Semaphore.hh

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#ifndef SEMAPHORE_HH
#define SEMAPHORE_HH

#include "noncopyable.hh"
#include <cassert>
#include <condition_variable>
#include <mutex>

namespace openmsx {

class Semaphore : private noncopyable
{
public:
        explicit Semaphore(unsigned value);
        void up();
        void down();

private:
        std::mutex mutex;
        std::condition_variable condition;
        unsigned value;
};

class ScopedLock : private noncopyable
{
public:
        ScopedLock()
                : lock(nullptr)
        {
        }

        explicit ScopedLock(Semaphore& lock_)
                : lock(nullptr)
        {
                take(lock_);
        }

        ~ScopedLock()
        {
                release();
        }

        void take(Semaphore& lock_)
        {
                assert(!lock);
                lock = &lock_;
                lock->down();
        }

        void release()
        {
                if (lock) {
                        lock->up();
                        lock = nullptr;
                }
        }

private:
        Semaphore* lock;
};

} // namespace openmsx

#endif