Add location backed system clock

This provides a permissionless way to use the location (e.g. GNSS)
provided time data for more accurate time keeping.

Test: atest LocationManagerTest#testGnssProvidedClock
Bug: 123530510
Change-Id: Ifbc45997868040abbb3e1399a8649911afb0af05

api/current.txt

@@ -35419,6 +35419,7 @@ package android.os {
   }
 
   public final class SystemClock {
+    method @NonNull public static java.time.Clock currentGnssTimeClock();
     method public static long currentThreadTimeMillis();
     method public static long elapsedRealtime();
     method public static long elapsedRealtimeNanos();

core/java/android/os/SystemClock.java

@@ -19,6 +19,8 @@ package android.os;
 import android.annotation.NonNull;
 import android.app.IAlarmManager;
 import android.content.Context;
+import android.location.ILocationManager;
+import android.location.LocationTime;
 import android.util.Slog;
 
 import dalvik.annotation.optimization.CriticalNative;
@@ -313,4 +315,33 @@ public final class SystemClock {
             }
         };
     }
+
+    /**
+     * Returns a {@link Clock} that starts at January 1, 1970 00:00:00.0 UTC,
+     * synchronized using the device's location provider.
+     *
+     * @throws DateTimeException when the location provider has not had a location fix since boot.
+     */
+    public static @NonNull Clock currentGnssTimeClock() {
+        return new SimpleClock(ZoneOffset.UTC) {
+            private final ILocationManager mMgr = ILocationManager.Stub
+                    .asInterface(ServiceManager.getService(Context.LOCATION_SERVICE));
+            @Override
+            public long millis() {
+                LocationTime time;
+                try {
+                    time = mMgr.getGnssTimeMillis();
+                } catch (RemoteException e) {
+                    e.rethrowFromSystemServer();
+                    return 0;
+                }
+                if (time == null) {
+                    throw new DateTimeException("Gnss based time is not available.");
+                }
+                long currentNanos = elapsedRealtimeNanos();
+                long deltaMs = (currentNanos - time.getElapsedRealtimeNanos()) / 1000000L;
+                return time.getTime() + deltaMs;
+            }
+        };
+    }
 }

location/java/android/location/ILocationManager.aidl

@@ -29,6 +29,7 @@ import android.location.IGnssNavigationMessageListener;
 import android.location.ILocationListener;
 import android.location.Location;
 import android.location.LocationRequest;
+import android.location.LocationTime;
 import android.os.Bundle;
 
 import com.android.internal.location.ProviderProperties;
@@ -104,6 +105,7 @@ interface ILocationManager
     void setTestProviderLocation(String provider, in Location loc, String opPackageName);
     void setTestProviderEnabled(String provider, boolean enabled, String opPackageName);
     List<LocationRequest> getTestProviderCurrentRequests(String provider, String opPackageName);
+    LocationTime getGnssTimeMillis();
 
     // --- deprecated ---
     void setTestProviderStatus(String provider, int status, in Bundle extras, long updateTime,

location/java/android/location/LocationTime.aidl

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019, 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.location;
+
+parcelable LocationTime;

location/java/android/location/LocationTime.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2019 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.location;
+
+import android.annotation.NonNull;
+import android.os.Parcel;
+import android.os.Parcelable;
+
+/**
+ * Data class for passing location derived time.
+ * @hide
+ */
+public final class LocationTime implements Parcelable {
+
+    private final long mTime;
+    private final long mElapsedRealtimeNanos;
+
+    public LocationTime(long time, long elapsedRealtimeNanos) {
+        mTime = time;
+        mElapsedRealtimeNanos = elapsedRealtimeNanos;
+    }
+
+    /**
+     * The current time, according to the Gnss location provider. */
+    public long getTime() {
+        return mTime;
+    }
+
+    /**
+     * The elapsed nanos since boot {@link #getTime} was computed at.
+     */
+    public long getElapsedRealtimeNanos() {
+        return mElapsedRealtimeNanos;
+    }
+
+    @Override
+    public void writeToParcel(Parcel out, int flags) {
+        out.writeLong(mTime);
+        out.writeLong(mElapsedRealtimeNanos);
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    public static final @NonNull Parcelable.Creator<LocationTime> CREATOR =
+            new Parcelable.Creator<LocationTime>() {
+                public LocationTime createFromParcel(Parcel in) {
+                    long time = in.readLong();
+                    long elapsedRealtimeNanos = in.readLong();
+                    return new LocationTime(time, elapsedRealtimeNanos);
+                }
+
+                public LocationTime[] newArray(int size) {
+                    return new LocationTime[size];
+                }
+            };
+}

services/core/java/com/android/server/LocationManagerService.java

@@ -64,6 +64,7 @@ import android.location.INetInitiatedListener;
 import android.location.Location;
 import android.location.LocationManager;
 import android.location.LocationRequest;
+import android.location.LocationTime;
 import android.os.Binder;
 import android.os.Bundle;
 import android.os.Handler;
@@ -2684,6 +2685,19 @@ public class LocationManagerService extends ILocationManager.Stub {
         }
     }
 
+    @Override
+    public LocationTime getGnssTimeMillis() {
+        synchronized (mLock) {
+            Location location = mLastLocation.get(LocationManager.GPS_PROVIDER);
+            if (location == null) {
+                return null;
+            }
+            long currentNanos = SystemClock.elapsedRealtimeNanos();
+            long deltaMs = (currentNanos - location.getElapsedRealtimeNanos()) / 1000000L;
+            return new LocationTime(location.getTime() + deltaMs, currentNanos);
+        }
+    }
+
     @Override
     public boolean injectLocation(Location location) {
         mContext.enforceCallingPermission(android.Manifest.permission.LOCATION_HARDWARE,