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localcharset.c

/* Determine a canonical name for the current locale's character encoding.

   Copyright (C) 2000-2003 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify it
   under the terms of the GNU Library General Public License as published
   by the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
   USA.  */

/* Written by Bruno Haible <bruno@clisp.org>.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

/* Specification.  */
#include "localcharset.h"

#if HAVE_STDDEF_H
# include <stddef.h>
#endif

#include <stdio.h>
#if HAVE_STRING_H
# include <string.h>
#else
# include <strings.h>
#endif
#if HAVE_STDLIB_H
# include <stdlib.h>
#endif

#if defined _WIN32 || defined __WIN32__
# undef WIN32                   /* avoid warning on mingw32 */
# define WIN32
#endif

#if defined __EMX__
/* Assume EMX program runs on OS/2, even if compiled under DOS.  */
# define OS2
#endif

#if !defined WIN32
# if HAVE_LANGINFO_CODESET
#  include <langinfo.h>
# else
#  if HAVE_SETLOCALE
#   include <locale.h>
#  endif
# endif
#elif defined WIN32
# define WIN32_LEAN_AND_MEAN
# include <windows.h>
#endif
#if defined OS2
# define INCL_DOS
# include <os2.h>
#endif

#if ENABLE_RELOCATABLE
# include "relocatable.h"
#else
# define relocate(pathname) (pathname)
#endif

#if defined _WIN32 || defined __WIN32__ || defined __EMX__ || defined __DJGPP__
  /* Win32, OS/2, DOS */
# define ISSLASH(C) ((C) == '/' || (C) == '\\')
#endif

#ifndef DIRECTORY_SEPARATOR
# define DIRECTORY_SEPARATOR '/'
#endif

#ifndef ISSLASH
# define ISSLASH(C) ((C) == DIRECTORY_SEPARATOR)
#endif

#ifdef HAVE_GETC_UNLOCKED
# undef getc
# define getc getc_unlocked
#endif

/* The following static variable is declared 'volatile' to avoid a
   possible multithread problem in the function get_charset_aliases. If we
   are running in a threaded environment, and if two threads initialize
   'charset_aliases' simultaneously, both will produce the same value,
   and everything will be ok if the two assignments to 'charset_aliases'
   are atomic. But I don't know what will happen if the two assignments mix.  */
#if __STDC__ != 1
# define volatile               /* empty */
#endif
/* Pointer to the contents of the charset.alias file, if it has already been
   read, else NULL.  Its format is:
   ALIAS_1 '\0' CANONICAL_1 '\0' ... ALIAS_n '\0' CANONICAL_n '\0' '\0'  */
static const char *volatile charset_aliases;

/* Return a pointer to the contents of the charset.alias file.  */
static const char *
get_charset_aliases()
{
    const char *cp;

    cp = charset_aliases;
    if (cp == NULL) {
#if !(defined VMS || defined WIN32)
        FILE *fp;
        const char *dir = relocate(LIBDIR);
        const char *base = "charset.alias";
        char *file_name;

        /* Concatenate dir and base into freshly allocated file_name.  */
        {
            size_t dir_len = strlen(dir);
            size_t base_len = strlen(base);
            int add_slash = (dir_len > 0 && !ISSLASH(dir[dir_len - 1]));
            file_name = (char *) malloc(dir_len + add_slash + base_len + 1);
            if (file_name != NULL) {
                memcpy(file_name, dir, dir_len);
                if (add_slash)
                    file_name[dir_len] = DIRECTORY_SEPARATOR;
                memcpy(file_name + dir_len + add_slash, base, base_len + 1);
            }
        }

        if (file_name == NULL || (fp = fopen(file_name, "r")) == NULL)
            /* Out of memory or file not found, treat it as empty.  */
            cp = "";
        else {
            /* Parse the file's contents.  */
            int c;
            char buf1[50 + 1];
            char buf2[50 + 1];
            char *res_ptr = NULL;
            size_t res_size = 0;
            size_t l1, l2;

