文章目錄

• • 1 Linux內(nèi)核鏈表介紹
  • • 1.1 移植Linux內(nèi)核鏈表
    • • 1.1.1 Linux內(nèi)核鏈表的位置及依賴
      • 1.1.2 移植時(shí)的注意事項(xiàng)
    • 1.2 Linux內(nèi)核鏈表剖析
    • • 1.2.1 Linux內(nèi)核鏈表的實(shí)現(xiàn)
      • 1.2.2 Linux內(nèi)核鏈表的結(jié)點(diǎn)定義
      • 1.2.3 Linux內(nèi)核鏈表的創(chuàng)建及初始化
      • 1.2.4 Linux內(nèi)核鏈表的插入操作
      • 1.2.5 Linux內(nèi)核鏈表的刪除操作
      • 1.2.6 Linux內(nèi)核的遍歷
      • 1.2.7 Linux內(nèi)核鏈表的簡(jiǎn)單使用
      • 1.2.8 Linux內(nèi)核鏈表總結(jié)
      • 1.2.9 LinuxList源碼
  • 2 雙向循環(huán)鏈表的實(shí)現(xiàn)
  • • 2.1 繼承層次圖
    • 2.2 雙向循環(huán)鏈表的設(shè)計(jì)思路
    • 2.3 代碼實(shí)現(xiàn)
    • 2.4 思考

1 Linux內(nèi)核鏈表介紹

1.1 移植Linux內(nèi)核鏈表

移植Linux內(nèi)核鏈表，使其使用于非GNU編譯器。

1.1.1 Linux內(nèi)核鏈表的位置及依賴

位置：

• {linux-2.6.39}\\include\linux\list.h

依賴：

• #include <linux/types.h>
• #include <linux/stddef.h>
• #include <linux/poison.h>
• #include <linux/prefetch.h>

1.1.2 移植時(shí)的注意事項(xiàng)

清除文件間的依賴：

• 剝離依賴文件中與鏈表實(shí)現(xiàn)相關(guān)的代碼。

清除平臺(tái)相關(guān)代碼（GNU C）：

• ({})
• typeof
• _builtin_prefetch
• static inline

1.2 Linux內(nèi)核鏈表剖析

1.2.1 Linux內(nèi)核鏈表的實(shí)現(xiàn)

Linux內(nèi)核鏈表的實(shí)現(xiàn)：

• 帶頭結(jié)點(diǎn)的雙向循環(huán)鏈表，且頭結(jié)點(diǎn)為表中成員。
• 頭結(jié)點(diǎn)的next指針指向首結(jié)點(diǎn)。
• 頭結(jié)點(diǎn)的prev指針指向尾結(jié)點(diǎn)。

