Diligent Engine API Reference: D:/GitHub/DiligentEngine/DiligentCore/Common/interface/LockHelper.h Source File

Diligent Engine API Reference

LockHelper.h
1 /* Copyright 2015-2018 Egor Yusov
2 *
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
10 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
11 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF ANY PROPRIETARY RIGHTS.
12 *
13 * In no event and under no legal theory, whether in tort (including negligence),
14 * contract, or otherwise, unless required by applicable law (such as deliberate
15 * and grossly negligent acts) or agreed to in writing, shall any Contributor be
16 * liable for any damages, including any direct, indirect, special, incidental,
17 * or consequential damages of any character arising as a result of this License or
18 * out of the use or inability to use the software (including but not limited to damages
19 * for loss of goodwill, work stoppage, computer failure or malfunction, or any and
20 * all other commercial damages or losses), even if such Contributor has been advised
21 * of the possibility of such damages.
22 */
23
24 #pragma once
25
26 #include <thread>
27 #include <mutex>
28 #include <condition_variable>
29
30 #include "Atomics.h"
31
32 namespace ThreadingTools
33 {
34
35 class LockFlag
36 {
37 public:
38 enum {LOCK_FLAG_UNLOCKED = 0, LOCK_FLAG_LOCKED = 1};
39 LockFlag(Atomics::Long InitFlag = LOCK_FLAG_UNLOCKED)
40 {
41 //m_Flag.store(InitFlag);
42 m_Flag = InitFlag;
43 }
44
45 operator Atomics::Long()const{return m_Flag;}
46
47 private:
48 friend class LockHelper;
49 Atomics::AtomicLong m_Flag;
50 };
51
52 class LockHelper
53 {
54 public:
55
56 LockHelper() :
57 m_pLockFlag(nullptr)
58 {
59 }
60 LockHelper(LockFlag &LockFlag) :
61 m_pLockFlag(nullptr)
62 {
63 Lock(LockFlag);
64 }
65
66 LockHelper( LockHelper &&LockHelper ) :
67 m_pLockFlag( std::move(LockHelper.m_pLockFlag) )
68 {
69 LockHelper.m_pLockFlag = nullptr;
70 }
71
72 const LockHelper& operator = (LockHelper &&LockHelper)
73 {
74 m_pLockFlag = std::move( LockHelper.m_pLockFlag );
75 LockHelper.m_pLockFlag = nullptr;
76 return *this;
77 }
78
79 ~LockHelper()
80 {
81 Unlock();
82 }
83
84 static bool UnsafeTryLock(LockFlag &LockFlag)
85 {
86 return Atomics::AtomicCompareExchange( LockFlag.m_Flag,
87 static_cast<Atomics::Long>( LockFlag::LOCK_FLAG_LOCKED ),
88 static_cast<Atomics::Long>( LockFlag::LOCK_FLAG_UNLOCKED) ) == LockFlag::LOCK_FLAG_UNLOCKED;
89 }
90
91 bool TryLock(LockFlag &LockFlag)
92 {
93 if( UnsafeTryLock( LockFlag) )
94 {
95 m_pLockFlag = &LockFlag;
96 return true;
97 }
98 else
99 return false;
100 }
101
102 static void UnsafeLock(LockFlag &LockFlag)
103 {
104 while( !UnsafeTryLock( LockFlag ) )
105 std::this_thread::yield();
106 }
107
108 void Lock(LockFlag &LockFlag)
109 {
110 VERIFY( m_pLockFlag == NULL, "Object already locked" );
111 // Wait for the flag to become unlocked and lock it
112 while( !TryLock( LockFlag ) )
113 std::this_thread::yield();
114 }
115
116 static void UnsafeUnlock(LockFlag &LockFlag)
117 {
118 LockFlag.m_Flag = LockFlag::LOCK_FLAG_UNLOCKED;
119 }
120
121 void Unlock()
122 {
123 if( m_pLockFlag )
124 UnsafeUnlock(*m_pLockFlag);
125 m_pLockFlag = NULL;
126 }
127
128 private:
129 LockFlag *m_pLockFlag;
130 LockHelper( const LockHelper &LockHelper );
131 const LockHelper& operator = ( const LockHelper &LockHelper );
132 };
133
134 class Signal
135 {
136 public:
137 Signal() {}
138
139 // http://en.cppreference.com/w/cpp/thread/condition_variable
140 void Trigger()
141 {
142 // The thread that intends to modify the variable has to
143 // * acquire a std::mutex (typically via std::lock_guard)
144 // * perform the modification while the lock is held
145 // * execute notify_one or notify_all on the std::condition_variable (the lock does not need to be held for notification)
146 {
147 // std::condition_variable works only with std::unique_lock<std::mutex>
148 std::lock_guard<std::mutex> Lock(m_Mutex);
149 m_bIsTriggered = true;
150 }
151 // Unlocking is done before notifying, to avoid waking up the waiting
152 // thread only to block again (see notify_one for details)
153 m_CondVar.notify_one();
154 }
155
156 void Wait()
157 {
158 // Any thread that intends to wait on std::condition_variable has to
159 // * acquire a std::unique_lock<std::mutex>, on the SAME MUTEX as used to protect the shared variable
160 // * execute wait, wait_for, or wait_until. The wait operations atomically release the mutex
161 // and suspend the execution of the thread.
162 // * When the condition variable is notified, a timeout expires, or a spurious wakeup occurs,
163 // the thread is awakened, and the mutex is atomically reacquired:
164 // - The thread should then check the condition and resume waiting if the wake up was spurious.
165 std::unique_lock<std::mutex> Lock(m_Mutex);
166 if (!m_bIsTriggered)
167 {
168 m_CondVar.wait(Lock, [&] {return m_bIsTriggered; });
169 }
170 }
171
172 void Reset()
173 {
174 std::lock_guard<std::mutex> Lock(m_Mutex);
175 m_bIsTriggered = false;
176 }
177
178 volatile bool IsTriggered()const { return m_bIsTriggered; }
179
180 private:
181
182 std::mutex m_Mutex;
183 std::condition_variable m_CondVar;
184 volatile bool m_bIsTriggered = false;
185
186 Signal(const Signal&) = delete;
187 Signal& operator = (const Signal&) = delete;
188 };
189
190 }
std
Definition: AdvancedMath.h:316
ThreadingTools
Definition: LockHelper.h:32