Linux内核－链表

linux内核链表的定义（定义了双向链表，不含数据域）

定义在　/linux-source-3.13.0/include/linux/types.h 头文件中．

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

我们可以利用这个数据结构定义含有数据域的链表，如：

 struct my_list
 {
         void * mydata;   //void * 可以指向任何类型的数据
         struct list_head list;  //隐藏了链表指针
 } 

 链表的声明和初始化宏（list.h）

定义在　/linux-source-3.13.0/include/linux/list.h 中．

 #define LIST_HEAD_INIT(name) { &(name), &(name) }

初始化一个名为name的双向链表的头节点．（name.pre = &name , name.next = &name）

 #define LIST_HEAD(name) \
         struct list_head name = LIST_HEAD_INIT(name)

通过调用LIST_HEAD，来声明和初始化一个自己的链表头，产生一个空链表．如：LIST_HEAD（mylist_head）

 在链表添加一个节点

定义在　/linux-source-3.13.0/include/linux/list.h 中

具体实现：

 /*
  * Insert a new entry between two known consecutive entries.
  *
  * This is only for internal list manipulation where we know
  * the prev/next entries already!
  */
 #ifndef CONFIG_DEBUG_LIST
 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;
 }
 #else
 extern void __list_add(struct list_head *new,
                               struct list_head *prev,
                               struct list_head *next);
 #endif

 /**
  * 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)　//在head节点后插入new节点，循环链表没有首尾，head可以是任意节点
 {
         __list_add(new, head, head->next);
 }

 /**
  * list_add_tail - add a new entry
  * @new: new entry to be added
  * @head: list head to add it before
  *
  * Insert a new entry before the specified head.
  * This is useful for implementing queues.
  */
 static inline void list_add_tail(struct list_head *new, struct list_head *head)　//在head节点前插入new节点
 {
         __list_add(new, head->prev, head);
 }

 遍历链表

定义在　/linux-source-3.13.0/include/linux/list.h 中

 /**
  * list_for_each        -       iterate over a list
  * @pos:        the &struct list_head to use as a loop cursor.
  * @head:       the head for your list.
  */
 #define list_for_each(pos, head) \
         for (pos = (head)->next; pos != (head); pos = pos->next)

它实际上是一个for循环，利用传入的pos作为循环变量，从表头开始逐顶向后（next方向）移动pos，直至回到head.

 /**
  * list_entry - get the struct for this entry
  * @ptr:        the &struct list_head pointer.
  * @type:       the type of the struct this is embedded in.
  * @member:     the name of the list_struct within the struct.
  */
 #define list_entry(ptr, type, member) \
         container_of(ptr, type, member)

list_entry宏：从结构体（type）某成员变量（menber）指针（prt）来求出该结构体（type）的首指针．