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1 /* | 1 /* |
2 * Copyright 2016 The WebRTC Project Authors. All rights reserved. | 2 * Copyright 2016 The WebRTC Project Authors. All rights reserved. |
3 * | 3 * |
4 * Use of this source code is governed by a BSD-style license | 4 * Use of this source code is governed by a BSD-style license |
5 * that can be found in the LICENSE file in the root of the source | 5 * that can be found in the LICENSE file in the root of the source |
6 * tree. An additional intellectual property rights grant can be found | 6 * tree. An additional intellectual property rights grant can be found |
7 * in the file PATENTS. All contributing project authors may | 7 * in the file PATENTS. All contributing project authors may |
8 * be found in the AUTHORS file in the root of the source tree. | 8 * be found in the AUTHORS file in the root of the source tree. |
9 */ | 9 */ |
10 | 10 |
11 #include "RTCUIApplicationStatusObserver.h" | 11 #include "RTCUIApplicationStatusObserver.h" |
12 | 12 |
13 #if defined(WEBRTC_IOS) | 13 #if defined(WEBRTC_IOS) |
14 | 14 |
15 #import <UIKit/UIKit.h> | 15 #import <UIKit/UIKit.h> |
16 | 16 |
17 #include "webrtc/rtc_base/checks.h" | 17 #include "webrtc/rtc_base/checks.h" |
18 | 18 |
19 @interface RTCUIApplicationStatusObserver () | 19 @interface RTCUIApplicationStatusObserver () |
20 | 20 |
21 @property(nonatomic, assign) BOOL initialized; | 21 @property(nonatomic, assign) BOOL initialized; |
22 @property(nonatomic, assign) UIApplicationState state; | 22 @property(nonatomic, assign) UIApplicationState state; |
tkchin_webrtc
2017/09/13 18:32:02
State is read and written to from multiple threads
andersc
2017/09/14 08:08:45
Acknowledged.
| |
23 | 23 |
24 @end | 24 @end |
25 | 25 |
26 @implementation RTCUIApplicationStatusObserver { | 26 @implementation RTCUIApplicationStatusObserver { |
27 BOOL _initialized; | 27 BOOL _initialized; |
28 dispatch_block_t _initializeBlock; | 28 dispatch_block_t _initializeBlock; |
29 dispatch_semaphore_t _waitForInitializeSemaphore; | |
29 UIApplicationState _state; | 30 UIApplicationState _state; |
30 | 31 |
31 id<NSObject> _activeObserver; | 32 id<NSObject> _activeObserver; |
32 id<NSObject> _backgroundObserver; | 33 id<NSObject> _backgroundObserver; |
33 } | 34 } |
34 | 35 |
35 @synthesize initialized = _initialized; | 36 @synthesize initialized = _initialized; |
36 @synthesize state = _state; | 37 @synthesize state = _state; |
37 | 38 |
38 + (instancetype)sharedInstance { | 39 + (instancetype)sharedInstance { |
39 static id sharedInstance; | 40 static id sharedInstance; |
40 static dispatch_once_t onceToken; | 41 static dispatch_once_t onceToken; |
41 dispatch_once(&onceToken, ^{ | 42 dispatch_once(&onceToken, ^{ |
42 sharedInstance = [[self alloc] init]; | 43 sharedInstance = [[self alloc] init]; |
43 }); | 44 }); |
44 | 45 |
45 return sharedInstance; | 46 return sharedInstance; |
46 } | 47 } |
47 | 48 |
49 // Method to make sure observers are added and the initialization block is | |
50 // scheduled to run on the main queue. | |
51 + (void)prepareForUse { | |
tkchin_webrtc
2017/09/13 18:32:02
This class feels more complex than it needs to be.