            for (;;) {
                c = getc(fp);
                if (c == EOF)
                    break;
                if (c == '\n' || c == ' ' || c == '\t')
                    continue;
                if (c == '#') {
                    /* Skip comment, to end of line.  */
                    do
                        c = getc(fp);
                    while (!(c == EOF || c == '\n'));
                    if (c == EOF)
                        break;
                    continue;
                }
                ungetc(c, fp);
                if (fscanf(fp, "%50s %50s", buf1, buf2) < 2)
                    break;
                l1 = strlen(buf1);
                l2 = strlen(buf2);
                if (res_size == 0) {
                    res_size = l1 + 1 + l2 + 1;
                    res_ptr = (char *) malloc(res_size + 1);
                }
                else {
                    res_size += l1 + 1 + l2 + 1;
                    res_ptr = (char *) realloc(res_ptr, res_size + 1);
                }
                if (res_ptr == NULL) {
                    /* Out of memory. */
                    res_size = 0;
                    break;
                }
                strcpy(res_ptr + res_size - (l2 + 1) - (l1 + 1), buf1);
                strcpy(res_ptr + res_size - (l2 + 1), buf2);
            }
            fclose(fp);
            if (res_size == 0)
                cp = "";
            else {
                *(res_ptr + res_size) = '\0';
                cp = res_ptr;
            }
        }

        if (file_name != NULL)
            free(file_name);

#else

# if defined VMS
        /* To avoid the troubles of an extra file charset.alias_vms in the
           sources of many GNU packages, simply inline the aliases here.  */
        /* The list of encodings is taken from the OpenVMS 7.3-1 documentation
           "Compaq C Run-Time Library Reference Manual for OpenVMS systems"
           section 10.7 "Handling Different Character Sets".  */
        cp = "ISO8859-1" "\0" "ISO-8859-1" "\0"
            "ISO8859-2" "\0" "ISO-8859-2" "\0"
            "ISO8859-5" "\0" "ISO-8859-5" "\0"
            "ISO8859-7" "\0" "ISO-8859-7" "\0"
            "ISO8859-8" "\0" "ISO-8859-8" "\0"
            "ISO8859-9" "\0" "ISO-8859-9" "\0"
            /* Japanese */
            "eucJP" "\0" "EUC-JP" "\0"
            "SJIS" "\0" "SHIFT_JIS" "\0"
            "DECKANJI" "\0" "DEC-KANJI" "\0" "SDECKANJI" "\0" "EUC-JP" "\0"
            /* Chinese */
            "eucTW" "\0" "EUC-TW" "\0"
            "DECHANYU" "\0" "DEC-HANYU" "\0" "DECHANZI" "\0" "GB2312" "\0"
            /* Korean */
            "DECKOREAN" "\0" "EUC-KR" "\0";
# endif

# if defined WIN32
        /* To avoid the troubles of installing a separate file in the same
           directory as the DLL and of retrieving the DLL's directory at
           runtime, simply inline the aliases here.  */

        cp = "CP936" "\0" "GBK" "\0"
            "CP1361" "\0" "JOHAB" "\0"
            "CP20127" "\0" "ASCII" "\0"
            "CP20866" "\0" "KOI8-R" "\0"
            "CP21866" "\0" "KOI8-RU" "\0"
            "CP28591" "\0" "ISO-8859-1" "\0"
            "CP28592" "\0" "ISO-8859-2" "\0"
            "CP28593" "\0" "ISO-8859-3" "\0"
            "CP28594" "\0" "ISO-8859-4" "\0"
            "CP28595" "\0" "ISO-8859-5" "\0"
            "CP28596" "\0" "ISO-8859-6" "\0"
            "CP28597" "\0" "ISO-8859-7" "\0"
            "CP28598" "\0" "ISO-8859-8" "\0"
            "CP28599" "\0" "ISO-8859-9" "\0"
            "CP28605" "\0" "ISO-8859-15" "\0";
# endif
#endif

        charset_aliases = cp;
    }

    return cp;
}

/* Determine the current locale's character encoding, and canonicalize it
   into one of the canonical names listed in config.charset.
   The result must not be freed; it is statically allocated.
   If the canonical name cannot be determined, the result is a non-canonical
   name.  */

