text: /**
   * ============================================================================
   *
   * Copyright (C) 2018, Hisilicon Technologies Co., Ltd. All Rights Reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   *   1 Redistributions of source code must retain the above copyright notice,
   *     this list of conditions and the following disclaimer.
   *
   *   2 Redistributions in binary form must reproduce the above copyright notice,
   *     this list of conditions and the following disclaimer in the documentation
   *     and/or other materials provided with the distribution.
   *
   *   3 Neither the names of the copyright holders nor the names of the
   *   contributors may be used to endorse or promote products derived from this
   *   software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   * ============================================================================
   */
  
  #ifndef THREAD_SAFE_QUEUE_H_
  #define THREAD_SAFE_QUEUE_H_
  
  #include <mutex>
  #include <queue>
  
  template<typename T>
  class ThreadSafeQueue {
      public:
  
    /**
     * @brief ThreadSafeQueue constructor
     * @param [in] capacity: the queue capacity
     */
      ThreadSafeQueue(uint32_t capacity) {
      // check the input value: capacity is valid
          if (capacity >= kMinQueueCapacity && capacity <= kMaxQueueCapacity) {
              queueCapacity = capacity;
          } 
          else { // the input value: capacity is invalid, set the default value
              queueCapacity = kDefaultQueueCapacity;
          }
      }
  
    /**
     * @brief ThreadSafeQueue constructor
     */
      ThreadSafeQueue() {
          queueCapacity = kDefaultQueueCapacity;
      }
  
    /**
     * @brief ThreadSafeQueue destructor
     */
      ~ThreadSafeQueue() = default;
  
    /**
     * @brief push data to queue
     * @param [in] input_value: the value will push to the queue
     * @return true: success to push data; false: fail to push data
     */
      bool Push(T input_value) {
          std::lock_guard<std::mutex> lock(mutex_);
  
      // check current size is less than capacity
          if (queue_.size() < queueCapacity) {
              queue_.push(input_value);
              return true;
          }
  
          return false;
      }
  
    /**
     * @brief pop data from queue
     * @return true: success to pop data; false: fail to pop data
     */
      T Pop() {
          std::lock_guard<std::mutex> lock(mutex_);
          if (queue_.empty()) { // check the queue is empty
          return nullptr;
          }
  
          T tmp_ptr = queue_.front();
          queue_.pop();
          return tmp_ptr;
      }
  
    /**
     * @brief check the queue is empty
     * @return true: the queue is empty; false: the queue is not empty
     */
      bool empty() {
          std::lock_guard<std::mutex> lock(mutex_);
          return queue_.empty();
      }
  
    /**
     * @brief get the queue size
     * @return the queue size
     */
      int size() {
          std::lock_guard<std::mutex> lock(mutex_);
          return queue_.size();
      }
  
      private:
          std::queue<T> queue_; // the queue
  
          uint32_t queueCapacity; // queue capacity
  
          mutable std::mutex mutex_; // the mutex value
  
          const uint32_t kMinQueueCapacity = 1; // the minimum queue capacity
  
          const uint32_t kMaxQueueCapacity = 10000; // the maximum queue capacity
  
          const uint32_t kDefaultQueueCapacity = 10; // default queue capacity
  };
  
  #endif /* THREAD_SAFE_QUEUE_H_ */
  