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authorEric Andersen <andersen@codepoet.org>2001-09-15 08:31:43 +0000
committerEric Andersen <andersen@codepoet.org>2001-09-15 08:31:43 +0000
commit31900584d5e2398ee8d0f3cad0c85678f0444bfe (patch)
tree2ac81769dc73fcf19dc9d8f6c6ab51cec7837ae4 /libc/misc/file/lockf.c
parent07187c6aff8079e6d9267f32a5f0cc722df72dec (diff)
Add lockf
Diffstat (limited to 'libc/misc/file/lockf.c')
-rw-r--r--libc/misc/file/lockf.c70
1 files changed, 70 insertions, 0 deletions
diff --git a/libc/misc/file/lockf.c b/libc/misc/file/lockf.c
new file mode 100644
index 000000000..3d6f46290
--- /dev/null
+++ b/libc/misc/file/lockf.c
@@ -0,0 +1,70 @@
+/* Copyright (C) 1994, 1996, 1997, 1998, 2000 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., 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;
+ }
+
+ return fcntl(fd, cmd, &fl);
+}