#ifndef __LIST_H__
#define __LIST_H__

typedef struct _list list_t;

struct _list
{
    list_t *next, *prev;
};

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

#define LIST_HEAD(name) \
    list_t name = LIST_HEAD_INIT(name)

static inline void INIT_LIST_HEAD(list_t *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!
 */
static inline void __list_add(list_t *lnew, list_t *prev, list_t *next)
{
    next->prev = lnew;
    lnew->next = next;
    lnew->prev = prev;
    prev->next = lnew;
}

/**
 * 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(list_t *lnew, list_t *head)
{
    __list_add(lnew, 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(list_t *lnew, list_t *head)
{
    __list_add(lnew, 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 inline void __list_del(list_t * prev, list_t * 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.
 */
static inline void __list_del_entry(list_t *entry)
{
    __list_del(entry->prev, entry->next);
}

static inline void list_del(list_t *entry)
{
    __list_del(entry->prev, entry->next);
    entry->next = NULL;
    entry->prev = NULL;
}

/**
 * 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 inline void list_replace(list_t *old, list_t *lnew)
{
    lnew->next = old->next;
    lnew->next->prev = lnew;
    lnew->prev = old->prev;
    lnew->prev->next = lnew;
}

static inline void list_replace_init(list_t *old, list_t *lnew)
{
    list_replace(old, lnew);
    INIT_LIST_HEAD(old);
}

/**
 * list_del_init - deletes entry from list and reinitialize it.
 * @entry: the element to delete from the list.
 */
static inline void list_del_init(list_t *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 inline void list_move(list_t *list, list_t *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 inline void list_move_tail(list_t *list, list_t *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 inline int list_is_last(const list_t *list, const list_t *head)
{
    return list->next == head;
}

/**
 * list_empty - tests whether a list is empty
 * @head: the list to test.
 */
static inline int list_empty(const list_t *head)
{
    return head->next == head;
}

#define container_of(ptr, type, member) ({                      \
        const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
        (type *)( (char *)__mptr - offsetof(type,member) );})



/**
 * 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_head 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_head 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_last_entry - get the last 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_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_last_entry(ptr, type, member) \
	list_entry((ptr)->prev, type, member)

/**
 * list_first_entry_or_null - 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_head within the struct.
 *
 * Note that if the list is empty, it returns NULL.
 */
#define list_first_entry_or_null(ptr, type, member) \
	(!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)

/**
 * list_next_entry - get the next element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define list_next_entry(pos, member) \
	list_entry((pos)->member.next, typeof(*(pos)), member)

/**
 * list_prev_entry - get the prev element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define list_prev_entry(pos, member) \
	list_entry((pos)->member.prev, typeof(*(pos)), 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; 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; 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; \
         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_head within the struct.
 */
#define list_for_each_entry(pos, head, member)              \
	for (pos = list_first_entry(head, typeof(*pos), member);	\
         &pos->member != (head);    \
	     pos = list_next_entry(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_head within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member)          \
	for (pos = list_last_entry(head, typeof(*pos), member);		\
         &pos->member != (head);    \
	     pos = list_prev_entry(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_head 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_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_head within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)          \
    for (pos = list_first_entry(head, typeof(*pos), member),    \
        n = list_next_entry(pos, member);                       \
         &pos->member != (head);                                \
         pos = n, n = list_next_entry(n, member))


#endif