Restructure the yaml package.

pkg/yaml/lib/src/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.
 
-part of yaml;
+library yaml_map;
+
+import 'deep_equals.dart';
+import 'utils.dart';
 
 /// 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 defines `==` structurally. That is, `yamlMap1 == yamlMap2` if they
 ///     have the same contents.
 ///  *  It has a compatible [hashCode] method.
 class YamlMap implements Map {
-  Map _map;
+  final Map _map;
 
   YamlMap() : _map = new Map();
 
   YamlMap.from(Map map) : _map = new Map.from(map);
 
   YamlMap._wrap(this._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));
   Iterable get keys => _map.keys.map(_unwrapKey);
   Iterable get values => _map.values;
   int get length => _map.length;
   bool get isEmpty => _map.isEmpty;
   String toString() => _map.toString();
 
-  int get hashCode => _hashCode(_map);
+  int get hashCode => hashCodeFor(_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;
     } else if (obj is Map) {
       return new YamlMap._wrap(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 {
-  var value;
+  final value;
 
   _WrappedHashKey(this.value);
 
-  int get hashCode => _hashCode(value);
+  int get hashCode => hashCodeFor(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.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 _hashCode(obj.keys, parents) ^
-        _hashCode(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 ^= _hashCode(e, parents);
-      }
-      return hash;
-    }
-    return obj.hashCode;
-  } finally {
-    parents.removeLast();
-  }
-}