1.2.2 Linux內(nèi)核鏈表的結(jié)點(diǎn)定義

問(wèn)題：數(shù)據(jù)放在哪里？

使用struct list_head自定義鏈表結(jié)點(diǎn)。

1.2.3 Linux內(nèi)核鏈表的創(chuàng)建及初始化

1.2.4 Linux內(nèi)核鏈表的插入操作

• 在鏈表頭部插入：list_add(new, head)。
• 在鏈表尾部插入：list_add_tail(new, head)。

1.2.5 Linux內(nèi)核鏈表的刪除操作

1.2.6 Linux內(nèi)核的遍歷

• 正向遍歷：list_for_each(pos, head)。
• 逆向遍歷：list_for_each_prev(pos, head)。

1.2.7 Linux內(nèi)核鏈表的簡(jiǎn)單使用

#include <stdio.h> #include "LinuxList.h"void list_demo_1() {struct Node{struct list_head head;int value;};struct Node l = {0};struct list_head* list = (struct list_head*)&l;struct list_head* slider = NULL;int i = 0;INIT_LIST_HEAD(list);printf("Insert begin ...\n");for(i=0; i<5; i++){struct Node* n = (struct Node*)malloc(sizeof(struct Node));n->value = i;list_add_tail((struct list_head*)n, list);}list_for_each(slider, list){printf("%d\n", ((struct Node*)slider)->value);}printf("Insert end ...\n");printf("Delete begin ...\n");list_for_each(slider, list){if( ((struct Node*)slider)->value == 3 ){list_del(slider);free(slider);break;}}list_for_each(slider, list){printf("%d\n", ((struct Node*)slider)->value);}printf("Delete end ...\n"); }void list_demo_2() {struct Node{int value;struct list_head head;};struct Node l = {0};struct list_head* list = &l.head;struct list_head* slider = NULL;int i = 0;INIT_LIST_HEAD(list);printf("Insert begin ...\n");for(i=0; i<5; i++){struct Node* n = (struct Node*)malloc(sizeof(struct Node));n->value = i;list_add(&n->head, list);}list_for_each(slider, list){printf("%d\n", list_entry(slider, struct Node, head)->value);}printf("Insert end ...\n");printf("Delete begin ...\n");list_for_each(slider, list){struct Node* n = list_entry(slider, struct Node, head);if( n->value == 3 ){list_del(slider);free(n);break;}}list_for_each(slider, list){printf("%d\n", list_entry(slider, struct Node, head)->value);}printf("Delete end ...\n"); }int main() {// list_demo_1();// list_demo_2();return 0; }

1.2.8 Linux內(nèi)核鏈表總結(jié)

• Linux內(nèi)核鏈表移植時(shí)需要剔除依賴及平臺(tái)相關(guān)代碼。
• Linux內(nèi)核鏈表是帶頭結(jié)點(diǎn)的雙向循環(huán)鏈表。
• 使用Linux內(nèi)核鏈表時(shí)需要自定義鏈表結(jié)點(diǎn)。
  • 將struct list_head作為結(jié)點(diǎn)結(jié)構(gòu)體的第一個(gè)成員或最后一個(gè)成員。
  • struct list_head不是第一個(gè)成員時(shí)，需要使用list_entry宏。
  • list_entry的定義中使用了container_of宏。

