shared_value.c

#include <stdio.h>


typedef struct Semaphore {

} Semaphore;

void semaphore_init(Semaphore *sem, int value);
void semaphore_wait(Semaphore *sem);
void semaphore_signal(Semaphore *sem);


Semaphore p1Ready;
Semaphore p1New;
Semaphore p2Ready;
Semaphore p2New;
Semaphore p3Ready;
Semaphore p3New;
int x;


int main() {
    // Will start by p0 waiting on p1-p3. That way they have an opportunity
    // to print the first value which is '0'.
    semaphore_init(&p1Ready, 0);
    semaphore_init(&p1New, 1);
    semaphore_init(&p2Ready, 0);
    semaphore_init(&p2New, 1);
    semaphore_init(&p3Ready, 0);
    semaphore_init(&p3New, 1);
    x = 0;
    // Start processes...
    
    return 0;
}

void process0() {
    while (1) {
        semaphore_wait(&p1Ready);
        semaphore_wait(&p2Ready);
        semaphore_wait(&p3Ready);
        x++;
        semaphore_signal(&p1New);
        semaphore_signal(&p2New);
        semaphore_signal(&p3New);
    }
}

void process1() {
    while (1) {
        semaphore_wait(&p1New);
        printf("Process 1 says: %d", x);
        semaphore_signal(&p1Ready);
    }
}

void process2() {
    while (1) {
        semaphore_wait(&p2New);
        if (x % 2 == 0) {
            printf("Process 2 says: %d", x);
        }
        semaphore_signal(&p2Ready);
    }
}

void process3() {
    while (1) {
        semaphore_wait(&p3New);
        if (x % 3 == 0) {
            printf("Process 3 says: %d", x);
        }
        semaphore_signal(&p3Ready);
    }
}

void semaphore_init(Semaphore *sem, int value) {
    
}

void semaphore_wait(Semaphore *sem) {
    
}

void semaphore_signal(Semaphore *sem) {
    
}