iconv/gconv_charset.c

   1 /* Charset name normalization.
   2    Copyright (C) 2020-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19
  20 #include <stdlib.h>
  21 #include <ctype.h>
  22 #include <locale.h>
  23 #include <stdbool.h>
  24 #include <string.h>
  25 #include <sys/stat.h>
  26 #include "gconv_int.h"
  27 #include "gconv_charset.h"
  28
  29
  30 /* This function returns a pointer to the last suffix in a conversion code
  31    string.  Valid suffixes matched by this function are of the form: '/' or ','
  32    followed by arbitrary text that doesn't contain '/' or ','.  It does not
  33    edit the string in any way.  The caller is expected to parse the suffix and
  34    remove it (by e.g. truncating the string) before the next call.  */
  35 static char *
  36 find_suffix (char *s)
  37 {
  38   /* The conversion code is in the form of a triplet, separated by '/' chars.
  39      The third component of the triplet contains suffixes. If we don't have two
  40      slashes, we don't have a suffix.  */
  41
  42   int slash_count = 0;
  43   char *suffix_term = NULL;
  44
  45   for (int i = 0; s[i] != '\0'; i++)
  46     switch (s[i])
  47       {
  48         case '/':
  49           slash_count++;
  50           /* Fallthrough */
  51         case ',':
  52           suffix_term = &s[i];
  53       }
  54
  55   if (slash_count >= 2)
  56     return suffix_term;
  57
  58   return NULL;
  59 }
  60
  61
  62 struct gconv_parsed_code
  63 {
  64   char *code;
  65   bool translit;
  66   bool ignore;
  67 };
  68
  69
  70 /* This function parses an iconv_open encoding PC.CODE, strips any suffixes
  71    (such as TRANSLIT or IGNORE) from it and sets corresponding flags in it.  */
  72 static void
  73 gconv_parse_code (struct gconv_parsed_code *pc)
  74 {
  75   pc->translit = false;
  76   pc->ignore = false;
  77
  78   while (1)
  79     {
  80       /* First drop any trailing whitespaces and separators.  */
  81       size_t len = strlen (pc->code);
  82       while ((len > 0)
  83              && (isspace (pc->code[len - 1])
  84                  || pc->code[len - 1] == ','
  85                  || pc->code[len - 1] == '/'))
  86         len--;
  87
  88       pc->code[len] = '\0';
  89
  90       if (len == 0)
  91         return;
  92
  93       char * suffix = find_suffix (pc->code);
  94       if (suffix == NULL)
  95         {
  96           /* At this point, we have processed and removed all suffixes from the
  97              code and what remains of the code is suffix free.  */
  98           return;
  99         }
 100       else
 101         {
 102           /* A suffix is processed from the end of the code array going
 103              backwards, one suffix at a time.  The suffix is an index into the
 104              code character array and points to: one past the end of the code
 105              and any unprocessed suffixes, and to the beginning of the suffix
 106              currently being processed during this iteration.  We must process
 107              this suffix and then drop it from the code by terminating the
 108              preceding text with NULL.
 109
 110              We want to allow and recognize suffixes such as:
 111
 112              "/TRANSLIT"         i.e. single suffix
 113              "//TRANSLIT"        i.e. single suffix and multiple separators
 114              "//TRANSLIT/IGNORE" i.e. suffixes separated by "/"
 115              "/TRANSLIT//IGNORE" i.e. suffixes separated by "//"
 116              "//IGNORE,TRANSLIT" i.e. suffixes separated by ","
 117              "//IGNORE,"         i.e. trailing ","
 118              "//TRANSLIT/"       i.e. trailing "/"
 119              "//TRANSLIT//"      i.e. trailing "//"
 120              "/"                 i.e. empty suffix.
