Add a CallbackRegistry class to base/ to manage callbacks

base/callback_list_internal.cc

+// Copyright 2013 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/callback_list_internal.h"
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+
+namespace base {
+namespace internal {
+
+CallbackListImpl::Iterator::Iterator(
+    const base::WeakPtr<CallbackListImpl>& list)
+    : list_(list),
+      index_(0) {
+  ++list_->active_iterator_count_;
+}
+
+CallbackListImpl::Iterator::Iterator(const Iterator& iter)
+    : list_(iter.list_),
+      index_(iter.index_) {
+  ++list_->active_iterator_count_;
+}
+
+CallbackListImpl::Iterator::~Iterator() {
+  if (list_ && --list_->active_iterator_count_ == 0) {
+    list_->Compact();
+  }
+}
+
+CallbackBase* CallbackListImpl::Iterator::GetNext() {
+  if (!list_)
+    return NULL;
+  size_t max_index = list_->callbacks_.size();
+  while (index_ < max_index && !list_->callbacks_[index_])
+    ++index_;
+  return index_ < max_index ? list_->callbacks_[index_++] : NULL;
+}
+
+// static
+void CallbackListImpl::CheckedRemove(
+    const base::WeakPtr<CallbackListImpl>& list,
+    base::internal::CallbackBase* cb) {
+  list->Remove(cb);
+}
+
+CallbackListImpl::CallbackListImpl()
+    : active_iterator_count_(0),
+      weak_factory_(this) {}
+
+CallbackListImpl::~CallbackListImpl() {
+  Clear();
+}
+
+void CallbackListImpl::Clear() {
+  if (active_iterator_count_) {
+    for (size_t i = 0; i < callbacks_.size(); ++i) {
+      CallbackBase* tmp = callbacks_[i];
+      delete tmp;
+      callbacks_[i] = NULL;
+    }
+  } else {
+    for (size_t i = 0; i < callbacks_.size(); ++i)
+      delete callbacks_[i];
+    callbacks_.clear();
+  }
+}
+
+void CallbackListImpl::AssertEmpty() {
+  DCHECK(active_iterator_count_ == 0 && callbacks_.size() == 0);

[awong, 2013/09/05 22:34:58]

This should be a CHECK(). In production, if this is false, we leave ourselves
open to a UaF.

+}
+
+void CallbackListImpl::Remove(base::internal::CallbackBase* cb) {
+  for (size_t i = 0; i < callbacks_.size(); i++) {
+    if (callbacks_[i] == cb) {
+      CallbackBase* tmp = callbacks_[i];
+      delete tmp;
+      if (active_iterator_count_) {
+        callbacks_[i] = NULL;
+      } else {
+        callbacks_.erase(callbacks_.begin() + i);
+      }
+      return;
+    }
+  }
+}
+
+base::Closure CallbackListImpl::Add(base::internal::CallbackBase* cb) {
+  callbacks_.push_back(cb);
+  return base::Bind(&CallbackListImpl::CheckedRemove,
+                    weak_factory_.GetWeakPtr(), cb);
+}
+
+CallbackListImpl::Iterator CallbackListImpl::GetIterator() {
+  return Iterator(weak_factory_.GetWeakPtr());
+}
+
+void CallbackListImpl::Compact() {
+  callbacks_.erase(
+      std::remove(callbacks_.begin(), callbacks_.end(),
+                  static_cast<base::internal::CallbackBase*>(NULL)),
+                  callbacks_.end());
+}
+
+}   // namespace internal
+}   // namespace base