S01_PAMIEC_DZIELONA_06

/*
Stwórz trzy procesy, które b ę d ą wymienia ł y mi ę dzy sobą dane poprzez dwa obszary
pami ę ci dzielonej (np. niech proces drugi po ś redniczy w wymianie danych pomi ę dzy
pierwszym i drugim obszarem pami ę ci dzielonej).
*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <unistd.h>
#include <wait.h>
#include <time.h>

void error_exit(const char *msg)
{
    perror(msg);
    exit(EXIT_FAILURE);
}

void lock_mutex(int mux)
{
    struct sembuf lock_mutex = {0, -1, 0};
    if(semop(mux, &lock_mutex, 1) == -1)
        error_exit("lock_mutex");
}

void unlock_mutex(int mux)
{
    struct sembuf unlock_mutex = {0, 1, 0};
    if(semop(mux, &unlock_mutex, 1) == -1)
        error_exit("unlock_mutex");
}

void first_process(int shmid, int mux)
{
    int *shared_memory;
    int random_number = (rand() % 10) + 1;

    if((shared_memory = (int *)shmat(shmid, NULL, 0)) == (void *)-1)
        error_exit("first_shmat");

    lock_mutex(mux);
    (*shared_memory) = random_number;
    unlock_mutex(mux);
    printf("Proces 1: Zapisuje do pamieci dzielonej liczbe: %d\n", *shared_memory);

    if(shmdt((void *)shared_memory) == -1)
        error_exit("first_shmdt");
}

void second_process(int shmids[], int mux)
{
    int *first_shared_memory;
    int *second_shared_memory;

    if((first_shared_memory = shmat(shmids[0], NULL, 0)) == (void *)-1)
        error_exit("second_shmat");
    if((second_shared_memory = shmat(shmids[1], NULL, 0)) == (void *)-1)
        error_exit("second_shmat");
    lock_mutex(mux);
    (*second_shared_memory) = (*first_shared_memory);
    unlock_mutex(mux);

    printf("Proces 2: Przekazuje liczbe %d z pierwszej pamieci dzielonej do drugiej\n",
            *second_shared_memory);
    if(shmdt(first_shared_memory) || shmdt(second_shared_memory) == -1)
        error_exit("second_shmdt");
}

void third_process(int shmid, int mux)
{
    int *shared_memory;

    if((shared_memory = (int *)shmat(shmid, NULL, 0)) == (void *)-1)
        error_exit("third_shmat");
    printf("Proces 3: Otrzymana wartosc: %d\n", *shared_memory);

    if(shmdt(shared_memory) == -1)
        error_exit("third_shmdt");
}

int main(void)
{
    pid_t pids;
    int shmids[2];
    int mux;

    srand(time((time_t *)NULL));
    for(int i = 0; i < 2; i++)
        if((shmids[i] = shmget(IPC_PRIVATE, SHMLBA, 0775 | IPC_CREAT | IPC_EXCL)) == -1)
            error_exit("shmget");

    if((mux = semget(IPC_PRIVATE, 2, 0775 | IPC_CREAT | IPC_EXCL)) == -1)
        error_exit("semget");

    for(int i = 0; i < 2; i++)
        if(semctl(mux, i, SETVAL, 1) == -1)
            error_exit("semctl");

    for(int i = 0; i < 3; i++){
        pids = fork();
        if(pids == -1)
            error_exit("fork");
        else if(pids == 0){
            switch(i){
                case 0:
                    first_process(shmids[0], mux);
                    break;
                case 1:
                    second_process(shmids, mux);
                    break;
                case 2:
                    third_process(shmids[1], mux);
                    break;
                default:
                    error_exit("switch");
            }
            return EXIT_SUCCESS;
        }
    }

    for(int i = 0; i < 3; i++)
        if(wait(NULL) == -1)
            error_exit("wait");

    if(semctl(mux, 0, IPC_RMID, NULL) == -1)
        error_exit("semctl");

    for(int i = 0; i < 2; i++)
        if(shmctl(shmids[i], IPC_RMID, NULL) == -1)
            error_exit("shmctl_rmid");

    return EXIT_SUCCESS;
}