Experimental semaphore with unix pipe

lock.c

typedef struct {
    int reader;
    int writer;
} semaphore;

semaphore make_semaphore(int n) {
    int pipe_fd[2];
    pipe(pipe_fd);
    semaphore result = {
            .reader = pipe_fd[0],
            .writer = pipe_fd[1],
    };
    // Write to pipe
    char c;
    while (n--)
        write(result.writer, &c, sizeof(c));
    return result;
}

void semaphore_acquire(semaphore *s) {
    char c;
    read(s->reader, &c, sizeof(c));
}

void semaphore_release(semaphore *s) {
    char c;
    write(s->writer, &c, sizeof(c));
}