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base/deferred_sequenced_task_runner.cc

Index: base/deferred_sequenced_task_runner.cc
diff --git a/base/deferred_sequenced_task_runner.cc b/base/deferred_sequenced_task_runner.cc
new file mode 100644
index 0000000000000000000000000000000000000000..18b91a43b69d61b63d275cb9758109b47625ab3a
--- /dev/null
+++ b/base/deferred_sequenced_task_runner.cc
@@ -0,0 +1,95 @@
+// Copyright (c) 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/deferred_sequenced_task_runner.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+
+namespace base {
+
+DeferredSequencedTaskRunner::DeferredTask::DeferredTask() {
+}
+
+DeferredSequencedTaskRunner::DeferredTask::~DeferredTask() {
+}
+
+DeferredSequencedTaskRunner::DeferredSequencedTaskRunner(
+    const scoped_refptr<SequencedTaskRunner>& target_task_runner)
+    : started_(false),
+      target_task_runner_(target_task_runner) {
+}
+
+DeferredSequencedTaskRunner::~DeferredSequencedTaskRunner() {
+}
+
+bool DeferredSequencedTaskRunner::PostDelayedTask(
+    const tracked_objects::Location& from_here,
+    const Closure& task,
+    TimeDelta delay) {
+  AutoLock lock(lock_);
+  if (started_) {
+    DCHECK(deferred_tasks_queue_.empty());
+    return target_task_runner_->PostDelayedTask(from_here, task, delay);
+  }
+
+  QueueDeferredTask(from_here, task, delay, false /* is_non_nestable */);
+  return true;
+}
+
+bool DeferredSequencedTaskRunner::RunsTasksOnCurrentThread() const {
+  return target_task_runner_->RunsTasksOnCurrentThread();
+}
+
+bool DeferredSequencedTaskRunner::PostNonNestableDelayedTask(
+    const tracked_objects::Location& from_here,
+    const Closure& task,
+    TimeDelta delay) {
+  AutoLock lock(lock_);
+  if (started_) {
+    DCHECK(deferred_tasks_queue_.empty());
+    return target_task_runner_->PostNonNestableDelayedTask(from_here,
+                                                           task,
+                                                           delay);
+  }
+  QueueDeferredTask(from_here, task, delay, true /* is_non_nestable */);
+  return true;
+}
+
+void DeferredSequencedTaskRunner::QueueDeferredTask(
+    const tracked_objects::Location& from_here,
+    const Closure& task,
+    TimeDelta delay,
+    bool is_non_nestable) {
+  DeferredTask deferred_task;
+  deferred_task.posted_from = from_here;
+  deferred_task.task = task;
+  deferred_task.delay = delay;
+  deferred_task.is_non_nestable = is_non_nestable;
+  deferred_tasks_queue_.push_back(deferred_task);
+}
+
+
+void DeferredSequencedTaskRunner::Start() {
+  AutoLock lock(lock_);
+  DCHECK(!started_);
+  started_ = true;
+  for (std::vector<DeferredTask>::iterator i = deferred_tasks_queue_.begin();
+      i != deferred_tasks_queue_.end();
+      i = deferred_tasks_queue_.erase(i)) {

[willchan no longer on Chromium, 2013/04/17 15:40:19]

I just saw this implementation, I missed it before. This looks like an n^2
algorithm, right? It looks to me like it'll erase from the front, which will
lead to memmove()'ing all the vector elements forward. Perhaps we should just
NULL out (er, I guess it's a struct, so just default construct the struct) the
element after posting the task. Then clear the queue at the end of the loop.

[msarda, 2013/04/17 16:24:40]

Done.

+    const DeferredTask& task = *i;
+    if (task.is_non_nestable) {
+      target_task_runner_->PostNonNestableDelayedTask(task.posted_from,
+                                                      task.task,
+                                                      task.delay);
+    } else {
+      target_task_runner_->PostDelayedTask(task.posted_from,
+                                           task.task,
+                                           task.delay);
+    }
+  }
+  DCHECK(deferred_tasks_queue_.empty());
+}
+
+}  // namespace base