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// Copyright (c) 2012 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/base_export.h"
#include "base/bind.h"
#include "base/sequenced_task_runner.h"
namespace base {
// A SingleThreadTaskRunner is a SequencedTaskRunner with one more
// guarantee; namely, that all tasks are run on a single dedicated
// thread. Most use cases require only a SequencedTaskRunner, unless
// there is a specific need to run tasks on only a single thread.
// SingleThreadTaskRunner implementations might:
// - Post tasks to an existing thread's MessageLoop (see
// MessageLoop::task_runner()).
// - Create their own worker thread and MessageLoop to post tasks to.
// - Add tasks to a FIFO and signal to a non-MessageLoop thread for them to
// be processed. This allows TaskRunner-oriented code run on threads
// running other kinds of message loop, e.g. Jingle threads.
class BASE_EXPORT SingleThreadTaskRunner : public SequencedTaskRunner {
// A more explicit alias to RunsTasksInCurrentSequence().
bool BelongsToCurrentThread() const { return RunsTasksInCurrentSequence(); }
#if defined(STARBOARD)
// Like PostTask, but blocks until the posted task completes. Returns false
// and does not block if task was not posted.
virtual void PostBlockingTask(const base::Location& from_here,
const Closure& task);
// Adds a fence at the end of this MessageLoop's task queue, and then blocks
// until it has been reached. It is forbidden to call this method from the
// thread of the MessageLoop being posted to. One should exercise extreme
// caution when using this, as blocking between MessageLoops can cause
// deadlocks and is contraindicated in the Actor model of multiprogramming.
void WaitForFence() {
struct Fence {
static void Task() {}
PostBlockingTask(FROM_HERE, base::Bind(&Fence::Task));
~SingleThreadTaskRunner() override = default;
} // namespace base