1 /*
2  * Copyright 2017 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 androidx.work.impl.utils;
18 
19 import android.content.Context;
20 import android.content.SharedPreferences;
21 import android.support.annotation.RestrictTo;
22 
23 /**
24  * Generates unique IDs that are persisted in {@link SharedPreferences}.
25  *
26  * @hide
27  */
28 @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
29 public class IdGenerator {
30 
31     /** The initial id used for JobInfos, Firebase Jobs & and Alarms. */
32     public static final int INITIAL_ID = 0;
33 
34     static final String PREFERENCE_FILE_KEY = "androidx.work.util.id";
35     static final String NEXT_JOB_SCHEDULER_ID_KEY = "next_job_scheduler_id";
36     static final String NEXT_FIREBASE_ALARM_ID_KEY = "next_firebase_alarm_id";
37     static final String NEXT_ALARM_MANAGER_ID_KEY = "next_alarm_manager_id";
38 
39     private SharedPreferences mSharedPrefs;
40 
41     /**
42      * Constructs a {@link IdGenerator}.
43      *
44      * @param context {@link Context} to get the {@link SharedPreferences} from.
45      */
IdGenerator(Context context)46     public IdGenerator(Context context) {
47         mSharedPrefs = context.getSharedPreferences(PREFERENCE_FILE_KEY, Context.MODE_PRIVATE);
48     }
49 
50     /**
51      * Generates IDs for {@link android.app.job.JobInfo} jobs given a reserved range.
52      */
nextJobSchedulerIdWithRange(int minInclusive, int maxInclusive)53     public int nextJobSchedulerIdWithRange(int minInclusive, int maxInclusive) {
54         synchronized (IdGenerator.class) {
55             int id = nextId(NEXT_JOB_SCHEDULER_ID_KEY);
56             if (id < minInclusive || id > maxInclusive) {
57                 // outside the range, re-start at minInclusive.
58                 id = minInclusive;
59                 update(NEXT_JOB_SCHEDULER_ID_KEY, id + 1);
60             }
61             return id;
62         }
63     }
64 
65     /**
66      * Generates IDs for Firebase Delayed Alarm Receiver jobs.
67      */
nextFirebaseAlarmId()68     public int nextFirebaseAlarmId() {
69         synchronized (IdGenerator.class) {
70             return nextId(NEXT_FIREBASE_ALARM_ID_KEY);
71         }
72     }
73 
74     /**
75      * Generates IDs for {@link android.app.AlarmManager} work.
76      */
nextAlarmManagerId()77     public int nextAlarmManagerId() {
78         synchronized (IdGenerator.class) {
79             return nextId(NEXT_ALARM_MANAGER_ID_KEY);
80         }
81     }
82 
83     /**
84      * Returns the next available ID based on a persisted counter.
85      * Resets ID counter to 0 when the ID exceeded {@link Integer#MAX_VALUE}.
86      * @param key String matching the particular counter to retrieve
87      * @return next available id
88      */
nextId(String key)89     private int nextId(String key) {
90         int id = mSharedPrefs.getInt(key, INITIAL_ID);
91         int nextId = (id == Integer.MAX_VALUE) ? INITIAL_ID : id + 1;
92         update(key, nextId);
93         return id;
94     }
95 
update(String key, int value)96     private void update(String key, int value) {
97         mSharedPrefs.edit().putInt(key, value).apply();
98     }
99 }
100