content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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
   *
   *     https://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.
   */
  package org.apache.avro.ipc.stats;
  
  /** Encapsulates the passing of time. */
  class Stopwatch {
    /** Encapsulates ticking time sources. */
    interface Ticks {
      /**
       * Returns a number of "ticks" in nanoseconds. This should be monotonically
       * non-decreasing.
       */
      long ticks();
    }
  
    /** Default System time source. */
    public final static Ticks SYSTEM_TICKS = new SystemTicks();
  
    private Ticks ticks;
    private long start;
    private long elapsed = -1;
    private boolean running;
  
    public Stopwatch(Ticks ticks) {
      this.ticks = ticks;
    }
  
    /** Returns seconds that have elapsed since start() */
    public long elapsedNanos() {
      if (running) {
        return this.ticks.ticks() - start;
      } else {
        if (elapsed == -1)
          throw new IllegalStateException();
        return elapsed;
      }
    }
  
    /** Starts the stopwatch. */
    public void start() {
      if (running)
        throw new IllegalStateException();
      start = ticks.ticks();
      running = true;
    }
  
    /** Stops the stopwatch and calculates the elapsed time. */
    public void stop() {
      if (!running)
        throw new IllegalStateException();
      elapsed = ticks.ticks() - start;
      running = false;
    }
  
    /** Implementation of Ticks using System.nanoTime(). */
    private static class SystemTicks implements Ticks {
      @Override
      public long ticks() {
        return System.nanoTime();
      }
    }
  }
  