sysdeps/mach/hurd/ftok.c

   1 /* Copyright (C) 1995, 1996, 2000, 2005 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995.
   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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <sys/ipc.h>
  21 #include <sys/stat.h>
  22
  23 \f
  24 /* In the Hurd, we use the second-to-most-significant bit as flag for
  25    private keys.  We use a different order of the components so that
  26    the biggest one---the inode number---is affected by this.  */
  27
  28 key_t
  29 ftok (const char *pathname, int proj_id)
  30 {
  31   struct stat64 st;
  32   key_t key;
  33
  34   if (__stat64 (pathname, &st) < 0)
  35     return (key_t) -1;
  36
  37   key = ((st.st_dev & 0xff) | ((proj_id & 0xff) << 8)
  38          | ((st.st_ino & 0x3fff) << 16));
  39
  40   return key;
  41 }