android-34/com/android/internal/telephony/NitzStateMachine.java

/*
 * Copyright 2018 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 com.android.internal.telephony;

import android.annotation.NonNull;
import android.content.ContentResolver;
import android.content.Context;
import android.os.SystemClock;
import android.os.SystemProperties;
import android.provider.Settings;

import com.android.internal.util.IndentingPrintWriter;

import java.io.FileDescriptor;
import java.io.PrintWriter;

/**
 * An interface for the Android component that handles NITZ and related signals for time and time
 * zone detection.
 *
 * {@hide}
 */
public interface NitzStateMachine {

    /**
     * Called when the country suitable for time zone detection is detected.
     *
     * @param countryIsoCode the countryIsoCode to use for time zone detection, may be "" for test
     *     cells only, otherwise {@link #handleCountryUnavailable()} should be called
     */
    void handleCountryDetected(@NonNull String countryIsoCode);

    /**
     * Informs the {@link NitzStateMachine} that the network has become available.
     */
    void handleNetworkAvailable();

    /**
     * Informs the {@link NitzStateMachine} that the network has become unavailable. Any network
     * state, i.e. NITZ, should be cleared.
     */
    void handleNetworkUnavailable();

    /**
     * Informs the {@link NitzStateMachine} that any previously detected country supplied via
     * {@link #handleCountryDetected(String)} is no longer valid.
     */
    void handleCountryUnavailable();

    /**
     * Handle a new NITZ signal being received.
     */
    void handleNitzReceived(@NonNull NitzSignal nitzSignal);

    /**
     * Handle the user putting the device into or out of airplane mode
     * @param on true if airplane mode has been turned on, false if it's been turned off.
     */
    void handleAirplaneModeChanged(boolean on);

    /**
     * Dumps the current in-memory state to the supplied PrintWriter.
     */
    void dumpState(PrintWriter pw);

    /**
     * Dumps the time / time zone logs to the supplied IndentingPrintWriter.
     */
    void dumpLogs(FileDescriptor fd, IndentingPrintWriter ipw, String[] args);

    /**
     * A proxy over read-only device state that allows things like system properties, elapsed
     * realtime clock to be faked for tests.
     */
    interface DeviceState {

        /**
         * If the elapsed realtime between two NITZ signals is greater than this value then the
         * second signal cannot be ignored.
         */
        int getNitzUpdateSpacingMillis();

        /**
         * If Unix epoch time between two NITZ signals is greater than this value then the second
         * signal cannot be ignored.
         */
        int getNitzUpdateDiffMillis();

        /**
         * If the device connects to a telephony network and was disconnected from a telephony
         * network for less than this time, a previously received NITZ signal can be restored.
         *
         * <p>The restored NITZ may not be from the same network as the current network. It is
         * intended to be a relatively small value to allow for brief disconnections. Larger values
         * increase the likelihood that the device has moved to a different network and/or time
         * zone.
         */
        int getNitzNetworkDisconnectRetentionMillis();

        /**
         * Returns true if the {@code gsm.ignore-nitz} system property is set to "yes".
         */
        boolean getIgnoreNitz();

        /**
         * Returns the same value as {@link SystemClock#elapsedRealtime()}.
         */
        long elapsedRealtimeMillis();

        /**
         * Returns the same value as {@link System#currentTimeMillis()}.
         */
        long currentTimeMillis();
    }

    /**
     * The real implementation of {@link DeviceState}.
     *
     * {@hide}
     */
    class DeviceStateImpl implements DeviceState {

        /** The default value to use for {@link #getNitzUpdateSpacingMillis()}. 10 minutes. */
        private static final int NITZ_UPDATE_SPACING_MILLIS_DEFAULT = 1000 * 60 * 10;
        private final int mNitzUpdateSpacingMillis;

        /** The default value to use for {@link #getNitzUpdateDiffMillis()}. 2 seconds. */
        private static final int NITZ_UPDATE_DIFF_MILLIS_DEFAULT = 2000;
        private final int mNitzUpdateDiffMillis;

        /**
         * The default value to use for {@link #getNitzNetworkDisconnectRetentionMillis()}.
         * 5 minutes.
         */
        private static final int NITZ_NETWORK_DISCONNECT_RETENTION_MILLIS_DEFAULT = 1000 * 60 * 5;
        private final int mNitzNetworkDisconnectRetentionMillis;

        private final ContentResolver mCr;

        public DeviceStateImpl(Phone phone) {
            Context context = phone.getContext();
            mCr = context.getContentResolver();
            mNitzUpdateSpacingMillis =
                    SystemProperties.getInt("ro.nitz_update_spacing",
                            NITZ_UPDATE_SPACING_MILLIS_DEFAULT);
            mNitzUpdateDiffMillis =
                    SystemProperties.getInt("ro.nitz_update_diff", NITZ_UPDATE_DIFF_MILLIS_DEFAULT);
            mNitzNetworkDisconnectRetentionMillis =
                    SystemProperties.getInt("ro.nitz_network_disconnect_retention",
                            NITZ_NETWORK_DISCONNECT_RETENTION_MILLIS_DEFAULT);
        }

        @Override
        public int getNitzUpdateSpacingMillis() {
            return Settings.Global.getInt(mCr, Settings.Global.NITZ_UPDATE_SPACING,
                    mNitzUpdateSpacingMillis);
        }

        @Override
        public int getNitzUpdateDiffMillis() {
            return Settings.Global.getInt(mCr, Settings.Global.NITZ_UPDATE_DIFF,
                    mNitzUpdateDiffMillis);
        }

        @Override
        public int getNitzNetworkDisconnectRetentionMillis() {
            return Settings.Global.getInt(mCr, Settings.Global.NITZ_NETWORK_DISCONNECT_RETENTION,
                    mNitzNetworkDisconnectRetentionMillis);
        }

        @Override
        public boolean getIgnoreNitz() {
            String ignoreNitz = SystemProperties.get("gsm.ignore-nitz");
            return ignoreNitz != null && ignoreNitz.equals("yes");
        }

        @Override
        public long elapsedRealtimeMillis() {
            return SystemClock.elapsedRealtime();
        }

        @Override
        public long currentTimeMillis() {
            return System.currentTimeMillis();
        }
    }
}