Add support for file locking

tests/standalone/io/file_lock_script.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file

[Lasse Reichstein Nielsen, 2015/01/08 11:59:22]

2015

[Søren Gjesse, 2015/01/09 13:06:20]

Done.

+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+//
+// Script used by the file_lock_test.dart test.
+
+import "dart:io";
+
+main(List<String> args) {
+  File file = new File(args[0]);
+  int start = null;
+  int end = null;
+  var  mode = FileLock.EXCLUSIVE;

[Lasse Reichstein Nielsen, 2015/01/08 11:59:22]

Consider making arguments optional, so:
  if (args.length > 1 && args[1] != 'null') ...

[Søren Gjesse, 2015/01/09 13:06:20]

The test code that calls this script always passes all arguments.

+  if (args[1] != 'null') {
+    start = int.parse(args[1]);
+  }
+  if (args[2] != 'null') {
+    end = int.parse(args[2]);
+  }
+  if (args[3] == 'SHARED') {
+    mode = FileLock.SHARED;
+  }
+  var raf = file.openSync(mode: WRITE);
+  try {
+    print('calling lockSync: $start $end $mode');
+    raf.lockSync(start, end, mode);
+  } catch (e) {
+    print('LOCK FAILED');
+    raf.closeSync();
+    return;
+  }
+  print('LOCK SUCCEEDED');
+  raf.closeSync();

[kustermann, 2015/01/08 12:54:27]

move the raf.closeSync() into a finally? - then you don't need it twice.

[Søren Gjesse, 2015/01/09 13:06:20]

Done.

+}