1.2.9 LinuxList源碼

/* LinuxList.h */#ifndef _LINUX_LIST_H #define _LINUX_LIST_H// #include <linux/types.h> // #include <linux/stddef.h> // #include <linux/poison.h> // #include <linux/prefetch.h>#ifndef offsetof #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) #endif#ifndef container_of #define container_of(ptr, type, member) ((type *)((char *)ptr - offsetof(type,member))) #endif#define prefetch(x) ((void)x)#define LIST_POISON1 (NULL) #define LIST_POISON2 (NULL)struct list_head {struct list_head *next, *prev; };struct hlist_head {struct hlist_node *first; };struct hlist_node {struct hlist_node *next, **pprev; };/** Simple doubly linked list implementation.** Some of the internal functions ("__xxx") are useful when* manipulating whole lists rather than single entries, as* sometimes we already know the next/prev entries and we can* generate better code by using them directly rather than* using the generic single-entry routines.*/#define LIST_HEAD_INIT(name) { &(name), &(name) }#define LIST_HEAD(name) \struct list_head name = LIST_HEAD_INIT(name)static void INIT_LIST_HEAD(struct list_head *list) {list->next = list;list->prev = list; }/** 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 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 void list_add(struct list_head *new, struct list_head *head) {__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 void list_add_tail(struct list_head *new, struct list_head *head) {__list_add(new, head->prev, head); }/** Delete a list entry by making the prev/next entries* point to each other.** This is only for internal list manipulation where we know* the prev/next entries already!*/ static 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.*/ #ifndef CONFIG_DEBUG_LIST static void __list_del_entry(struct list_head *entry) {__list_del(entry->prev, entry->next); }static void list_del(struct list_head *entry) {__list_del(entry->prev, entry->next);entry->next = LIST_POISON1;entry->prev = LIST_POISON2; } #else extern void __list_del_entry(struct list_head *entry); extern void list_del(struct list_head *entry); #endif/*** list_replace - replace old entry by new one* @old : the element to be replaced* @new : the new element to insert** If @old was empty, it will be overwritten.*/ static void list_replace(struct list_head *old,struct list_head *new) {new->next = old->next;new->next->prev = new;new->prev = old->prev;new->prev->next = new; }static void list_replace_init(struct list_head *old,struct list_head *new) {list_replace(old, new);INIT_LIST_HEAD(old); }/*** list_del_init - deletes entry from list and reinitialize it.* @entry: the element to delete from the list.*/ static void list_del_init(struct list_head *entry) {__list_del_entry(entry);INIT_LIST_HEAD(entry); }/*** list_move - delete from one list and add as another's head* @list: the entry to move* @head: the head that will precede our entry*/ static void list_move(struct list_head *list, struct list_head *head) {__list_del_entry(list);list_add(list, head); }/*** list_move_tail - delete from one list and add as another's tail* @list: the entry to move* @head: the head that will follow our entry*/ static void list_move_tail(struct list_head *list,struct list_head *head) {__list_del_entry(list);list_add_tail(list, head); }/*** list_is_last - tests whether @list is the last entry in list @head* @list: the entry to test* @head: the head of the list*/ static int list_is_last(const struct list_head *list,const struct list_head *head) {return list->next == head; }/*** list_empty - tests whether a list is empty* @head: the list to test.*/ static int list_empty(const struct list_head *head) {return head->next == head; }/*** list_empty_careful - tests whether a list is empty and not being modified* @head: the list to test** Description:* tests whether a list is empty _and_ checks that no other CPU might be* in the process of modifying either member (next or prev)** NOTE: using list_empty_careful() without synchronization* can only be safe if the only activity that can happen* to the list entry is list_del_init(). Eg. it cannot be used* if another CPU could re-list_add() it.*/ static int list_empty_careful(const struct list_head *head) {struct list_head *next = head->next;return (next == head) && (next == head->prev); }/*** list_rotate_left - rotate the list to the left* @head: the head of the list*/ static void list_rotate_left(struct list_head *head) {struct list_head *first;if (!list_empty(head)) {first = head->next;list_move_tail(first, head);} }/*** list_is_singular - tests whether a list has just one entry.* @head: the list to test.*/ static int list_is_singular(const struct list_head *head) {return !list_empty(head) && (head->next == head->prev); }static void __list_cut_position(struct list_head *list,struct list_head *head, struct list_head *entry) {struct list_head *new_first = entry->next;list->next = head->next;list->next->prev = list;list->prev = entry;entry->next = list;head->next = new_first;new_first->prev = head; }/*** list_cut_position - cut a list into two* @list: a new list to add all removed entries* @head: a list with entries* @entry: an entry within head, could be the head itself* and if so we won't cut the list** This helper moves the initial part of @head, up to and* including @entry, from @head to @list. You should* pass on @entry an element you know is on @head. @list* should be an empty list or a list you do not care about* losing its data.**/ static void list_cut_position(struct list_head *list,struct list_head *head, struct list_head *entry) {if (list_empty(head))return;if (list_is_singular(head) &&(head->next != entry && head != entry))return;if (entry == head)INIT_LIST_HEAD(list);else__list_cut_position(list, head, entry); }static void __list_splice(const struct list_head *list,struct list_head *prev,struct list_head *next) {struct list_head *first = list->next;struct list_head *last = list->prev;first->prev = prev;prev->next = first;last->next = next;next->prev = last; }/*** list_splice - join two lists, this is designed for stacks* @list: the new list to add.* @head: the place to add it in the first list.*/ static void list_splice(const struct list_head *list,struct list_head *head) {if (!list_empty(list))__list_splice(list, head, head->next); }/*** list_splice_tail - join two lists, each list being a queue* @list: the new list to add.