Kooperative Koroutinen-Ausgabe mittels Switch-Case-Fallthrough-Zustandsautomaten

#include <stdio.h>
 
typedef struct {
    int state;
    int index;
} Coroutine;
 
int process_stream(Coroutine* cr, const int* buffer, int size) {
    switch (cr->state) {
        case 0:
            for (cr->index = 0; cr->index < size; cr->index++) {
                cr->state = 1;
                return buffer[cr->index];
                case 1:;
            }
    }
    cr->state = -1;
    return -1;
}