container_of的實現

面試的過程中，container_of的實現很重要:

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

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

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

offserof：

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