/*
 * Ouroboros - Copyright (C) 2016
 *
 * 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.
 *
 *    Sander Vrijders <sander.vrijders@intec.ugent.be>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#ifndef OUROBOROS_LIST_H
#define OUROBOROS_LIST_H

/*
 * This file is from the Linux Kernel (include/linux/list.h)
 * and modified by simply removing hardware prefetching of list items.
 * Here by copyright, credits attributed to wherever they belong.
 * Kulesh Shanmugasundaram (kulesh [squiggly] isis.poly.edu)
 */

struct list_head {
        struct list_head * next, * prev;
};

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

#define LIST_HEAD(name)                                 \
        struct list_head name = LIST_HEAD_INIT(name)

#define INIT_LIST_HEAD(ptr) do {                                \
                (ptr)->next = (ptr); (ptr)->prev = (ptr);       \
        } while (0)

/**
 * 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.
 */
void list_add(struct list_head * new,
              struct list_head * head);

/**
 * 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.
 */
void list_add_tail(struct list_head * new,
                   struct list_head * head);

/**
 * 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.
 */
void list_del(struct list_head * entry);

/**
 * list_del_init - deletes entry from list and reinitialize it.
 * @entry: the element to delete from the list.
 */
void list_del_init(struct 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
 */
void list_move(struct list_head * list,
               struct list_head * 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
 */
void list_move_tail(struct list_head * list,
                    struct list_head * head);

/**
 * list_empty - tests whether a list is empty
 * @head: the list to test.
 */
int list_empty(struct list_head * head);

/**
 * list_splice - join two lists
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
void list_splice(struct list_head * list,
                 struct list_head * 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
 */
void list_splice_init(struct list_head * list,
                      struct list_head * head);

/**
 * 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)                                   \
        ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

/**
 * list_first_entry - get the struct for the first entry
 * expects the list to be non-empty
 * @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_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 counter.
 * @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 counter.
 * @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 counter.
 * @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)

#endif
