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