Add lockf

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);
+}