choc_SpinLock.h

//
//    ██████ ██   ██  ██████   ██████
//   ██      ██   ██ ██    ██ ██            ** Classy Header-Only Classes **
//   ██      ███████ ██    ██ ██
//   ██      ██   ██ ██    ██ ██           https://github.com/Tracktion/choc
//    ██████ ██   ██  ██████   ██████
//
//   CHOC is (C)2022 Tracktion Corporation, and is offered under the terms of the ISC license:
//
//   Permission to use, copy, modify, and/or distribute this software for any purpose with or
//   without fee is hereby granted, provided that the above copyright notice and this permission
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#ifndef CHOC_SPINLOCK_HEADER_INCLUDED
#define CHOC_SPINLOCK_HEADER_INCLUDED

#include <atomic>

namespace choc::threading
{

//==============================================================================
/**
    A minimal no-frills spin-lock.

    To use an RAII pattern for locking a SpinLock, it's compatible with the normal
    scoped guard locking classes in the standard library.
*/
struct SpinLock
{
    SpinLock() = default;
    ~SpinLock() = default;

    void lock();
    bool try_lock();
    void unlock();

private:
    std::atomic_flag flag = ATOMIC_FLAG_INIT;
};


//==============================================================================
//        _        _           _  _
//     __| |  ___ | |_   __ _ (_)| | ___
//    / _` | / _ \| __| / _` || || |/ __|
//   | (_| ||  __/| |_ | (_| || || |\__ \ _  _  _
//    \__,_| \___| \__| \__,_||_||_||___/(_)(_)(_)
//
//   Code beyond this point is implementation detail...
//
//==============================================================================

inline void SpinLock::lock()     { while (flag.test_and_set (std::memory_order_acquire)) {} }
inline bool SpinLock::try_lock() { return ! flag.test_and_set (std::memory_order_acquire); }
inline void SpinLock::unlock()   { flag.clear(); }

} // choc::fifo

#endif