Add a library for manipulating stack traces.

pkg/stack_trace/lib/src/frame.dart

Index: pkg/stack_trace/lib/src/frame.dart
diff --git a/pkg/stack_trace/lib/src/frame.dart b/pkg/stack_trace/lib/src/frame.dart
new file mode 100644
index 0000000000000000000000000000000000000000..fdf4fe0d538b61e5110bcab3f21aa029a3be3b69
--- /dev/null
+++ b/pkg/stack_trace/lib/src/frame.dart
@@ -0,0 +1,88 @@
+// 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 frame;
+
+import 'dart:uri';
+
+import 'package:pathos/path.dart' as path;
+
+import 'trace.dart';
+
+final _nativeFrameRegExp = new RegExp(
+    r'^#\d+\s+([^\s].*) \((.+):(\d+):(\d+)\)$');
+
+/// A single stack frame. Each frame points to a precise location in Dart code.
+class Frame {
+  /// The URI of the file in which the code is located.
+  ///
+  /// This URI will usually have the scheme `dart`, `file`, `http`, or `https`.
+  final Uri uri;
+
+  /// The line number on which the code location is located.
+  final int line;
+
+  /// The column number of the code location.
+  final int column;
+
+  /// The name of the member in which the code location occurs.
+  ///
+  /// Anonymous closures are represented as `<fn>` in this member string.
+  final String member;
+
+  /// Whether this stack frame comes from the Dart core libraries.
+  bool get isCore => uri.scheme == 'dart';
+
+  /// Returns a human-friendly description of the library that this stack frame
+  /// comes from.
+  ///
+  /// This will usually be the string form of [uri], but a relative path will be
+  /// used if possible.
+  String get library {
+    // TODO(nweiz): handle relative URIs here as well once pathos supports that.
+    if (uri.scheme != 'file') return uri.toString();
+    return path.relative(uri.path);
+  }
+
+  /// A human-friendly description of the code location.
+  ///
+  /// For Dart core libraries, this will omit the line and column information,
+  /// since those are useless for baked-in libraries.
+  String get location {
+    if (isCore) return library;
+    return '$library $line:$column';
+  }
+
+  /// Returns a single frame of the current stack.
+  ///
+  /// By default, this will return the frame above the current method. If
+  /// [level] is `0`, it will return the current method's frame; if [level] is
+  /// higher than `1`, it will return higher frames.
+  factory Frame.caller([int level=1]) {
+    if (level < 0) {
+      throw new ArgumentError("Argument [level] must be greater than or equal "
+          "to 0.");
+    }
+
+    return new Trace.current(level + 1).frames.first;
+  }
+
+  /// Parses a string representation of a stack frame.
+  ///
+  /// [frame] should be formatted in the same way as a native stack trace frame.
+  factory Frame.parse(String frame) {
+    var match = _nativeFrameRegExp.firstMatch(frame);
+    if (match == null) {
+      throw new FormatException("Couldn't parse stack trace line '$frame'.");
+    }
+
+    var uri = new Uri.fromString(match[2]);
+    var member = match[1].replaceAll("<anonymous closure>", "<fn>");
+    return new Frame(uri, int.parse(match[3]), int.parse(match[4]), member);
+  }
+
+  Frame(this.uri, this.line, this.column, this.member);
+
+  String toString() => '$location in $member';
+}