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
 
#include <Jolt/Core/Atomics.h>
 
// Determine which platform specific construct we'll use
JPH_SUPPRESS_WARNINGS_STD_BEGIN
#ifdef JPH_PLATFORM_WINDOWS
    // We include windows.h in the cpp file, the semaphore itself is a void pointer
#elif defined(JPH_PLATFORM_LINUX) || defined(JPH_PLATFORM_ANDROID) || defined(JPH_PLATFORM_BSD) || defined(JPH_PLATFORM_WASM)
    #include <semaphore.h>
    #define JPH_USE_PTHREADS
#elif defined(JPH_PLATFORM_MACOS) || defined(JPH_PLATFORM_IOS)
    #include <dispatch/dispatch.h>
    #define JPH_USE_GRAND_CENTRAL_DISPATCH
#elif defined(JPH_PLATFORM_BLUE)
    // Jolt/Core/PlatformBlue.h should have defined everything that is needed below
#else
    #include <mutex>
    #include <condition_variable>
#endif
JPH_SUPPRESS_WARNINGS_STD_END
 
JPH_NAMESPACE_BEGIN

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:
#if defined(JPH_PLATFORM_WINDOWS) || defined(JPH_USE_PTHREADS) || defined(JPH_USE_GRAND_CENTRAL_DISPATCH) || defined(JPH_PLATFORM_BLUE)
#ifdef JPH_PLATFORM_WINDOWS
    using SemaphoreType = void *;
#elif defined(JPH_USE_PTHREADS)
    using SemaphoreType = sem_t;
#elif defined(JPH_USE_GRAND_CENTRAL_DISPATCH)
    using SemaphoreType = dispatch_semaphore_t;
#elif defined(JPH_PLATFORM_BLUE)
    using SemaphoreType = JPH_PLATFORM_BLUE_SEMAPHORE;
#endif
    alignas(JPH_CACHE_LINE_SIZE) atomic<int> mCount { 0 };                  
    SemaphoreType           mSemaphore { };                                 
#else
    // Other platforms: Emulate a semaphore using a mutex, condition variable and count
    std::mutex              mLock;
    std::condition_variable mWaitVariable;
    atomic<int>             mCount { 0 };
#endif
};
 
JPH_NAMESPACE_END