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container_of macro...

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Its been a while since I used the container_of macro, however, it can 
come in handy wrt creating linked data-structures. Here is an example I 
coded up, just to see if I could do it from scratch, after all these years:
________________________________
#include <stdio.h>
#include <stddef.h>
#include <assert.h>


struct ct_slist_node
{
     struct ct_slist_node* next;
};

struct ct_slist
{
     struct ct_slist_node* head;
};

#define ct_container_of(m_ptr, m_type, m_member) \
     ((void*)((unsigned char*)(m_ptr) - offsetof(m_type, m_member)))


void
ct_slist_push(
     struct ct_slist* self,
     struct ct_slist_node* node
) {
     node->next = self->head;
     self->head = node;
}

struct ct_slist_node*
     ct_slist_pop(
         struct ct_slist* self
     ) {
     struct ct_slist_node* node = self->head;
     if (node) self->head = node->next;
     return node;
}



struct foo
{
     int a;
     struct ct_slist_node next;
     char b;
     long c;
};



int main(void)
{
     struct foo foo;
     struct foo* pfoo = ct_container_of(&foo.next, struct foo, next);

     printf("&foo.next = %p\n", &foo.next);
     printf("&foo = %p\n", &foo);
     printf("pfoo = %p\n", pfoo);

     assert(&foo == pfoo);

     {
#define N 42

         struct foo foo[N];
         struct ct_slist slist = { NULL };

         printf("\npush...\n");
         for (unsigned int i = 0; i < N; ++i)
         {
             printf("&foo[%u] = %p\n", i, foo + i);
             ct_slist_push(&slist, &foo[i].next);
         }

         printf("\npop...\n");
         for (unsigned int i = 0; i < N; ++i)
         {
             struct ct_slist_node* node = ct_slist_pop(&slist);
             struct foo* pfoo = ct_container_of(node, struct foo, next);
             printf("pfoo = %p = &foo[%u - %u - 1] = %p\n", pfoo, N, i, 
&foo[N - i - 1]);
             assert(pfoo == &foo[N - i - 1]);
         }
     }

     return 0;
}
________________________________

How many people here use it?

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Thread

container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-08 17:24 -0800
  Re: container_of macro... Öö Tiib <ootiib@hot.ee> - 2021-03-09 02:06 -0800
    Re: container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-10 17:02 -0800
  Re: container_of macro... Kaz Kylheku <563-365-8930@kylheku.com> - 2021-03-09 15:59 +0000
    Re: container_of macro... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-03-09 17:35 +0000
      Re: container_of macro... Kaz Kylheku <563-365-8930@kylheku.com> - 2021-03-09 17:51 +0000
        Re: container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-10 17:13 -0800
    Re: container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-10 17:05 -0800
  Re: container_of macro... William Ahern <william@25thandClement.com> - 2021-03-09 18:56 -0800
    Re: container_of macro... Kaz Kylheku <563-365-8930@kylheku.com> - 2021-03-10 03:47 +0000
      Re: container_of macro... William Ahern <william@25thandClement.com> - 2021-03-12 17:01 -0800
        Re: container_of macro... Jim <jim.cromie@gmail.com> - 2021-03-16 22:14 -0700
    Re: container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-10 17:07 -0800

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