Optimize work with absolute paths.

pkg/analyzer/lib/src/util/absolute_path.dart

Index: pkg/analyzer/lib/src/util/absolute_path.dart
diff --git a/pkg/analyzer/lib/src/util/absolute_path.dart b/pkg/analyzer/lib/src/util/absolute_path.dart
new file mode 100644
index 0000000000000000000000000000000000000000..1cd75c01f6e34f1c2f1798ddd749d54bdfc6f08a
--- /dev/null
+++ b/pkg/analyzer/lib/src/util/absolute_path.dart
@@ -0,0 +1,70 @@
+// Copyright (c) 2015, 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 engine.utilities.absolute_path;

[Brian Wilkerson, 2015/11/14 17:30:25]

The library name should be "analyzer.src.util.absolute_path". (Although I'd like
it better if the directory name were "utilities". :-)

[scheglov, 2015/11/14 22:40:12]

Done.

+
+/// The class for manipulating absolute paths.
+class AbsolutePathContext {
+  final String separator;
+
+  AbsolutePathContext(this.separator);
+
+  /// Append the given [suffix] the given absolute [parent].

[Brian Wilkerson, 2015/11/14 17:30:25]

"[suffix]" --> "relative [suffix] to"

[scheglov, 2015/11/14 22:40:12]

Done.

+  ///
+  ///     context.append('/path/to', 'foo'); // -> 'path/to/foo'

[Brian Wilkerson, 2015/11/14 17:30:24]

Missing leading '/' in result.

[scheglov, 2015/11/14 22:40:12]

Done.

+  ///
+  /// The given [suffix] cannot be an absolute path or use `..`.
+  String append(String parent, String suffix) {
+    return '$parent$separator$suffix';
+  }
+
+  /// Gets the part of [path] after the last separator on the context's

[Brian Wilkerson, 2015/11/14 17:30:25]

"Gets" --> "Return"
"[path]" --> "the absolute [path]"

[scheglov, 2015/11/14 22:40:12]

Done.

+  /// platform.
+  ///
+  ///     context.basename('/path/to/foo.dart'); // -> 'foo.dart'
+  ///     context.basename('/path/to');          // -> 'to'
+  String basename(String path) {
+    int index = path.lastIndexOf(separator);
+    return path.substring(index + 1);
+  }
+
+  /// Gets the part of [path] before the last separator.

[Brian Wilkerson, 2015/11/14 17:30:25]

"Gets" --> "Return"
"[path]" --> "the absolute [path]"

[scheglov, 2015/11/14 22:40:12]

Done.

+  ///
+  ///     context.dirname('/path/to/foo.dart'); // -> '/path/to'
+  ///     context.dirname('/path/to');          // -> '/path'
+  String dirname(String path) {
+    int index = path.lastIndexOf(separator);
+    return index != -1 ? path.substring(0, index) : index;
+  }
+
+  /// Returns `true` if [child] is a path beneath `parent`, and `false`
+  /// otherwise.

[Brian Wilkerson, 2015/11/14 17:30:25]

"`parent`" --> "[parent]"
"." --> ". Both the [child] and [parent] paths must be absolute paths."

[scheglov, 2015/11/14 22:40:12]

Done.

+  ///
+  ///     context.isWithin('/root/path', '/root/path/a'); // -> true
+  ///     context.isWithin('/root/path', '/root/other'); // -> false
+  ///     context.isWithin('/root/path', '/root/path'); // -> false
+  bool isWithin(String parent, String child) {
+    return child.startsWith(parent + separator);
+  }
+
+  /// If the given [child] is within the given [parent], then returns the
+  /// relative path from [parent] to [child]. Otherwise returns `null`.

[Brian Wilkerson, 2015/11/14 17:30:24]

"`." --> "`. Both the [child] and [parent] paths must be absolute paths."

[scheglov, 2015/11/14 22:40:12]

Done.

+  ///
+  ///     context.relative('/root/path/a/b.dart', '/root/path'); // -> 'a/b.dart'
+  ///     context.relative('/root/other.dart', '/root/path'); // -> null
+  String relative(String child, String parent) {
+    String parentPrefix = parent + separator;
+    if (child.startsWith(parentPrefix)) {
+      return child.substring(parentPrefix.length);
+    }
+    return null;
+  }
+
+  /// Splits [path] into its components using [separator].
+  ///
+  ///     context.split('/path/to/foo'); // -> ['', 'path', 'to', 'foo']
+  List<String> split(String path) {
+    return path.split(separator);
+  }
+}