Method PushFront

be/src/util/internal-queue.h:114–128

Pushes the node onto the queue's head. This is O(1).

  /// Pushes the node onto the queue's head. This is O(1).
  void PushFront(T* n) {
    Node* node = (Node*)n;
    DCHECK(node->next == nullptr);
    DCHECK(node->prev == nullptr);
    DCHECK(node->parent_queue == nullptr);
    node->parent_queue = this;
    {
      std::lock_guard<LockType> lock(lock_);
      if (head_ != nullptr) head_->prev = node;
      node->next = head_;
      head_ = node;
      if (tail_ == nullptr) tail_ = node;
      ++size_;
    }
  }

  /// Dequeues an element from the queue's head. Returns nullptr if the queue
  /// is empty. This is O(1).