container_of用法及实现

赖明煦
2023-12-01
container_of 有的情况下,只知道 struct结构中莫个成员的指针,而需要知道整个struct的指针 (如网卡驱动里面,list)
struct DDD {
        int a;
        int b;
        int c;
        int d;
};
struct DDD  ddd;
|------------|  <-------  得到这个
|      a         |
|------------|
|      b         |
|------------|
|      c         |  <-------  已知这个
|------------|
|      d         |
|------------|
 
//得到成员在结构
#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\n",&ddd,&ddd.c);
   struct DDD * p= container_of(&ddd.c,struct DDD,c);
   printf("calc p is %p  \r\n",p); 
   return 0;
}
/*
output:
ddd  is   0x601030 and ddd.c is 0x601038 
calc  p is 0x601030 
结果与想象
*/

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