container_of

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container_of

已知结构体某个元素的地址，获取这个结构体起始地址。定义如下

/**
* container_of - cast a member of a structure out to the containing structure
* @ptr:     the pointer to the member.
* @type:     the type of the container struct this is embedded in.
* @member:     the name of the member within the struct.
*
*/
#define container_of(ptr, type, member) ({             \
const typeof( ((type *)0)->member ) *__mptr = (ptr);     \
(type *)( (char *)__mptr - offsetof(type,member) );})

例如：

typdef struct {
    int x;
    int y;
} Point;

Point p;

int *a = &p.x

assert(&p == container_of(a, Point, x));

在linux下c编程中主要用作通过链表等数据结构获得父容器,这种用法非常常见。

typdef struct list_node_s{
    struct list_node_s* next;
}list_node_t;

typdef struct user_s {
    char *name;
    char *pwd;
    list_node_t node;
}user_t;

user_t u1, u2;
u1.node.next = &u2.node;

assert(&u2 == container_of(u1.node.next, user_t, node))

http://blog.csdn.net/zhuxiaowei716/article/details/7562986

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