/** * This is a very small example that shows how to use * protothreads. The program consists of two protothreads that wait * for each other to toggle a variable. */ /* We must always include pt.h in our protothreads code. */ #include "pt.h" #include /* For printf(). */ /* Two flags that the two protothread functions use. */ static int protothread1_flag, protothread2_flag; /** * The first protothread function. A protothread function must always * return an integer, but must never explicitly return - returning is * performed inside the protothread statements. * * The protothread function is driven by the main loop further down in * the code. */ static int protothread1(struct pt *pt) { /* A protothread function must begin with PT_BEGIN() which takes a pointer to a struct pt. */ PT_BEGIN(pt); /* We loop forever here. */ while(1) { /* Wait until the other protothread has set its flag. */ PT_WAIT_UNTIL(pt, protothread2_flag != 0); printf("Protothread 1 running\n"); /* We then reset the other protothread's flag, and set our own flag so that the other protothread can run. */ protothread2_flag = 0; protothread1_flag = 1; /* And we loop. */ } /* All protothread functions must end with PT_END() which takes a pointer to a struct pt. */ PT_END(pt); } /** * The second protothread function. This is almost the same as the * first one. */ static int protothread2(struct pt *pt) { PT_BEGIN(pt); while(1) { /* Let the other protothread run. */ protothread2_flag = 1; /* Wait until the other protothread has set its flag. */ PT_WAIT_UNTIL(pt, protothread1_flag != 0); printf("Protothread 2 running\n"); /* We then reset the other protothread's flag. */ protothread1_flag = 0; /* And we loop. */ } PT_END(pt); } /** * Finally, we have the main loop. Here is where the protothreads are * initialized and scheduled. First, however, we define the * protothread state variables pt1 and pt2, which hold the state of * the two protothreads. */ static struct pt pt1, pt2; int main(void) { /* Initialize the protothread state variables with PT_INIT(). */ PT_INIT(&pt1); PT_INIT(&pt2); /* * Then we schedule the two protothreads by repeatedly calling their * protothread functions and passing a pointer to the protothread * state variables as arguments. */ while(1) { protothread1(&pt1); protothread2(&pt2); } }
