Runes, a bi-directional code-point iterator/iterable.

tests/corelib/string_runes_test.dart

+// Copyright (c) 2011, 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.
+
+main() {
+  test(String s, List<int> expectedRunes) {
+    Runes runes = s.runes;
+    Expect.identical(s, runes.string);
+
+    // for-in
+    var res = [];
+    for (int rune in runes) {
+      res.add(rune);
+    }
+    Expect.listEquals(expectedRunes, res);
+
+    // manual iteration, backwards.
+    res = [];
+    for (var it = runes.iterator..reset(s.length); it.movePrevious();) {
+      res.add(it.current);
+    }
+    Expect.listEquals(expectedRunes.reversed.toList(), res);
+
+    // Setting rawIndex.
+    RuneIterator it = runes.iterator;
+    it.rawIndex = 1;
+    Expect.equals(expectedRunes[1], it.current);
+
+    it = runes.iterator;
+    it.moveNext();
+    Expect.equals(0, it.rawIndex);
+    it.moveNext();
+    Expect.equals(1, it.rawIndex);
+    it.moveNext();
+    Expect.isTrue(1 < it.rawIndex);
+    it.rawIndex = 1;
+    Expect.equals(1, it.rawIndex);
+    Expect.equals(expectedRunes[1], it.current);
+
+    // Reset, moveNext.
+    it.reset(1);
+    Expect.equals(null, it.rawIndex);
+    Expect.equals(null, it.current);
+    it.moveNext();
+    Expect.equals(1, it.rawIndex);
+    Expect.equals(expectedRunes[1], it.current);
+
+    // Reset, movePrevious.
+    it.reset(1);
+    Expect.equals(null, it.rawIndex);
+    Expect.equals(null, it.current);
+    it.movePrevious();
+    Expect.equals(0, it.rawIndex);
+    Expect.equals(expectedRunes[0], it.current);
+
+    // .map
+    Expect.listEquals(expectedRunes.map((x) => x.toRadixString(16)).toList(),
+                      runes.map((x) => x.toRadixString(16)).toList());
+  }
+
+  // First character must be single-code-unit for test.
+  test("abc", [0x61, 0x62, 0x63]);
+  test("\x00\u0000\u{000000}", [0, 0, 0]);
+  test("\u{ffff}\u{10000}\u{10ffff}", [0xffff, 0x10000, 0x10ffff]);

[erikcorry, 2013/02/13 08:58:54]

Can we have at least one test case where the 10 bits from the lead surrogate are
different from the 10 bits from the trail surrogate?

+  String string = new String.fromCharCodes(
+      [0xdc00, 0xd800, 61, 0xd800, 0xdc00, 62, 0xdc00, 0xd800]);
+  test(string, [0xdc00, 0xd800, 61, 0x10000, 62, 0xdc00, 0xd800]);
+
+  // Setting position in the middle of a surrogate pair is not allowed.
+  var r = new Runes("\u{10000}");
+  var it = r.iterator;
+  it.moveNext();
+  Expect.equals(0x10000, it.current);
+
+  // Setting rawIndex inside surrogate pair.
+  Expect.throws(() { it.rawIndex = 1; }, (e) => e is Error);
+  Expect.throws(() { it.reset(1); }, (e) => e is Error);
+}