base::Bind: Implement CancelableCallback to replace CancelableTaske.

base/cancelable_callback.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"

[csilv, 2011/11/23 19:37:30]

add includes for base/bind.h and base/compiler_specific.h.

[James Hawkins, 2011/11/23 22:12:52]

Done.

+
+#include "base/logging.h"
+
+namespace base {
+
+CancelableCallback::CancelableCallback()
+    : ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {
+}
+
+CancelableCallback::CancelableCallback(const base::Closure& callback)
+    : ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)),
+      callback_(callback) {
+  DCHECK_EQ(false, callback.is_null());
+  BindForwarder();
+}
+
+CancelableCallback::~CancelableCallback() {}
+
+void CancelableCallback::Cancel() {
+  weak_factory_.InvalidateWeakPtrs();
+  callback_.Reset();

[awong, 2011/11/23 19:58:23]

We should have a unittest assert that the wrapped callback (specifically, it's
bound arguments) are dropped when we Cancel(), or Reset() the
CancelableCallback.

Being able to depend on this contract seems important.

[James Hawkins, 2011/11/23 22:12:52]

Done.

+}
+
+void CancelableCallback::Reset(const base::Closure& callback) {
+  DCHECK_EQ(false, callback.is_null());
+
+  // Outstanding tasks (e.g., posted to a message loop) must not be called.
+  Cancel();
+
+  // |forwarder_| is no longer valid after Cancel(), so re-bind.
+  BindForwarder();
+
+  callback_ = callback;
+}
+
+const base::Closure& CancelableCallback::callback() const {
+  return forwarder_;
+}
+
+bool CancelableCallback::is_null() const {
+  return callback_.is_null();
+}
+
+void CancelableCallback::RunCallback() {
+  callback_.Run();
+}
+
+void CancelableCallback::BindForwarder() {
+  forwarder_ = base::Bind(&CancelableCallback::RunCallback,
+                          weak_factory_.GetWeakPtr());
+}
+
+}