Add a basic YAML processor. Much of the language is still unimplemented.

utils/yaml/yaml_map.dart

+// Copyright (c) 2012, 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.
+
+/**
+ * This class wraps behaves almost identically to the normal Dart Map
+ * implementation, with the following differences:
+ *
+ * * It allows null, NaN, boolean, list, and map keys.
+ * * It is itself Hashable.
+ * * It defines `==` structurally. That is, `yamlMap1 == yamlMap2` if they have
+ *   the same contents.
+ */
+class YamlMap implements Map, Hashable {
+  Map _map;
+
+  YamlMap() : _map = new Map();
+
+  YamlMap.from(Map map) : _map = new Map.from(map);
+
+  bool containsValue(value) => _map.containsValue(value);
+  bool containsKey(key) => _map.containsKey(_wrapKey(key));
+  operator [](key) => _map[_wrapKey(key)];
+  operator []=(key, value) { _map[_wrapKey(key)] = value; }
+  putIfAbsent(key, ifAbsent()) => _map.putIfAbsent(_wrapKey(key), ifAbsent);
+  remove(key) => _map.remove(_wrapKey(key));
+  void clear() => _map.clear();
+  void forEach(void f(key, value)) =>
+    _map.forEach((k, v) => f(_unwrapKey(k), v));
+  Collection getKeys() => _map.getKeys().map(_unwrapKey);
+  Collection getValues() => _map.getValues();
+  int get length() => _map.length;
+  bool isEmpty() => _map.isEmpty();
+  String toString() => _map.toString();
+
+  int hashCode() => _hashCode(_map);
+
+  bool operator ==(other) {
+    if (other is! YamlMap) return false;
+    return deepEquals(this, other);
+  }
+
+  /** Wraps an object for use as a key in the map. */
+  _wrapKey(obj) {
+    if (obj != null && obj is! bool && obj is! List &&
+        (obj is! double || !obj.isNan()) &&
+        (obj is! Map || obj is YamlMap)) {
+      return obj;
+    }
+    return new _WrappedHashKey(obj);
+  }
+
+  /** Unwraps an object that was used as a key in the map. */
+  _unwrapKey(obj) => obj is _WrappedHashKey ? obj.value : obj;
+}
+
+/**
+ * A class for wrapping normally-unhashable objects that are being used as keys
+ * in a YamlMap.
+ */
+class _WrappedHashKey implements Hashable {
+  var value;
+
+  _WrappedHashKey(this.value);
+
+  int hashCode() => _hashCode(value);
+
+  String toString() => value.toString();
+
+  /** This is defined as both values being structurally equal. */
+  bool operator ==(other) {
+    if (other is! _WrappedHashKey) return false;
+    return deepEquals(this.value, other.value);
+  }
+}
+
+/**
+ * Returns the hash code for [obj]. This includes null, true, false, maps, and
+ * lists. Also handles self-referential structures.
+ */
+int _hashCode(obj, [List parents]) {
+  if (parents == null) {
+    parents = [];
+  } else if (parents.some((p) => 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 _hashCode(obj.getKeys(), parents) ^
+        _hashCode(obj.getValues(), parents);
+    }
+    if (obj is List) {
+      // 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 ^= _hashCode(e, parents);
+      }
+      return hash;
+    }
+    return obj.hashCode();
+  } finally {
+    parents.removeLast();
+  }
+}