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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 "net/dns/serial_worker.h"
#include "base/bind.h"
#include "base/check_op.h"
#include "base/location.h"
#include "base/notreached.h"
#include "base/task/post_task.h"
#include "base/task/thread_pool.h"
#include "base/threading/sequenced_task_runner_handle.h"
#include "base/threading/thread_task_runner_handle.h"
namespace net {
SerialWorker::SerialWorker()
: base::RefCountedDeleteOnSequence<SerialWorker>(
base::SequencedTaskRunnerHandle::Get()),
state_(IDLE) {}
SerialWorker::~SerialWorker() = default;
void SerialWorker::WorkNow() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
switch (state_) {
case IDLE:
// We are posting weak pointer to OnWorkJobFinished to avoid leak when
// PostTaskAndReply fails to post task back to the original
// task runner. In this case the callback is not destroyed, and the
// weak reference allows SerialWorker instance to be deleted.
base::ThreadPool::PostTaskAndReply(
FROM_HERE,
{base::MayBlock(), base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
base::BindOnce(&SerialWorker::DoWork, this),
base::BindOnce(&SerialWorker::OnWorkJobFinished,
weak_factory_.GetWeakPtr()));
state_ = WORKING;
return;
case WORKING:
// Remember to re-read after |DoRead| finishes.
state_ = PENDING;
return;
case CANCELLED:
case PENDING:
return;
default:
NOTREACHED() << "Unexpected state " << state_;
}
}
void SerialWorker::Cancel() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
state_ = CANCELLED;
}
void SerialWorker::OnWorkJobFinished() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
switch (state_) {
case CANCELLED:
return;
case WORKING:
state_ = IDLE;
this->OnWorkFinished();
return;
case PENDING:
state_ = IDLE;
WorkNow();
return;
default:
NOTREACHED() << "Unexpected state " << state_;
}
}
} // namespace net
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