heron/common/src/cpp/threads/pcqueue.h

/*
 * Copyright 2015 Twitter, Inc.
 *
 * 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.
 */

////////////////////////////////////////////////////////////////////
//
// This file consists of ciass definition of a producer consumer queue
//
/////////////////////////////////////////////////////////////////////

#if !defined(__PC_QUEUE_H)
#define __PC_QUEUE_H

#include <queue>
#include <vector>
#include <mutex>
#include <condition_variable>
#include "basics/sptypes.h"

template <typename T>
class PCQueue {
 public:
  PCQueue() {}
  virtual ~PCQueue() throw() {}

  PCQueue(const PCQueue& pcqueue) = delete;
  PCQueue& operator=(const PCQueue& pcqueue) = delete;

  void enqueue(T _item);
  void enqueue_all(T _item, sp_int32 _ntimes);

  T dequeue(void);
  T trydequeue(bool&);
  sp_uint32 trydequeuen(sp_uint32 _n, std::vector<T>& _queue);

  sp_int32 size(void);

 protected:
  std::queue<T> queue_;

  std::condition_variable cond_;
  std::mutex mutex_;
};

template <typename T>
void PCQueue<T>::enqueue(T _item) {
  std::unique_lock<std::mutex> m(mutex_);
  queue_.push(_item);

  cond_.notify_one();
}

template <typename T>
void PCQueue<T>::enqueue_all(T _item, sp_int32 _ntimes) {
  std::unique_lock<std::mutex> m(mutex_);

  for (sp_int32 i = 0; i < _ntimes; i++) {
    queue_.push(_item);
  }

  cond_.notify_one();
}

template <typename T>
T PCQueue<T>::dequeue() {
  std::unique_lock<std::mutex> m(mutex_);

  while (queue_.empty()) cond_.wait(m);

  T item = queue_.front();
  queue_.pop();
  return item;
}

template <typename T>
T PCQueue<T>::trydequeue(bool& _dequeued) {
  std::unique_lock<std::mutex> m(mutex_);
  if (queue_.empty()) {
    _dequeued = false;
    return NULL;
  }
  T item = queue_.front();
  queue_.pop();
  _dequeued = true;
  return item;
}

template <typename T>
sp_uint32 PCQueue<T>::trydequeuen(sp_uint32 _ntodequeue, std::vector<T>& _retval) {
  std::unique_lock<std::mutex> m(mutex_);

  sp_uint32 dequeued = 0;
  while (!queue_.empty() && dequeued < _ntodequeue) {
    T item = queue_.front();
    queue_.pop();
    _retval.push_back(item);
    dequeued++;
  }
  return dequeued;
}

template <typename T>
sp_int32 PCQueue<T>::size(void) {
  std::unique_lock<std::mutex> m(mutex_);
  sp_int32 retval = queue_.size();
  return retval;
}

#endif