sysdeps/mach/hurd/readlink.c

   1 /* Copyright (C) 1991, 1992, 1993, 1994, 1995 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 Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 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 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <unistd.h>
  21 #include <hurd.h>
  22 #include <hurd/paths.h>
  23 #include <fcntl.h>
  24 #include <string.h>
  25
  26 /* Read the contents of the symbolic link FILE_NAME into no more than
  27    LEN bytes of BUF.  The contents are not null-terminated.
  28    Returns the number of characters read, or -1 for errors.  */
  29 ssize_t
  30 DEFUN(__readlink, (file_name, buf, len),
  31       CONST char *file_name AND char *buf AND size_t len)
  32 {
  33   error_t err;
  34   file_t file;
  35   char mybuf[2048], *transp = mybuf;
  36   mach_msg_type_number_t translen = sizeof (mybuf);
  37
  38   file = __file_name_lookup (file_name, O_NOTRANS, 0);
  39   if (file == MACH_PORT_NULL)
  40     return -1;
  41
  42   err = __file_get_translator (file, &transp, &translen);
  43   __mach_port_deallocate (__mach_task_self (), file);
  44
  45   if (err)
  46     return __hurd_fail (err);
  47
  48   if (translen < sizeof (_HURD_SYMLINK) ||
  49       memcmp (transp, _HURD_SYMLINK, sizeof (_HURD_SYMLINK)))
  50     /* The file is not actually a symlink.  */
  51     err = EINVAL;
  52   else
  53     {
  54       /* This is a symlink; its translator is "/hurd/symlink\0target\0".  */
  55       if (len >= translen - sizeof (_HURD_SYMLINK))
  56         {
  57           len = translen - sizeof (_HURD_SYMLINK);
  58           if (transp[translen - 1] == '\0')
  59             /* Remove the null terminator.  */
  60             --len;
  61         }
  62       if (buf == NULL)
  63         /* This call is just to find out how large a buffer is required.  */
  64         len = translen - sizeof (_HURD_SYMLINK) - 1;
  65       else
  66         /* Copy into the user's buffer.  */
  67         memcpy (buf, transp + sizeof (_HURD_SYMLINK), len);
  68     }
  69
  70   if (transp != mybuf)
  71     __vm_deallocate (__mach_task_self (), (vm_address_t) transp, translen);
  72
  73   return err ? __hurd_fail (err) : len;
  74 }
  75
  76 weak_alias (__readlink, readlink)