sysdeps/mach/hurd/readlink.c

   1 /* Copyright (C) 1991-2018 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <unistd.h>
  19 #include <hurd.h>
  20 #include <hurd/paths.h>
  21 #include <fcntl.h>
  22 #include <string.h>
  23
  24 /* Read the contents of the symbolic link FILE_NAME into no more than
  25    LEN bytes of BUF.  The contents are not null-terminated.
  26    Returns the number of characters read, or -1 for errors.  */
  27 ssize_t
  28 __readlink (const char *file_name, char *buf, size_t len)
  29 {
  30   error_t err;
  31   file_t file;
  32   struct stat64 st;
  33
  34   file = __file_name_lookup (file_name, O_READ | O_NOLINK, 0);
  35   if (file == MACH_PORT_NULL)
  36     return -1;
  37
  38   err = __io_stat (file, &st);
  39   if (! err)
  40     if (S_ISLNK (st.st_mode))
  41       {
  42         char *rbuf = buf;
  43
  44         err = __io_read (file, &rbuf, &len, 0, len);
  45         if (!err && rbuf != buf)
  46           {
  47             memcpy (buf, rbuf, len);
  48             __vm_deallocate (__mach_task_self (), (vm_address_t)rbuf, len);
  49           }
  50       }
  51     else
  52       err = EINVAL;
  53
  54   __mach_port_deallocate (__mach_task_self (), file);
  55
  56   if (err)
  57     return __hurd_fail (err);
  58   else
  59     return len;
  60 }
  61 weak_alias (__readlink, readlink)