container_of: don't put member_ptr in container_off.
[ccan] / ccan / container_of / _info
1 #include <stdio.h>
2 #include <string.h>
3 #include "config.h"
4
5 /**
6  * container_of - routine for upcasting
7  *
8  * It is often convenient to create code where the caller registers a pointer
9  * to a generic structure and a callback.  The callback might know that the
10  * pointer points to within a larger structure, and container_of gives a
11  * convenient and fairly type-safe way of returning to the enclosing structure.
12  *
13  * This idiom is an alternative to providing a void * pointer for every
14  * callback.
15  *
16  * Example:
17  *      #include <stdio.h>
18  *      #include <ccan/container_of/container_of.h>
19  *
20  *      struct timer {
21  *              void *members;
22  *      };
23  *
24  *      struct info {
25  *              int my_stuff;
26  *              struct timer timer;
27  *      };
28  *
29  *      static void register_timer(struct timer *timer)
30  *      {
31  *              //...
32  *      }
33  *
34  *      static void my_timer_callback(struct timer *timer)
35  *      {
36  *              struct info *info = container_of(timer, struct info, timer);
37  *              printf("my_stuff is %u\n", info->my_stuff);
38  *      }
39  *
40  *      int main(void)
41  *      {
42  *              struct info info = { .my_stuff = 1 };
43  *
44  *              register_timer(&info.timer);
45  *              // ...
46  *              return 0;
47  *      }
48  *
49  * License: Public domain
50  * Author: Rusty Russell <rusty@rustcorp.com.au>
51  */
52 int main(int argc, char *argv[])
53 {
54         if (argc != 2)
55                 return 1;
56
57         if (strcmp(argv[1], "depends") == 0) {
58                 printf("ccan/check_type\n");
59                 return 0;
60         }
61
62         return 1;
63 }