libc/misc/file/lockf64.c

   1 /* Copyright (C) 1994, 1996, 1997, 1998, 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 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 not,
  16    see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <_lfs_64.h>
  19
  20 #include <sys/types.h>
  21 #include <unistd.h>
  22 #include <fcntl.h>
  23 #include <errno.h>
  24 #include <string.h>
  25 #include <sys/syscall.h>
  26
  27 #ifdef __NR_fcntl64
  28 #define flock flock64
  29 #define fcntl fcntl64
  30 #undef F_GETLK
  31 #define F_GETLK F_GETLK64
  32 #undef F_SETLK
  33 #define F_SETLK F_SETLK64
  34 #else
  35 #endif
  36
  37
  38 /* lockf is a simplified interface to fcntl's locking facilities.  */
  39
  40 int lockf64 (int fd, int cmd, off64_t len64)
  41 {
  42     struct flock fl;
  43     off_t len = (off_t) len64;
  44
  45     if (len64 != (off64_t) len)
  46     {
  47         /* We can't represent the length.  */
  48         __set_errno(EOVERFLOW);
  49         return -1;
  50     }
  51
  52     memset((char *) &fl, '\0', sizeof (fl));
  53
  54     /* lockf is always relative to the current file position.  */
  55     fl.l_whence = SEEK_CUR;
  56     fl.l_start = 0;
  57     fl.l_len = len;
  58
  59     switch (cmd)
  60     {
  61         case F_TEST:
  62             /* Test the lock: return 0 if FD is unlocked or locked by this process;
  63                return -1, set errno to EACCES, if another process holds the lock.  */
  64             fl.l_type = F_RDLCK;
  65             if (fcntl (fd, F_GETLK, &fl) < 0)
  66                 return -1;
  67             if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
  68                 return 0;
  69             __set_errno(EACCES);
  70             return -1;
  71
  72         case F_ULOCK:
  73             fl.l_type = F_UNLCK;
  74             cmd = F_SETLK;
  75             break;
  76         case F_LOCK:
  77             fl.l_type = F_WRLCK;
  78             cmd = F_SETLKW;
  79             break;
  80         case F_TLOCK:
  81             fl.l_type = F_WRLCK;
  82             cmd = F_SETLK;
  83             break;
  84
  85         default:
  86             __set_errno(EINVAL);
  87             return -1;
  88     }
  89
  90     return fcntl(fd, cmd, &fl);
  91 }