lib/unicodeio.c

   1 /* Unicode character output to streams with locale dependent encoding.
   2
   3    Copyright (C) 2000-2003, 2006, 2008-2024 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Bruno Haible <haible@clisp.cons.org>.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include "unicodeio.h"
  24
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <errno.h>
  28
  29 #if HAVE_ICONV
  30 # include <iconv.h>
  31 #endif
  32
  33 #include <error.h>
  34
  35 #include "gettext.h"
  36 #define _(msgid) gettext (msgid)
  37 #define N_(msgid) msgid
  38
  39 #include "localcharset.h"
  40 #include "unistr.h"
  41
  42 /* When we pass a Unicode character to iconv(), we must pass it in a
  43    suitable encoding. The standardized Unicode encodings are
  44    UTF-8, UCS-2, UCS-4, UTF-16, UTF-16BE, UTF-16LE, UTF-7.
  45    UCS-2 supports only characters up to \U0000FFFF.
  46    UTF-16 and variants support only characters up to \U0010FFFF.
  47    UTF-7 is way too complex and not supported by glibc-2.1.
  48    UCS-4 specification leaves doubts about endianness and byte order
  49    mark. glibc currently interprets it as big endian without byte order
  50    mark, but this is not backed by an RFC.
  51    So we use UTF-8. It supports characters up to \U7FFFFFFF and is
  52    unambiguously defined.  */
  53
  54 /* Luckily, the encoding's name is platform independent.  */
  55 #define UTF8_NAME "UTF-8"
  56
  57 /* Converts the Unicode character CODE to its multibyte representation
  58    in the current locale and calls the SUCCESS callback on the resulting
  59    byte sequence.  If an error occurs, invokes the FAILURE callback instead,
  60    passing it CODE and an English error string.
  61    Returns whatever the callback returned.
  62    Assumes that the locale doesn't change between two calls.  */
  63 long
  64 unicode_to_mb (unsigned int code,
  65                long (*success) (const char *buf, size_t buflen,
  66                                 void *callback_arg),
  67                long (*failure) (unsigned int code, const char *msg,
  68                                 void *callback_arg),
  69                void *callback_arg)
  70 {
  71   static int initialized;
  72   static int is_utf8;
  73 #if HAVE_ICONV
  74   static iconv_t utf8_to_local;
  75 #endif
  76
  77   char inbuf[6];
  78   int count;
  79
  80   if (!initialized)
  81     {
  82       const char *charset = locale_charset ();
  83
  84       is_utf8 = !strcmp (charset, UTF8_NAME);
  85 #if HAVE_ICONV
  86       if (!is_utf8)
  87         {
  88           utf8_to_local = iconv_open (charset, UTF8_NAME);
  89           if (utf8_to_local == (iconv_t)(-1))
  90             /* For an unknown encoding, assume ASCII.  */
  91             utf8_to_local = iconv_open ("ASCII", UTF8_NAME);
  92         }
  93 #endif
  94       initialized = 1;
  95     }
  96
  97   /* Test whether the utf8_to_local converter is available at all.  */
  98   if (!is_utf8)
  99     {
 100 #if HAVE_ICONV
 101       if (utf8_to_local == (iconv_t)(-1))
 102         return failure (code, N_("iconv function not usable"), callback_arg);
 103 #else
 104       return failure (code, N_("iconv function not available"), callback_arg);
 105 #endif
 106     }
 107
 108   /* Convert the character to UTF-8.  */
 109   count = u8_uctomb ((unsigned char *) inbuf, code, sizeof (inbuf));
 110   if (count < 0)
 111     return failure (code, N_("character out of range"), callback_arg);
 112
 113 #if HAVE_ICONV
 114   if (!is_utf8)
 115     {
 116       char outbuf[25];
 117       const char *inptr;
 118       size_t inbytesleft;
 119       char *outptr;
 120       size_t outbytesleft;
 121       size_t res;
 122
 123       inptr = inbuf;
 124       inbytesleft = count;
 125       outptr = outbuf;
 126       outbytesleft = sizeof (outbuf);
 127
 128       /* Convert the character from UTF-8 to the locale's charset.  */
 129       res = iconv (utf8_to_local,
 130                    (ICONV_CONST char **)&inptr, &inbytesleft,
 131                    &outptr, &outbytesleft);
 132       /* Analyze what iconv() actually did and distinguish replacements
 133          that are OK (no need to invoke the FAILURE callback), such as
 134            - replacing GREEK SMALL LETTER MU with MICRO SIGN, or
 135            - replacing FULLWIDTH COLON with ':', or
 136            - replacing a Unicode TAG character (U+E00xx) with an empty string,
 137          from replacements that are worse than the FAILURE callback, such as
 138            - replacing 'ç' with '?' (NetBSD, Solaris 11) or '*' (musl) or
 139              NUL (IRIX).  */
 140       if (inbytesleft > 0 || res == (size_t)(-1)
 141           /* Irix iconv() inserts a NUL byte if it cannot convert.  */
 142 # if !defined _LIBICONV_VERSION && (defined sgi || defined __sgi)
 143           || (res > 0 && code != 0 && outptr - outbuf == 1 && *outbuf == '\0')
 144 # endif
 145           /* FreeBSD iconv(), NetBSD iconv(), and Solaris 11 iconv() insert
 146              a '?' if they cannot convert.  */
 147 # if !defined _LIBICONV_VERSION || (_LIBICONV_VERSION == 0x10b && defined __APPLE__)
 148           || (res > 0 && outptr - outbuf == 1 && *outbuf == '?')
