atoms/semaphore.hh

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#ifndef ATOMS_SEMAPHORE_HH
#define ATOMS_SEMAPHORE_HH

#ifdef WORKING_SEM_T
#include <semaphore.h>
#endif
#include <atoms/gen.hh>
#ifndef WORKING_SEM_T
#include <atoms/mutex.hh>
#include <atoms/condition.hh>
#endif

namespace atoms {

class Semaphore {
public:
    Semaphore(unsigned n);
    ~Semaphore();

    class Mon : public Monitor {
    public:
        Mon(Semaphore &s, bool l = true) : s(s), locked(false) {
            if (l) lock();
        }

        ~Mon() { if (locked) unlock(); }

        void lock() {
            assert(!locked);
#ifdef WORKING_SEM_T
            int retval;
            while ((retval = sem_wait(&s)) == -1 && errno == EINTR) ;
            assert(retval == 0);
#else
            Mutex::Mon mm(m);
            assert(count <= n);
            while (count == n)
                c.wait(mm);
#endif
            locked = true;
        }

        void unlock() {
            assert(locked);
#ifdef WORKING_SEM_T
            int retval = sem_post(&s);
#else
            Mutex::Mon mm(m);
            assert(count >= 1);
            if (count-- == n)
                c.signal();
#endif
            assert(retval == 0);
        }

    private:
        Semaphore &s;
        bool locked;
    };

private:
#ifdef WORKING_SEM_T
    sem_t sem;
#else
    unsigned n, count;
    Mutex m;
    Condition c;
#endif
};

} // namespace atoms
#endif // !ATOMS_SEMAPHORE_HH

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