libcharset/lib/localcharset.c

   1 /* Determine a canonical name for the current locale's character encoding.
   2
   3    Copyright (C) 2000-2001 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify it
   6    under the terms of the GNU Library General Public License as published
   7    by the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with this program; if not, write to the Free Software
  17    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  18    USA.  */
  19
  20 /* Written by Bruno Haible <haible@clisp.cons.org>.  */
  21
  22 #ifdef HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #if HAVE_STDDEF_H
  27 # include <stddef.h>
  28 #endif
  29
  30 #include <stdio.h>
  31 #if HAVE_STRING_H
  32 # include <string.h>
  33 #else
  34 # include <strings.h>
  35 #endif
  36 #if HAVE_STDLIB_H
  37 # include <stdlib.h>
  38 #endif
  39
  40 #if defined _WIN32 || defined __WIN32__
  41 # undef WIN32   /* avoid warning on mingw32 */
  42 # define WIN32
  43 #endif
  44
  45 #ifndef WIN32
  46 # if HAVE_LANGINFO_CODESET
  47 #  include <langinfo.h>
  48 # else
  49 #  if HAVE_SETLOCALE
  50 #   include <locale.h>
  51 #  endif
  52 # endif
  53 #else /* WIN32 */
  54 # define WIN32_LEAN_AND_MEAN
  55 # include <windows.h>
  56 #endif
  57
  58 #ifndef DIRECTORY_SEPARATOR
  59 # define DIRECTORY_SEPARATOR '/'
  60 #endif
  61
  62 #ifndef ISSLASH
  63 # define ISSLASH(C) ((C) == DIRECTORY_SEPARATOR)
  64 #endif
  65
  66 /* The following static variable is declared 'volatile' to avoid a
  67    possible multithread problem in the function get_charset_aliases. If we
  68    are running in a threaded environment, and if two threads initialize
  69    'charset_aliases' simultaneously, both will produce the same value,
  70    and everything will be ok if the two assignments to 'charset_aliases'
  71    are atomic. But I don't know what will happen if the two assignments mix.  */
  72 #if __STDC__ != 1
  73 # define volatile /* empty */
  74 #endif
  75 /* Pointer to the contents of the charset.alias file, if it has already been
  76    read, else NULL.  Its format is:
  77    ALIAS_1 '\0' CANONICAL_1 '\0' ... ALIAS_n '\0' CANONICAL_n '\0' '\0'  */
  78 static const char * volatile charset_aliases;
  79
  80 /* Return a pointer to the contents of the charset.alias file.  */
  81 static const char *
  82 get_charset_aliases ()
  83 {
  84   const char *cp;
  85
  86   cp = charset_aliases;
  87   if (cp == NULL)
  88     {
  89 #ifndef WIN32
  90       FILE *fp;
  91       const char *dir = LIBDIR;
  92       const char *base = "charset.alias";
  93       char *file_name;
  94
  95       /* Concatenate dir and base into freshly allocated file_name.  */
  96       {
  97         size_t dir_len = strlen (dir);
  98         size_t base_len = strlen (base);
  99         int add_slash = (dir_len > 0 && !ISSLASH (dir[dir_len - 1]));
 100         file_name = (char *) malloc (dir_len + add_slash + base_len + 1);
 101         if (file_name != NULL)
 102           {
 103             memcpy (file_name, dir, dir_len);
 104             if (add_slash)
 105               file_name[dir_len] = DIRECTORY_SEPARATOR;
 106             memcpy (file_name + dir_len + add_slash, base, base_len + 1);
 107           }
 108       }
 109
 110       if (file_name == NULL || (fp = fopen (file_name, "r")) == NULL)
 111         /* Out of memory or file not found, treat it as empty.  */
 112         cp = "";
 113       else
 114         {
 115           /* Parse the file's contents.  */
 116           int c;
 117           char buf1[50+1];
 118           char buf2[50+1];
 119           char *res_ptr = NULL;
 120           size_t res_size = 0;
 121           size_t l1, l2;
 122
 123           for (;;)
 124             {
 125               c = getc (fp);
 126               if (c == EOF)
 127                 break;
 128               if (c == '\n' || c == ' ' || c == '\t')
 129                 continue;
 130               if (c == '#')
 131                 {
 132                   /* Skip comment, to end of line.  */
 133                   do
 134                     c = getc (fp);
 135                   while (!(c == EOF || c == '\n'));
 136                   if (c == EOF)
