clk.c

/*
 * This file is done for you.
 * Probably you will not need to change anything.
 * This file represents an emulated clock for simulation purpose only.
 * It is not a real part of operating system!
 */

#include "headers.h"

int shmid;
int generatorSem;
void up(int sem);

/* Clear the resources before exit */
void cleanup(int signum)
{
    shmctl(shmid, IPC_RMID, NULL);
    semctl(generatorSem, 0, IPC_RMID, 0);
    printf("Clock terminating!\n");
    exit(0);
}

/* This file represents the system clock for ease of calculations */
int main(int argc, char *argv[])
{
    printf("Clock starting\n");
    signal(SIGINT, cleanup);
    int clk = 0;
    //Create shared memory for one integer variable 4 bytes
    shmid = shmget(SHKEY, 4, IPC_CREAT | 0644);
    if ((long)shmid == -1)
    {
        perror("Error in creating shm!");
        exit(-1);
    }
    int *shmaddr = (int *)shmat(shmid, (void *)0, 0);
    if ((long)shmaddr == -1)
    {
        perror("Error in attaching the shm in clock!");
        exit(-1);
    }
    *shmaddr = clk; /* initialize shared memory */

    key_t key_id = ftok("keyfile", SEM1KEY);
    generatorSem = semget(key_id, 1, 0666 | IPC_CREAT);
    while (1)
    {
        sleep(1);
        (*shmaddr)++;
        up(generatorSem);
    }
}

void up(int sem)
{
    union Semun semun;
    semun.val = 1;
    if (semctl(sem, 0, SETVAL, semun) == -1)
    {
        perror("error in up");
    }
}