#ifdef STATIC
STATIC
#endif
const char *
locale_charset()
{
    const char *codeset;
    const char *aliases;

#if !(defined WIN32 || defined OS2)

# if HAVE_LANGINFO_CODESET

    /* Most systems support nl_langinfo (CODESET) nowadays.  */
    codeset = nl_langinfo(CODESET);

# else

    /* On old systems which lack it, use setlocale or getenv.  */
    const char *locale = NULL;

    /* But most old systems don't have a complete set of locales.  Some
       (like SunOS 4 or DJGPP) have only the C locale.  Therefore we don't
       use setlocale here; it would return "C" when it doesn't support the
       locale name the user has set.  */
#  if HAVE_SETLOCALE && 0
    locale = setlocale(LC_CTYPE, NULL);
#  endif
    if (locale == NULL || locale[0] == '\0') {
        locale = getenv("LC_ALL");
        if (locale == NULL || locale[0] == '\0') {
            locale = getenv("LC_CTYPE");
            if (locale == NULL || locale[0] == '\0')
                locale = getenv("LANG");
        }
    }

    /* On some old systems, one used to set locale = "iso8859_1". On others,
       you set it to "language_COUNTRY.charset". In any case, we resolve it
       through the charset.alias file.  */
    codeset = locale;

# endif

#elif defined WIN32

    static char buf[2 + 10 + 1];

    /* Woe32 has a function returning the locale's codepage as a number.  */
    sprintf(buf, "CP%u", GetACP());
    codeset = buf;

#elif defined OS2

    const char *locale;
    static char buf[2 + 10 + 1];
    ULONG cp[3];
    ULONG cplen;

    /* Allow user to override the codeset, as set in the operating system,
       with standard language environment variables.  */
    locale = getenv("LC_ALL");
    if (locale == NULL || locale[0] == '\0') {
        locale = getenv("LC_CTYPE");
        if (locale == NULL || locale[0] == '\0')
            locale = getenv("LANG");
    }
    if (locale != NULL && locale[0] != '\0') {
        /* If the locale name contains an encoding after the dot, return it.  */
        const char *dot = strchr(locale, '.');

        if (dot != NULL) {
            const char *modifier;

            dot++;
            /* Look for the possible @... trailer and remove it, if any.  */
            modifier = strchr(dot, '@');
            if (modifier == NULL)
                return dot;
            if (modifier - dot < sizeof(buf)) {
                memcpy(buf, dot, modifier - dot);
                buf[modifier - dot] = '\0';
                return buf;
            }
        }

        /* Resolve through the charset.alias file.  */
        codeset = locale;
    }
    else {
        /* OS/2 has a function returning the locale's codepage as a number.  */
        if (DosQueryCp(sizeof(cp), cp, &cplen))
            codeset = "";
        else {
            sprintf(buf, "CP%u", cp[0]);
            codeset = buf;
        }
    }

#endif

    if (codeset == NULL)
        /* The canonical name cannot be determined.  */
        codeset = "";

    /* Resolve alias. */
    for (aliases = get_charset_aliases();
         *aliases != '\0';
         aliases += strlen(aliases) + 1, aliases += strlen(aliases) + 1)
        if (strcmp(codeset, aliases) == 0
            || (aliases[0] == '*' && aliases[1] == '\0')) {
            codeset = aliases + strlen(aliases) + 1;
            break;
        }

    /* Don't return an empty string.  GNU libc and GNU libiconv interpret
       the empty string as denoting "the locale's character encoding",
       thus GNU libiconv would call this function a second time.  */
    if (codeset[0] == '\0')
        codeset = "ASCII";

    return codeset;
}

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