 149 # endif
 150           /* musl libc iconv() inserts a '*' if it cannot convert.  */
 151 # if !defined _LIBICONV_VERSION && MUSL_LIBC
 152           || (res > 0 && outptr - outbuf == 1 && *outbuf == '*')
 153 # endif
 154          )
 155         return failure (code, NULL, callback_arg);
 156
 157       /* Get back to the initial shift state.  */
 158       res = iconv (utf8_to_local, NULL, NULL, &outptr, &outbytesleft);
 159       if (res == (size_t)(-1))
 160         return failure (code, NULL, callback_arg);
 161
 162       return success (outbuf, outptr - outbuf, callback_arg);
 163     }
 164 #endif
 165
 166   /* At this point, is_utf8 is true, so no conversion is needed.  */
 167   return success (inbuf, count, callback_arg);
 168 }
 169
 170 /* Simple success callback that outputs the converted string.
 171    The STREAM is passed as callback_arg.  */
 172 long
 173 fwrite_success_callback (const char *buf, size_t buflen, void *callback_arg)
 174 {
 175   FILE *stream = (FILE *) callback_arg;
 176
 177   /* The return value of fwrite can be ignored here, because under normal
 178      conditions (STREAM is an open stream and not wide-character oriented)
 179      when fwrite() returns a value != buflen it also sets STREAM's error
 180      indicator.  */
 181   fwrite (buf, 1, buflen, stream);
 182   return 0;
 183 }
 184
 185 /* Simple failure callback that displays an error and exits.  */
 186 static long
 187 exit_failure_callback (unsigned int code, const char *msg,
 188                        _GL_UNUSED void *callback_arg)
 189 {
 190   if (msg == NULL)
 191     error (1, 0, _("cannot convert U+%04X to local character set"), code);
 192   else
 193     error (1, 0, _("cannot convert U+%04X to local character set: %s"), code,
 194            gettext (msg));
 195   return -1;
 196 }
 197
 198 /* Simple failure callback that displays a fallback representation in plain
 199    ASCII, using the same notation as ISO C99 strings.  */
 200 static long
 201 fallback_failure_callback (unsigned int code,
 202                            _GL_UNUSED const char *msg,
 203                            void *callback_arg)
 204 {
 205   FILE *stream = (FILE *) callback_arg;
 206
 207   if (code < 0x10000)
 208     fprintf (stream, "\\u%04X", code);
 209   else
 210     fprintf (stream, "\\U%08X", code);
 211   return -1;
 212 }
 213
 214 /* Outputs the Unicode character CODE to the output stream STREAM.
 215    Upon failure, exit if exit_on_error is true, otherwise output a fallback
 216    notation.  */
 217 void
 218 print_unicode_char (FILE *stream, unsigned int code, int exit_on_error)
 219 {
 220   /* Simplify this subset to avoid potential iconv() issues
 221      for that range at least.  */
 222   if (32 <= code && code < 128)
 223     {
 224       char code_char = code;
 225       fwrite_success_callback (&code_char, sizeof code_char, stream);
 226     }
 227   else
 228     unicode_to_mb (code, fwrite_success_callback,
 229                    exit_on_error
 230                    ? exit_failure_callback
 231                    : fallback_failure_callback,
 232                    stream);
 233 }