1 /*
2  * Copyright 2022 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 package androidx.work.impl
17 
18 import androidx.work.impl.model.WorkGenerationalId
19 import androidx.work.impl.model.WorkSpec
20 import androidx.work.impl.model.generationalId
21 
22 // Impl note: it is **not** a data class on purpose.
23 // Multiple schedulers can create `StartStopToken`-s for the same workSpecId, and `StartStopToken`
24 // objects should be different. If two schedulers request to start a work with the same
25 // `workSpecId`, Processor dedups those requests. However, if the work is cancelled, both
26 // of the schedules will request `Processor` to stop the work as well. That can lead to tricky race
27 // when one scheduler quickly cancels the work and schedules it again, while another stalls
28 // and tries to cancel the work afterwards. In this situation the freshly scheduled work shouldn't
29 // be cancelled because the second scheduler tries to cancel already cancelled work.
30 // So Processor class relies on StartStopToken-s being different and stores StartStopToken
31 // with the same workSpecId in the set to differentiate between past and future run requests.
32 class StartStopToken(val id: WorkGenerationalId)
33 
34 interface StartStopTokens {
tokenFornull35     fun tokenFor(id: WorkGenerationalId): StartStopToken
36 
37     fun remove(id: WorkGenerationalId): StartStopToken?
38 
39     fun remove(workSpecId: String): List<StartStopToken>
40 
41     fun contains(id: WorkGenerationalId): Boolean
42 
43     fun tokenFor(spec: WorkSpec) = tokenFor(spec.generationalId())
44 
45     fun remove(spec: WorkSpec) = remove(spec.generationalId())
46 
47     companion object {
48         @JvmStatic
49         @JvmOverloads
50         fun create(synchronized: Boolean = true): StartStopTokens {
51             val tokens = StartStopTokensImpl()
52             return if (synchronized) {
53                 SynchronizedStartStopTokensImpl(tokens)
54             } else {
55                 tokens
56             }
57         }
58     }
59 }
60 
61 private class StartStopTokensImpl : StartStopTokens {
62     private val runs = mutableMapOf<WorkGenerationalId, StartStopToken>()
63 
tokenFornull64     override fun tokenFor(id: WorkGenerationalId): StartStopToken {
65         return runs.getOrPut(id) { StartStopToken(id) }
66     }
67 
removenull68     override fun remove(id: WorkGenerationalId): StartStopToken? {
69         return runs.remove(id)
70     }
71 
removenull72     override fun remove(workSpecId: String): List<StartStopToken> {
73         val toRemove = runs.filterKeys { it.workSpecId == workSpecId }
74         toRemove.keys.forEach { runs.remove(it) }
75         return toRemove.values.toList()
76     }
77 
containsnull78     override fun contains(id: WorkGenerationalId): Boolean {
79         return runs.contains(id)
80     }
81 }
82 
83 private class SynchronizedStartStopTokensImpl(private val delegate: StartStopTokens) :
84     StartStopTokens {
85 
86     private val lock = Any()
87 
tokenFornull88     override fun tokenFor(id: WorkGenerationalId): StartStopToken {
89         return synchronized(lock) { delegate.tokenFor(id) }
90     }
91 
removenull92     override fun remove(id: WorkGenerationalId): StartStopToken? {
93         return synchronized(lock) { delegate.remove(id) }
94     }
95 
removenull96     override fun remove(workSpecId: String): List<StartStopToken> {
97         return synchronized(lock) { delegate.remove(workSpecId) }
98     }
99 
containsnull100     override fun contains(id: WorkGenerationalId): Boolean {
101         return synchronized(lock) { delegate.contains(id) }
102     }
103 }
104