base::Bind: Implement CancelableCallback to replace CancelableTaske.

base/cancelable_callback_unittest.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/cancelable_callback.h"

[willchan no longer on Chromium, 2011/11/24 00:44:30]

goes first

[James Hawkins, 2011/11/24 02:47:48]

I read (on either c-style or chromium-dev) that this only applies if there is
not a corresponding implementation file for myclass.h.  Same thing as my
previous reply though: I'll just make the change.

[awong, 2011/11/24 02:56:53]

Will has caught me on this previously, but it doesn't stick in my head. :-/ 
Style guide got modified somewhere in the last year or two. It used to be as you
had it originally.

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Names_...

+#include "base/memory/ref_counted.h"
+#include "base/message_loop.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace {
+
+class TestRefCounted : public RefCountedThreadSafe<TestRefCounted> {
+ private:
+  friend class RefCountedThreadSafe<TestRefCounted>;
+  ~TestRefCounted() {};
+};
+
+void Increment(int* count) { (*count)++; }
+void IncrementBy(int* count, int n) { (*count) += n; }
+void RefCountedParam(const scoped_refptr<TestRefCounted>& ref_counted) {}
+
+// Cancel().
+//  - Callback can be run multiple times.
+//  - After Cancel(), Run() completes but has no effect.
+TEST(CancelableCallbackTest, Cancel) {
+  int count = 0;
+  CancelableCallback cancelable(
+      base::Bind(Increment, base::Unretained(&count)));
+
+  base::Closure callback = cancelable.callback();
+  callback.Run();
+  EXPECT_EQ(1, count);
+
+  callback.Run();
+  EXPECT_EQ(2, count);
+
+  cancelable.Cancel();
+  callback.Run();
+  EXPECT_EQ(2, count);
+}
+
+// Cancel() called multiple times.
+//  - Cancel() cancels all copies of the wrapped callback.
+TEST(CancelableCallbackTest, MultipleCancel) {
+  int count = 0;
+  CancelableCallback cancelable(
+      base::Bind(Increment, base::Unretained(&count)));

[willchan no longer on Chromium, 2011/11/24 00:44:30]

I always forget, doesn't Increment need & before it?

[awong, 2011/11/24 01:00:03]

I had thought it did, but I have again learned that I don't understand the type
promotion rules from functions to function pointers.

Let's add it in for good measure though.

[James Hawkins, 2011/11/24 02:47:48]

Hmm, I was really sure I've seen this fail to compile before...though I suppose
I don't understand the circumstances either.  This change works for me on Linux,
so we'll see if it sticks.

[awong, 2011/11/24 02:56:53]

I *know* I went through and fixed a bunch that failed to compile.  But jam found
a case of the auto-promotion happening.  Function type and array type
auto-promotion.  The bane of my life.

+
+  base::Closure callback1 = cancelable.callback();
+  cancelable.Cancel();
+
+  callback1.Run();
+  EXPECT_EQ(0, count);
+
+  base::Closure callback2 = cancelable.callback();
+  callback2.Run();
+  EXPECT_EQ(0, count);
+
+  // Cancel() should have no effect, but callback() is still runnable.
+  base::Closure callback3 = cancelable.callback();
+  cancelable.Cancel();
+  callback3.Run();
+  EXPECT_EQ(0, count);
+}
+
+// CancelableCallback destroyed before callback is run.
+//  - Destruction of CancelableCallback cancels outstanding callbacks.
+TEST(CancelableCallbackTest, CallbackCanceledOnDestruction) {
+  int count = 0;
+  base::Closure callback;
+
+  {
+    CancelableCallback cancelable(
+        base::Bind(Increment, base::Unretained(&count)));
+
+    callback = cancelable.callback();
+    callback.Run();
+    EXPECT_EQ(1, count);
+  }
+
+  callback.Run();
+  EXPECT_EQ(1, count);
+}
+
+// Cancel() called on bound closure with a RefCounted parameter.
+//  - Cancel drops wrapped callback (and, implicitly, its bound arguments).
+TEST(CancelableCallbackTest, CancelDropsCallback) {
+  scoped_refptr<TestRefCounted> ref_counted = new TestRefCounted;
+  EXPECT_TRUE(ref_counted->HasOneRef());
+
+  CancelableCallback cancelable(base::Bind(RefCountedParam, ref_counted));
+  EXPECT_FALSE(cancelable.IsCancelled());
+  EXPECT_TRUE(ref_counted.get());
+  EXPECT_FALSE(ref_counted->HasOneRef());
+
+  // There is only one reference to |ref_counted| after the Cancel().
+  cancelable.Cancel();
+  EXPECT_TRUE(cancelable.IsCancelled());
+  EXPECT_TRUE(ref_counted.get());
+  EXPECT_TRUE(ref_counted->HasOneRef());
+}
+
+// Reset().
+//  - Reset() replaces the existing wrapped callback with a new callback.
+//  - Reset() deactivates outstanding callbacks.
+TEST(CancelableCallbackTest, Reset) {
+  int count = 0;
+  CancelableCallback cancelable(
+      base::Bind(Increment, base::Unretained(&count)));
+
+  base::Closure callback = cancelable.callback();
+  callback.Run();
+  EXPECT_EQ(1, count);
+
+  callback.Run();
+  EXPECT_EQ(2, count);
+
+  cancelable.Reset(
+      base::Bind(IncrementBy, base::Unretained(&count), 3));
+  EXPECT_FALSE(cancelable.IsCancelled());
+
+  // The stale copy of the cancelable callback is non-null.
+  ASSERT_FALSE(callback.is_null());
+
+  // The stale copy of the cancelable callback is no longer active.
+  callback.Run();
+  EXPECT_EQ(2, count);
+
+  base::Closure callback2 = cancelable.callback();
+  ASSERT_FALSE(callback2.is_null());
+
+  callback2.Run();
+  EXPECT_EQ(5, count);
+}
+
+// IsCanceled().
+//  - Cancel() transforms the CancelableCallback into a cancelled state.
+TEST(CancelableCallbackTest, IsNull) {
+  CancelableCallback cancelable;
+  EXPECT_TRUE(cancelable.IsCancelled());
+
+  int count = 0;
+  cancelable.Reset(base::Bind(Increment,
+                              base::Unretained(&count)));
+  EXPECT_FALSE(cancelable.IsCancelled());
+
+  cancelable.Cancel();
+  EXPECT_TRUE(cancelable.IsCancelled());
+}
+
+// CancelableCallback posted to a MessageLoop with PostTask.
+//  - Callbacks posted to a MessageLoop can be cancelled.
+TEST(CancelableCallbackTest, PostTask) {
+  MessageLoop loop(MessageLoop::TYPE_DEFAULT);
+
+  int count = 0;
+  CancelableCallback cancelable(base::Bind(Increment,
+                                           base::Unretained(&count)));
+
+  MessageLoop::current()->PostTask(FROM_HERE, cancelable.callback());
+  MessageLoop::current()->PostTask(FROM_HERE, MessageLoop::QuitClosure());
+  MessageLoop::current()->Run();
+
+  EXPECT_EQ(1, count);
+
+  MessageLoop::current()->PostTask(FROM_HERE, cancelable.callback());
+  MessageLoop::current()->PostTask(FROM_HERE, MessageLoop::QuitClosure());
+
+  // Cancel before running the message loop.
+  cancelable.Cancel();
+  MessageLoop::current()->Run();
+
+  // Callback never ran due to cancellation; count is the same.
+  EXPECT_EQ(1, count);
+}
+
+}  // namespace
+}  // namespace base