Add a QueueList class to the collection package.

pkg/collection/test/queue_list_test.dart

+// 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.
+
+import "package:collection/collection.dart";
+import "package:unittest/unittest.dart";
+
+void main() {
+  group("new QueueList()", () {
+    test("creates an empty QueueList", () {
+      expect(new QueueList(), isEmpty);
+    });
+
+    test("takes an initial capacity", () {
+      expect(new QueueList(100), isEmpty);
+    });
+  });
+
+  test("new QueueList.from() copies the contents of an iterable", () {
+    expect(new QueueList.from([1, 2, 3].skip(1)), equals([2, 3]));
+  });
+
+  group("add()", () {
+    test("adds an element to the end of the queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      queue.add(4);
+      expect(queue, equals([1, 2, 3, 4]));
+    });
+
+    test("expands a full queue", () {
+      var queue = atCapacity();
+      queue.add(9);
+      expect(queue, equals([1, 2, 3, 4, 5, 6, 7, 8, 9]));
+    });
+  });
+
+  group("addAll()", () {
+    test("adds elements to the end of the queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      queue.addAll([4, 5, 6]);
+      expect(queue, equals([1, 2, 3, 4, 5, 6]));
+    });
+
+    test("expands a full queue", () {
+      var queue = atCapacity();
+      queue.addAll([9, 10]);
+      expect(queue, equals([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]));
+    });
+  });
+
+  group("addFirst()", () {
+    test("adds an element to the beginning of the queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      queue.addFirst(0);
+      expect(queue, equals([0, 1, 2, 3]));
+    });
+
+    test("expands a full queue", () {
+      var queue = atCapacity();
+      queue.addFirst(0);
+      expect(queue, equals([0, 1, 2, 3, 4, 5, 6, 7, 8]));
+    });
+  });
+
+  group("removeFirst()", () {
+    test("removes an element from the beginning of the queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      expect(queue.removeFirst(), equals(1));
+      expect(queue, equals([2, 3]));
+    });
+
+    test("removes an element from the beginning of a queue with an internal "
+        "gap", () {
+      var queue = withInternalGap();
+      expect(queue.removeFirst(), equals(1));
+      expect(queue, equals([2, 3, 4, 5, 6, 7]));
+    });
+
+    test("removes an element from the beginning of a queue at capacity", () {
+      var queue = atCapacity();
+      expect(queue.removeFirst(), equals(1));
+      expect(queue, equals([2, 3, 4, 5, 6, 7, 8]));
+    });
+
+    test("throws a StateError for an empty queue", () {
+      expect(new QueueList().removeFirst, throwsStateError);
+    });
+  });
+
+  group("removeLast()", () {
+    test("removes an element from the end of the queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      expect(queue.removeLast(), equals(3));
+      expect(queue, equals([1, 2]));
+    });
+
+    test("removes an element from the end of a queue with an internal gap", () {
+      var queue = withInternalGap();
+      expect(queue.removeLast(), equals(7));
+      expect(queue, equals([1, 2, 3, 4, 5, 6]));
+    });
+
+    test("removes an element from the end of a queue at capacity", () {
+      var queue = atCapacity();
+      expect(queue.removeLast(), equals(8));
+      expect(queue, equals([1, 2, 3, 4, 5, 6, 7]));
+    });
+
+    test("throws a StateError for an empty queue", () {
+      expect(new QueueList().removeLast, throwsStateError);
+    });
+  });
+
+  group("length", () {
+    test("returns the length of a queue", () {
+      expect(new QueueList.from([1, 2, 3]).length, equals(3));
+    });
+
+    test("returns the length of a queue with an internal gap", () {
+      expect(withInternalGap().length, equals(7));
+    });
+
+    test("returns the length of a queue at capacity", () {
+      expect(atCapacity().length, equals(8));
+    });
+  });
+
+  group("length=", () {
+    test("shrinks a larger queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      queue.length = 1;
+      expect(queue, equals([1]));
+    });
+
+    test("grows a smaller queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      queue.length = 5;
+      expect(queue, equals([1, 2, 3, null, null]));
+    });
+
+    test("throws a RangeError if length is less than 0", () {
+      expect(() => new QueueList().length = -1, throwsRangeError);
+    });
+  });
+
+  group("[]", () {
+    test("returns individual entries in the queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      expect(queue[0], equals(1));
+      expect(queue[1], equals(2));
+      expect(queue[2], equals(3));
+    });
+
+    test("returns individual entries in a queue with an internal gap", () {
+      var queue = withInternalGap();
+      expect(queue[0], equals(1));
+      expect(queue[1], equals(2));
+      expect(queue[2], equals(3));
+      expect(queue[3], equals(4));
+      expect(queue[4], equals(5));
+      expect(queue[5], equals(6));
+      expect(queue[6], equals(7));
+    });
+  });
+
+  group("[]=", () {
+    test("sets individual entries in the queue", () {
+      var queue = new QueueList.from([1, 2, 3]);
+      queue[0] = "a";
+      queue[1] = "b";
+      queue[2] = "c";
+      expect(queue, equals(["a", "b", "c"]));
+    });
+
+    test("sets individual entries in a queue with an internal gap", () {
+      var queue = withInternalGap();
+      queue[0] = "a";
+      queue[1] = "b";
+      queue[2] = "c";
+      queue[3] = "d";
+      queue[4] = "e";
+      queue[5] = "f";
+      queue[6] = "g";
+      expect(queue, equals(["a", "b", "c", "d", "e", "f", "g"]));
+    });
+  });
+
+  group("throws a modification error for", () {
+    var queue;
+    setUp(() {
+      queue = new QueueList.from([1, 2, 3]);
+    });
+
+    test("add", () {
+      expect(() => queue.forEach((_) => queue.add(4)),
+          throwsConcurrentModificationError);
+    });
+
+    test("addAll", () {
+      expect(() => queue.forEach((_) => queue.addAll([4, 5, 6])),
+          throwsConcurrentModificationError);
+    });
+
+    test("addFirst", () {
+      expect(() => queue.forEach((_) => queue.addFirst(0)),
+          throwsConcurrentModificationError);
+    });
+
+    test("removeFirst", () {
+      expect(() => queue.forEach((_) => queue.removeFirst()),
+          throwsConcurrentModificationError);
+    });
+
+    test("removeLast", () {
+      expect(() => queue.forEach((_) => queue.removeLast()),
+          throwsConcurrentModificationError);
+    });
+
+    test("length=", () {
+      expect(() => queue.forEach((_) => queue.length = 1),
+          throwsConcurrentModificationError);
+    });
+  });
+}
+
+/// Returns a queue whose internal ring buffer is full.
+QueueList atCapacity() {
+  // Use addAll because [new QueueList.from(List)] won't use the default initial
+  // capacity of 8.