 121
 122              Unknown suffixes are silently discarded and ignored.  */
 123
 124           if ((__strcasecmp_l (suffix,
 125                                GCONV_TRIPLE_SEPARATOR
 126                                GCONV_TRANSLIT_SUFFIX,
 127                                _nl_C_locobj_ptr) == 0)
 128               || (__strcasecmp_l (suffix,
 129                                   GCONV_SUFFIX_SEPARATOR
 130                                   GCONV_TRANSLIT_SUFFIX,
 131                                   _nl_C_locobj_ptr) == 0))
 132             pc->translit = true;
 133
 134           if ((__strcasecmp_l (suffix,
 135                                GCONV_TRIPLE_SEPARATOR
 136                                GCONV_IGNORE_ERRORS_SUFFIX,
 137                                _nl_C_locobj_ptr) == 0)
 138               || (__strcasecmp_l (suffix,
 139                                   GCONV_SUFFIX_SEPARATOR
 140                                   GCONV_IGNORE_ERRORS_SUFFIX,
 141                                   _nl_C_locobj_ptr) == 0))
 142             pc->ignore = true;
 143
 144           /* We just processed this suffix.  We can now drop it from the
 145              code string by truncating it at the suffix's position.  */
 146           suffix[0] = '\0';
 147         }
 148     }
 149 }
 150
 151
 152 /* This function accepts the charset names of the source and destination of the
 153    conversion and populates *conv_spec with an equivalent conversion
 154    specification that may later be used by __gconv_open.  The charset names
 155    might contain options in the form of suffixes that alter the conversion,
 156    e.g. "ISO-10646/UTF-8/TRANSLIT".  It processes the charset names, ignoring
 157    and truncating any suffix options in fromcode, and processing and truncating
 158    any suffix options in tocode.  Supported suffix options ("TRANSLIT" or
 159    "IGNORE") when found in tocode lead to the corresponding flag in *conv_spec
 160    to be set to true.  Unrecognized suffix options are silently discarded.  If
 161    the function succeeds, it returns conv_spec back to the caller.  It returns
 162    NULL upon failure.  conv_spec must be allocated and freed by the caller.  */
 163 struct gconv_spec *
 164 __gconv_create_spec (struct gconv_spec *conv_spec, const char *fromcode,
 165                    const char *tocode)
 166 {
 167   struct gconv_parsed_code pfc, ptc;
 168   struct gconv_spec *ret = NULL;
 169
 170   pfc.code = __strdup (fromcode);
 171   ptc.code = __strdup (tocode);
 172
 173   if ((pfc.code == NULL)
 174       || (ptc.code == NULL))
 175     goto out;
 176
 177   gconv_parse_code (&pfc);
 178   gconv_parse_code (&ptc);
 179
 180   /* We ignore suffixes in the fromcode because that is how the current
 181      implementation has always handled them.  Only suffixes in the tocode are
 182      processed and handled.  The reality is that invalid input in the input
 183      character set should only be ignored if the fromcode specifies IGNORE.
 184      The current implementation ignores invalid input in the input character
 185      set if the tocode contains IGNORE.  We preserve this behavior for
 186      backwards compatibility.  In the future we may split the handling of
 187      IGNORE to allow a finer grained specification of ignoring invalid input
 188      and/or ignoring invalid output.  */
 189   conv_spec->translit = ptc.translit;
 190   conv_spec->ignore = ptc.ignore;
 191
 192   /* 3 extra bytes because 1 extra for '\0', and 2 extra so strip might
 193      be able to add one or two trailing '/' characters if necessary.  */
 194   conv_spec->fromcode = malloc (strlen (fromcode) + 3);
 195   if (conv_spec->fromcode == NULL)
 196     goto out;
 197
 198   conv_spec->tocode = malloc (strlen (tocode) + 3);
 199   if (conv_spec->tocode == NULL)
 200     {
 201       free (conv_spec->fromcode);
 202       conv_spec->fromcode = NULL;
 203       goto out;
 204     }
 205
 206   /* Strip unrecognized characters and ensure that the code has two '/'
 207      characters as per conversion code triplet specification.  */
 208   strip (conv_spec->fromcode, pfc.code);
 209   strip (conv_spec->tocode, ptc.code);
 210   ret = conv_spec;
 211
 212 out:
 213   free (pfc.code);
 214   free (ptc.code);
 215
 216   return ret;
 217 }
 218 libc_hidden_def (__gconv_create_spec)
 219
 220
 221 void
 222 __gconv_destroy_spec (struct gconv_spec *conv_spec)
 223 {
 224   free (conv_spec->fromcode);
 225   free (conv_spec->tocode);
 226   return;
 227 }
 228 libc_hidden_def (__gconv_destroy_spec)