[dart:io] Namespaces for file IO

runtime/bin/namespace_patch.dart

Index: runtime/bin/namespace_patch.dart
diff --git a/runtime/bin/namespace_patch.dart b/runtime/bin/namespace_patch.dart
new file mode 100644
index 0000000000000000000000000000000000000000..8fc6463b38d35111e5b8032908bf74ec61e66605
--- /dev/null
+++ b/runtime/bin/namespace_patch.dart
@@ -0,0 +1,45 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+class _NamespaceImpl extends NativeFieldWrapperClass1 implements _Namespace {
+  _NamespaceImpl._();
+
+  static _NamespaceImpl _create(_NamespaceImpl namespace, var n)
+      native "Namespace_Create";
+  static int _getPointer(_NamespaceImpl namespace)
+      native "Namespace_GetPointer";
+  static int _getDefault() native "Namespace_GetDefault";
+
+  // If the platform supports "namespaces", this method is called by the
+  // embedder with the platform-specific namespace information.
+  static _NamespaceImpl _cachedNamespace = null;
+  static void _setupNamespace(var namespace) {
+    _cachedNamespace = _create(new _NamespaceImpl._(), namespace);
+  }
+
+  static _NamespaceImpl get _namespace {
+    if (_cachedNamespace == null) {
+      // The embedder has not supplied a namespace before one is needed, so
+      // instead use a safe-ish default value.
+      _cachedNamespace = _create(new _NamespaceImpl._(), _getDefault());
+    }
+    return _cachedNamespace;
+  }
+
+  static int get _namespacePointer => _getPointer(_namespace);
+}
+
+@patch
+class _Namespace {
+  @patch
+  static void _setupNamespace(var namespace) {
+    _NamespaceImpl._setupNamespace(namespace);
+  }
+
+  @patch
+  static _Namespace get _namespace => _NamespaceImpl._namespace;
+
+  @patch
+  static int get _namespacePointer => _NamespaceImpl._namespacePointer;
+}