Add EnumSet.

pkg/compiler/lib/src/util/enumset.dart

Index: pkg/compiler/lib/src/util/enumset.dart
diff --git a/pkg/compiler/lib/src/util/enumset.dart b/pkg/compiler/lib/src/util/enumset.dart
new file mode 100644
index 0000000000000000000000000000000000000000..953a8733626b4b93937b083018833eb8d4b35a6a
--- /dev/null
+++ b/pkg/compiler/lib/src/util/enumset.dart
@@ -0,0 +1,199 @@
+// Copyright (c) 2016, 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 dart2js.util.enumset;
+
+import 'dart:collection';
+
+/// A set of enum values based on a bit mask of the shifted enum indices.
+abstract class EnumSet<E> {
+  /// Creates an empty mutable set.
+  factory EnumSet() = _EnumSet<E>;
+
+  /// Creates a mutable set from the bit mask [value].
+  factory EnumSet.fromValue(int value) = _EnumSet<E>.fromValue;
+
+  /// Creates an immutable set from the bit mask [value].
+  const factory EnumSet.fixed(int value) = _ConstEnumSet<E>;
+
+  /// Create a set containing the [values]. If [fixed] is `true` the set is
+  /// immutable.
+  factory EnumSet.fromValues(Iterable<E> values, {bool fixed: false}) {
+    if (fixed) {
+      return new _ConstEnumSet<E>.fromValues(values);
+    } else {
+      return new _EnumSet<E>.fromValues(values);
+    }
+  }
+
+  const EnumSet._();
+
+  /// The bit mask of the shifted indices for the enum values in this set.
+  int get value;
+
+  /// Adds [enumValue] to this set.
+  void add(E enumValue);
+
+  /// Removes [enumValue] from this set.
+  void remove(E enumValue);
+
+  /// Clears this set.
+  void clear();
+
+  /// Returns `true` if [enumValue] is in this set.
+  bool contains(E enumValue) {
+    return (value & (1 << (enumValue as dynamic).index)) != 0;
+  }
+
+  /// Returns an [Iterable] of the values is in this set using [values] to
+  /// convert the stored indices to enum values.
+  ///
+  /// The method is typically called with the `values` property of the enum
+  /// class as argument:
+  ///
+  ///     EnumSet<EnumClass> set = ...
+  ///     Iterable<EnumClass> iterable = set.iterable(EnumClass.values);
+  ///
+  Iterable<E> iterable(List<E> values) {
+    return new _EnumSetIterable(this, values);
+  }
+
+  /// Returns `true` if this and [other] have any elements in common.
+  bool intersects(EnumSet<E> other) {
+    return (value & other.value) != 0;
+  }
+
+  /// Returns `true` if this set is empty.
+  bool get isEmpty => value == 0;
+
+  int get hashCode => value.hashCode * 19;
+
+  bool operator ==(other) {
+    if (identical(this, other)) return true;
+    if (other is! EnumSet<E>) return false;
+    return value == other.value;
+  }
+
+  String toString() {
+    if (value == 0) return '0';
+    int index = value.bitLength - 1;
+    StringBuffer sb = new StringBuffer();
+    int mask = 1 << index;
+    while (index >= 0) {
+      sb.write((value & mask) != 0 ? '1' : '0');
+      index--;
+      mask >>= 1;
+    }
+    return sb.toString();
+  }
+}
+
+/// Mutable implementation of [EnumSet].
+class _EnumSet<E> extends EnumSet<E> {
+  int _value;
+
+  _EnumSet() : this.fromValue(0);
+
+  _EnumSet.fromValue(this._value) : super._();
+
+  _EnumSet.fromValues(Iterable<E> values)
+      : this._value = 0,
+        super._() {
+    values.forEach(add);
+  }
+
+  int get value => _value;
+
+  void add(E enumValue) {
+    _value |= 1 << (enumValue as dynamic).index;
+  }
+
+  void remove(E enumValue) {
+    _value &= ~(1 << (enumValue as dynamic).index);
+  }
+
+  void clear() {
+    _value = 0;
+  }
+}
+
+/// Immutable implementation of [EnumSet].
+class _ConstEnumSet<E> extends EnumSet<E> {
+  final int value;
+
+  const _ConstEnumSet(this.value) : super._();
+
+  factory _ConstEnumSet.fromValues(Iterable<E> values) {
+    int value = 0;
+    void add(E enumValue) {
+      if (enumValue != null) {
+        value |= 1 << (enumValue as dynamic).index;
+      }
+    }
+    values.forEach(add);
+    return new _ConstEnumSet(value);
+  }
+
+  @override
+  void add(E enumValue) {
+    throw new UnsupportedError('EnumSet.add');
+  }
+
+  @override
+  void clear() {
+    throw new UnsupportedError('EnumSet.clear');
+  }
+
+  @override
+  void remove(E enumValue) {
+    throw new UnsupportedError('EnumSet.remove');
+  }
+}
+
+class _EnumSetIterable<E> extends IterableBase<E> {
+  final EnumSet<E> _enumSet;
+  final List<E> _values;
+
+  _EnumSetIterable(this._enumSet, this._values);
+
+  @override
+  Iterator<E> get iterator => new _EnumSetIterator(_enumSet.value, _values);
+}
+
+class _EnumSetIterator<E> implements Iterator<E> {
+  int _value;
+  int _index;
+  int _mask;
+  final List<E> _values;
+  E _current;
+
+  _EnumSetIterator(this._value, this._values);
+
+  @override
+  E get current => _current;
+
+  @override
+  bool moveNext() {
+    if (_value == 0) {
+      return false;
+    } else {
+      if (_mask == null) {
+        _index = _value.bitLength - 1;
+        _mask = 1 << _index;
+      }
+      _current = null;
+      while (_index >= 0) {
+        if (_mask & _value != 0) {
+          _current = _values[_index];
+        }
+        _mask >>= 1;
+        _index--;
+        if (_current != null) {
+          break;
+        }
+      }
+      return _current != null;
+    }
+  }
+}