98 lines
2.4 KiB
C
98 lines
2.4 KiB
C
|
/**
|
||
|
* 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 <stdio.h> /* 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);
|
||
|
}
|
||
|
}
|