base::Bind: Implement a 1-arity CancelableCallback and use this to implement

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/cancelable_callback.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop.h"
@@ skipping 10 matching lines @@
 
 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(
+  CancelableClosure 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.
+//  - Calling Cancel() more than once has no effect.
+//  - After Cancel(), callback() returns a null callback.
 TEST(CancelableCallbackTest, MultipleCancel) {
   int count = 0;
-  CancelableCallback cancelable(
+  CancelableClosure cancelable(
       base::Bind(&Increment, base::Unretained(&count)));
 
   base::Closure callback1 = cancelable.callback();
+  base::Closure callback2 = 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.
+  // Calling Cancel() again has no effect.
+  cancelable.Cancel();
+
+  // callback() of a cancelled callback is null.
   base::Closure callback3 = cancelable.callback();
-  cancelable.Cancel();
-  callback3.Run();
-  EXPECT_EQ(0, count);
+  EXPECT_TRUE(callback3.is_null());
 }
 
 // CancelableCallback destroyed before callback is run.
 //  - Destruction of CancelableCallback cancels outstanding callbacks.
 TEST(CancelableCallbackTest, CallbackCanceledOnDestruction) {
   int count = 0;
   base::Closure callback;
 
   {
-    CancelableCallback cancelable(
+    CancelableClosure 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));
+  CancelableClosure 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(
+  CancelableClosure 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(
@@ skipping 10 matching lines @@
   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;
+  CancelableClosure 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,
+  CancelableClosure 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