Program Listing for File semaphore.h

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#pragma once

#include <atomic>

namespace gpa {
namespace concurrent {

// wrapper around platform semaphore APIs
class Semaphore
{
public:
    Semaphore(long initialValue = 0);
    ~Semaphore();
    Semaphore(const Semaphore&) = delete;
    Semaphore& operator=(const Semaphore&) = delete;

    void Post();

    void PostAll();

    void Wait();

    bool Wait(long timeoutMS);

private:
    // track number of threads waiting on this semaphore
    std::atomic<uint32_t> mNumWaiting;

    // opaque storage for platform-specific semaphore types
    struct __t
    {
        char m_val[64];
    };

    __t m_t
#if defined(__linux__)
        // POSIX futex code will abort if this is not aligned
        __attribute__((aligned(64)))
#endif  // __linux__
        ;
};

}  // namespace concurrent
}  // namespace gpa