lib/link.c

   1 /* Emulate link on platforms that lack it, namely native Windows platforms.
   2
   3    Copyright (C) 2009-2014 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 Lesser General Public License as published by
   7    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
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program; if not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 #include <unistd.h>
  21
  22 #include <errno.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/stat.h>
  26
  27 #if !HAVE_LINK
  28 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  29
  30 #  define WIN32_LEAN_AND_MEAN
  31 #  include <windows.h>
  32
  33 /* CreateHardLink was introduced only in Windows 2000.  */
  34 typedef BOOL (WINAPI * CreateHardLinkFuncType) (LPCTSTR lpFileName,
  35                                                 LPCTSTR lpExistingFileName,
  36                                                 LPSECURITY_ATTRIBUTES lpSecurityAttributes);
  37 static CreateHardLinkFuncType CreateHardLinkFunc = NULL;
  38 static BOOL initialized = FALSE;
  39
  40 static void
  41 initialize (void)
  42 {
  43   HMODULE kernel32 = GetModuleHandle ("kernel32.dll");
  44   if (kernel32 != NULL)
  45     {
  46       CreateHardLinkFunc =
  47         (CreateHardLinkFuncType) GetProcAddress (kernel32, "CreateHardLinkA");
  48     }
  49   initialized = TRUE;
  50 }
  51
  52 int
  53 link (const char *file1, const char *file2)
  54 {
  55   char *dir;
  56   size_t len1 = strlen (file1);
  57   size_t len2 = strlen (file2);
  58   if (!initialized)
  59     initialize ();
  60   if (CreateHardLinkFunc == NULL)
  61     {
  62       /* System does not support hard links.  */
  63       errno = EPERM;
  64       return -1;
  65     }
  66   /* Reject trailing slashes on non-directories; mingw does not
  67      support hard-linking directories.  */
  68   if ((len1 && (file1[len1 - 1] == '/' || file1[len1 - 1] == '\\'))
  69       || (len2 && (file2[len2 - 1] == '/' || file2[len2 - 1] == '\\')))
  70     {
  71       struct stat st;
  72       if (stat (file1, &st) == 0 && S_ISDIR (st.st_mode))
  73         errno = EPERM;
  74       else
  75         errno = ENOTDIR;
  76       return -1;
  77     }
  78   /* CreateHardLink("b/.","a",NULL) creates file "b", so we must check
  79      that dirname(file2) exists.  */
  80   dir = strdup (file2);
  81   if (!dir)
  82     return -1;
  83   {
  84     struct stat st;
  85     char *p = strchr (dir, '\0');
  86     while (dir < p && (*--p != '/' && *p != '\\'));
  87     *p = '\0';
  88     if (p != dir && stat (dir, &st) == -1)
  89       {
  90         int saved_errno = errno;
  91         free (dir);
  92         errno = saved_errno;
  93         return -1;
  94       }
  95     free (dir);
  96   }
  97   /* Now create the link.  */
  98   if (CreateHardLinkFunc (file2, file1, NULL) == 0)
  99     {
 100       /* It is not documented which errors CreateHardLink() can produce.
 101        * The following conversions are based on tests on a Windows XP SP2
 102        * system. */
 103       DWORD err = GetLastError ();
 104       switch (err)
 105         {
 106         case ERROR_ACCESS_DENIED:
 107           errno = EACCES;
 108           break;
 109
 110         case ERROR_INVALID_FUNCTION:    /* fs does not support hard links */
 111           errno = EPERM;
 112           break;
 113
 114         case ERROR_NOT_SAME_DEVICE:
 115           errno = EXDEV;
 116           break;
 117
 118         case ERROR_PATH_NOT_FOUND:
 119         case ERROR_FILE_NOT_FOUND:
 120           errno = ENOENT;
 121           break;
 122
 123         case ERROR_INVALID_PARAMETER:
 124           errno = ENAMETOOLONG;
 125           break;
 126
 127         case ERROR_TOO_MANY_LINKS:
 128           errno = EMLINK;
 129           break;
 130
 131         case ERROR_ALREADY_EXISTS:
 132           errno = EEXIST;
 133           break;
 134
 135         default:
 136           errno = EIO;
 137         }
 138       return -1;
 139     }
 140
 141   return 0;
 142 }
 143
 144 # else /* !Windows */
 145
 146 #  error "This platform lacks a link function, and Gnulib doesn't provide a replacement. This is a bug in Gnulib."
 147
 148 # endif /* !Windows */
 149 #else /* HAVE_LINK */
 150
 151 # undef link
 152
 153 /* Create a hard link from FILE1 to FILE2, working around platform bugs.  */
 154 int
 155 rpl_link (char const *file1, char const *file2)
 156 {
 157   size_t len1;
 158   size_t len2;
 159   struct stat st;
 160
 161   /* Don't allow IRIX to dereference dangling file2 symlink.  */
 162   if (!lstat (file2, &st))
 163     {
 164       errno = EEXIST;
 165       return -1;
 166     }
 167
 168   /* Reject trailing slashes on non-directories.  */
 169   len1 = strlen (file1);
 170   len2 = strlen (file2);
 171   if ((len1 && file1[len1 - 1] == '/')
 172       || (len2 && file2[len2 - 1] == '/'))
 173     {
 174       /* Let link() decide whether hard-linking directories is legal.
 175          If stat() fails, then link() should fail for the same reason
 176          (although on Solaris 9, link("file/","oops") mistakenly
 177          succeeds); if stat() succeeds, require a directory.  */
 178       if (stat (file1, &st))
 179         return -1;
 180       if (!S_ISDIR (st.st_mode))
 181         {
 182           errno = ENOTDIR;
 183           return -1;
 184         }
 185     }
 186   else
 187     {
 188       /* Fix Cygwin 1.5.x bug where link("a","b/.") creates file "b".  */
 189       char *dir = strdup (file2);
 190       char *p;
 191       if (!dir)
 192         return -1;
 193       /* We already know file2 does not end in slash.  Strip off the
 194          basename, then check that the dirname exists.  */
 195       p = strrchr (dir, '/');
 196       if (p)
 197         {
 198           *p = '\0';
 199           if (stat (dir, &st) == -1)
 200             {
 201               int saved_errno = errno;
 202               free (dir);
 203               errno = saved_errno;
 204               return -1;
 205             }
 206         }
 207       free (dir);
 208     }
 209   return link (file1, file2);
 210 }
 211 #endif /* HAVE_LINK */