内核中的list
2015-09-25 11:39
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学习链表的实现,还是觉得linux下的显得不错。
今天爬取了份可以用在linux下的代码。不必要重复造轮子了。对于这份代码的详细说明,请参考 《Linux Kernel Linked List Explained》
如下代码的获取路径
http://isis.poly.edu/kulesh/stuff/src/klist/list.h
list.h
下面代码是给出的测试用例(也可以作为其函数的用法示例哦)
其可以从http://isis.poly.edu/kulesh/stuff/src/klist/test_list.c 下载
mylist.c
学习链表的实现,还是觉得linux下的显得不错。
今天爬取了份可以用在linux下的代码。不必要重复造轮子了。对于这份代码的详细说明,请参考 《Linux Kernel Linked List Explained》
如下代码的获取路径
http://isis.poly.edu/kulesh/stuff/src/klist/list.h
list.h
1 #ifndef __LIST_H 2 #define __LIST_H 3 4 /* This file is from Linux Kernel (include/linux/list.h) 5 * and modified by simply removing hardware prefetching of list items. 6 * Here by copyright, credits attributed to wherever they belong. 7 * Kulesh Shanmugasundaram (kulesh [squiggly] isis.poly.edu) 8 */ 9 10 /* 11 * Simple doubly linked list implementation. 12 * 13 * Some of the internal functions (“__xxx”) are useful when 14 * manipulating whole lists rather than single entries, as 15 * sometimes we already know the next/prev entries and we can 16 * generate better code by using them directly rather than 17 * using the generic single-entry routines. 18 */ 19 20 struct list_head { 21 struct list_head *next, *prev; 22 }; 23 24 #define LIST_HEAD_INIT(name) { &(name), &(name) } 25 26 #define LIST_HEAD(name) \ 27 struct list_head name = LIST_HEAD_INIT(name) 28 29 static inline void INIT_LIST_HEAD(struct list_head *list) 30 { 31 list->next = list; 32 list->prev = list; 33 } 34 /* 35 * Insert a new entry between two known consecutive entries. 36 * 37 * This is only for internal list manipulation where we know 38 * the prev/next entries already! 39 */ 40 static inline void __list_add(struct list_head *new, 41 struct list_head *prev, 42 struct list_head *next) 43 { 44 next->prev = new; 45 new->next = next; 46 new->prev = prev; 47 prev->next = new; 48 } 49 50 /** 51 * list_add – add a new entry 52 * @new: new entry to be added 53 * @head: list head to add it after 54 * 55 * Insert a new entry after the specified head. 56 * This is good for implementing stacks. 57 */ 58 static inline void list_add(struct list_head *new, struct list_head *head) 59 { 60 __list_add(new, head, head->next); 61 } 62 63 /** 64 * list_add_tail – add a new entry 65 * @new: new entry to be added 66 * @head: list head to add it before 67 * 68 * Insert a new entry before the specified head. 69 * This is useful for implementing queues. 70 */ 71 static inline void list_add_tail(struct list_head *new, struct list_head *head) 72 { 73 __list_add(new, head->prev, head); 74 } 75 76 /* 77 * Delete a list entry by making the prev/next entries 78 * point to each other. 79 * 80 * This is only for internal list manipulation where we know 81 * the prev/next entries already! 82 */ 83 static inline void __list_del(struct list_head *prev, struct list_head *next) 84 { 85 next->prev = prev; 86 prev->next = next; 87 } 88 89 /** 90 * list_del – deletes entry from list. 91 * @entry: the element to delete from the list. 92 * Note: list_empty on entry does not return true after this, the entry is in an undefined state. 93 */ 94 static inline void list_del(struct list_head *entry) 95 { 96 __list_del(entry->prev, entry->next); 97 entry->next = (void *) 0; 98 entry->prev = (void *) 0; 99 } 100 101 /** 102 * list_del_init – deletes entry from list and reinitialize it. 103 * @entry: the element to delete from the list. 104 */105 static inline void list_del_init(struct list_head *entry) 106 { 107 __list_del(entry->prev, entry->next); 108 INIT_LIST_HEAD(entry); 109 } 110 111 /** 112 * list_move – delete from one list and add as another’s head 113 * @list: the entry to move 114 * @head: the head that will precede our entry 115 */116 static inline void list_move(struct list_head *list, struct list_head *head) 117 { 118 __list_del(list->prev, list->next); 119 list_add(list, head); 120 } 121 122 /** 123 * list_move_tail – delete from one list and add as another’s tail 124 * @list: the entry to move 125 * @head: the head that will follow our entry 126 */127 static inline void list_move_tail(struct list_head *list, 128 struct list_head *head) 129 { 130 __list_del(list->prev, list->next); 131 list_add_tail(list, head); 132 } 133 134 /** 135 * list_empty – tests whether a list is empty 136 * @head: the list to test. 137 */138 static inline int list_empty(struct list_head *head) 139 { 140 return head->next == head; 141 } 142 143 static inline void __list_splice(struct list_head *list, 144 struct list_head *head) 145 { 146 struct list_head *first = list->next; 147 struct list_head *last = list->prev; 148 struct list_head *at = head->next; 149 150 first->prev = head; 151 head->next = first; 152 153 last->next = at; 154 at->prev = last; 155 } 156 157 /** 158 * list_splice – join two lists 159 * @list: the new list to add. 160 * @head: the place to add it in the first list. 161 */162 static inline void list_splice(struct list_head *list, struct list_head *head) 163 { 164 if (!list_empty(list)) 165 __list_splice(list, head); 166 } 167 168 /** 169 * list_splice_init – join two lists and reinitialise the emptied list. 170 * @list: the new list to add. 171 * @head: the place to add it in the first list. 172 * 173 * The list at @list is reinitialised 174 */175 static inline void list_splice_init(struct list_head *list, 176 struct list_head *head) 177 { 178 if (!list_empty(list)) { 179 __list_splice(list, head); 180 INIT_LIST_HEAD(list); 181 } 182 } 183 184 /** 185 * list_entry – get the struct for this entry 186 * @ptr: the &struct list_head pointer. 187 * @type: the type of the struct this is embedded in. 188 * @member: the name of the list_struct within the struct. 189 */190 #define list_entry(ptr, type, member) \191 ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member))) 192 193 /** 194 * list_for_each - iterate over a list 195 * @pos: the &struct list_head to use as a loop counter. 196 * @head: the head for your list. 197 */198 #define list_for_each(pos, head) \199 for (pos = (head)->next; pos != (head); \ 200 pos = pos->next) 201 /** 202 * list_for_each_prev - iterate over a list backwards 203 * @pos: the &struct list_head to use as a loop counter. 204 * @head: the head for your list. 205 */206 #define list_for_each_prev(pos, head) \207 for (pos = (head)->prev; pos != (head); \ 208 pos = pos->prev) 209 210 /** 211 * list_for_each_safe - iterate over a list safe against removal of list entry 212 * @pos: the &struct list_head to use as a loop counter. 213 * @n: another &struct list_head to use as temporary storage 214 * @head: the head for your list. 215 */216 #define list_for_each_safe(pos, n, head) \217 for (pos = (head)->next, n = pos->next; pos != (head);\ 218 pos = n, n = pos->next) 219 220 221 /** 222 * list_for_each_entry - iterate over list of given type 223 * @pos: the type * to use as a loop counter. 224 * @head: the head for your list. 225 * @member: the name of the list_struct within the struct. 226 */227 #define list_for_each_entry(pos, head, member) \228 for (pos = list_entry((head)->next,typeof(*pos), member); \ 229 &pos->member != (head); \ 230 pos = list_entry(pos->member.next, typeof(*pos), member)) 231 232 /** 233 * list_for_each_entry_safe – iterate over list of given type safe against removal of list entry 234 * @pos: the type * to use as a loop counter. 235 * @n: another type * to use as temporary storage 236 * @head: the head for your list. 237 * @member: the name of the list_struct within the struct. 238 */239 #define list_for_each_entry_safe(pos, n, head, member) \240 for (pos = list_entry((head)->next, typeof(*pos), member), \ 241 n = list_entry(pos->member.next, typeof(*pos), member); \ 242 &pos->member != (head); \ 243 pos = n, n = list_entry(n->member.next, typeof(*n), member)) 244 245 #endif
下面代码是给出的测试用例(也可以作为其函数的用法示例哦)
其可以从http://isis.poly.edu/kulesh/stuff/src/klist/test_list.c 下载
