Semaphore.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2023 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#pragma once
 
JPH_SUPPRESS_WARNINGS_STD_BEGIN
#include <atomic>
#include <mutex>
#include <condition_variable>
JPH_SUPPRESS_WARNINGS_STD_END
 
JPH_NAMESPACE_BEGIN
 
// Things we're using from STL
using std::atomic;
using std::mutex;
using std::condition_variable;
 
class JPH_EXPORT Semaphore
{
public:
                        Semaphore();
                        ~Semaphore();
 
    void                Release(uint inNumber = 1);
 
    void                Acquire(uint inNumber = 1);
 
    inline int          GetValue() const                                { return mCount.load(std::memory_order_relaxed); }
 
private:
#ifdef JPH_PLATFORM_WINDOWS
    // On windows we use a semaphore object since it is more efficient than a lock and a condition variable
    alignas(JPH_CACHE_LINE_SIZE) atomic<int> mCount { 0 };              
    void *              mSemaphore;                                     
#else
    // Other platforms: Emulate a semaphore using a mutex, condition variable and count
    mutex               mLock;
    condition_variable  mWaitVariable;
    atomic<int>         mCount { 0 };
#endif
};
 
JPH_NAMESPACE_END