1/*	$NetBSD: tdelete.c,v 1.8 2016/01/20 20:47:41 christos Exp $	*/
2
3/*
4 * Tree search generalized from Knuth (6.2.2) Algorithm T just like
5 * the AT&T man page says.
6 *
7 * The node_t structure is for internal use only, lint doesn't grok it.
8 *
9 * Written by reading the System V Interface Definition, not the code.
10 *
11 * Totally public domain.
12 */
13
14#include <sys/cdefs.h>
15#if defined(LIBC_SCCS) && !defined(lint)
16__RCSID("$NetBSD: tdelete.c,v 1.8 2016/01/20 20:47:41 christos Exp $");
17#endif /* LIBC_SCCS and not lint */
18
19#include <assert.h>
20#define _SEARCH_PRIVATE
21#include <search.h>
22#include <stdlib.h>
23
24
25/* find a node with key "vkey" in tree "vrootp" */
26void *
27tdelete(const void *vkey, void **vrootp,
28    int (*compar)(const void *, const void *))
29{
30	node_t **rootp = (node_t **)vrootp;
31	node_t *p, *q, *r;
32	int  cmp;
33
34	_DIAGASSERT(vkey != NULL);
35	_DIAGASSERT(compar != NULL);
36
37	if (rootp == NULL || (p = *rootp) == NULL)
38		return NULL;
39
40	while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
41		p = *rootp;
42		rootp = (cmp < 0) ?
43		    &(*rootp)->llink :		/* follow llink branch */
44		    &(*rootp)->rlink;		/* follow rlink branch */
45		if (*rootp == NULL)
46			return NULL;		/* key not found */
47	}
48	r = (*rootp)->rlink;			/* D1: */
49	if ((q = (*rootp)->llink) == NULL)	/* Left NULL? */
50		q = r;
51	else if (r != NULL) {			/* Right link is NULL? */
52		if (r->llink == NULL) {		/* D2: Find successor */
53			r->llink = q;
54			q = r;
55		} else {			/* D3: Find NULL link */
56			for (q = r->llink; q->llink != NULL; q = r->llink)
57				r = q;
58			r->llink = q->rlink;
59			q->llink = (*rootp)->llink;
60			q->rlink = (*rootp)->rlink;
61		}
62	}
63	free(*rootp);				/* D4: Free node */
64	*rootp = q;				/* link parent to new node */
65	return p;
66}
67