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Added stdc++11 mutex locking and added a Read Write lock support
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Garrett Potts
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Sep 18, 2017
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,189 @@ | ||
| /** | ||
| * This code was derived from https://gist.github.com/mshockwave | ||
| * | ||
| */ | ||
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| #ifndef ossimRWm_lockHEADER | ||
| #define ossimRWm_lockHEADER | ||
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| #include <condition_variable> | ||
| #include <mutex> | ||
| #include <atomic> | ||
| #include <limits> | ||
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| namespace ossim { | ||
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| enum WaitGenre { | ||
| SPIN=0, | ||
| SLEEP=1 | ||
| }; | ||
| /** | ||
| * Code was derived from https://gist.github.com/mshockwave | ||
| * | ||
| * Has a pure c++11 implementation for read/write locks | ||
| * allowing one to choose the locking technique to use. | ||
| * | ||
| * You currently can choose between a SLEEP or SPIN technique | ||
| * for locking | ||
| * | ||
| * At the bottom we added typedefs so you do not have | ||
| * to specify the template values. | ||
| * | ||
| * | ||
| * Example: | ||
| * @code | ||
| * ossim::RWSleepLock mutex; | ||
| * // enter a section that just needs read only access | ||
| * { | ||
| * ossim::ScopeReadSleepLock lock(mutex); | ||
| * } | ||
| * // enter some section that requires write | ||
| * { | ||
| * ossim::ScopeWriteSleepLock lock(mutex); | ||
| * } | ||
| * @endCode | ||
| */ | ||
| template <WaitGenre WAIT_GENRE> | ||
| class RWLock { | ||
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| std::mutex m_waitMutex; | ||
| std::condition_variable m_waitConditional; | ||
| std::atomic_int m_refCounter; | ||
| const int MIN_INT; | ||
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| public: | ||
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| RWLock(); | ||
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| void lockWrite(); | ||
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| bool tryLockWrite(); | ||
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| void unlockWrite(); | ||
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| void lockRead(); | ||
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| bool tryLockRead(); | ||
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| void unlockRead(); | ||
| }; | ||
|
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| template <WaitGenre WAIT_GENRE> | ||
| RWLock<WAIT_GENRE>::RWLock() : | ||
| m_refCounter(0), | ||
| MIN_INT(std::numeric_limits<int>::min()){} | ||
|
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| template <> | ||
| void RWLock<SPIN>::lockWrite() { | ||
|
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| int expected = 0; | ||
| while(!m_refCounter.compare_exchange_weak(expected, MIN_INT, | ||
| std::memory_order_acquire, | ||
| std::memory_order_relaxed)){ | ||
| expected = 0; | ||
| } | ||
| } | ||
| template <> | ||
| void RWLock<SLEEP>::lockWrite(){ | ||
| int expected = 0; | ||
| if(!m_refCounter.compare_exchange_strong(expected, MIN_INT, | ||
| std::memory_order_acquire, | ||
| std::memory_order_relaxed)){ | ||
| expected = 0; | ||
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| std::unique_lock<std::mutex> lk(m_waitMutex); | ||
| m_waitConditional.wait(lk, [this,&expected] { | ||
| if(!m_refCounter.compare_exchange_strong(expected, MIN_INT, | ||
| std::memory_order_acquire, | ||
| std::memory_order_relaxed)){ | ||
| expected = 0; | ||
| return false; | ||
| } | ||
| return true; | ||
| }); | ||
| lk.unlock(); | ||
| } | ||
| } | ||
|
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| template <WaitGenre WAIT_GENRE> | ||
| bool RWLock<WAIT_GENRE>::tryLockWrite() { | ||
| int expected = 0; | ||
| return m_refCounter.compare_exchange_strong(expected, MIN_INT, | ||
| std::memory_order_acquire, | ||
| std::memory_order_relaxed); | ||
| } | ||
|
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| template <WaitGenre WAIT_GENRE> | ||
| void RWLock<WAIT_GENRE>::unlockWrite() { | ||
| m_refCounter.store(0, std::memory_order_release); | ||
| if(WAIT_GENRE == SLEEP) | ||
| m_waitConditional.notify_all(); | ||
| } | ||
|
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| template <> | ||
| void RWLock<SPIN>::lockRead() { | ||
| while(m_refCounter.fetch_add(1, std::memory_order_acquire) < 0){ | ||
| m_refCounter.fetch_sub(1, std::memory_order_release); | ||
| } | ||
| } | ||
| template <> | ||
| void RWLock<SLEEP>::lockRead() { | ||
| if(m_refCounter.fetch_add(1, std::memory_order_acquire) < 0){ | ||
| m_refCounter.fetch_sub(1, std::memory_order_release); | ||
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| std::unique_lock<std::mutex> lk(m_waitMutex); | ||
| m_waitConditional.wait(lk, [this]{ | ||
| return m_refCounter.fetch_add(1, std::memory_order_acquire) >= 0; | ||
| }); | ||
| lk.unlock(); | ||
| } | ||
| } | ||
|
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| template <WaitGenre WAIT_GENRE> | ||
| bool RWLock<WAIT_GENRE>::tryLockRead() { | ||
| return m_refCounter.fetch_add(1, std::memory_order_acquire) >= 0; | ||
| } | ||
|
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| template <WaitGenre WAIT_GENRE> | ||
| void RWLock<WAIT_GENRE>::unlockRead() { | ||
| m_refCounter.fetch_sub(1, std::memory_order_release); | ||
| if(WAIT_GENRE == SLEEP) | ||
| m_waitConditional.notify_one(); | ||
| } | ||
|
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| template <WaitGenre WAIT_GENRE> | ||
| class ScopeReadLock { | ||
| RWLock<WAIT_GENRE> &m_lock; | ||
| public: | ||
| ScopeReadLock(RWLock<WAIT_GENRE> &lock) : m_lock(lock) { | ||
| m_lock.lockRead(); | ||
| } | ||
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| ~ScopeReadLock() { | ||
| m_lock.unlockRead(); | ||
| } | ||
| }; | ||
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| template <WaitGenre WAIT_GENRE> | ||
| class ScopeWriteLock { | ||
| RWLock<WAIT_GENRE> &m_lock; | ||
| public: | ||
| ScopeWriteLock(RWLock<WAIT_GENRE> &lock) : m_lock(lock) { | ||
| m_lock.lockWrite(); | ||
| } | ||
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| ~ScopeWriteLock() { | ||
| m_lock.unlockWrite(); | ||
| } | ||
| }; | ||
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| typedef RWLock<SLEEP> RWSleepLock; | ||
| typedef RWLock<SPIN> RWSpinLock; | ||
| typedef ScopeWriteLock<SLEEP> ScopeWriteSleepLock; | ||
| typedef ScopeWriteLock<SPIN> ScopeWriteSpinLock; | ||
| typedef ScopeReadLock<SLEEP> ScopeReadSleepLock; | ||
| typedef ScopeReadLock<SPIN> ScopeReadSpinLock; | ||
|
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| }; | ||
|
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| #endif |
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