sysvipc/ftok.c

   1 /* Copyright (C) 1995-2017 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sys/ipc.h>
  20 #include <sys/stat.h>
  21
  22 key_t
  23 ftok (const char *pathname, int proj_id)
  24 {
  25   struct stat64 st;
  26   key_t key;
  27
  28   if (__xstat64 (_STAT_VER, pathname, &st) < 0)
  29     return (key_t) -1;
  30
  31   key = ((st.st_ino & 0xffff) | ((st.st_dev & 0xff) << 16)
  32          | ((proj_id & 0xff) << 24));
  33
  34   return key;
  35 }