C语言设计模式：迭代器

C语言实现迭代器有很多方法，linux内核的经典代码在文件include\linux\list.h中：

#define LIST_POISON1  ((void *) 0x00100100)
#define LIST_POISON2  ((void *) 0x00200200)

struct list_head {
struct list_head *next, *prev;
};

#define INIT_LIST_HEAD(ptr) do { \
(ptr)->next = (ptr); (ptr)->prev = (ptr); \
} while (0)

static inline void __list_add(struct list_head *new,
     struct list_head *prev,
     struct list_head *next)
{
next->prev = new;
new->next = next;
new->prev = prev;
prev->next = new;