Add LineScanner and SpanScanner classes to string_scanner.

pkg/string_scanner/test/line_scanner_test.dart

Index: pkg/string_scanner/test/line_scanner_test.dart
diff --git a/pkg/string_scanner/test/line_scanner_test.dart b/pkg/string_scanner/test/line_scanner_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..636fb69095da65924f3ed6eef9e7b8bede5b7143
--- /dev/null
+++ b/pkg/string_scanner/test/line_scanner_test.dart
@@ -0,0 +1,106 @@
+// Copyright (c) 2014, 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 string_scanner.line_scanner_test;
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:unittest/unittest.dart';
+
+void main() {
+  var scanner;
+  setUp(() {
+    scanner = new LineScanner('foo\nbar\nbaz');
+  });
+
+  test('begins with line and column 0', () {
+    expect(scanner.line, equals(0));
+    expect(scanner.column, equals(0));
+  });
+
+  group("scan()", () {
+    test("consuming no newlines increases the column but not the line", () {
+      scanner.scan('foo');
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(3));
+    });
+
+    test("consuming a newline resets the column and increases the line", () {
+      scanner.expect('foo\nba');
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(2));
+    });
+
+    test("consuming multiple newlines resets the column and increases the line",
+        () {
+      scanner.expect('foo\nbar\nb');
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(1));
+    });
+  });
+
+  group("readChar()", () {
+    test("on a non-newline character increases the column but not the line",
+        () {
+      scanner.readChar();
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(1));
+    });
+
+    test("consuming a newline resets the column and increases the line", () {
+      scanner.expect('foo');
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(3));
+
+      scanner.readChar();
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(0));
+    });
+  });
+
+  group("position=", () {
+    test("forward through newlines sets the line and column", () {
+      scanner.position = 9; // "foo\nbar\nb"
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(1));
+    });
+
+    test("forward through no newlines sets the column", () {
+      scanner.position = 2; // "fo"
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(2));
+    });
+
+    test("backward through newlines sets the line and column", () {
+      scanner.scan("foo\nbar\nbaz");
+      scanner.position = 2; // "fo"
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(2));
+    });
+
+    test("backard through no newlines sets the column", () {

[Bob Nystrom, 2014/05/28 21:28:57]

"backward"

[nweiz, 2014/05/28 23:56:34]

Done.

+      scanner.scan("foo\nbar\nbaz");
+      scanner.position = 9; // "foo\nbar\nb"
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(1));
+    });
+  });
+
+  test("state= restores the line, column, and position", () {
+    scanner.scan('foo\nb');
+    var state = scanner.state;
+
+    scanner.scan('ar\nba');
+    scanner.state = state;
+    expect(scanner.rest, equals('ar\nbaz'));
+    expect(scanner.line, equals(1));
+    expect(scanner.column, equals(1));
+  });
+
+  test("state= rejects a foreign state", () {
+    scanner.scan('foo\nb');
+
+    expect(() => new LineScanner(scanner.string).state = scanner.state,
+        throwsArgumentError);
+  });
+}