initial import

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 <sys/types.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+/* 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);
+}