1 files changed, 74 insertions, 0 deletions
diff --git a/io/lockf.c b/io/lockf.c
new file mode 100644
index 0000000000..7b23f66bc9
--- /dev/null
+++ b/io/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);
+}