103 lines
2.7 KiB
C++
103 lines
2.7 KiB
C++
#pragma once
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#include <condition_variable>
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class readWriteLock {
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fastlock m_readLock;
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fastlock m_writeLock;
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std::condition_variable_any m_cv;
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int m_readCount = 0;
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int m_writeCount = 0;
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bool m_writeWaiting = false;
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bool m_notify = true;
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public:
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readWriteLock(const char *name) : m_readLock(name), m_writeLock(name) {}
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void acquireRead() {
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std::unique_lock<fastlock> rm(m_readLock);
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while (m_writeCount > 0 || m_writeWaiting)
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m_cv.wait(rm);
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m_readCount++;
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}
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bool tryAcquireRead() {
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std::unique_lock<fastlock> rm(m_readLock, std::defer_lock);
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if (!rm.try_lock())
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return false;
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if (m_writeCount > 0 || m_writeWaiting)
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return false;
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m_readCount++;
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return true;
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}
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void acquireWrite(bool exclusive = true) {
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std::unique_lock<fastlock> rm(m_readLock);
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m_writeWaiting = true;
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while (m_readCount > 0)
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m_cv.wait(rm);
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if (exclusive) {
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/* Another thread might have the write lock while we have the read lock
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but won't be able to release it until they can acquire the read lock
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so release the read lock and try again instead of waiting to avoid deadlock */
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while(!m_writeLock.try_lock())
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m_cv.wait(rm);
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}
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m_writeCount++;
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m_writeWaiting = false;
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}
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void upgradeWrite(bool exclusive = true) {
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releaseRead();
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acquireWrite(exclusive);
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}
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bool tryAcquireWrite(bool exclusive = true) {
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std::unique_lock<fastlock> rm(m_readLock, std::defer_lock);
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if (!rm.try_lock())
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return false;
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if (m_readCount > 0)
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return false;
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if (exclusive)
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if (!m_writeLock.try_lock())
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return false;
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m_writeCount++;
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return true;
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}
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void releaseRead() {
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std::unique_lock<fastlock> rm(m_readLock);
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m_readCount--;
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if (m_notify)
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m_cv.notify_all();
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}
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void releaseWrite(bool exclusive = true) {
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std::unique_lock<fastlock> rm(m_readLock);
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serverAssert(m_writeCount > 0);
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if (exclusive)
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m_writeLock.unlock();
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m_writeCount--;
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if (m_notify)
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m_cv.notify_all();
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}
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void downgradeWrite(bool exclusive = true) {
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releaseWrite(exclusive);
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acquireRead();
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}
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void setNotify(bool notify) {
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m_notify = notify;
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}
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bool hasReader() {
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return m_readCount > 0;
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}
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bool hasWriter() {
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return m_writeCount > 0;
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}
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bool writeWaiting() {
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return m_writeWaiting;
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}
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}; |