Add DevNullQueue, a fuzzing helper to drop stuff

/*

 * Copyright 2020 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#pragma once

#include "os/queue.h"

namespace bluetooth {

namespace os {

namespace fuzzing {

// Drops stuff you send it, and banishes it into the void.

template <typename T>

class DevNullQueue {

 public:

  DevNullQueue(IQueueDequeue<T>* queue, Handler* handler) : queue_(queue), handler_(handler) {}

  ~DevNullQueue() {}

  void Start() {

    queue_->RegisterDequeue(handler_, common::Bind(&DevNullQueue::Dump, common::Unretained(this)));

  }

  void Stop() {

    queue_->UnregisterDequeue();

  }

  void Dump() {

    queue_->TryDequeue();

  }

 private:

  IQueueDequeue<T>* queue_;

  Handler* handler_;

};

}  // namespace fuzzing

}  // namespace os

}  // namespace bluetooth