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/* Determine a canonical name for the current locale's character encoding.
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   Copyright (C) 2000-2003 Free Software Foundation, Inc.
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   This program is free software; you can redistribute it and/or modify it
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   under the terms of the GNU Library General Public License as published
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   by the Free Software Foundation; either version 2, or (at your option)
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   any later version.
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   This program is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   Library General Public License for more details.
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   You should have received a copy of the GNU Library General Public
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   License along with this program; if not, write to the Free Software
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   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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   USA.  */
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/* Written by Bruno Haible <bruno@clisp.org>.  */
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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/* Specification.  */
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#include "localcharset.h"
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#if HAVE_STDDEF_H
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# include <stddef.h>
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#endif
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#include <stdio.h>
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#if HAVE_STRING_H
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# include <string.h>
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#else
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# include <strings.h>
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#endif
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#if HAVE_STDLIB_H
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# include <stdlib.h>
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#endif
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#if defined _WIN32 || defined __WIN32__
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# undef WIN32   /* avoid warning on mingw32 */
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# define WIN32
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#endif
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#if defined __EMX__
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/* Assume EMX program runs on OS/2, even if compiled under DOS.  */
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# define OS2
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#endif
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#if !defined WIN32
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# if HAVE_LANGINFO_CODESET
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#  include <langinfo.h>
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# else
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#  if HAVE_SETLOCALE
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#   include <locale.h>
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#  endif
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# endif
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#elif defined WIN32
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# define WIN32_LEAN_AND_MEAN
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# include <windows.h>
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#endif
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#if defined OS2
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# define INCL_DOS
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# include <os2.h>
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#endif
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#if ENABLE_RELOCATABLE
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# include "relocatable.h"
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#else
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# define relocate(pathname) (pathname)
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#endif
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#if defined _WIN32 || defined __WIN32__ || defined __EMX__ || defined __DJGPP__
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  /* Win32, OS/2, DOS */
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# define ISSLASH(C) ((C) == '/' || (C) == '\\')
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#endif
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#ifndef DIRECTORY_SEPARATOR
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# define DIRECTORY_SEPARATOR '/'
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#endif
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#ifndef ISSLASH
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# define ISSLASH(C) ((C) == DIRECTORY_SEPARATOR)
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#endif
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#if HAVE_DECL_GETC_UNLOCKED
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# undef getc
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# define getc getc_unlocked
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#endif
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/* The following static variable is declared 'volatile' to avoid a
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   possible multithread problem in the function get_charset_aliases. If we
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   are running in a threaded environment, and if two threads initialize
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   'charset_aliases' simultaneously, both will produce the same value,
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   and everything will be ok if the two assignments to 'charset_aliases'
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   are atomic. But I don't know what will happen if the two assignments mix.  */
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#if __STDC__ != 1
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# define volatile /* empty */
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#endif
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/* Pointer to the contents of the charset.alias file, if it has already been
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   read, else NULL.  Its format is:
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   ALIAS_1 '\0' CANONICAL_1 '\0' ... ALIAS_n '\0' CANONICAL_n '\0' '\0'  */
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static const char * volatile charset_aliases;
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/* Return a pointer to the contents of the charset.alias file.  */
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static const char *
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get_charset_aliases ()
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{
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  const char *cp;
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  cp = charset_aliases;
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  if (cp == NULL)
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    {
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#if !(defined VMS || defined WIN32)
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      FILE *fp;
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      const char *dir = relocate (LIBDIR);
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      const char *base = "charset.alias";
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      char *file_name;
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      /* Concatenate dir and base into freshly allocated file_name.  */
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      {
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        size_t dir_len = strlen (dir);
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        size_t base_len = strlen (base);
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        int add_slash = (dir_len > 0 && !ISSLASH (dir[dir_len - 1]));
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        file_name = (char *) malloc (dir_len + add_slash + base_len + 1);
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        if (file_name != NULL)
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          {
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            memcpy (file_name, dir, dir_len);
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            if (add_slash)
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              file_name[dir_len] = DIRECTORY_SEPARATOR;
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            memcpy (file_name + dir_len + add_slash, base, base_len + 1);
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          }
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      }
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      if (file_name == NULL || (fp = fopen (file_name, "r")) == NULL)
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        /* Out of memory or file not found, treat it as empty.  */
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        cp = "";
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      else
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        {
