1/*
2 * Copyright (C) 2017 The Android Open Source Project
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
17package com.android.server.testutils;
18
19import android.os.SystemClock;
20
21import java.util.function.LongSupplier;
22
23/**
24 * A time supplier (in the format of a {@code long} as the amount of milliseconds) similar
25 * to {@link SystemClock#uptimeMillis()}, but with the ability to {@link #fastForward}
26 * and {@link #rewind}
27 *
28 * Implements {@link LongSupplier} to be interchangeable with {@code SystemClock::uptimeMillis}
29 *
30 * Can be provided to {@link TestHandler} to "mock time" for the delayed execution testing
31 *
32 * @see OffsettableClock.Stopped for a version of this clock that does not advance on its own
33 */
34public class OffsettableClock implements LongSupplier {
35    private long mOffset = 0L;
36
37    /**
38     * @return Current time in milliseconds, according to this clock
39     */
40    public long now() {
41        return realNow() + mOffset;
42    }
43
44    /**
45     * Can be overriden with a constant for a clock that stands still, and is only ever moved
46     * manually
47     */
48    public long realNow() {
49        return SystemClock.uptimeMillis();
50    }
51
52    public void fastForward(long timeMs) {
53        mOffset += timeMs;
54    }
55    public void rewind(long timeMs) {
56        fastForward(-timeMs);
57    }
58    public void reset() {
59        mOffset = 0;
60    }
61
62    /** @deprecated Only present for {@link LongSupplier} contract */
63    @Override
64    @Deprecated
65    public long getAsLong() {
66        return now();
67    }
68
69    /**
70     * An {@link OffsettableClock} that does not advance with real time, and can only be
71     * advanced manually via {@link #fastForward}
72     */
73    public static class Stopped extends OffsettableClock {
74        @Override
75        public long realNow() {
76            return 0L;
77        }
78    }
79}
80