From 28f540f45bbacd939bfd07f213bcad2bf730b1bf Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Sat, 18 Feb 1995 01:27:10 +0000 Subject: initial import --- io/lockf.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 io/lockf.c (limited to 'io/lockf.c') diff --git a/io/lockf.c b/io/lockf.c new file mode 100644 index 0000000000..91664197ae --- /dev/null +++ b/io/lockf.c @@ -0,0 +1,68 @@ +/* Copyright (C) 1994 Free Software Foundation, Inc. +This file is part of the GNU C Library. + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#include +#include +#include +#include + +/* lockf is a simplified interface to fcntl's locking facilities. */ + +int +lockf (int fd, int cmd, off_t len) +{ + struct flock fl; + + switch (cmd) + { + case F_TEST: + /* Test the lock: return 0 if FD is unlocked or locked by this process; + return -1, set errno to EACCES, if another process holds the lock. */ + if (fcntl (fd, F_GETLK, &fl) < 0) + return -1; + if (fl.l_type == F_UNLCK || fl.l_pid == getpid ()) + return 0; + errno = EACCES; + return -1; + + case F_ULOCK: + fl.l_type = F_UNLCK; + cmd = F_SETLK; + break; + case F_LOCK: + fl.l_type = F_WRLCK; + cmd = F_SETLKW; + break; + case F_TLOCK: + fl.l_type = F_WRLCK; + cmd = F_SETLK; + break; + + default: + errno = EINVAL; + return -1; + } + + /* lockf is always relative to the current file position. */ + fl.l_whence = SEEK_CUR; + fl.l_start = 0; + + fl.l_len = len; + + return fcntl (fd, cmd, &fl); +} -- cgit v1.2.3