====== SpinLock implementation in C++ ======

{{tag>cpp dev}}

Since I read the book **Game Engine Architecture** I was looking for a way to implement a simple **SpinLock** in C++. And actually it turns out this is (almost) readily available from boost.

====== ======

I used the following reference pages:

  * [[https://jiafei427.wordpress.com/2016/08/24/spinlock-v-s-mutex-v-s-atomics/|This page clearly shows that you don't want to use mutexes in many situations]].
  * [[https://www.boost.org/doc/libs/1_54_0/doc/html/atomic/usage_examples.html#boost_atomic.usage_examples.example_spinlock|The official boost spinlock implementation template]]
  * [[https://stackoverflow.com/questions/19742993/implementing-a-spinlock-in-boost-example-needed|The source I used for my own implementation]].


And in the end, if will fit in a single simple header file: <sxh cpp>#ifndef NV_SPINLOCK_H_
#define NV_SPINLOCK_H_

#include <boost/atomic.hpp>
#include <boost/thread.hpp>

namespace nv {

class SpinLock
{
    boost::atomic_flag flag; // it differs from std::atomic_flag a bit -
                             // does not require ATOMIC_FLAG_INIT
public:
    void lock()
    {
        while( flag.test_and_set(boost::memory_order_acquire) )
            ;
    }
    bool try_lock()
    {
        return !flag.test_and_set(boost::memory_order_acquire);
    }
    void unlock()
    {
        flag.clear(boost::memory_order_release);
    }
};

typedef boost::lock_guard<SpinLock> SpinLockGuard;

};

#endif</sxh>