1// Copyright 2016 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/threading/thread_task_runner_handle.h"
6
7#include <utility>
8
9#include "base/lazy_instance.h"
10#include "base/logging.h"
11#include "base/threading/sequenced_task_runner_handle.h"
12#include "base/threading/thread_local.h"
13
14namespace base {
15
16namespace {
17
18base::LazyInstance<base::ThreadLocalPointer<ThreadTaskRunnerHandle>>::Leaky
19    lazy_tls_ptr = LAZY_INSTANCE_INITIALIZER;
20
21}  // namespace
22
23// static
24scoped_refptr<SingleThreadTaskRunner> ThreadTaskRunnerHandle::Get() {
25  ThreadTaskRunnerHandle* current = lazy_tls_ptr.Pointer()->Get();
26  DCHECK(current);
27  return current->task_runner_;
28}
29
30// static
31bool ThreadTaskRunnerHandle::IsSet() {
32  return !!lazy_tls_ptr.Pointer()->Get();
33}
34
35ThreadTaskRunnerHandle::ThreadTaskRunnerHandle(
36    scoped_refptr<SingleThreadTaskRunner> task_runner)
37    : task_runner_(std::move(task_runner)) {
38  DCHECK(task_runner_->BelongsToCurrentThread());
39  // No SequencedTaskRunnerHandle (which includes ThreadTaskRunnerHandles)
40  // should already be set for this thread.
41  DCHECK(!SequencedTaskRunnerHandle::IsSet());
42  lazy_tls_ptr.Pointer()->Set(this);
43}
44
45ThreadTaskRunnerHandle::~ThreadTaskRunnerHandle() {
46  DCHECK(task_runner_->BelongsToCurrentThread());
47  DCHECK_EQ(lazy_tls_ptr.Pointer()->Get(), this);
48  lazy_tls_ptr.Pointer()->Set(nullptr);
49}
50
51}  // namespace base
52