mylist.c
1 #include <stdio.h> 2 #include <stdlib.h> 3 4 #include "list.h" 5 6 7 struct kool_list{ 8 int to; 9 struct list_head list; 10 int from; 11 }; 12 13 int main(int argc, char **argv){ 14 15 struct kool_list *tmp; 16 struct list_head *pos, *q; 17 unsigned int i; 18 19 struct kool_list mylist; 20 INIT_LIST_HEAD(&mylist.list); 21 /* or you could have declared this with the following macro 22 * LIST_HEAD(mylist); which declares and initializes the list 23 */ 24 25 /* adding elements to mylist */ 26 for(i=5; i!=0; --i){ 27 tmp= (struct kool_list *)malloc(sizeof(struct kool_list)); 28 29 /* INIT_LIST_HEAD(&tmp->list); 30 * 31 * this initializes a dynamically allocated list_head. we 32 * you can omit this if subsequent call is add_list() or 33 * anything along that line because the next, prev 34 * fields get initialized in those functions. 35 */ 36 printf("enter to and from:"); 37 scanf("%d %d", &tmp->to, &tmp->from); 38 39 /* add the new item 'tmp' to the list of items in mylist */ 40 list_add(&(tmp->list), &(mylist.list)); 41 /* you can also use list_add_tail() which adds new items to 42 * the tail end of the list 43 */ 44 } 45 printf("\n"); 46 47 48 /* now you have a circularly linked list of items of type struct kool_list. 49 * now let us go through the items and print them out 50 */ 51 52 53 /* list_for_each() is a macro for a for loop. 54 * first parameter is used as the counter in for loop. in other words, inside the 55 * loop it points to the current item's list_head. 56 * second parameter is the pointer to the list. it is not manipulated by the macro. 57 */ 58 printf("traversing the list using list_for_each()\n"); 59 list_for_each(pos, &mylist.list){ 60 61 /* at this point: pos->next points to the next item's 'list' variable and 62 * pos->prev points to the previous item's 'list' variable. Here item is 63 * of type struct kool_list. But we need to access the item itself not the 64 * variable 'list' in the item! macro list_entry() does just that. See "How 65 * does this work?" below for an explanation of how this is done. 66 */ 67 tmp= list_entry(pos, struct kool_list, list); 68 69 /* given a pointer to struct list_head, type of data structure it is part of, 70 * and it's name (struct list_head's name in the data structure) it returns a 71 * pointer to the data structure in which the pointer is part of. 72 * For example, in the above line list_entry() will return a pointer to the 73 * struct kool_list item it is embedded in! 74 */ 75 76 printf("to= %d from= %d\n", tmp->to, tmp->from); 77 78 } 79 printf("\n"); 80 /* since this is a circularly linked list. you can traverse the list in reverse order 81 * as well. all you need to do is replace 'list_for_each' with 'list_for_each_prev' 82 * everything else remain the same! 83 * 84 * Also you can traverse the list using list_for_each_entry() to iterate over a given 85 * type of entries. For example: 86 */ 87 printf("traversing the list using list_for_each_entry()\n"); 88 list_for_each_entry(tmp, &mylist.list, list){ 89 printf("to= %d from= %d\n", tmp->to, tmp->from); 90 } 91 list_for_each_entry(tmp,&mylist.list,list){ 92 if(tmp->to == 2) 93 break; 94 } 95 printf("to = %d from %d\n",tmp->to,tmp->from); 96 printf("\n"); 97 98 99 /* now let's be good and free the kool_list items. since we will be removing items 100 * off the list using list_del() we need to use a safer version of the list_for_each() 101 * macro aptly named list_for_each_safe(). Note that you MUST use this macro if the loop 102 * involves deletions of items (or moving items from one list to another). 103 */104 printf("deleting the list using list_for_each_safe()\n"); 105 list_for_each_safe(pos, q, &mylist.list){ 106 tmp= list_entry(pos, struct kool_list, list); 107 printf("freeing item to= %d from= %d\n", tmp->to, tmp->from); 108 list_del(pos); 109 free(tmp); 110 } 111 112 return 0; 113 }
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