant_use_monetary;
            }

            if (strNE(save_monetary_locale, save_input_locale)) {
                if (! setlocale(LC_MONETARY, save_input_locale)) {
                    Safefree(save_monetary_locale);
                    goto cant_use_monetary;
                }
            }
        }

        /* Here the current LC_MONETARY is set to the locale of the category
         * whose information is desired. */

        if (lc && lc->currency_symbol) {
            if (! is_utf8_string((U8 *) lc->currency_symbol, 0)) {
                illegal_utf8 = TRUE;
            }
            else if (is_ascii_string((U8 *) lc->currency_symbol, 0)) {
                only_ascii = TRUE;
            }
        }

        /* If we changed it, restore LC_MONETARY to its original locale */
        if (save_monetary_locale) {
            setlocale(LC_MONETARY, save_monetary_locale);
            Safefree(save_monetary_locale);
        }

        Safefree(save_input_locale);

        /* It isn't a UTF-8 locale if the symbol is not legal UTF-8; otherwise
         * assume the locale is UTF-8 if and only if the symbol is non-ascii
         * UTF-8.  (We can't really tell if the locale is UTF-8 or not if the
         * symbol is just a '$', so we err on the side of it not being UTF-8)
         * */
        return (illegal_utf8)
                ? FALSE
                : ! only_ascii;

    }
  cant_use_monetary:

#   endif /* USE_LOCALE_MONETARY */
#endif /* HAS_LOCALECONV */

#if 0 && defined(HAS_STRERROR) && defined(USE_LOCALE_MESSAGES)

/* This code is ifdefd out because it was found to not be necessary in testing
 * on our dromedary test machine, which has over 700 locales.  There, looking
 * at just the currency symbol gave essentially the same results as doing this
 * extra work.  Executing this also caused segfaults in miniperl.  I left it in
 * so as to avoid rewriting it if real-world experience indicates that
 * dromedary is an outlier.  Essentially, instead of returning abpve if we
 * haven't found illegal utf8, we continue on and examine all the strerror()
 * messages on the platform for utf8ness.  If all are ASCII, we still don't
 * know the answer; but otherwise we have a pretty good indication of the
 * utf8ness.  The reason this doesn't necessarily help much is that the
 * messages may not have been translated into the locale.  The currency symbol
 * is much more likely to have been translated.  The code below would need to
 * be altered somewhat to just be a continuation of testing the currency
 * symbol. */
        int e;
        unsigned int failures = 0, non_ascii = 0;
        char *save_messages_locale = NULL;

        /* Like above for LC_CTYPE, we set LC_MESSAGES to the locale of the
         * desired category, if it isn't that locale already */

        if (category != LC_MESSAGES) {

            save_messages_locale = stdize_locale(savepv(setlocale(LC_MESSAGES,
                                                                  NULL)));
            if (! save_messages_locale) {
                goto cant_use_messages;
            }

            if (strEQ(save_messages_locale, save_input_locale)) {
                Safefree(save_input_locale);
            }
            else if (! setlocale(LC_MESSAGES, save_input_locale)) {
                Safefree(save_messages_locale);
                goto cant_use_messages;
            }
        }

        /* Here the current LC_MESSAGES is set to the locale of the category
         * whose information is desired.  Look through all the messages */

        for (e = 0;
#ifdef HAS_SYS_ERRLIST
             e <= sys_nerr
#endif
             ; e++)
        {
            const U8* const errmsg = (U8 *) Strerror(e) ;
            if (!errmsg)
                break;
            if (! is_utf8_string(errmsg, 0)) {
                failures++;
                break;
            }
            else if (! is_ascii_string(errmsg, 0)) {
                non_ascii++;
            }
        }

        /* And, if we changed it, restore LC_MESSAGES to its original locale */
        if (save_messages_locale) {
            setlocale(LC_MESSAGES, save_messages_locale);
            Safefree(save_messages_locale);
        }

        /* Any non-UTF-8 message means not a UTF-8 locale; if all are valid,
         * any non-ascii means it is one; otherwise we assume it isn't */
        return (failures) ? FALSE : non_ascii;

    }
  cant_use_messages:

#endif

    Safefree(save_input_locale);
    return FALSE;
}

#endif

/*
 * Local variables:
 * c-indentation-style: bsd
 * c-basic-offset: 4
 * indent-tabs-mode: nil
 * End:
 *
 * ex: set ts=8 sts=4 sw=4 et:
 */