diff options
| author | Konstantin Belousov <kib@FreeBSD.org> | 2025-12-25 23:38:25 +0000 |
|---|---|---|
| committer | Konstantin Belousov <kib@FreeBSD.org> | 2025-12-29 17:18:55 +0000 |
| commit | b8c99e7d912f0dad84cec80f8c4331646b87a3ec (patch) | |
| tree | e74d6f2b4bbec0e489a81f4e13fe154b4d184a94 | |
| parent | 04a664d87607d25d87baf56903090707cc91e2e0 (diff) | |
libc: add glibc-compatible tdestroy(3)
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
| -rw-r--r-- | include/search.h | 1 | ||||
| -rw-r--r-- | lib/libc/stdlib/Makefile.inc | 1 | ||||
| -rw-r--r-- | lib/libc/stdlib/Symbol.map | 1 | ||||
| -rw-r--r-- | lib/libc/stdlib/tdestroy.c | 68 |
4 files changed, 71 insertions, 0 deletions
diff --git a/include/search.h b/include/search.h index 0615da2b42ba..5ac25a0d491f 100644 --- a/include/search.h +++ b/include/search.h @@ -77,6 +77,7 @@ void twalk(const posix_tnode *, void (*)(const posix_tnode *, VISIT, int)); int hcreate_r(size_t, struct hsearch_data *); void hdestroy_r(struct hsearch_data *); int hsearch_r(ENTRY, ACTION, ENTRY **, struct hsearch_data *); +void tdestroy(void *, void (*)(void *)); #endif __END_DECLS diff --git a/lib/libc/stdlib/Makefile.inc b/lib/libc/stdlib/Makefile.inc index 37a927b0597b..e46a8d7340b2 100644 --- a/lib/libc/stdlib/Makefile.inc +++ b/lib/libc/stdlib/Makefile.inc @@ -67,6 +67,7 @@ MISRCS+= \ strtouq.c \ system.c \ tdelete.c \ + tdestroy.c \ tfind.c \ tsearch.c \ twalk.c diff --git a/lib/libc/stdlib/Symbol.map b/lib/libc/stdlib/Symbol.map index 8b7e97c3cbdc..03a6d0b543ac 100644 --- a/lib/libc/stdlib/Symbol.map +++ b/lib/libc/stdlib/Symbol.map @@ -134,6 +134,7 @@ FBSD_1.8 { FBSD_1.9 { memalignment; recallocarray; + tdestroy; }; FBSDprivate_1.0 { diff --git a/lib/libc/stdlib/tdestroy.c b/lib/libc/stdlib/tdestroy.c new file mode 100644 index 000000000000..c324e151da11 --- /dev/null +++ b/lib/libc/stdlib/tdestroy.c @@ -0,0 +1,68 @@ +/* + * Copyright 2025 The FreeBSD Foundation + * + * SPDX-License-Identifier: BSD-2-Clause + * + * This software was developed by Konstantin Belousov <kib@FreeBSD.org> + * 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; + } +} |