* @head: the place to add it in the first list.*/ static void list_splice_tail(struct list_head *list,struct list_head *head) {if (!list_empty(list))__list_splice(list, head->prev, head); }/*** list_splice_init - join two lists and reinitialise the emptied list.* @list: the new list to add.* @head: the place to add it in the first list.** The list at @list is reinitialised*/ static void list_splice_init(struct list_head *list,struct list_head *head) {if (!list_empty(list)) {__list_splice(list, head, head->next);INIT_LIST_HEAD(list);} }/*** list_splice_tail_init - join two lists and reinitialise the emptied list* @list: the new list to add.* @head: the place to add it in the first list.** Each of the lists is a queue.* The list at @list is reinitialised*/ static void list_splice_tail_init(struct list_head *list,struct list_head *head) {if (!list_empty(list)) {__list_splice(list, head->prev, head);INIT_LIST_HEAD(list);} }/*** 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_first_entry - get the first element from a list* @ptr: the list head to take the element from.* @type: the type of the struct this is embedded in.* @member: the name of the list_struct within the struct.** Note, that list is expected to be not empty.*/ #define list_first_entry(ptr, type, member) \list_entry((ptr)->next, type, member)/*** 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; prefetch(pos->next), pos != (head); \pos = pos->next)/*** __list_for_each - iterate over a list* @pos: the &struct list_head to use as a loop cursor.* @head: the head for your list.** This variant differs from list_for_each() in that it's the* simplest possible list iteration code, no prefetching is done.* Use this for code that knows the list to be very short (empty* or 1 entry) most of the time.*/ #define __list_for_each(pos, head) \for (pos = (head)->next; pos != (head); pos = pos->next)/*** list_for_each_prev - iterate over a list backwards* @pos: the &struct list_head to use as a loop cursor.* @head: the head for your list.*/ #define list_for_each_prev(pos, head) \for (pos = (head)->prev; prefetch(pos->prev), pos != (head); \pos = pos->prev)/*** list_for_each_safe - iterate over a list safe against removal of list entry* @pos: the &struct list_head to use as a loop cursor.* @n: another &struct list_head to use as temporary storage* @head: the head for your list.*/ #define list_for_each_safe(pos, n, head) \for (pos = (head)->next, n = pos->next; pos != (head); \pos = n, n = pos->next)/*** list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry* @pos: the &struct list_head to use as a loop cursor.* @n: another &struct list_head to use as temporary storage* @head: the head for your list.*/ #define list_for_each_prev_safe(pos, n, head) \for (pos = (head)->prev, n = pos->prev; \prefetch(pos->prev), pos != (head); \pos = n, n = pos->prev)/*** list_for_each_entry - iterate over list of given type* @pos: the type * to use as a loop cursor.* @head: the head for your list.* @member: the name of the list_struct within the struct.*/ #define list_for_each_entry(pos, head, member) \for (pos = list_entry((head)->next, typeof(*pos), member); \prefetch(pos->member.next), &pos->member != (head); \pos = list_entry(pos->member.next, typeof(*pos), member))/*** list_for_each_entry_reverse - iterate backwards over list of given type.* @pos: the type * to use as a loop cursor.* @head: the head for your list.* @member: the name of the list_struct within the struct.*/ #define list_for_each_entry_reverse(pos, head, member) \for (pos = list_entry((head)->prev, typeof(*pos), member); \prefetch(pos->member.prev), &pos->member != (head); \pos = list_entry(pos->member.prev, typeof(*pos), member))/*** list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()* @pos: the type * to use as a start point* @head: the head of the list* @member: the name of the list_struct within the struct.** Prepares a pos entry for use as a start point in list_for_each_entry_continue().*/ #define list_prepare_entry(pos, head, member) \((pos) ? : list_entry(head, typeof(*pos), member))/*** list_for_each_entry_continue - continue iteration over list of given type* @pos: the type * to use as a loop cursor.* @head: the head for your list.* @member: the name of the list_struct within the struct.** Continue to iterate over list of given type, continuing after* the current position.*/ #define list_for_each_entry_continue(pos, head, member) \for (pos = list_entry(pos->member.next, typeof(*pos), member); \prefetch(pos->member.next), &pos->member != (head); \pos = list_entry(pos->member.next, typeof(*pos), member))/*** list_for_each_entry_continue_reverse - iterate backwards from the given point* @pos: the type * to use as a loop cursor.* @head: the head for your list.* @member: the name of the list_struct within the struct.** Start to iterate over list of given type backwards, continuing after* the current position.*/ #define list_for_each_entry_continue_reverse(pos, head, member) \for (pos = list_entry(pos->member.prev, typeof(*pos), member); \prefetch(pos->member.prev), &pos->member != (head); \pos = list_entry(pos->member.prev, typeof(*pos), member))/*** list_for_each_entry_from - iterate over list of given type from the current point* @pos: the type * to use as a loop cursor.* @head: the head for your list.* @member: the name of the list_struct within the struct.** Iterate over list of given type, continuing from current position.*/ #define list_for_each_entry_from(pos, head, member) \for (; prefetch(pos->member.next), &pos->member != (head); \pos = list_entry(pos->member.next, typeof(*pos), member))/*** list_for_each_entry_safe - iterate over list of given type safe against removal of list entry* @pos: the type * to use as a loop cursor.* @n: another type * to use as temporary storage* @head: the head for your list.* @member: the name of the list_struct within the struct.*/ #define list_for_each_entry_safe(pos, n, head, member) \for (pos = list_entry((head)->next, typeof(*pos), member), \n = list_entry(pos->member.next, typeof(*pos), member); \&pos->member != (head); \pos = n, n = list_entry(n->member.next, typeof(*n), member))/*** list_for_each_entry_safe_continue - continue list iteration safe against removal* @pos: the type * to use as a loop cursor.* @n: another type * to use as temporary storage* @head: the head for your list.