A brief introduction of C coroutine library

1. C Coroutine
Multiple tasks with single CPU

2. Outline
1. Process, Thread, Event
2. Coroutine
3. C Couroutline Library
4. Protothread
5. Reference

3. Process, Thread, Event
● Process & Thread
○ Resource cost
○ Resource lock
○ process1/thread1(io1,do1), process2/thread2(io2,
do2)
● Event
○ Lots of nested callbacks
○ set(io1,do1); set(io2,do2); loop_event();

4. Coroutine
foo() {
static int i;
for(i = 0; i < 10; i++){
printf(“%dn”, i);
yield i;
}
}
foo(); // 0
foo(); // 1

5. Coroutine
a() {
a_init();
while(!io1()) yield;
do1();
}
b() {
b_init();
while(!io2()) yield;
do2();
}
loop{a(); b();};

6. C Coroutine Library
● Protothread
○ switch case
● State threads
○ longjmp + setjmp
● couroutine
○ ucontext

7. Protothread
int function(void) {
static int i, state;
switch (state) {
case 0: /* start of function */
for (i = 0; i < 10; i++) {
state = __LINE__ + 2; /* so we will come back to "case __LINE__" */
return i;
case __LINE__:; /* resume control straight after the return */
}
}
}

8. Protothread

9. Reference
● http://programmers.stackexchange.
com/questions/147182/
● http://coolshell.cn/articles/10975.html
● http://coolshell.cn/articles/12012.html