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/* GNU Mailutils -- a suite of utilities for electronic mail
Copyright (C) 2011-2025 Free Software Foundation, Inc.
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 3 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, see
<http://www.gnu.org/licenses/>. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <mailutils/errno.h>
#include <mailutils/sys/list.h>
static void
_list_append_entry (struct _mu_list *list, struct list_data *ent)
{
ent->prev = list->head.prev;
ent->next = &list->head;
list->head.prev->next = ent;
list->head.prev = ent;
list->count++;
}
static void
_list_qsort (mu_list_t list, int cmp (const void *, const void *, void *),
void *data)
{
struct list_data *cur, *middle;
struct _mu_list high_list, low_list;
size_t n;
if (list->count < 2)
return;
if (list->count == 2)
{
if (cmp (list->head.prev->item, list->head.next->item, data) < 0)
{
cur = list->head.prev;
list->head.prev = list->head.next;
list->head.next = cur;
list->head.next->prev = &list->head;
list->head.next->next = list->head.prev;
list->head.prev->next = &list->head;
list->head.prev->prev = list->head.next;
}
return;
}
middle = list->head.next;
for (n = list->count / 2; n > 0; n--)
middle = middle->next;
/* Split into two sublists */
_mu_list_init (&high_list);
_mu_list_init (&low_list);
for (cur = list->head.next; cur != &list->head; )
{
struct list_data *next = cur->next;
cur->next = NULL;
if (cur != middle)
{
if (cmp (middle->item, cur->item, data) < 0)
_list_append_entry (&high_list, cur);
else
_list_append_entry (&low_list, cur);
}
cur = next;
}
/* Sort both sublists recursively */
_list_qsort (&low_list, cmp, data);
_list_qsort (&high_list, cmp, data);
/* Join low_list + middle + high_list */
if (low_list.head.prev == _mu_list_null (&low_list))
cur = &low_list.head;
else
cur = low_list.head.prev;
cur->next = middle;
middle->prev = cur;
middle->next = &low_list.head;
low_list.head.prev = middle;
cur = middle;
if (high_list.head.next != _mu_list_null (&high_list))
{
cur->next = high_list.head.next;
high_list.head.next->prev = cur;
low_list.head.prev = high_list.head.prev;
low_list.head.prev->next = &low_list.head;
low_list.count += high_list.count;
}
/* Return the resulting list */
list->head.next = low_list.head.next;
list->head.next->prev = _mu_list_null (list);
list->head.prev = low_list.head.prev;
list->head.prev->next = _mu_list_null (list);
}
void
mu_list_sort_r (mu_list_t list,
int (*comp) (const void *, const void *, void *), void *data)
{
if (list)
_list_qsort (list, comp, data);
}
static int
callcomp (const void *a, const void *b, void *data)
{
mu_list_comparator_t comp = data;
return comp (a, b);
}
void
mu_list_sort (mu_list_t list, mu_list_comparator_t comp)
{
if (list)
_list_qsort (list, callcomp, comp ? comp : list->comp);
}
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