fs/jffs2/mergesort.c

   1 // SPDX-License-Identifier: MIT
   2 /*
   3  * This file is copyright 2001 Simon Tatham.
   4  * Rewritten from original source 2006 by Dan Merillat for use in u-boot.
   5  *
   6  * Original code can be found at:
   7  * http://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html
   8  */
   9
  10 #include <common.h>
  11 #include "jffs2_private.h"
  12
  13 int sort_list(struct b_list *list)
  14 {
  15         struct b_node *p, *q, *e, **tail;
  16         int k, psize, qsize;
  17
  18         if (!list->listHead)
  19                 return 0;
  20
  21         for (k = 1; k < list->listCount; k *= 2) {
  22                 tail = &list->listHead;
  23                 for (p = q = list->listHead; p; p = q) {
  24                         /* step 'k' places from p; */
  25                         for (psize = 0; q && psize < k; psize++)
  26                                 q = q->next;
  27                         qsize = k;
  28
  29                         /* two lists, merge them. */
  30                         while (psize || (qsize && q)) {
  31                                 /* merge the next element */
  32                                 if (psize == 0 ||
  33                                     ((qsize && q) &&
  34                                      list->listCompare(p, q))) {
  35                                         /* p is empty, or p > q, so q next */
  36                                         e = q;
  37                                         q = q->next;
  38                                         qsize--;
  39                                 } else {
  40                                         e = p;
  41                                         p = p->next;
  42                                         psize--;
  43                                 }
  44                                 e->next = NULL; /* break accidental loops. */
  45                                 *tail = e;
  46                                 tail = &e->next;
  47                         }
  48                 }
  49         }
  50         return 0;
  51 }