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
   *
   *     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.
   */
  package org.apache.beam.runners.direct;
  
  import java.util.concurrent.TimeUnit;
  import org.joda.time.Instant;
  
  /** A {@link Clock} that uses {@link System#nanoTime()} to track the progress of time. */
  class NanosOffsetClock implements Clock {
    private final long baseMillis;
    private final long nanosAtBaseMillis;
  
    public static NanosOffsetClock create() {
      return new NanosOffsetClock();
    }
  
    private NanosOffsetClock() {
      baseMillis = System.currentTimeMillis();
      nanosAtBaseMillis = System.nanoTime();
    }
  
    @Override
    public Instant now() {
      return new Instant(
          baseMillis
              + TimeUnit.MILLISECONDS.convert(
                  System.nanoTime() - nanosAtBaseMillis, TimeUnit.NANOSECONDS));
    }
  }
  