1 /*
2  * Copyright (C) 2015 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 #include "AutoConditionLock.h"
18 
19 namespace android {
20 
WaitableMutexWrapper(Mutex * mutex)21 WaitableMutexWrapper::WaitableMutexWrapper(Mutex* mutex) : mMutex{mutex}, mState{false} {}
22 
~WaitableMutexWrapper()23 WaitableMutexWrapper::~WaitableMutexWrapper() {}
24 
25 // Locks manager-owned mutex
AutoConditionLock(const std::shared_ptr<WaitableMutexWrapper> & manager)26 AutoConditionLock::AutoConditionLock(const std::shared_ptr<WaitableMutexWrapper>& manager) :
27         mManager{manager}, mAutoLock{manager->mMutex}, mAcquired(false) {}
28 
29 // Unlocks manager-owned mutex
~AutoConditionLock()30 AutoConditionLock::~AutoConditionLock() {
31     // Unset the condition and wake everyone up before releasing lock
32     if (mAcquired) {
33         mManager->mState = false;
34         mManager->mCondition.broadcast();
35     }
36 }
37 
waitAndAcquire(const std::shared_ptr<WaitableMutexWrapper> & manager,nsecs_t waitTime)38 std::unique_ptr<AutoConditionLock> AutoConditionLock::waitAndAcquire(
39         const std::shared_ptr<WaitableMutexWrapper>& manager, nsecs_t waitTime) {
40 
41     if (manager == nullptr || manager->mMutex == nullptr) {
42         // Bad input, return null
43         return std::unique_ptr<AutoConditionLock>{nullptr};
44     }
45 
46     // Acquire scoped lock
47     std::unique_ptr<AutoConditionLock> scopedLock(new AutoConditionLock(manager));
48 
49     // Figure out what time in the future we should hit the timeout
50     nsecs_t failTime = systemTime(SYSTEM_TIME_MONOTONIC) + waitTime;
51 
52     // Wait until we timeout, or success
53     while(manager->mState) {
54         status_t ret = manager->mCondition.waitRelative(*(manager->mMutex), waitTime);
55         if (ret != NO_ERROR) {
56             // Timed out or whatever, return null
57             return std::unique_ptr<AutoConditionLock>{nullptr};
58         }
59         waitTime = failTime - systemTime(SYSTEM_TIME_MONOTONIC);
60     }
61 
62     // Set the condition and return
63     manager->mState = true;
64     scopedLock->mAcquired = true;
65     return scopedLock;
66 }
67 
waitAndAcquire(const std::shared_ptr<WaitableMutexWrapper> & manager)68 std::unique_ptr<AutoConditionLock> AutoConditionLock::waitAndAcquire(
69         const std::shared_ptr<WaitableMutexWrapper>& manager) {
70 
71     if (manager == nullptr || manager->mMutex == nullptr) {
72         // Bad input, return null
73         return std::unique_ptr<AutoConditionLock>{nullptr};
74     }
75 
76     // Acquire scoped lock
77     std::unique_ptr<AutoConditionLock> scopedLock(new AutoConditionLock(manager));
78 
79     // Wait until we timeout, or success
80     while(manager->mState) {
81         status_t ret = manager->mCondition.wait(*(manager->mMutex));
82         if (ret != NO_ERROR) {
83             // Timed out or whatever, return null
84             return std::unique_ptr<AutoConditionLock>{nullptr};
85         }
86     }
87 
88     // Set the condition and return
89     manager->mState = true;
90     scopedLock->mAcquired = true;
91     return scopedLock;
92 }
93 
94 }; // namespace android
95