* @member: the name of the list_struct within the struct.** Iterate over list of given type, continuing after current point,* safe against removal of list entry.*/ #define list_for_each_entry_safe_continue(pos, n, head, member) \for (pos = list_entry(pos->member.next, typeof(*pos), member), \n = list_entry(pos->member.next, typeof(*pos), member); \&pos->member != (head); \pos = n, n = list_entry(n->member.next, typeof(*n), member))/*** list_for_each_entry_safe_from - iterate over list from current point safe against removal* @pos: the type * to use as a loop cursor.* @n: another type * to use as temporary storage* @head: the head for your list.* @member: the name of the list_struct within the struct.** Iterate over list of given type from current point, safe against* removal of list entry.*/ #define list_for_each_entry_safe_from(pos, n, head, member) \for (n = list_entry(pos->member.next, typeof(*pos), member); \&pos->member != (head); \pos = n, n = list_entry(n->member.next, typeof(*n), member))/*** list_for_each_entry_safe_reverse - iterate backwards over list safe against removal* @pos: the type * to use as a loop cursor.* @n: another type * to use as temporary storage* @head: the head for your list.* @member: the name of the list_struct within the struct.** Iterate backwards over list of given type, safe against removal* of list entry.*/ #define list_for_each_entry_safe_reverse(pos, n, head, member) \for (pos = list_entry((head)->prev, typeof(*pos), member), \n = list_entry(pos->member.prev, typeof(*pos), member); \&pos->member != (head); \pos = n, n = list_entry(n->member.prev, typeof(*n), member))/*** list_safe_reset_next - reset a stale list_for_each_entry_safe loop* @pos: the loop cursor used in the list_for_each_entry_safe loop* @n: temporary storage used in list_for_each_entry_safe* @member: the name of the list_struct within the struct.** list_safe_reset_next is not safe to use in general if the list may be* modified concurrently (eg. the lock is dropped in the loop body). An* exception to this is if the cursor element (pos) is pinned in the list,* and list_safe_reset_next is called after re-taking the lock and before* completing the current iteration of the loop body.*/ #define list_safe_reset_next(pos, n, member) \n = list_entry(pos->member.next, typeof(*pos), member)/** Double linked lists with a single pointer list head.* Mostly useful for hash tables where the two pointer list head is* too wasteful.* You lose the ability to access the tail in O(1).*/#define HLIST_HEAD_INIT { .first = NULL } #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL } #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL) static void INIT_HLIST_NODE(struct hlist_node *h) {h->next = NULL;h->pprev = NULL; }static int hlist_unhashed(const struct hlist_node *h) {return !h->pprev; }static int hlist_empty(const struct hlist_head *h) {return !h->first; }static void __hlist_del(struct hlist_node *n) {struct hlist_node *next = n->next;struct hlist_node **pprev = n->pprev;*pprev = next;if (next)next->pprev = pprev; }static void hlist_del(struct hlist_node *n) {__hlist_del(n);n->next = LIST_POISON1;n->pprev = LIST_POISON2; }static void hlist_del_init(struct hlist_node *n) {if (!hlist_unhashed(n)) {__hlist_del(n);INIT_HLIST_NODE(n);} }static void hlist_add_head(struct hlist_node *n, struct hlist_head *h) {struct hlist_node *first = h->first;n->next = first;if (first)first->pprev = &n->next;h->first = n;n->pprev = &h->first; }/* next must be != NULL */ static void hlist_add_before(struct hlist_node *n,struct hlist_node *next) {n->pprev = next->pprev;n->next = next;next->pprev = &n->next;*(n->pprev) = n; }static void hlist_add_after(struct hlist_node *n,struct hlist_node *next) {next->next = n->next;n->next = next;next->pprev = &n->next;if(next->next)next->next->pprev = &next->next; }/* after that we'll appear to be on some hlist and hlist_del will work */ static void hlist_add_fake(struct hlist_node *n) {n->pprev = &n->next; }/** Move a list from one list head to another. Fixup the pprev* reference of the first entry if it exists.*/ static void hlist_move_list(struct hlist_head *old,struct hlist_head *new) {new->first = old->first;if (new->first)new->first->pprev = &new->first;old->first = NULL; }#define hlist_entry(ptr, type, member) container_of(ptr,type,member)#define hlist_for_each(pos, head) \for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \pos = pos->next)#define hlist_for_each_safe(pos, n, head) \for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \pos = n)/*** hlist_for_each_entry - iterate over list of given type* @tpos: the type * to use as a loop cursor.* @pos: the &struct hlist_node to use as a loop cursor.* @head: the head for your list.* @member: the name of the hlist_node within the struct.*/ #define hlist_for_each_entry(tpos, pos, head, member) \for (pos = (head)->first; \pos && ({ prefetch(pos->next); 1;}) && \({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \pos = pos->next)/*** hlist_for_each_entry_continue - iterate over a hlist continuing after current point* @tpos: the type * to use as a loop cursor.* @pos: the &struct hlist_node to use as a loop cursor.* @member: the name of the hlist_node within the struct.*/ #define hlist_for_each_entry_continue(tpos, pos, member) \for (pos = (pos)->next; \pos && ({ prefetch(pos->next); 1;}) && \({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \pos = pos->next)/*** hlist_for_each_entry_from - iterate over a hlist continuing from current point* @tpos: the type * to use as a loop cursor.* @pos: the &struct hlist_node to use as a loop cursor.* @member: the name of the hlist_node within the struct.*/ #define hlist_for_each_entry_from(tpos, pos, member) \for (; pos && ({ prefetch(pos->next); 1;}) && \({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \pos = pos->next)/*** hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry* @tpos: the type * to use as a loop cursor.* @pos: the &struct hlist_node to use as a loop cursor.* @n: another &struct hlist_node to use as temporary storage* @head: the head for your list.* @member: the name of the hlist_node within the struct.*/ #define hlist_for_each_entry_safe(tpos, pos, n, head, member) \for (pos = (head)->first; \pos && ({ n = pos->next; 1; }) && \({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \pos = n)#endif

