Neil Fuller | 4773b9d | 2018-06-08 18:44:49 +0100 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2018 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 | |
| 17 | package android.util; |
| 18 | |
| 19 | import android.annotation.NonNull; |
| 20 | import android.annotation.Nullable; |
| 21 | import android.os.Parcel; |
| 22 | import android.os.SystemClock; |
| 23 | |
| 24 | import java.util.Objects; |
| 25 | |
| 26 | /** |
| 27 | * A value with an associated reference time. The reference time will typically be provided by the |
| 28 | * elapsed realtime clock. The elapsed realtime clock can be obtained using methods like |
| 29 | * {@link SystemClock#elapsedRealtime()} or {@link SystemClock#elapsedRealtimeClock()}. |
| 30 | * If a suitable clock is used the reference time can be used to identify the age of a value or |
| 31 | * ordering between values. |
| 32 | * |
| 33 | * <p>To read and write a timestamped value from / to a Parcel see |
| 34 | * {@link #readFromParcel(Parcel, ClassLoader, Class)} and |
| 35 | * {@link #writeToParcel(Parcel, TimestampedValue)}. |
| 36 | * |
| 37 | * @param <T> the type of the value with an associated timestamp |
| 38 | * @hide |
| 39 | */ |
| 40 | public final class TimestampedValue<T> { |
| 41 | private final long mReferenceTimeMillis; |
| 42 | private final T mValue; |
| 43 | |
| 44 | public TimestampedValue(long referenceTimeMillis, T value) { |
| 45 | mReferenceTimeMillis = referenceTimeMillis; |
| 46 | mValue = value; |
| 47 | } |
| 48 | |
| 49 | public long getReferenceTimeMillis() { |
| 50 | return mReferenceTimeMillis; |
| 51 | } |
| 52 | |
| 53 | public T getValue() { |
| 54 | return mValue; |
| 55 | } |
| 56 | |
| 57 | @Override |
| 58 | public boolean equals(Object o) { |
| 59 | if (this == o) { |
| 60 | return true; |
| 61 | } |
| 62 | if (o == null || getClass() != o.getClass()) { |
| 63 | return false; |
| 64 | } |
| 65 | TimestampedValue<?> that = (TimestampedValue<?>) o; |
| 66 | return mReferenceTimeMillis == that.mReferenceTimeMillis |
| 67 | && Objects.equals(mValue, that.mValue); |
| 68 | } |
| 69 | |
| 70 | @Override |
| 71 | public int hashCode() { |
| 72 | return Objects.hash(mReferenceTimeMillis, mValue); |
| 73 | } |
| 74 | |
| 75 | /** |
| 76 | * Read a {@link TimestampedValue} from a parcel that was stored using |
| 77 | * {@link #writeToParcel(Parcel, TimestampedValue)}. |
| 78 | * |
| 79 | * <p>The marshalling/unmarshalling of the value relies upon {@link Parcel#writeValue(Object)} |
| 80 | * and {@link Parcel#readValue(ClassLoader)} and so this method can only be used with types |
| 81 | * supported by those methods. |
| 82 | * |
| 83 | * @param in the Parcel to read from |
| 84 | * @param classLoader the ClassLoader to pass to {@link Parcel#readValue(ClassLoader)} |
| 85 | * @param valueClass the expected type of the value, typically the same as {@code <T>} but can |
| 86 | * also be a subclass |
| 87 | * @throws RuntimeException if the value read is not compatible with {@code valueClass} or the |
| 88 | * object could not be read |
| 89 | */ |
| 90 | @SuppressWarnings("unchecked") |
| 91 | @NonNull |
| 92 | public static <T> TimestampedValue<T> readFromParcel( |
| 93 | @NonNull Parcel in, @Nullable ClassLoader classLoader, Class<? extends T> valueClass) { |
| 94 | long referenceTimeMillis = in.readLong(); |
| 95 | T value = (T) in.readValue(classLoader); |
| 96 | // Equivalent to static code: if (!(value.getClass() instanceof {valueClass})) { |
| 97 | if (value != null && !valueClass.isAssignableFrom(value.getClass())) { |
| 98 | throw new RuntimeException("Value was of type " + value.getClass() |
| 99 | + " is not assignable to " + valueClass); |
| 100 | } |
| 101 | return new TimestampedValue<>(referenceTimeMillis, value); |
| 102 | } |
| 103 | |
| 104 | /** |
| 105 | * Write a {@link TimestampedValue} to a parcel so that it can be read using |
| 106 | * {@link #readFromParcel(Parcel, ClassLoader, Class)}. |
| 107 | * |
| 108 | * <p>The marshalling/unmarshalling of the value relies upon {@link Parcel#writeValue(Object)} |
| 109 | * and {@link Parcel#readValue(ClassLoader)} and so this method can only be used with types |
| 110 | * supported by those methods. |
| 111 | * |
| 112 | * @param dest the Parcel |
| 113 | * @param timestampedValue the value |
| 114 | * @throws RuntimeException if the value could not be written to the Parcel |
| 115 | */ |
| 116 | public static void writeToParcel( |
| 117 | @NonNull Parcel dest, @NonNull TimestampedValue<?> timestampedValue) { |
| 118 | dest.writeLong(timestampedValue.mReferenceTimeMillis); |
| 119 | dest.writeValue(timestampedValue.mValue); |
| 120 | } |
| 121 | } |