text: // Copyright 2010-2018, Google Inc.
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * 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.
  //     * Neither the name of Google Inc. nor the names of its
  // 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
  // OWNER 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 MOZC_BASE_STOPWATCH_H_
  #define MOZC_BASE_STOPWATCH_H_
  
  #include "base/port.h"
  
  namespace mozc {
  
  class Stopwatch {
   public:
    enum StopwatchState {
      STOPWATCH_RUNNING,
      STOPWATCH_STOPPED,
    };
  
    // Initializes a new stopwatch object, starts measuring elapsed time,
    // and returns the stopwatch object.
    static Stopwatch StartNew();
  
    Stopwatch();
  
    // Sets elapsed time to zero.
    // Stops the time counting.
    void Reset();
  
    // (Re)starts the time counting.
    // This function does not reset elapsed time so that you can use Start()
    // to accumulate a periodic activity.
    void Start();
  
    // Stops the time counting.
    // This function does not reset elapsed time so that you can use Start()
    // to accumulate a periodic activity.
    void Stop();
  
    // Returns the elapsed time as millisecond.
    int64 GetElapsedMilliseconds();
  
    // Returns the elapsed time as microsecond.
    double GetElapsedMicroseconds();
  
    // Returns the elapsed time as nanosecond.
    double GetElapsedNanoseconds();
  
    // Returns the elapsed time as ticks.
    int64 GetElapsedTicks();
  
    // Returns true if the time counting is on-going.
    bool IsRunning() const;
  
   private:
    StopwatchState state_;
    int64 frequency_;
    int64 start_timestamp_;
    int64 elapsed_timestamp_;
  };
  
  }  // namespace mozc
  
  #endif  // MOZC_BASE_STOPWATCH_H_
  