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1   /*
2    * Copyright (C) 2008 The Guava Authors
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package com.google.common.testing;
18  
19  import static com.google.common.base.Preconditions.checkArgument;
20  
21  import com.google.common.annotations.Beta;
22  import com.google.common.annotations.GwtCompatible;
23  import com.google.common.base.Ticker;
24  import java.util.concurrent.TimeUnit;
25  import java.util.concurrent.atomic.AtomicLong;
26  
27  /**
28   * A Ticker whose value can be advanced programmatically in test.
29   * <p>
30   * The ticker can be configured so that the time is incremented whenever {@link #read} is called:
31   * see {@link #setAutoIncrementStep}.
32   * <p>
33   * This class is thread-safe.
34   *
35   * @author Jige Yu
36   * @since 10.0
37   */
38  @Beta
39  @GwtCompatible
40  public class FakeTicker extends Ticker {
41  
42    private final AtomicLong nanos = new AtomicLong();
43    private volatile long autoIncrementStepNanos;
44  
45    /** Advances the ticker value by {@code time} in {@code timeUnit}. */
46    public FakeTicker advance(long time, TimeUnit timeUnit) {
47      return advance(timeUnit.toNanos(time));
48    }
49  
50    /** Advances the ticker value by {@code nanoseconds}. */
51    public FakeTicker advance(long nanoseconds) {
52      nanos.addAndGet(nanoseconds);
53      return this;
54    }
55  
56    /**
57     * Sets the increment applied to the ticker whenever it is queried.
58     *
59     * <p>The default behavior is to auto increment by zero. i.e: The ticker is left unchanged when
60     * queried.
61     */
62    public FakeTicker setAutoIncrementStep(long autoIncrementStep, TimeUnit timeUnit) {
63      checkArgument(autoIncrementStep >= 0, "May not auto-increment by a negative amount");
64      this.autoIncrementStepNanos = timeUnit.toNanos(autoIncrementStep);
65      return this;
66    }
67  
68    @Override public long read() {
69      return nanos.getAndAdd(autoIncrementStepNanos);
70    }
71  }