TaskScheduler [3/9] Task and Sequence

base/task_scheduler/sequence_sort_key.cc

Index: base/task_scheduler/sequence_sort_key.cc
diff --git a/base/task_scheduler/sequence_sort_key.cc b/base/task_scheduler/sequence_sort_key.cc
new file mode 100644
index 0000000000000000000000000000000000000000..809224bce5f161c7574a5826bac85e5a2d73aa0c
--- /dev/null
+++ b/base/task_scheduler/sequence_sort_key.cc
@@ -0,0 +1,31 @@
+// Copyright 2016 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/task_scheduler/sequence_sort_key.h"
+
+namespace base {
+namespace internal {
+
+SequenceSortKey::SequenceSortKey(TaskPriority priority,
+                                 TimeTicks next_task_sequenced_time)
+    : priority_(priority),
+      next_task_sequenced_time_(next_task_sequenced_time) {}
+
+bool SequenceSortKey::operator<(const SequenceSortKey& other) const {
+  // Sort by highest priority first, earliest post time second.

[gab, 2016/02/18 20:22:34]

Actually (sorry I know I wrote this...), how about we be even more explicit here
and say:

// This SequenceSortKey is considered less important than |other| if its lower
priority or if it has the same priority but its next task was posted later than
|other|'s.

(the reason I'm having second thoughts is that I realized it isn't obvious that
< means lower priority (if you think of a queue as a vector then being <, i.e.
on the LHS, actually means you're first...)

[fdoray, 2016/02/18 20:52:04]

Done.

+  const int priority_diff =
+      static_cast<TaskPriorityUnderlyingType>(other.priority_) -
+      static_cast<TaskPriorityUnderlyingType>(priority_);
+  return priority_diff != 0
+             ? priority_diff > 0
+             : next_task_sequenced_time_ > other.next_task_sequenced_time_;
+}
+
+bool SequenceSortKey::operator==(const SequenceSortKey& other) const {
+  return priority_ == other.priority_ &&
+         next_task_sequenced_time_ == other.next_task_sequenced_time_;
+}
+
+}  // namespace internal
+}  // namespace base