 137                     break;
 138                   continue;
 139                 }
 140               ungetc (c, fp);
 141               if (fscanf(fp, "%50s %50s", buf1, buf2) < 2)
 142                 break;
 143               l1 = strlen (buf1);
 144               l2 = strlen (buf2);
 145               if (res_size == 0)
 146                 {
 147                   res_size = l1 + 1 + l2 + 1;
 148                   res_ptr = malloc (res_size + 1);
 149                 }
 150               else
 151                 {
 152                   res_size += l1 + 1 + l2 + 1;
 153                   res_ptr = realloc (res_ptr, res_size + 1);
 154                 }
 155               if (res_ptr == NULL)
 156                 {
 157                   /* Out of memory. */
 158                   res_size = 0;
 159                   break;
 160                 }
 161               strcpy (res_ptr + res_size - (l2 + 1) - (l1 + 1), buf1);
 162               strcpy (res_ptr + res_size - (l2 + 1), buf2);
 163             }
 164           fclose (fp);
 165           if (res_size == 0)
 166             cp = "";
 167           else
 168             {
 169               *(res_ptr + res_size) = '\0';
 170               cp = res_ptr;
 171             }
 172         }
 173
 174       if (file_name != NULL)
 175         free (file_name);
 176
 177 #else /* WIN32 */
 178
 179       /* To avoid the troubles of installing a separate file in the same
 180          directory as the DLL and of retrieving the DLL's directory at
 181          runtime, simply inline the aliases here.  */
 182
 183       cp = "CP936" "\0" "GBK" "\0"
 184            "CP1361" "\0" "JOHAB" "\0";
 185 #endif
 186
 187       charset_aliases = cp;
 188     }
 189
 190   return cp;
 191 }
 192
 193 /* Determine the current locale's character encoding, and canonicalize it
 194    into one of the canonical names listed in config.charset.
 195    The result must not be freed; it is statically allocated.
 196    If the canonical name cannot be determined, the result is a non-canonical
 197    name.  */
 198
 199 #ifdef STATIC
 200 STATIC
 201 #endif
 202 const char *
 203 locale_charset ()
 204 {
 205   const char *codeset;
 206   const char *aliases;
 207
 208 #ifndef WIN32
 209
 210 # if HAVE_LANGINFO_CODESET
 211
 212   /* Most systems support nl_langinfo (CODESET) nowadays.  */
 213   codeset = nl_langinfo (CODESET);
 214
 215 # else
 216
 217   /* On old systems which lack it, use setlocale or getenv.  */
 218   const char *locale = NULL;
 219
 220   /* But most old systems don't have a complete set of locales.  Some
 221      (like SunOS 4 or DJGPP) have only the C locale.  Therefore we don't
 222      use setlocale here; it would return "C" when it doesn't support the
 223      locale name the user has set.  */
 224 #  if HAVE_SETLOCALE && 0
 225   locale = setlocale (LC_CTYPE, NULL);
 226 #  endif
 227   if (locale == NULL || locale[0] == '\0')
 228     {
 229       locale = getenv ("LC_ALL");
 230       if (locale == NULL || locale[0] == '\0')
 231         {
 232           locale = getenv ("LC_CTYPE");
 233           if (locale == NULL || locale[0] == '\0')
 234             locale = getenv ("LANG");
 235         }
 236     }
 237
 238   /* On some old systems, one used to set locale = "iso8859_1". On others,
 239      you set it to "language_COUNTRY.charset". In any case, we resolve it
 240      through the charset.alias file.  */
 241   codeset = locale;
 242
 243 # endif
 244
 245 #else /* WIN32 */
 246
 247   static char buf[2 + 10 + 1];
 248
 249   /* Win32 has a function returning the locale's codepage as a number.  */
 250   sprintf (buf, "CP%u", GetACP ());
 251   codeset = buf;
 252
 253 #endif
 254
 255   if (codeset == NULL)
 256     /* The canonical name cannot be determined.  */
 257     codeset = "";
 258
 259   /* Resolve alias. */
 260   for (aliases = get_charset_aliases ();
 261        *aliases != '\0';
 262        aliases += strlen (aliases) + 1, aliases += strlen (aliases) + 1)
 263     if (strcmp (codeset, aliases) == 0
 264         || (aliases[0] == '*' && aliases[1] == '\0'))
 265       {
 266         codeset = aliases + strlen (aliases) + 1;
 267         break;
 268       }
 269
 270   return codeset;
 271 }