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          /* Parse the file's contents.  */
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          int c;
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          char buf1[50+1];
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          char buf2[50+1];
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          char *res_ptr = NULL;
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          size_t res_size = 0;
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          size_t l1, l2;
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          for (;;)
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            {
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              c = getc (fp);
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              if (c == EOF)
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                break;
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              if (c == '\n' || c == ' ' || c == '\t')
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                continue;
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              if (c == '#')
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                {
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                  /* Skip comment, to end of line.  */
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                  do
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                    c = getc (fp);
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                  while (!(c == EOF || c == '\n'));
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                  if (c == EOF)
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                    break;
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                  continue;
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                }
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              ungetc (c, fp);
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              if (fscanf (fp, "%50s %50s", buf1, buf2) < 2)
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                break;
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              l1 = strlen (buf1);
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              l2 = strlen (buf2);
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              if (res_size == 0)
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                {
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                  res_size = l1 + 1 + l2 + 1;
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                  res_ptr = (char *) malloc (res_size + 1);
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                }
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              else
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                {
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                  res_size += l1 + 1 + l2 + 1;
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                  res_ptr = (char *) realloc (res_ptr, res_size + 1);
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                }
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              if (res_ptr == NULL)
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                {
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                  /* Out of memory. */
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                  res_size = 0;
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                  break;
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                }
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              strcpy (res_ptr + res_size - (l2 + 1) - (l1 + 1), buf1);
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              strcpy (res_ptr + res_size - (l2 + 1), buf2);
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            }
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          fclose (fp);
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          if (res_size == 0)
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            cp = "";
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          else
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            {
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              *(res_ptr + res_size) = '\0';
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              cp = res_ptr;
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            }
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        }
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      if (file_name != NULL)
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        free (file_name);
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#else
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# if defined VMS
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      /* To avoid the troubles of an extra file charset.alias_vms in the
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         sources of many GNU packages, simply inline the aliases here.  */
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      /* The list of encodings is taken from the OpenVMS 7.3-1 documentation
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         "Compaq C Run-Time Library Reference Manual for OpenVMS systems"
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         section 10.7 "Handling Different Character Sets".  */
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      cp = "ISO8859-1" "\0" "ISO-8859-1" "\0"
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           "ISO8859-2" "\0" "ISO-8859-2" "\0"
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           "ISO8859-5" "\0" "ISO-8859-5" "\0"
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           "ISO8859-7" "\0" "ISO-8859-7" "\0"
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           "ISO8859-8" "\0" "ISO-8859-8" "\0"
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           "ISO8859-9" "\0" "ISO-8859-9" "\0"
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           /* Japanese */
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           "eucJP" "\0" "EUC-JP" "\0"
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           "SJIS" "\0" "SHIFT_JIS" "\0"
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           "DECKANJI" "\0" "DEC-KANJI" "\0"
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           "SDECKANJI" "\0" "EUC-JP" "\0"
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           /* Chinese */
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           "eucTW" "\0" "EUC-TW" "\0"
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           "DECHANYU" "\0" "DEC-HANYU" "\0"
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           "DECHANZI" "\0" "GB2312" "\0"
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           /* Korean */
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           "DECKOREAN" "\0" "EUC-KR" "\0";
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# endif
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# if defined WIN32
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      /* To avoid the troubles of installing a separate file in the same
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         directory as the DLL and of retrieving the DLL's directory at
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         runtime, simply inline the aliases here.  */
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      cp = "CP936" "\0" "GBK" "\0"
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           "CP1361" "\0" "JOHAB" "\0"
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           "CP20127" "\0" "ASCII" "\0"
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           "CP20866" "\0" "KOI8-R" "\0"
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           "CP21866" "\0" "KOI8-RU" "\0"
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           "CP28591" "\0" "ISO-8859-1" "\0"
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           "CP28592" "\0" "ISO-8859-2" "\0"
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           "CP28593" "\0" "ISO-8859-3" "\0"
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           "CP28594" "\0" "ISO-8859-4" "\0"
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           "CP28595" "\0" "ISO-8859-5" "\0"
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           "CP28596" "\0" "ISO-8859-6" "\0"
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           "CP28597" "\0" "ISO-8859-7" "\0"
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           "CP28598" "\0" "ISO-8859-8" "\0"
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           "CP28599" "\0" "ISO-8859-9" "\0"
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           "CP28605" "\0" "ISO-8859-15" "\0";
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# endif
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#endif
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      charset_aliases = cp;
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    }
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  return cp;
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}
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/* Determine the current locale's character encoding, and canonicalize it
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   into one of the canonical names listed in config.charset.
