message: Add some convenience function to blocking_queue
diff: @@ -69,6 +69,37 @@ public:
  return next;
  }
  +
  + // Obtain a reference to the queue's mutex
  + std::mutex& mutex()
  + {
  + return mutex_;
  + }
  +
  + //-------------------------------------------------------------------------
  + // Some convenience functions to access the underlying data structure
  + //
  +
  + bool unsafe_empty() const
  + {
  + return queue_.empty();
  + }
  +
  + size_t unsafe_size() const
  + {
  + return queue_.size();
  + }
  +
  + T unsafe_front()
  + {
  + return queue_.front();
  + }
  +
  + void unsafe_pop_front()
  + {
  + queue_.pop_front();
  + }
  +
  private:
  // The queue
  