andersc
2017/09/14 08:08:45
I agree, and I mentioned a solution similar to tha
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52 __unused RTCUIApplicationStatusObserver *observer = [self sharedInstance]; | |
53 } | |
54 | |
48 - (id)init { | 55 - (id)init { |
49 if (self = [super init]) { | 56 if (self = [super init]) { |
50 NSNotificationCenter *center = [NSNotificationCenter defaultCenter]; | 57 NSNotificationCenter *center = [NSNotificationCenter defaultCenter]; |
51 __weak RTCUIApplicationStatusObserver *weakSelf = self; | 58 __weak RTCUIApplicationStatusObserver *weakSelf = self; |
52 _activeObserver = [center addObserverForName:UIApplicationDidBecomeActiveNot ification | 59 _activeObserver = [center addObserverForName:UIApplicationDidBecomeActiveNot ification |
53 object:nil | 60 object:nil |
54 queue:[NSOperationQueue mainQueue] | 61 queue:[NSOperationQueue mainQueue] |
55 usingBlock:^(NSNotification *note) { | 62 usingBlock:^(NSNotification *note) { |
56 weakSelf.state = | 63 weakSelf.state = |
57 [UIApplication sharedApplication].ap plicationState; | 64 [UIApplication sharedApplication].ap plicationState; |
58 }]; | 65 }]; |
59 | 66 |
60 _backgroundObserver = [center addObserverForName:UIApplicationDidEnterBackgr oundNotification | 67 _backgroundObserver = [center addObserverForName:UIApplicationDidEnterBackgr oundNotification |
61 object:nil | 68 object:nil |
62 queue:[NSOperationQueue mainQueue ] | 69 queue:[NSOperationQueue mainQueue ] |
63 usingBlock:^(NSNotification *note) { | 70 usingBlock:^(NSNotification *note) { |
64 weakSelf.state = | 71 weakSelf.state = |
65 [UIApplication sharedApplication ].applicationState; | 72 [UIApplication sharedApplication ].applicationState; |
66 }]; | 73 }]; |
67 | 74 |
75 _waitForInitializeSemaphore = dispatch_semaphore_create(1); | |
68 _initialized = NO; | 76 _initialized = NO; |
69 _initializeBlock = dispatch_block_create(DISPATCH_BLOCK_INHERIT_QOS_CLASS, ^ { | 77 _initializeBlock = dispatch_block_create(DISPATCH_BLOCK_INHERIT_QOS_CLASS, ^ { |
70 weakSelf.state = [UIApplication sharedApplication].applicationState; | 78 weakSelf.state = [UIApplication sharedApplication].applicationState; |
71 weakSelf.initialized = YES; | 79 weakSelf.initialized = YES; |
72 }); | 80 }); |
73 | 81 |
74 dispatch_async(dispatch_get_main_queue(), _initializeBlock); | 82 dispatch_async(dispatch_get_main_queue(), _initializeBlock); |
75 } | 83 } |
76 | 84 |
77 return self; | 85 return self; |
78 } | 86 } |
79 | 87 |
80 - (void)dealloc { | 88 - (void)dealloc { |
81 NSNotificationCenter *center = [NSNotificationCenter defaultCenter]; | 89 NSNotificationCenter *center = [NSNotificationCenter defaultCenter]; |
82 [center removeObserver:_activeObserver]; | 90 [center removeObserver:_activeObserver]; |
83 [center removeObserver:_backgroundObserver]; | 91 [center removeObserver:_backgroundObserver]; |
84 } | 92 } |
85 | 93 |
86 - (BOOL)isApplicationActive { | 94 - (BOOL)isApplicationActive { |
95 // NOTE: The function `dispatch_block_wait` can only legally be called once. | |
96 // Because of this, if several threads call the `isApplicationActive` method b efore | |
97 // the `_initializeBlock` has been executed, instead of multiple threads calli ng | |
98 // `dispatch_block_wait`, the other threads need to wait for the first waiting thread | |
99 // instead. | |
87 if (!_initialized) { | 100 if (!_initialized) { |
88 long ret = dispatch_block_wait(_initializeBlock, | 101 dispatch_semaphore_wait(_waitForInitializeSemaphore, DISPATCH_TIME_FOREVER); |
89 dispatch_time(DISPATCH_TIME_NOW, 10.0 * NSEC_ PER_SEC)); | 102 if (!_initialized) { |
90 RTC_DCHECK_EQ(ret, 0); | 103 long ret = dispatch_block_wait(_initializeBlock, |
104 dispatch_time(DISPATCH_TIME_NOW, 10.0 * NSE C_PER_SEC)); | |
tkchin_webrtc
2017/09/13 18:32:02
What's the benefit of setting a short timeout here
andersc
2017/09/14 08:08:46
10 seconds was picked to be a long timeout. A test
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105 RTC_DCHECK_EQ(ret, 0); | |
106 } | |
107 dispatch_semaphore_signal(_waitForInitializeSemaphore); | |
91 } | 108 } |
92 return _state == UIApplicationStateActive; | 109 return _state == UIApplicationStateActive; |
93 } | 110 } |
94 | 111 |
95 @end | 112 @end |
96 | 113 |
97 #endif // WEBRTC_IOS | 114 #endif // WEBRTC_IOS |
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