FIFO.h

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// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
 
 
#ifndef ALICEO2_FIFOUTILS_H_
#define ALICEO2_FIFOUTILS_H_
 
#include <deque>
#include <mutex>
#include <stdexcept>
 
namespace o2
{
namespace utils
{
 
template <typename T>
class FIFO
{
 public:
  size_t size() const
  {
    std::lock_guard<std::mutex> lock(mMutex);
    return mQueue.size();
  }
 
  void clear()
  {
    std::lock_guard<std::mutex> lock(mMutex);
    mQueue.clear();
  }
 
  bool empty() const
  {
    std::lock_guard<std::mutex> lock(mMutex);
    return mQueue.empty();
  }
 
  template <typename... Args>
  void push(Args&&... args)
  {
    std::lock_guard<std::mutex> lock(mMutex);
    mQueue.emplace_back(std::forward<Args>(args)...);
  }
 
  void pop()
  {
    std::lock_guard<std::mutex> lock(mMutex);
    if (!mQueue.empty()) {
      mQueue.pop_front();
    }
  }
 
  const T& front() const
  {
    std::lock_guard<std::mutex> lock(mMutex);
    if (mQueue.empty()) {
      throw std::runtime_error("attempt to access front of empty queue");
    }
    return mQueue.front();
  }
 
  T& front()
  {
    std::lock_guard<std::mutex> lock(mMutex);
    if (mQueue.empty()) {
      throw std::runtime_error("attempt to access front of empty queue");
    }
    return mQueue.front();
  }
 
  const T* frontPtr() const
  {
    std::lock_guard<std::mutex> lock(mMutex);
    if (mQueue.empty()) {
      return nullptr;
    }
    return &mQueue.front();
  }
 
  T* frontPtr()
  {
    std::lock_guard<std::mutex> lock(mMutex);
    if (mQueue.empty()) {
      return nullptr;
    }
    return &mQueue.front();
  }
 
  auto& getQueue() const { return mQueue; }
 
 private:
  mutable std::mutex mMutex;
  std::deque<T> mQueue{};
};
 
} // namespace utils
} // namespace o2
 
#endif