S01_SEMAFORY_04

/*
Zademonstruj synchronizację operacji zapisu i odczytu dla łącza nazwa- nego, przy pomocy semaforów.
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <sys/sem.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/wait.h>

#define FIFO_DIR "fifo"
#define MESSAGE "Jakas wiadomosc!"

void sem_up(int semid)
{
    struct sembuf up_operation = {0, 1, 0};

    if(semop(semid, &up_operation, 1) == -1){
        perror("up_semop");
        exit(EXIT_FAILURE);
    }
}

void sem_down(int semid)
{
    struct sembuf down_operation = {0, -1, 0};

    if(semop(semid, &down_operation, 1) == -1){
        perror("down_semop");
        exit(EXIT_FAILURE);
    }
}

int main(void)
{
    int fifofd, semid;
    pid_t pid;

    if(mkfifo(FIFO_DIR, 0775) == -1){
        perror("mkfifo");
        return EXIT_FAILURE;
    }

    if((semid = semget(IPC_PRIVATE, 1, 0600 | IPC_CREAT | IPC_EXCL)) == -1){
        perror("semget");
        return EXIT_FAILURE;
    }

    if(semctl(semid, 0, SETVAL, 1) == -1){
        perror("setval_semctl");
        return EXIT_FAILURE;
    }

    if((fifofd = open(FIFO_DIR, O_RDWR)) == -1){
        perror("open");
        return EXIT_FAILURE;
    }

    pid = fork();
    if(pid == -1){
        perror("fork");
        return EXIT_FAILURE;
    }
    else if(pid == 0){
        sem_down(semid);

        for(int i = 0; i < 10; i++){
            if(write(fifofd, &i, sizeof(int)) == -1){
                perror("write");
                return EXIT_FAILURE;
            }
        }

        if(close(fifofd) == -1){
            perror("child_close");
            return EXIT_FAILURE;
        }

        sem_up(semid);
    }
    else{
        for(int i = 0; i < 10; i++){
            int buffer;
            if(read(fifofd, &buffer, sizeof(int)) == -1){
                perror("read");
                return EXIT_FAILURE;
            }
            printf("%d ", buffer);
        }
        printf("\n");

        if(close(fifofd) == -1){
            perror("parent_close");
            return EXIT_FAILURE;
        }

        if(semctl(semid, 0, IPC_RMID) == -1){
            perror("semctl");
            return EXIT_FAILURE;
        }

        if(unlink(FIFO_DIR) == -1){
            perror("unlink");
            return EXIT_FAILURE;
        }
    }

    return EXIT_SUCCESS;
}