Restructure the yaml package.

pkg/yaml/lib/src/utils.dart

+// Copyright (c) 2013, 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.
+
+library utils;
+
+/// Returns the hash code for [obj]. This includes null, true, false, maps, and
+/// lists. Also handles self-referential structures.
+int hashCodeFor(obj, [List parents]) {
+  if (parents == null) {
+    parents = [];
+  } else if (parents.any((p) => identical(p, obj))) {
+    return -1;
+  }
+
+  parents.add(obj);
+  try {
+    if (obj == null) return 0;
+    if (obj == true) return 1;
+    if (obj == false) return 2;
+    if (obj is Map) {
+      return hashCodeFor(obj.keys, parents) ^
+        hashCodeFor(obj.values, parents);
+    }
+    if (obj is Iterable) {
+      // This is probably a really bad hash function, but presumably we'll get
+      // this in the standard library before it actually matters.
+      int hash = 0;
+      for (var e in obj) {
+        hash ^= hashCodeFor(e, parents);
+      }
+      return hash;
+    }
+    return obj.hashCode;
+  } finally {
+    parents.removeLast();
+  }
+}
+