#ifndef _GUARDER_H
#define _GUARDER_H

#include <sys/types.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <unistd.h>

class guarder{
private:
    const int shmid;
    const int semid;

    void semaphoreOp(int op) {
        struct sembuf sb{};
        sb.sem_num = 0;
        sb.sem_op = op;
        sb.sem_flg = 0;
        semop(semid, &sb, 1);
    }

    void setFlag(bool value)
    {
        semaphoreOp(-1);
        bool *flag = static_cast<bool *>(shmat(shmid, nullptr, 0));
        *flag = value;
        shmdt(flag);
        semaphoreOp(1);
    }

public:
    guarder() : shmid(shmget(IPC_PRIVATE, sizeof(bool), 0666 | IPC_CREAT)), semid(semget(IPC_PRIVATE, 1, 0666 | IPC_CREAT))
    {
        setFlagOff();
    }

    void setFlagOff()
    {
        setFlag(false);
    }

    void setFlagOn()
    {
        setFlag(true);
    }

    bool isFlagOn()
    {
        semaphoreOp(-1);
        bool *flag = static_cast<bool *>(shmat(shmid, nullptr, 0));
        bool ret = *flag;
        shmdt(flag);
        semaphoreOp(1);
        return ret;
    }

    ~guarder()
    {
        shmctl(shmid, IPC_RMID, nullptr);
        semctl(semid, 0, IPC_RMID);
    }

};

#endif // _GUARDER_H