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2 雙向循環(huán)鏈表的實(shí)現(xiàn)

直接使用Linux內(nèi)核鏈表實(shí)現(xiàn)雙向循環(huán)鏈表。

2.1 繼承層次圖

2.2 雙向循環(huán)鏈表的設(shè)計(jì)思路

數(shù)據(jù)結(jié)點(diǎn)之間在邏輯上構(gòu)成雙向循環(huán)鏈表，頭結(jié)點(diǎn)僅用于結(jié)點(diǎn)的定位。

實(shí)現(xiàn)思路：

• 通過(guò)模板定義DualCircleList類，繼承自DualLinkList類。
• 在DualCircleList內(nèi)部使用Linux內(nèi)核鏈表進(jìn)行實(shí)現(xiàn)。
• 使用struct list_head定義DualCircleList的頭結(jié)點(diǎn)。
• 特殊處理：循環(huán)遍歷時(shí)忽略頭結(jié)點(diǎn)。

實(shí)現(xiàn)要點(diǎn)：

• 通過(guò)list_head進(jìn)行目標(biāo)結(jié)點(diǎn)定位（position(i)）。
• 通過(guò)list_entry將list_head指針轉(zhuǎn)換為目標(biāo)結(jié)點(diǎn)指針。
• 通過(guò)list_for_each實(shí)現(xiàn)int find(const T& e)函數(shù)。
• 遍歷函數(shù)中的next()和pre()需要考慮跳過(guò)頭結(jié)點(diǎn)。

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2.3 代碼實(shí)現(xiàn)

