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      1 /*
      2  * Copyright (C) 2006 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.os;
     18 
     19 import com.google.android.collect.Maps;
     20 
     21 import java.util.HashMap;
     22 import java.util.concurrent.TimeoutException;
     23 
     24 /**
     25  * Controls and utilities for low-level {@code init} services.
     26  *
     27  * @hide
     28  */
     29 public class SystemService {
     30 
     31     private static HashMap<String, State> sStates = Maps.newHashMap();
     32 
     33     /**
     34      * State of a known {@code init} service.
     35      */
     36     public enum State {
     37         RUNNING("running"),
     38         STOPPING("stopping"),
     39         STOPPED("stopped"),
     40         RESTARTING("restarting");
     41 
     42         State(String state) {
     43             sStates.put(state, this);
     44         }
     45     }
     46 
     47     private static Object sPropertyLock = new Object();
     48 
     49     static {
     50         SystemProperties.addChangeCallback(new Runnable() {
     51             @Override
     52             public void run() {
     53                 synchronized (sPropertyLock) {
     54                     sPropertyLock.notifyAll();
     55                 }
     56             }
     57         });
     58     }
     59 
     60     /** Request that the init daemon start a named service. */
     61     public static void start(String name) {
     62         SystemProperties.set("ctl.start", name);
     63     }
     64 
     65     /** Request that the init daemon stop a named service. */
     66     public static void stop(String name) {
     67         SystemProperties.set("ctl.stop", name);
     68     }
     69 
     70     /** Request that the init daemon restart a named service. */
     71     public static void restart(String name) {
     72         SystemProperties.set("ctl.restart", name);
     73     }
     74 
     75     /**
     76      * Return current state of given service.
     77      */
     78     public static State getState(String service) {
     79         final String rawState = SystemProperties.get("init.svc." + service);
     80         final State state = sStates.get(rawState);
     81         if (state != null) {
     82             return state;
     83         } else {
     84             return State.STOPPED;
     85         }
     86     }
     87 
     88     /**
     89      * Check if given service is {@link State#STOPPED}.
     90      */
     91     public static boolean isStopped(String service) {
     92         return State.STOPPED.equals(getState(service));
     93     }
     94 
     95     /**
     96      * Check if given service is {@link State#RUNNING}.
     97      */
     98     public static boolean isRunning(String service) {
     99         return State.RUNNING.equals(getState(service));
    100     }
    101 
    102     /**
    103      * Wait until given service has entered specific state.
    104      */
    105     public static void waitForState(String service, State state, long timeoutMillis)
    106             throws TimeoutException {
    107         final long endMillis = SystemClock.elapsedRealtime() + timeoutMillis;
    108         while (true) {
    109             synchronized (sPropertyLock) {
    110                 final State currentState = getState(service);
    111                 if (state.equals(currentState)) {
    112                     return;
    113                 }
    114 
    115                 if (SystemClock.elapsedRealtime() >= endMillis) {
    116                     throw new TimeoutException("Service " + service + " currently " + currentState
    117                             + "; waited " + timeoutMillis + "ms for " + state);
    118                 }
    119 
    120                 try {
    121                     sPropertyLock.wait(timeoutMillis);
    122                 } catch (InterruptedException e) {
    123                 }
    124             }
    125         }
    126     }
    127 
    128     /**
    129      * Wait until any of given services enters {@link State#STOPPED}.
    130      */
    131     public static void waitForAnyStopped(String... services)  {
    132         while (true) {
    133             synchronized (sPropertyLock) {
    134                 for (String service : services) {
    135                     if (State.STOPPED.equals(getState(service))) {
    136                         return;
    137                     }
    138                 }
    139 
    140                 try {
    141                     sPropertyLock.wait();
    142                 } catch (InterruptedException e) {
    143                 }
    144             }
    145         }
    146     }
    147 }
    148