lib/canonicalize.c

   1 /* Return the canonical absolute name of a given file.
   2    Copyright (C) 1996-2001, 2002, 2003 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; see the file COPYING.
  16    If not, write to the Free Software Foundation,
  17    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 #ifdef HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 #ifdef STDC_HEADERS
  24 # include <stdlib.h>
  25 #else
  26 void free ();
  27 #endif
  28
  29 #if defined STDC_HEADERS || defined HAVE_STRING_H
  30 # include <string.h>
  31 #else
  32 # include <strings.h>
  33 #endif
  34
  35 #if HAVE_SYS_PARAM_H
  36 # include <sys/param.h>
  37 #endif
  38
  39 #include <sys/stat.h>
  40
  41 #include <errno.h>
  42
  43 #include "path-concat.h"
  44 #include "xalloc.h"
  45 #include "xgetcwd.h"
  46
  47 #ifndef errno
  48 extern int errno;
  49 #endif
  50
  51 #ifndef __set_errno
  52 # define __set_errno(Val) errno = (Val)
  53 #endif
  54
  55 #if !HAVE_RESOLVEPATH
  56
  57 /* If __PTRDIFF_TYPE__ is
  58    defined, as with GNU C, use that; that way we don't pollute the
  59    namespace with <stddef.h>'s symbols.  Otherwise, if <stddef.h> is
  60    available, include it and use ptrdiff_t.  In traditional C, long is
  61    the best that we can do.  */
  62
  63 # ifdef __PTRDIFF_TYPE__
  64 #  define PTR_INT_TYPE __PTRDIFF_TYPE__
  65 # else
  66 #  ifdef HAVE_STDDEF_H
  67 #   include <stddef.h>
  68 #   define PTR_INT_TYPE ptrdiff_t
  69 #  else
  70 #   define PTR_INT_TYPE long
  71 #  endif
  72 # endif
  73
  74 # include "pathmax.h"
  75 # include "xreadlink.h"
  76
  77 # ifdef STAT_MACROS_BROKEN
  78 #  undef S_ISLNK
  79 # endif
  80
  81 # ifndef S_ISLNK
  82 #  ifdef S_IFLNK
  83 #   define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
  84 #  endif
  85 # endif
  86
  87 #endif /* !HAVE_RESOLVEPATH */
  88
  89 /* Return the canonical absolute name of file NAME.  A canonical name
  90    does not contain any `.', `..' components nor any repeated path
  91    separators ('/') or symlinks.  All path components must exist.
  92    The result is malloc'd.  */
  93
  94 char *
  95 canonicalize_file_name (const char *name)
  96 {
  97 #if HAVE_RESOLVEPATH
  98
  99   char *resolved, *extra_buf = NULL;
 100   size_t resolved_size;
 101   ssize_t resolved_len;
 102
 103 #else /* !HAVE_RESOLVEPATH */
 104
 105   char *rpath, *dest, *extra_buf = NULL;
 106   const char *start, *end, *rpath_limit;
 107   size_t extra_len = 0;
 108   int num_links = 0;
 109
 110 #endif /* !HAVE_RESOLVEPATH */
 111
 112   if (name == NULL)
 113     {
 114       __set_errno (EINVAL);
 115       return NULL;
 116     }
 117
 118   if (name[0] == '\0')
 119     {
 120       __set_errno (ENOENT);
 121       return NULL;
 122     }
 123
 124 #if HAVE_RESOLVEPATH
 125
 126   /* All known hosts with resolvepath (e.g. Solaris 7) don't turn
 127      relative names into absolute ones, so prepend the working
 128      directory if the path is not absolute.  */
 129   if (name[0] != '/')
 130     {
 131       char *wd;
 132
 133       if (!(wd = xgetcwd ()));
 134         return NULL;
 135
 136       extra_buf = path_concat (wd, name, NULL);
 137       if (!extra_buf)
 138         xalloc_die ();
 139
 140       name = extra_buf;
 141       free (wd);
 142     }
 143
 144   resolved_size = strlen (name);
 145   while (1)
 146     {
 147       resolved_size = 2 * resolved_size + 1;
 148       resolved = xmalloc (resolved_size);
 149       resolved_len = resolvepath (name, resolved, resolved_size);
 150       if (resolved_len < resolved_size)
 151         break;
 152       free (resolved);
 153     }
 154
 155   if (resolved_len < 0)
 156     {
 157       free (resolved);
 158       resolved = NULL;
 159     }
 160
 161   free (extra_buf);
 162   return resolved;
 163
 164 #else /* !HAVE_RESOLVEPATH */
 165
 166   if (name[0] != '/')
 167     {
 168       rpath = xgetcwd ();
 169       if (!rpath)
 170         return NULL;
 171       dest = strchr (rpath, '\0');