[Lasse Reichstein Nielsen, 2014/10/29 07:04:44]

The buffer grows when the 8th element is added, so technically it's not full any
more. It's designed to never be full (because _head==_tail means the buffer is
empty, and being full would be indistinguishable from that).

[nweiz, 2014/10/29 20:49:36]

Done.

+  return new QueueList()..addAll([1, 2, 3, 4, 5, 6, 7, 8]);
+}
+
+/// Returns a queue whose internal tail has a lower index than its head.
+QueueList withInternalGap() {
+  var queue = new QueueList.from([null, null, null, null, 1, 2, 3, 4]);
+  for (var i = 0; i < 4; i++) {
+    queue.removeFirst();
+  }
+  for (var i = 5; i < 8; i++) {
+    queue.addLast(i);
+  }
+  return queue;
+}
+
+/// Returns a matcher that expects that a closure throws a
+/// [ConcurrentModificationError].
+final throwsConcurrentModificationError = throwsA(
+    new isInstanceOf<ConcurrentModificationError>(
+        "ConcurrentModificationError"));

[Lasse Reichstein Nielsen, 2014/10/29 07:04:44]

Consider copying some tests from tests/corelib/list_test.dart to test the List
behavior thoroughly.

[nweiz, 2014/10/29 20:49:36]

I think we can rely on the implementation of ListMixin to ensure that those are
correct given that the operations we implement are correct.