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/* 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., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301,

   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;

}