 172       if (dest < rpath + PATH_MAX)
 173         {
 174           rpath = xrealloc (rpath, PATH_MAX);
 175           rpath_limit = rpath + PATH_MAX;
 176         }
 177       else
 178         {
 179           rpath_limit = dest;
 180         }
 181     }
 182   else
 183     {
 184       rpath = xmalloc (PATH_MAX);
 185       rpath_limit = rpath + PATH_MAX;
 186       rpath[0] = '/';
 187       dest = rpath + 1;
 188     }
 189
 190   for (start = end = name; *start; start = end)
 191     {
 192       /* Skip sequence of multiple path-separators.  */
 193       while (*start == '/')
 194         ++start;
 195
 196       /* Find end of path component.  */
 197       for (end = start; *end && *end != '/'; ++end)
 198         /* Nothing.  */;
 199
 200       if (end - start == 0)
 201         break;
 202       else if (end - start == 1 && start[0] == '.')
 203         /* nothing */;
 204       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
 205         {
 206           /* Back up to previous component, ignore if at root already.  */
 207           if (dest > rpath + 1)
 208             while ((--dest)[-1] != '/');
 209         }
 210       else
 211         {
 212           struct stat st;
 213
 214           if (dest[-1] != '/')
 215             *dest++ = '/';
 216
 217           if (dest + (end - start) >= rpath_limit)
 218             {
 219               PTR_INT_TYPE dest_offset = dest - rpath;
 220               size_t new_size = rpath_limit - rpath;
 221
 222               if (end - start + 1 > PATH_MAX)
 223                 new_size += end - start + 1;
 224               else
 225                 new_size += PATH_MAX;
 226               rpath = (char *) xrealloc (rpath, new_size);
 227               rpath_limit = rpath + new_size;
 228
 229               dest = rpath + dest_offset;
 230             }
 231
 232           dest = memcpy (dest, start, end - start);
 233           dest += end - start;
 234           *dest = '\0';
 235
 236           if (lstat (rpath, &st) < 0)
 237             goto error;
 238
 239 # ifdef S_ISLNK
 240           if (S_ISLNK (st.st_mode))
 241             {
 242               char *buf;
 243               size_t n, len;
 244
 245 #  ifdef MAXSYMLINKS
 246               if (++num_links > MAXSYMLINKS)
 247                 {
 248                   __set_errno (ELOOP);
 249                   goto error;
 250                 }
 251 #  endif /* MAXSYMLINKS */
 252
 253               buf = xreadlink (rpath);
 254               if (!buf)
 255                 goto error;
 256
 257               n = strlen (buf);
 258               len = strlen (end);
 259
 260               if (!extra_len)
 261                 {
 262                   extra_len =
 263                     ((n + len + 1) > PATH_MAX) ? (n + len + 1) : PATH_MAX;
 264                   extra_buf = xmalloc (extra_len);
 265                 }
 266               else if ((n + len + 1) > extra_len)
 267                 {
 268                   extra_len = n + len + 1;
 269                   extra_buf = xrealloc (extra_buf, extra_len);
 270                 }
 271
 272               /* Careful here, end may be a pointer into extra_buf... */
 273               memmove (&extra_buf[n], end, len + 1);
 274               name = end = memcpy (extra_buf, buf, n);
 275
 276               if (buf[0] == '/')
 277                 dest = rpath + 1;       /* It's an absolute symlink */
 278               else
 279                 /* Back up to previous component, ignore if at root already: */
 280                 if (dest > rpath + 1)
 281                   while ((--dest)[-1] != '/');
 282
 283               free (buf);
 284             }
 285 # endif /* S_ISLNK */
 286         }
 287     }
 288   if (dest > rpath + 1 && dest[-1] == '/')
 289     --dest;
 290   *dest = '\0';
 291
 292   free (extra_buf);
 293   return rpath;
 294
 295 error:
 296   free (extra_buf);
 297   free (rpath);
 298   return NULL;
 299 #endif /* !HAVE_RESOLVEPATH */
 300 }