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/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
/* NetworkManager -- Network link manager
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301 USA.
*
* (C) Copyright 2017 Red Hat, Inc.
*/
#include "c-list-util.h"
/*****************************************************************************/
/**
* c_list_relink:
* @lst: the head list entry
*
* Takes an invalid list, that has undefined prev pointers.
* Only the next pointers are valid, and the tail's next
* pointer points to %NULL instead of the head.
*
* c_list_relink() fixes the list by updating all prev pointers
* and close the circular linking by pointing the tails' next
* pointer to @lst.
*
* The use of this function is to do a bulk update, that lets the
* list degredate by not updating the prev pointers. At the end,
* the list can be fixed by c_list_relink().
*/
void
c_list_relink (CList *lst)
{
CList *ls, *ls_prev;
ls_prev = lst;
ls = lst->next;
do {
ls->prev = ls_prev;
ls_prev = ls;
ls = ls->next;
} while (ls);
ls_prev->next = lst;
lst->prev = ls_prev;
}
/*****************************************************************************/
static CList *
_c_list_sort (CList *ls,
CListSortCmp cmp,
const void *user_data)
{
CList *ls1, *ls2;
CList head;
if (!ls->next)
return ls;
/* split list in two halfs @ls1 and @ls2. */
ls1 = ls;
ls2 = ls;
ls = ls->next;
while (ls) {
ls = ls->next;
if (!ls)
break;
ls = ls->next;
ls2 = ls2->next;
}
ls = ls2;
ls2 = ls->next;
ls->next = NULL;
/* recurse */
ls1 = _c_list_sort (ls1, cmp, user_data);
if (!ls2)
return ls1;
ls2 = _c_list_sort (ls2, cmp, user_data);
/* merge */
ls = &head;
for (;;) {
/* while invoking the @cmp function, the list
* elements are not properly linked. Don't try to access
* their next/prev pointers. */
if (cmp (ls1, ls2, user_data) <= 0) {
ls->next = ls1;
ls = ls1;
ls1 = ls1->next;
if (!ls1)
break;
} else {
ls->next = ls2;
ls = ls2;
ls2 = ls2->next;
if (!ls2)
break;
}
}
ls->next = ls1 ?: ls2;
return head.next;
}
/**
* c_list_sort_headless:
* @lst: the list.
* @cmp: compare function for sorting. While comparing two
* CList elements, their next/prev pointers are in undefined
* state.
* @user_data: user data for @cmp.
*
* Sorts the list @lst according to @cmp. Contrary to
* c_list_sort(), @lst is not the list head but a
* valid entry as well. This function returns the new
* list head.
*/
CList *
c_list_sort_headless (CList *lst,
CListSortCmp cmp,
const void *user_data)
{
if (!c_list_is_empty (lst)) {
lst->prev->next = NULL;
lst = _c_list_sort (lst, cmp, user_data);
c_list_relink (lst);
}
return lst;
}
/**
* c_list_sort:
* @head: the list head.
* @cmp: compare function for sorting. While comparing two
* CList elements, their next/prev pointers are in undefined
* state.
* @user_data: user data for @cmp.
*
* Sorts the list @head according to @cmp.
*/
void
c_list_sort (CList *head,
CListSortCmp cmp,
const void *user_data)
{
if ( !c_list_is_empty (head)
&& head->next->next != head) {
head->prev->next = NULL;
head->next = _c_list_sort (head->next, cmp, user_data);
c_list_relink (head);
}
}
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