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juce_ReadWriteLock.cpp
1/*
2 ==============================================================================
3
4 This file is part of the JUCE library.
5 Copyright (c) 2017 - ROLI Ltd.
6
7 JUCE is an open source library subject to commercial or open-source
8 licensing.
9
10 The code included in this file is provided under the terms of the ISC license
11 http://www.isc.org/downloads/software-support-policy/isc-license. Permission
12 To use, copy, modify, and/or distribute this software for any purpose with or
13 without fee is hereby granted provided that the above copyright notice and
14 this permission notice appear in all copies.
15
16 JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
17 EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
18 DISCLAIMED.
19
20 ==============================================================================
21*/
22
23 namespace juce
24{
25
26 ReadWriteLock::ReadWriteLock() noexcept
27{
28 readerThreads.ensureStorageAllocated (16);
29}
30
31 ReadWriteLock::~ReadWriteLock() noexcept
32{
33 jassert (readerThreads.size() == 0);
34 jassert (numWriters == 0);
35}
36
37//==============================================================================
38 void ReadWriteLock::enterRead() const noexcept
39{
40 while (! tryEnterRead())
41 readWaitEvent.wait (100);
42}
43
44 bool ReadWriteLock::tryEnterRead() const noexcept
45{
46 auto threadId = Thread::getCurrentThreadId();
47
48 const SpinLock::ScopedLockType sl (accessLock);
49
50 for (auto& readerThread : readerThreads)
51 {
52 if (readerThread.threadID == threadId)
53 {
54 readerThread.count++;
55 return true;
56 }
57 }
58
59 if (numWriters + numWaitingWriters == 0
60 || (threadId == writerThreadId && numWriters > 0))
61 {
62 readerThreads.add ({ threadId, 1 });
63 return true;
64 }
65
66 return false;
67}
68
69 void ReadWriteLock::exitRead() const noexcept
70{
71 auto threadId = Thread::getCurrentThreadId();
72 const SpinLock::ScopedLockType sl (accessLock);
73
74 for (int i = 0; i < readerThreads.size(); ++i)
75 {
76 auto& readerThread = readerThreads.getReference (i);
77
78 if (readerThread.threadID == threadId)
79 {
80 if (--(readerThread.count) == 0)
81 {
82 readerThreads.remove (i);
83
84 readWaitEvent.signal();
85 writeWaitEvent.signal();
86 }
87
88 return;
89 }
90 }
91
92 jassertfalse; // unlocking a lock that wasn't locked..
93}
94
95//==============================================================================
96 void ReadWriteLock::enterWrite() const noexcept
97{
98 auto threadId = Thread::getCurrentThreadId();
99 const SpinLock::ScopedLockType sl (accessLock);
100
101 while (! tryEnterWriteInternal (threadId))
102 {
103 ++numWaitingWriters;
104 accessLock.exit();
105 writeWaitEvent.wait (100);
106 accessLock.enter();
107 --numWaitingWriters;
108 }
109}
110
111 bool ReadWriteLock::tryEnterWrite() const noexcept
112{
113 const SpinLock::ScopedLockType sl (accessLock);
114 return tryEnterWriteInternal (Thread::getCurrentThreadId());
115}
116
117 bool ReadWriteLock::tryEnterWriteInternal (Thread::ThreadID threadId) const noexcept
118{
119 if (readerThreads.size() + numWriters == 0
120 || threadId == writerThreadId
121 || (readerThreads.size() == 1 && readerThreads.getReference (0).threadID == threadId))
122 {
123 writerThreadId = threadId;
124 ++numWriters;
125 return true;
126 }
127
128 return false;
129}
130
131 void ReadWriteLock::exitWrite() const noexcept
132{
133 const SpinLock::ScopedLockType sl (accessLock);
134
135 // check this thread actually had the lock..
136 jassert (numWriters > 0 && writerThreadId == Thread::getCurrentThreadId());
137
138 if (--numWriters == 0)
139 {
140 writerThreadId = {};
141
142 readWaitEvent.signal();
143 writeWaitEvent.signal();
144 }
145}
146
147} // namespace juce
juce::Array::ensureStorageAllocated
void ensureStorageAllocated(int minNumElements)
Definition: juce_Array.h:1062
juce::Array::size
int size() const noexcept
Definition: juce_Array.h:215
juce::Array::remove
void remove(int indexToRemove)
Definition: juce_Array.h:767
juce::Array::getReference
ElementType & getReference(int index) noexcept
Definition: juce_Array.h:267
juce::GenericScopedLock
Definition: juce_ScopedLock.h:55
juce::ReadWriteLock::ReadWriteLock
ReadWriteLock() noexcept
Definition: juce_ReadWriteLock.cpp:26
juce::ReadWriteLock::tryEnterRead
bool tryEnterRead() const noexcept
Definition: juce_ReadWriteLock.cpp:44
juce::ReadWriteLock::enterWrite
void enterWrite() const noexcept
Definition: juce_ReadWriteLock.cpp:96
juce::ReadWriteLock::~ReadWriteLock
~ReadWriteLock() noexcept
Definition: juce_ReadWriteLock.cpp:31
juce::ReadWriteLock::exitRead
void exitRead() const noexcept
Definition: juce_ReadWriteLock.cpp:69
juce::ReadWriteLock::enterRead
void enterRead() const noexcept
Definition: juce_ReadWriteLock.cpp:38
juce::ReadWriteLock::exitWrite
void exitWrite() const noexcept
Definition: juce_ReadWriteLock.cpp:131
juce::ReadWriteLock::tryEnterWrite
bool tryEnterWrite() const noexcept
Definition: juce_ReadWriteLock.cpp:111
juce::SpinLock::exit
void exit() const noexcept
Definition: juce_SpinLock.h:65
juce::SpinLock::enter
void enter() const noexcept
Definition: juce_Thread.cpp:334
juce::Thread::ThreadID
void * ThreadID
Definition: juce_Thread.h:304
juce::Thread::getCurrentThreadId
static ThreadID JUCE_CALLTYPE getCurrentThreadId()
juce::WaitableEvent::wait
bool wait(int timeOutMilliseconds=-1) const
Definition: juce_WaitableEvent.cpp:31
juce::WaitableEvent::signal
void signal() const
Definition: juce_WaitableEvent.cpp:57