container_of用法及び実現

container_of      ，    struct          ，       struct    （       ,list）

struct DDD {

        int a;

        int b;

        int c;

        int d;};struct DDD  ddd;

|------------|  <-------      

|      a         |

|------------|

|      b         |

|------------|

|      c         |  <-------      

|------------|

|      d         |

|------------|

 
  
//       

#define offsetof(TYPE, MEMBER) ((unsigned int) &((TYPE *)0)->MEMBER)

#define container_of(ptr, type, member) ({                      \

        const typeof(((type *)0)->member) * __mptr = (ptr);     \

        (type *)((char *)__mptr - offsetof(type, member)); })



int main()

{

   printf("ddd  is %p and ddd.c is %p \r
",&ddd,&ddd.c);

   struct DDD * p= container_of(&ddd.c,struct DDD,c);

   printf("calc p is %p  \r
",p); 

   return 0;

}

/*

output:

ddd  is   0x601030 and ddd.c is 0x601038 

calc  p is 0x601030 

     

*/