DualCircleList.h

#ifndef DUALCIRCLELIST_H #define DUALCIRCLELIST_H#include "CircleList.h" #include "LinuxList.h" #include "Exception.h"namespace LemonLib {template <typename T> class DualCircleList : public CircleList<T> { protected:struct Node{list_head head;T value;};list_head m_header;list_head* m_current;list_head* position(int i) const{list_head* ret = const_cast<list_head*>(&m_header);for (int p=0; p<i; p++){ret = ret->next;}return ret;}int mod(int i) const{return (this->m_length == 0) ? 0 : (i % this->m_length);}public:DualCircleList(){this->m_length = 0;this->m_step = 0;m_current = NULL;INIT_LIST_HEAD(&m_header);}bool insert(const T& e){insert(this->m_length, e);}bool insert(int i, const T& e){bool ret = true;Node* node = new Node();if (node != NULL){i = i % (this->m_length + 1);node->value = e;list_add_tail(&node->head, position(i)->next);this->m_length++;}else{THROW_EXCEPTION(NoEnoughMemoryException, "No enough memory to insert new element ...");}return ret;}bool remove(int i){bool ret = true;i = mod(i);ret = (0 <= i) && (i < this->m_length);if (ret){list_head* toDel = position(i)->next;if (m_current == toDel){m_current = m_current->next;}list_del(toDel);this->m_length--;delete list_entry(toDel, Node, head);}return ret;}bool set(int i, const T& e){bool ret = true;i = mod(i);ret = (0 <= i) && (i < this->m_length);if (ret){list_entry(position(i)->next, Node, head)->value = e;}return ret;}T get(int i) const{T ret;if (get(i, ret)){return ret;}else{THROW_EXCEPTION(InvalidParameterException, "Invalid parameter in get element ...");}}bool get(int i, T& e) const{bool ret = true;i = mod(i);ret = (0 <= i) && (i < this->m_length);if (ret){e = list_entry(position(i)->next, Node, head)->value;}return ret;}int find(const T& e) const{int ret = -1;int i = 0;list_head* slider = NULL;list_for_each(slider, &m_header){if (list_entry(slider, Node, head)->value == e){ret = i;break;}i++;}return ret;}int length() const{return this->m_length;}void clear(){while (this->m_length > 0){remove(0);}}bool move(int i, int step = 1){bool ret = (step > 0);i = mod(i);ret = ret && (0 <= i) && (i < this->m_length);if (ret){m_current = position(i)->next;this->m_step = step;}return ret;}bool end(){return (m_current == NULL) || (this->m_length == 0);}T current(){if (!end()){return list_entry(m_current, Node, head)->value;}else{THROW_EXCEPTION(InvalidOperationException, "invlaid to get current val...");}}bool next(){int i = 0;while ((i < this->m_step) && (!end())){if (m_current != &m_header){m_current = m_current->next;i++;}else{m_current = m_current->next;}}if (m_current == &m_header){m_current = m_current->next;}return (i == this->m_step);}bool prev(){int i = 0;while ((i < this->m_step) && (!end())){if (m_current != &m_header){m_current = m_current->prev;i++;}else{m_current = m_current->prev;}}if (m_current == &m_header){m_current = m_current->prev;}return (i == this->m_step);}~DualCircleList(){clear();}};}#endif // DUALCIRCLELIST_H

main.cpp

#include <iostream>#include "SmartPointer.h" #include "Exception.h" #include "Object.h" #include "List.h" #include "SeqList.h" #include "StaticList.h" #include "DynamicList.h" #include "Array.h" #include "StaticArray.h" #include "DynamicArray.h" #include "LinkList.h" #include "StaticLinkList.h" #include "Pointer.h" #include "SmartPointer.h" #include "SharedPointer.h" #include "CircleList.h" #include "DualLinkList.h" #include "StaticDualLinkList.h" #include "DualCircleList.h"using namespace std; using namespace LemonLib;int main() {DualCircleList<int> dl;for (int i=0; i<5; i++){dl.insert(i);}dl.move(dl.length()-1);for (int i=0; i<dl.length(); i++){cout << dl.current() << endl;dl.prev();}cout << dl.find(5) << endl;cout << dl.find(3) << endl;return 0; }

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2.4 思考

如下代碼中的pn1和pn2是否相等？為什么？

不相等，因?yàn)橛刑摵瘮?shù)指針的存在導(dǎo)致pn1和pn2不相等。

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