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#ifndef SIMPLE_LOCK_H
#define SIMPLE_LOCK_H
#if SUPPORT_THREADS
#include "AtomicOps.h"
#include "Semaphore.h"
// Simple, non-recursive mutual exclusion lock. Efficient when there is low contention.
// First tries to attain lock using atomic ops, then waits for lock using semaphores.
// Same idea as described here: http://preshing.com/20120226/roll-your-own-lightweight-mutex
class SimpleLock : public NonCopyable
{
public:
SimpleLock() : m_Count(0) {}
class AutoLock : public NonCopyable
{
public:
AutoLock( SimpleLock& lock ) : m_Lock(lock)
{
m_Lock.Lock();
}
~AutoLock()
{
m_Lock.Unlock();
}
private:
SimpleLock& m_Lock;
};
void Lock()
{
if (AtomicIncrement(&m_Count) != 1)
m_Semaphore.WaitForSignal();
}
void Unlock()
{
if (AtomicDecrement(&m_Count) != 0)
m_Semaphore.Signal();
}
private:
volatile int m_Count;
Semaphore m_Semaphore;
};
#endif // SUPPORT_THREADS
#endif
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