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      1 // Copyright (c) 2012 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/thread_task_runner_handle.h"
      6 
      7 #include "base/lazy_instance.h"
      8 #include "base/single_thread_task_runner.h"
      9 #include "base/threading/thread_local.h"
     10 
     11 namespace base {
     12 
     13 namespace {
     14 
     15 base::LazyInstance<base::ThreadLocalPointer<ThreadTaskRunnerHandle> >
     16     lazy_tls_ptr = LAZY_INSTANCE_INITIALIZER;
     17 
     18 }  // namespace
     19 
     20 // static
     21 scoped_refptr<SingleThreadTaskRunner> ThreadTaskRunnerHandle::Get() {
     22   ThreadTaskRunnerHandle* current = lazy_tls_ptr.Pointer()->Get();
     23   DCHECK(current);
     24   return current->task_runner_;
     25 }
     26 
     27 // static
     28 bool ThreadTaskRunnerHandle::IsSet() {
     29   return lazy_tls_ptr.Pointer()->Get() != NULL;
     30 }
     31 
     32 ThreadTaskRunnerHandle::ThreadTaskRunnerHandle(
     33     const scoped_refptr<SingleThreadTaskRunner>& task_runner)
     34     : task_runner_(task_runner) {
     35   DCHECK(task_runner_->BelongsToCurrentThread());
     36   DCHECK(!lazy_tls_ptr.Pointer()->Get());
     37   lazy_tls_ptr.Pointer()->Set(this);
     38 }
     39 
     40 ThreadTaskRunnerHandle::~ThreadTaskRunnerHandle() {
     41   DCHECK(task_runner_->BelongsToCurrentThread());
     42   DCHECK_EQ(lazy_tls_ptr.Pointer()->Get(), this);
     43   lazy_tls_ptr.Pointer()->Set(NULL);
     44 }
     45 
     46 }  // namespace base
     47