base: Refactor PendingTask out of MessageLoop.

base/pending_task.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/pending_task.h"
+
+#include "base/tracked_objects.h"
+
+namespace base {
+
+PendingTask::PendingTask(const tracked_objects::Location& posted_from,
+                         const base::Closure& task)
+    : base::TrackingInfo(posted_from, TimeTicks()),
+      task(task),
+      posted_from(posted_from),
+      sequence_num(0),
+      nestable(false) {
+}
+
+PendingTask::PendingTask(const tracked_objects::Location& posted_from,
+                         const base::Closure& task,
+                         TimeTicks delayed_run_time,
+                         bool nestable)
+    : base::TrackingInfo(posted_from, delayed_run_time),
+      task(task),
+      posted_from(posted_from),
+      sequence_num(0),
+      nestable(nestable) {
+}
+
+PendingTask::~PendingTask() {
+}
+
+bool PendingTask::operator<(const PendingTask& other) const {
+  // Since the top of a priority queue is defined as the "greatest" element, we
+  // need to invert the comparison here.  We want the smaller time to be at the
+  // top of the heap.
+
+  if (delayed_run_time < other.delayed_run_time)
+    return false;
+
+  if (delayed_run_time > other.delayed_run_time)
+    return true;
+
+  // If the times happen to match, then we use the sequence number to decide.
+  // Compare the difference to support integer roll-over.
+  return (sequence_num - other.sequence_num) > 0;
+}
+
+void TaskQueue::Swap(TaskQueue* queue) {
+  c.swap(queue->c);  // Calls std::deque::swap.
+}
+
+}  // namespace base