CircularBuffer.h

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/*
 * Copyright 2022 Stéphane Caron
 *
 * 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 incorporates work covered by the following copyright and
 * permission notice:
 *
 *     CircularBuffer class of mc_rtc
 *     Copyright 2012-2019 CNRS-UM LIRMM, CNRS-AIST JRL
 *     License: BSD-2-Clause (see licenses/LICENSE-mc_rtc)
 */
 
#pragma once
 
#include <spdlog/spdlog.h>
 
#include <atomic>
 
namespace mpacklog {
 
template <typename T, size_t Size>
struct CircularBuffer {
 public:
  enum { Capacity = Size + 1 };
 
  CircularBuffer() : head_(0), tail_(0) {
    if (!tail_.is_lock_free()) {
      spdlog::warn(
          "Your platform does not support std::atomic_size_t as lock-free "
          "operations");
    }
  }
 
  bool push(const T& item) {
    size_t tail = tail_;
    auto next_tail = increment(tail);
    if (next_tail != head_) {
      data_[tail] = item;
      tail_ = next_tail;
      return true;
    }
    return false;
  }
 
  bool pop(T& item) {
    const size_t head = head_;
    if (head == tail_) {
      return false;
    }
    item = data_[head];
    head_ = increment(head);
    return true;
  }
 
  bool empty() { return head_ == tail_; }
 
  size_t size() { return (tail_ + Capacity - head_) % Capacity; }
 
 private:
  size_t increment(size_t idx) const { return (idx + 1) % Capacity; }
 
  T data_[Capacity];
 
  std::atomic_size_t head_;
 
  std::atomic_size_t tail_;
};
 
}  // namespace mpacklog