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/*
* Circular doubly linked list implementation.
*
* Copyright (c) 2010 Marko Kreen, Skype Technologies OÜ
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <usual/list.h>
/* merge 2 ordered arrays into one */
static struct List *merge(list_cmp_f cmp_func, struct List *p, struct List *q)
{
struct List res[1], *tail = res, *e;
while (p && q) {
if (cmp_func(p, q) <= 0) {
e = p;
p = p->next;
} else {
e = q;
q = q->next;
}
tail->next = e;
tail = e;
}
tail->next = p ? p : q;
return res->next;
}
/*
* non-recursive merge sort
*
* uses singly-linked NULL-terminated arrays internally.
*/
void list_sort(struct List *list, list_cmp_f cmp_func)
{
int i, top = 0;
struct List *p;
struct List *stack[64];
if (list_empty(list))
return;
/* merge small sorted fragments into larger ones */
while (list->next != list) {
p = list->next;
list->next = p->next;
p->next = NULL;
for (i = 0; (i < top) && stack[i]; i++) {
p = merge(cmp_func, stack[i], p);
stack[i] = NULL;
}
stack[i] = p;
if (i == top)
top++;
}
/* merge remaining fragments */
for (p = NULL, i = 0; i < top; i++)
p = merge(cmp_func, stack[i], p);
/* restore proper List */
list->next = p;
for (p = list; p->next; p = p->next)
p->next->prev = p;
list->prev = p;
p->next = list;
}
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