io/lockf64.c

   1 /* Copyright (C) 1994,96,97,98,99,2000 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <sys/types.h>
  20 #include <unistd.h>
  21 #include <fcntl.h>
  22 #include <errno.h>
  23 #include <string.h>
  24
  25 /* lockf is a simplified interface to fcntl's locking facilities.  */
  26
  27 int
  28 lockf64 (int fd, int cmd, off64_t len64)
  29 {
  30   struct flock fl;
  31   off_t len = (off_t) len64;
  32
  33   if (len64 != (off64_t) len)
  34     {
  35       /* We can't represent the length.  */
  36       __set_errno (EOVERFLOW);
  37       return -1;
  38     }
  39
  40   memset ((char *) &fl, '\0', sizeof (fl));
  41
  42   /* lockf is always relative to the current file position.  */
  43   fl.l_whence = SEEK_CUR;
  44   fl.l_start = 0;
  45   fl.l_len = len;
  46
  47   switch (cmd)
  48     {
  49     case F_TEST:
  50       /* Test the lock: return 0 if FD is unlocked or locked by this process;
  51          return -1, set errno to EACCES, if another process holds the lock.  */
  52       fl.l_type = F_RDLCK;
  53       if (__fcntl (fd, F_GETLK, &fl) < 0)
  54         return -1;
  55       if (fl.l_type == F_UNLCK || fl.l_pid == __getpid ())
  56         return 0;
  57       __set_errno (EACCES);
  58       return -1;
  59
  60     case F_ULOCK:
  61       fl.l_type = F_UNLCK;
  62       cmd = F_SETLK;
  63       break;
  64     case F_LOCK:
  65       fl.l_type = F_WRLCK;
  66       cmd = F_SETLKW;
  67       break;
  68     case F_TLOCK:
  69       fl.l_type = F_WRLCK;
  70       cmd = F_SETLK;
  71       break;
  72
  73     default:
  74       __set_errno (EINVAL);
  75       return -1;
  76     }
  77
  78   return __fcntl (fd, cmd, &fl);
  79 }