| /* |
| * Copyright (C) 2021 The Android Open Source Project |
| * |
| * Licensed 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 android.app.time; |
| |
| import android.annotation.CurrentTimeMillisLong; |
| import android.annotation.ElapsedRealtimeLong; |
| import android.annotation.NonNull; |
| import android.annotation.Nullable; |
| import android.annotation.SystemApi; |
| import android.os.Parcel; |
| import android.os.Parcelable; |
| import android.os.TimestampedValue; |
| |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.Collections; |
| import java.util.List; |
| import java.util.Objects; |
| |
| /** |
| * A time signal from an External source. |
| * |
| * <p>External time suggestions are for use in situations where the Android device is part of a |
| * wider network of devices that are required to use a single time source, and where authority for |
| * the time is external to the Android device. For example, for the Android Auto use case where the |
| * Android device is part of a wider in-car network of devices that should display the same time. |
| * |
| * <p>Android allows for a single external source for time. If there are several external sources |
| * then it is left to the caller to prioritize / filter accordingly to ensure consistency. |
| * |
| * <p>External is one of several time "origins" that the Android platform supports. Stock Android |
| * allows for configuration of which origins can be used and the prioritization between them. Until |
| * an external suggestion is made, the Android device may use its own RTC to initialize the system |
| * clock during boot, and then accept suggestions from the configured origins. |
| * |
| * <p>The creator of an external suggestion is expected to be separate Android process, e.g. a |
| * process integrating with the external time source via a HAL or local network. The creator must |
| * capture the elapsed realtime reference clock, e.g. via {@link SystemClock#elapsedRealtime()}, |
| * when the Unix epoch time is first obtained (usually under a wakelock). This enables Android to |
| * adjust for latency introduced between suggestion creation and eventual use. Adjustments for other |
| * sources of latency, i.e. those before the external time suggestion is created, must be handled by |
| * the creator. |
| * |
| * <p>{@code elapsedRealtimeMillis} and {@code suggestionMillis} represent the suggested time. |
| * {@code suggestionMillis} is the number of milliseconds elapsed since 1/1/1970 00:00:00 UTC |
| * according to the Unix time scale. {@code elapsedRealtimeMillis} is the value of the elapsed |
| * realtime clock when {@code suggestionMillis} was established. Note that the elapsed realtime |
| * clock is considered accurate but it is volatile, so time suggestions cannot be persisted across |
| * device resets. |
| * |
| * <p>{@code debugInfo} contains debugging metadata associated with the suggestion. This is used to |
| * record why the suggestion exists and how it was entered. This information exists only to aid in |
| * debugging and therefore is used by {@link #toString()}, but it is not for use in detection logic |
| * and is not considered in {@link #hashCode()} or {@link #equals(Object)}. |
| * |
| * @hide |
| */ |
| @SystemApi |
| public final class ExternalTimeSuggestion implements Parcelable { |
| |
| public static final @NonNull Creator<ExternalTimeSuggestion> CREATOR = |
| new Creator<ExternalTimeSuggestion>() { |
| public ExternalTimeSuggestion createFromParcel(Parcel in) { |
| return ExternalTimeSuggestion.createFromParcel(in); |
| } |
| |
| public ExternalTimeSuggestion[] newArray(int size) { |
| return new ExternalTimeSuggestion[size]; |
| } |
| }; |
| |
| @NonNull |
| private final TimestampedValue<Long> mUnixEpochTime; |
| @Nullable |
| private ArrayList<String> mDebugInfo; |
| |
| /** |
| * Creates a time suggestion cross-referenced to the elapsed realtime clock. See {@link |
| * ExternalTimeSuggestion} for more details. |
| * |
| * @param elapsedRealtimeMillis the elapsed realtime clock reference for the suggestion |
| * @param suggestionMillis the suggested time in milliseconds since the start of the |
| * Unix epoch |
| */ |
| public ExternalTimeSuggestion(@ElapsedRealtimeLong long elapsedRealtimeMillis, |
| @CurrentTimeMillisLong long suggestionMillis) { |
| mUnixEpochTime = new TimestampedValue(elapsedRealtimeMillis, suggestionMillis); |
| } |
| |
| private static ExternalTimeSuggestion createFromParcel(Parcel in) { |
| TimestampedValue<Long> utcTime = in.readParcelable(null /* classLoader */); |
| ExternalTimeSuggestion suggestion = |
| new ExternalTimeSuggestion(utcTime.getReferenceTimeMillis(), utcTime.getValue()); |
| @SuppressWarnings("unchecked") |
| ArrayList<String> debugInfo = (ArrayList<String>) in.readArrayList(null /* classLoader */); |
| suggestion.mDebugInfo = debugInfo; |
| return suggestion; |
| } |
| |
| @Override |
| public int describeContents() { |
| return 0; |
| } |
| |
| @Override |
| public void writeToParcel(@NonNull Parcel dest, int flags) { |
| dest.writeParcelable(mUnixEpochTime, 0); |
| dest.writeList(mDebugInfo); |
| } |
| |
| /** |
| * {@hide} |
| */ |
| @NonNull |
| public TimestampedValue<Long> getUnixEpochTime() { |
| return mUnixEpochTime; |
| } |
| |
| /** |
| * Returns information that can be useful for debugging / logging. See {@link #addDebugInfo}. |
| */ |
| @NonNull |
| public List<String> getDebugInfo() { |
| return mDebugInfo == null |
| ? Collections.emptyList() |
| : Collections.unmodifiableList(mDebugInfo); |
| } |
| |
| /** |
| * Associates information with the instance that can be useful for debugging / logging. The |
| * information is present in {@link #toString()} but is not considered for {@link |
| * #equals(Object)} and {@link #hashCode()}. |
| */ |
| public void addDebugInfo(@NonNull String... debugInfos) { |
| if (mDebugInfo == null) { |
| mDebugInfo = new ArrayList<>(); |
| } |
| mDebugInfo.addAll(Arrays.asList(debugInfos)); |
| } |
| |
| @Override |
| public boolean equals(Object o) { |
| if (this == o) { |
| return true; |
| } |
| if (o == null || getClass() != o.getClass()) { |
| return false; |
| } |
| ExternalTimeSuggestion that = (ExternalTimeSuggestion) o; |
| return Objects.equals(mUnixEpochTime, that.mUnixEpochTime); |
| } |
| |
| @Override |
| public int hashCode() { |
| return Objects.hash(mUnixEpochTime); |
| } |
| |
| @Override |
| public String toString() { |
| return "ExternalTimeSuggestion{" + "mUnixEpochTime=" + mUnixEpochTime |
| + ", mDebugInfo=" + mDebugInfo |
| + '}'; |
| } |
| } |