aboutsummaryrefslogtreecommitdiff
path: root/sysdeps/generic/lockf.c
diff options
context:
space:
mode:
Diffstat (limited to 'sysdeps/generic/lockf.c')
-rw-r--r--sysdeps/generic/lockf.c74
1 files changed, 74 insertions, 0 deletions
diff --git a/sysdeps/generic/lockf.c b/sysdeps/generic/lockf.c
new file mode 100644
index 0000000..7b23f66
--- /dev/null
+++ b/sysdeps/generic/lockf.c
@@ -0,0 +1,74 @@
+/* Copyright (C) 1994,1996,1997,1998,2000,2003 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 Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+
+/* lockf is a simplified interface to fcntl's locking facilities. */
+
+int
+lockf (int fd, int cmd, off_t len)
+{
+ struct flock fl;
+
+ memset ((char *) &fl, '\0', sizeof (fl));
+
+ /* lockf is always relative to the current file position. */
+ fl.l_whence = SEEK_CUR;
+ fl.l_start = 0;
+ fl.l_len = len;
+
+ 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. */
+ fl.l_type = F_RDLCK;
+ if (__fcntl (fd, F_GETLK, &fl) < 0)
+ return -1;
+ if (fl.l_type == F_UNLCK || fl.l_pid == __getpid ())
+ return 0;
+ __set_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:
+ __set_errno (EINVAL);
+ return -1;
+ }
+
+ /* lockf() is a cancellation point but so is fcntl() if F_SETLKW is
+ used. Therefore we don't have to care about cancellation here,
+ the fcntl() function will take care of it. */
+ return __fcntl (fd, cmd, &fl);
+}