gistfile1.txt

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>

struct task {
    void *(*cb)(void *data);
    void *data;
    bool runnable;
};

struct scheduler {
    struct task *tasks;
    int current_task;
};

struct fib_state {
    int a, b;
};

struct inc_state {
    int cur;
};

void scheduler_schedule(struct scheduler *s)
{
    struct task *current = &s->tasks[s->current_task];

    if (!current->cb) {
        s->current_task = 0;
        return;
    }

    if (current->runnable) {
        void *data = current->cb(current->data);

        if (data) {
            current->data = data;
        } else {
            printf("Ending task %d\n", s->current_task);

            free(current->data);
            current->runnable = false;
        }
    }

    s->current_task++;
}

void *fibonacci(void *d)
{
    struct fib_state *s = d;
    int c;

    if (!d) {
        s = malloc(sizeof(*s));
        if (!s) abort();
        s->a = s->b = 1;
    } else {
        printf("fib: %d\n", s->a);

        c = s->a + s->b;
        s->a = s->b;
        s->b = c;
    }

    return s;
}

void *incrementa(void *d)
{
    struct inc_state *s = d;

    if (!d) {
        s = malloc(sizeof(*s));
        if (!s) abort();
        s->cur = 0;
    } else if (s->cur < 100) {
        printf("inc: %d\n", s->cur);
        s->cur++;
    } else {
        return NULL;
    }

    return s;
}

int main(void)
{
    struct scheduler scheduler = {
        .tasks = (struct task[]) {
            { .cb = fibonacci, .data = NULL, .runnable = true },
            { .cb = incrementa, .data = NULL, .runnable = true },
            { }
        },
        .current_task = 0
    };

    while (true) {
        scheduler_schedule(&scheduler);
    }
}