Add the beginnings of a Dart wrapper for libarchive.

utils/archive/options.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.
+
+#library('options');
+
+/**
+ * An individual option.
+ */
+class ArchiveOption {
+  /** The name of the option. */
+  final String name;
+
+  /** The value of the option. */
+  final value;
+
+  /** The module to which the option applies.*/
+  String module;
+
+  ArchiveOption(this.name, this.value, [this.module]);
+}
+
+/**
+ * A collection of options.
+ */
+class ArchiveOptions {
+  /** The internal options map. */
+  final Map<String, ArchiveOption> _options;
+
+  ArchiveOptions() : _options = <ArchiveOption>{};
+
+  /** Returns whether any options have been set. */
+  bool get isEmpty() => _options.isEmpty();
+
+  /**
+   * Sets an option. [value] should either be a bool or something with a
+   * reasonable `toString` method.
+   *
+   * To set the module for an option, use [operator[]].
+   */
+  void operator[]=(String name, value) {
+    _options[name] = new ArchiveOption(name, value);
+  }
+
+  /** Gets the option with the given name. */
+  ArchiveOption operator[](String name) {
+    return _options[name];
+  }
+
+  /**
+   * Serializes the options to the format understood by libarchive.
+   *
+   * Meant for internal use.
+   */
+  String serialize() {
+    return Strings.join(_options.getValues().map((option) {
+      if (option.value is Boolean) {
+        return '${option.value ? '!' : ''}${option.name}';
+      } else {
+        return '${option.name}=${option.value}';
+      }
+    }), ',');
+  }
+}