Mauerer app03.tex V1 - 09/04/2008 6:11pm Page 1210
Appendix C: Notes on C
List function implementation is based on acontainermechanism provided by the kernel to embed objects
in other objects. If structure A contains a substructure B, as in the following example, A is referred to as
the container of B:
struct A {
...
struct B {
} element;
...
} container;
When new elements are inserted in a list, the container property is not yet needed, as the following code
oflist_addshows:
<list.h>
/*
* Insert a new entry between two known consecutive entries.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
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);
}
Elements are also deleted in the classical textbook style:
<list.h>
#define LIST_POISON1 ((void *) 0x00100100)
#define LIST_POISON2 ((void *) 0x00200200)
/*
* Delete a list entry by making the prev/next entries
* point to each other.
*
* This is only for internal list manipulation where we know
