mirror of
https://github.com/freebsd/freebsd-src.git
synced 2026-11-07 04:36:52 -10:00
Konstantin Belousov
b8c99e7d91
The function clears the whole tree. Relnotes: yes Reviewed by: alc, emaste Discussed with: dougm Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D54365
69 lines
1.5 KiB
C
69 lines
1.5 KiB
C
/*
|
|
* Copyright 2025 The FreeBSD Foundation
|
|
*
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
*
|
|
* This software was developed by Konstantin Belousov <[email protected]>
|
|
* under sponsorship from the FreeBSD Foundation.
|
|
*/
|
|
|
|
#define _SEARCH_PRIVATE
|
|
#include <search.h>
|
|
#include <stdlib.h>
|
|
|
|
static void
|
|
nul_node_free(void *node __unused)
|
|
{
|
|
}
|
|
|
|
/* Find the leftmost node. */
|
|
static posix_tnode *
|
|
tdestroy_find_leftmost(posix_tnode *tn)
|
|
{
|
|
while (tn->llink != NULL)
|
|
tn = tn->llink;
|
|
return (tn);
|
|
}
|
|
|
|
/*
|
|
* This algorithm for non-recursive non-allocating destruction of the tree
|
|
* is described in
|
|
* https://codegolf.stackexchange.com/questions/478/free-a-binary-tree/489#489P
|
|
* and in https://devblogs.microsoft.com/oldnewthing/20251107-00/?p=111774.
|
|
*/
|
|
void
|
|
tdestroy(void *rootp, void (*node_free)(void *))
|
|
{
|
|
posix_tnode *tn, *tn_leftmost, *xtn;
|
|
|
|
tn = rootp;
|
|
if (tn == NULL)
|
|
return;
|
|
if (node_free == NULL)
|
|
node_free = nul_node_free;
|
|
tn_leftmost = tn;
|
|
|
|
while (tn != NULL) {
|
|
/*
|
|
* Make the right subtree the left subtree of the
|
|
* leftmost node, and recalculate the leftmost.
|
|
*/
|
|
tn_leftmost = tdestroy_find_leftmost(tn_leftmost);
|
|
if (tn->rlink != NULL) {
|
|
tn_leftmost->llink = tn->rlink;
|
|
tn_leftmost = tn_leftmost->llink;
|
|
}
|
|
|
|
/*
|
|
* At this point, all children of tn have been
|
|
* arranged to be reachable via tn->left. We can
|
|
* safely delete the current node and advance to its
|
|
* left child as the new root.
|
|
*/
|
|
xtn = tn->llink;
|
|
node_free(tn->key);
|
|
free(tn);
|
|
tn = xtn;
|
|
}
|
|
}
|