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   The result must not be freed; it is statically allocated.
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   If the canonical name cannot be determined, the result is a non-canonical
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   name.  */
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#ifdef STATIC
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STATIC
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#endif
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const char *
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locale_charset ()
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{
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  const char *codeset;
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  const char *aliases;
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#if !(defined WIN32 || defined OS2)
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# if HAVE_LANGINFO_CODESET
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  /* Most systems support nl_langinfo (CODESET) nowadays.  */
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  codeset = nl_langinfo (CODESET);
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# else
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  /* On old systems which lack it, use setlocale or getenv.  */
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  const char *locale = NULL;
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  /* But most old systems don't have a complete set of locales.  Some
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     (like SunOS 4 or DJGPP) have only the C locale.  Therefore we don't
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     use setlocale here; it would return "C" when it doesn't support the
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     locale name the user has set.  */
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#  if HAVE_SETLOCALE && 0
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  locale = setlocale (LC_CTYPE, NULL);
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#  endif
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  if (locale == NULL || locale[0] == '\0')
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    {
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      locale = getenv ("LC_ALL");
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      if (locale == NULL || locale[0] == '\0')
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        {
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          locale = getenv ("LC_CTYPE");
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          if (locale == NULL || locale[0] == '\0')
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            locale = getenv ("LANG");
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        }
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    }
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  /* On some old systems, one used to set locale = "iso8859_1". On others,
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     you set it to "language_COUNTRY.charset". In any case, we resolve it
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     through the charset.alias file.  */
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  codeset = locale;
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# endif
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#elif defined WIN32
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  static char buf[2 + 10 + 1];
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  /* Woe32 has a function returning the locale's codepage as a number.  */
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  sprintf (buf, "CP%u", GetACP ());
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  codeset = buf;
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#elif defined OS2
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  const char *locale;
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  static char buf[2 + 10 + 1];
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  ULONG cp[3];
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  ULONG cplen;
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  /* Allow user to override the codeset, as set in the operating system,
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     with standard language environment variables.  */
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  locale = getenv ("LC_ALL");
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  if (locale == NULL || locale[0] == '\0')
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    {
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      locale = getenv ("LC_CTYPE");
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      if (locale == NULL || locale[0] == '\0')
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        locale = getenv ("LANG");
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    }
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  if (locale != NULL && locale[0] != '\0')
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    {
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      /* If the locale name contains an encoding after the dot, return it.  */
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      const char *dot = strchr (locale, '.');
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      if (dot != NULL)
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        {
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          const char *modifier;
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          dot++;
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          /* Look for the possible @... trailer and remove it, if any.  */
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          modifier = strchr (dot, '@');
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          if (modifier == NULL)
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            return dot;
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          if (modifier - dot < sizeof (buf))
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            {
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              memcpy (buf, dot, modifier - dot);
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              buf [modifier - dot] = '\0';
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              return buf;
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            }
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        }
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      /* Resolve through the charset.alias file.  */
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      codeset = locale;
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    }
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  else
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    {
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      /* OS/2 has a function returning the locale's codepage as a number.  */
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      if (DosQueryCp (sizeof (cp), cp, &cplen))
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        codeset = "";
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      else
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        {
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          sprintf (buf, "CP%u", cp[0]);
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          codeset = buf;
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        }
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    }
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#endif
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  if (codeset == NULL)
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    /* The canonical name cannot be determined.  */
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    codeset = "";
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  /* Resolve alias. */
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  for (aliases = get_charset_aliases ();
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       *aliases != '\0';
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       aliases += strlen (aliases) + 1, aliases += strlen (aliases) + 1)
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    if (strcmp (codeset, aliases) == 0
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        || (aliases[0] == '*' && aliases[1] == '\0'))
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      {
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        codeset = aliases + strlen (aliases) + 1;
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        break;
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      }
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  /* Don't return an empty string.  GNU libc and GNU libiconv interpret
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     the empty string as denoting "the locale's character encoding",
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     thus GNU libiconv would call this function a second time.  */
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  if (codeset[0] == '\0')
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    codeset = "ASCII";
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  return codeset;
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}