Example of Linux kernel chain list (ii)

Linked list Use

I think the best way to get familiar with the kernel list is to look at a few simple examples, which is a very good material to better understand the list.

Here is an example that contains creating, adding, deleting, and traversing linked lists.

<span style= "FONT-SIZE:14PX;" ><span style= "color: #330099;" > #include <stdio.h> #include <stdlib.h> #include "list.h" struct kool_list{int to;struct list_head list; int from;};/ /Custom to link the data amount structure and contain the doubly linked list structure int main (int argc, char **argv) {struct kool_list *tmp;struct list_head *pos, *q;unsigned int i;str UCT kool_list Mylist;init_list_head (&mylist.list);//Initialize a list header/* to <span style= "font-family:arial, Helvetica, Sans-serif; " Add elements in >mylist </span><span style= "font-family:arial, Helvetica, Sans-serif;" > */</span>for (i=5; i!=0; i.) {tmp= (struct kool_list *) malloc (sizeof (struct kool_list));/* Init_list_head (  &tmp->list); * * This Initializes a dynamically allocated List_head.  We * can omit this if subsequent call was Add_list () or * anything along that line because the next, prev * Fields get Initialized in those functions. */printf ("Enter to and from:"), scanf ("%d%d", &tmp->to, &tmp->from);/* Add the new item ' TMP ' to the list OF Items in MyList */list_add (& (Tmp->list), & (Mylist.list));//Add new element node in the necklace table, TMP list/* You can also use List_ Add_tail () which adds new items to * the tail end of the list */}printf ("\ n");/* Now you have a circularly linked list of Items of type struct kool_list.  * Now let us go through the items and print them out *//* List_for_each () are a macro for a for loop. * First parameter is used as the counter on for loop. In other words, inside the * loop it points to the current item ' s list_head. * Second parameter is the pointer to the list. It is not a manipulated by the macro. */printf ("Traversing the list using List_for_each () \ n"); List_for_each (POS, &mylist.list) {//Traverse linked list, pos points to the element of the linked list in turn/* At this point:pos->next points to the next item ' s ' list ' variable and * pos->prev points to the previous item ' s ' L Ist ' variable. Here item is * of type struct kool_list. But we need to access the item itself not the * variable ' list ' in the item! Macro List_entry () does just that. SeeHow does * Does this work? "below for a explanation of how that is done. */tmp= List_entry (pos, struct kool_list, list);//Get data structure containing POS nodes <span style= "font-family:arial, Helvetica, Sans-serif; " >struct kool_list Pointer </span>/* Given a pointer to struct list_head, type of data structure it was part of, * and I T ' s name (struct List_head ' s name in the data structure) it returns a * pointer to the data structure in which the Pointe  R is part of.  * For example, on the above line List_entry () would return a pointer to the * struct Kool_list item It's embedded in! */printf ("to=%d from=%d\n", Tmp->to, Tmp->from);} printf ("\ n");/* Since this is a circularly linked list. You can traverse the list in reverse order * as well. All your need to do are replace ' list_for_each ' with ' list_for_each_prev ' * Everything else remain the same! * * Also You can traverse the list using List_for_each_entry () to iterate over a given * type of entries. For example: */printf ("Traversing the list usinG list_for_each_entry () \ n "); List_for_each_entry (TMP, &mylist.list, list) printf (" To=%d from=%d\n ", Tmp->to, Tmp->from);p rintf ("\ n");/* Now let's be good and free the kool_list items. Since we'll be removing items * off the list using List_del () We need to use a safer version of the List_for_each () * m Acro aptly named List_for_each_safe (). Note that you must use this macro if the loop * involves deletions of items (or moving items from one list to another). */printf ("Deleting the list using List_for_each_safe () \ n"); List_for_each_safe (POS, Q, &mylist.list) {tmp= list_ Entry (POS, struct kool_list, list); printf ("Freeing item to=%d from=%d\n", Tmp->to, Tmp->from); List_del (POS); Free (TMP);} return 0;} </span></span>

a few common API implementations of the kernel list are described in the example Linux kernel chain list (iii).

Example of Linux kernel chain list (ii)