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

  Copyright (C) 2000-2006 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  USA.  */

/* Written by Bruno Haible <[email protected]>.  */

#include <config.h>

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

#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#if defined _WIN32 || defined __WIN32__
# define WIN32_NATIVE
#endif

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

#if !defined WIN32_NATIVE
# if HAVE_LANGINFO_CODESET
#  include <langinfo.h>
# else
#  if 0 /* see comment below */
#   include <locale.h>
#  endif
# endif
# ifdef __CYGWIN__
#  define WIN32_LEAN_AND_MEAN
#  include <windows.h>
# endif
#elif defined WIN32_NATIVE
# 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

/* Get LIBDIR.  */
#ifndef LIBDIR
# include "configmake.h"
#endif

#if defined _WIN32 || defined __WIN32__ || defined __CYGWIN__ || defined __EMX__ || defined __DJGPP__
 /* Win32, Cygwin, 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

#if HAVE_DECL_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 (void)
{
 const char *cp;

 cp = charset_aliases;
 if (cp == NULL)
   {
#if !(defined VMS || defined WIN32_NATIVE || defined __CYGWIN__)
     FILE *fp;
     const char *dir;
     const char *base = "charset.alias";
     char *file_name;

     /* Make it possible to override the charset.alias location.  This is
        necessary for running the testsuite before "make install".  */
     dir = getenv ("CHARSETALIASDIR");
     if (dir == NULL || dir[0] == '\0')
       dir = relocate (LIBDIR);

     /* 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.  */
         char *res_ptr = NULL;
         size_t res_size = 0;

         for (;;)
           {
             int c;
             char buf1[50+1];
             char buf2[50+1];
             size_t l1, l2;
             char *old_res_ptr;

             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);
             old_res_ptr = res_ptr;
             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;
                 if (old_res_ptr != NULL)
                   free (old_res_ptr);
                 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_NATIVE || defined __CYGWIN__
     /* 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"
          "CP20936" "\0" "GB2312" "\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"
          "CP38598" "\0" "ISO-8859-8" "\0"
          "CP51932" "\0" "EUC-JP" "\0"
          "CP51936" "\0" "GB2312" "\0"
          "CP51949" "\0" "EUC-KR" "\0"
          "CP51950" "\0" "EUC-TW" "\0"
          "CP54936" "\0" "GB18030" "\0"
          "CP65001" "\0" "UTF-8" "\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 (void)
{
 const char *codeset;
 const char *aliases;

#if !(defined WIN32_NATIVE || defined OS2)

# if HAVE_LANGINFO_CODESET

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

#  ifdef __CYGWIN__
 /* Cygwin 2006 does not have locales.  nl_langinfo (CODESET) always
    returns "US-ASCII".  As long as this is not fixed, return the suffix
    of the locale name from the environment variables (if present) or
    the codepage as a number.  */
 if (codeset != NULL && strcmp (codeset, "US-ASCII") == 0)
   {
     const char *locale;
     static char buf[2 + 10 + 1];

     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;
               }
           }
       }

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

# 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 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_NATIVE

 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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