C语言设计模式：迭代器

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我是靠谱客的博主复杂大白，最近开发中收集的这篇文章主要介绍C语言设计模式：迭代器，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

C语言实现迭代器有很多方法，linux内核的经典代码在文件includelinuxlist.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;
}

/**
* list_add - add a new entry
* @new: new entry to be added
* @head: list head to add it after
*
* Insert a new entry after the specified head.
* This is good for implementing stacks.
*/
static inline void list_add(struct list_head *new, struct list_head *head)
{
__list_add(new, head, head->next);
}

static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
__list_add(new, head->prev, head);
}

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

/**
* list_del - deletes entry from list.
* @entry: the element to delete from the list.
* Note: list_empty on entry does not return true after this, the entry is
* in an undefined state.
*/
static inline void list_del(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
entry->next = LIST_POISON1;
entry->prev = LIST_POISON2;
}

static inline int list_empty(const struct list_head *head)
{
return head->next == head;
}

#define list_for_each(pos, head)
for (pos = (head)->next; prefetch(pos->next), pos != (head);
pos = pos->next)

#define list_for_each_safe(pos, n, head)
for (pos = (head)->next, n = pos->next; pos != (head);
pos = n, n = pos->next)

#define container_of(ptr, type, member) ({
const typeof( ((type *)0)->member ) *__mptr = (ptr);
(type *)( (char *)__mptr - offsetof(type,member) );})

#define list_entry(ptr, type, member)
container_of(ptr, type, member)