/*      $NetBSD: localcharset.c,v 1.1.1.1 2016/01/10 21:36:18 christos Exp $    */

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

  Copyright (C) 2000-2002 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 <[email protected]>.  */

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

#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 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 WIN32
     FILE *fp;
     const char *dir = 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

     /* 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.  */

# if defined WIN32
     cp = "CP936" "\0" "GBK" "\0"
          "CP1361" "\0" "JOHAB" "\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];

 /* Win32 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;
     }

 return codeset;
}

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