Refactor pkg/path.

pkg/path/lib/src/style/posix.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 path.style.posix;
+
+import '../parsed_path.dart';
+import '../style.dart';
+
+/// The style for POSIX paths.
+class PosixStyle extends Style {
+  PosixStyle();
+
+  final name = 'posix';
+  final separator = '/';
+  final separatorPattern = new RegExp(r'/');
+  final needsSeparatorPattern = new RegExp(r'[^/]$');
+  final rootPattern = new RegExp(r'^/');
+
+  String pathFromUri(Uri uri) {
+    if (uri.scheme == '' || uri.scheme == 'file') {
+      return Uri.decodeComponent(uri.path);
+    }
+    throw new ArgumentError("Uri $uri must have scheme 'file:'.");
+  }
+
+  Uri absolutePathToUri(String path) {
+    var parsed = new ParsedPath.parse(path, this);
+    if (parsed.parts.isEmpty) {
+      // If the path is a bare root (e.g. "/"), [components] will
+      // currently be empty. We add two empty components so the URL constructor
+      // produces "file:///", with a trailing slash.
+      parsed.parts.addAll(["", ""]);
+    } else if (parsed.hasTrailingSeparator) {
+      // If the path has a trailing slash, add a single empty component so the
+      // URI has a trailing slash as well.
+      parsed.parts.add("");
+    }
+
+    return new Uri(scheme: 'file', pathSegments: parsed.parts);
+  }
+}