suu

#include <stdio.h>
#include <stdlib.h>
#include <ucontext.h>
#include <signal.h>
#include <sys/time.h>

typedef struct Task Task;
struct Task {
    ucontext_t context;
    char taskChar;
    Task *next;
};

Task taskQueue;
Task *runningTask;

void enqueueTask(Task *newTask) {
    newTask->next = NULL;

    if (taskQueue.next == NULL) {
        taskQueue.next = newTask;
    } else {
        Task *lastTask = taskQueue.next;
        while (lastTask->next != NULL) {
            lastTask = lastTask->next;
        }
        lastTask->next = newTask;
    }
}

Task* dequeueTask() {
    if (taskQueue.next == NULL) {
        return NULL;
    }

    Task *nextTask = taskQueue.next;
    taskQueue.next = nextTask->next;
    nextTask->next = NULL;

    return nextTask;
}

void handleSignal(int signum) {
    Task *nextTask = dequeueTask();
    if (nextTask != NULL) {
        enqueueTask(runningTask);
        runningTask = nextTask;
        swapcontext(&taskQueue.context, &runningTask->context);
    }
}

void initializeTimer() {
    struct sigaction sa;
    sa.sa_handler = handleSignal;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(SIGALRM, &sa, NULL);

    // Set up the timer
    struct itimerval timer;
    timer.it_interval.tv_sec = 1;       // 1 second interval
    timer.it_interval.tv_usec = 0;
    timer.it_value = timer.it_interval;
    setitimer(ITIMER_REAL, &timer, NULL);
}

void* initializeLibrary() {
    taskQueue.next = NULL;
    runningTask = NULL;
    return NULL;
}

void taskFunction() {
    while (1) {
        printf("%c", runningTask->taskChar);  // Print the character associated with the task
        swapcontext(&runningTask->context, &taskQueue.context);
    }
}

int createTask(void (*startRoutine)(), char taskChar) {
    Task *newTask = (Task*) malloc(sizeof(Task));
    if (newTask == NULL) {
        return -1;
    }

    getcontext(&newTask->context);
    newTask->context.uc_stack.ss_sp = malloc(SIGSTKSZ);
    newTask->context.uc_stack.ss_size = SIGSTKSZ;
    newTask->context.uc_link = &taskQueue.context;

    newTask->taskChar = taskChar;

    makecontext(&newTask->context, startRoutine, 0);

    enqueueTask(newTask);

    return 0;
}

int main(int argc, char *argv[]) {
    initializeLibrary();

    if (argc != 3) {
        printf("The correct usage is: %s <firstTask> <secondTask>\n", argv[0]);
        return 1;
    }

    if (createTask(taskFunction, '+') != 0) {
        printf("ERROR WHILE CREATING TASK -> [firstTask]\n");
        return 1;
    }

    if (createTask(taskFunction, '-') != 0) {
        printf("ERROR WHILE CREATING TASK -> [secondTask]\n");
        return 1;
    }

    runningTask = dequeueTask();
    initializeTimer();

    while (1) {
        if (runningTask == NULL) {
            printf("\nAll tasks completed!\n");
            exit(0);
        }

        Task *nextTask = dequeueTask();
        if (nextTask != NULL) {
            enqueueTask(runningTask);
            runningTask = nextTask;
        }

        swapcontext(&taskQueue.context, &runningTask->context);
    }
}