text: /*
   * Copyright 2018 The Cartographer Authors
   *
   * 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.
   */
  
  #ifndef CARTOGRAPHER_METRICS_COUNTER_H_
  #define CARTOGRAPHER_METRICS_COUNTER_H_
  
  #include <map>
  #include <vector>
  
  namespace cartographer {
  namespace metrics {
  
  class Counter {
   public:
    // Counter instance that does nothing. Safe for use in static initializers.
    static Counter* Null();
  
    virtual ~Counter() = default;
    virtual void Increment() = 0;
    virtual void Increment(double by_value) = 0;
  };
  
  }  // namespace metrics
  }  // namespace cartographer
  
  #endif  // CARTOGRAPHER_METRICS_COUNTER_H_
  