1/*	$NetBSD: tdelete.c,v 1.3 1999/09/20 04:39:43 lukem 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 <assert.h>
15#define _SEARCH_PRIVATE
16#include <search.h>
17#include <stdlib.h>
18
19#define _DIAGASSERT assert
20
21
22
23/* delete node with given key */
24void *
25tdelete(const void *vkey,	/* key to be deleted */
26	void      **vrootp,	/* address of the root of tree */
27	int       (*compar)(const void *, const void *))
28{
29	node_t **rootp = (node_t **)vrootp;
30	node_t *p, *q, *r;
31	int  cmp;
32
33	_DIAGASSERT((uintptr_t)compar != (uintptr_t)NULL);
34
35	if (rootp == NULL || (p = *rootp) == NULL)
36		return NULL;
37
38	while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
39		p = *rootp;
40		rootp = (cmp < 0) ?
41		    &(*rootp)->llink :		/* follow llink branch */
42		    &(*rootp)->rlink;		/* follow rlink branch */
43		if (*rootp == NULL)
44			return NULL;		/* key not found */
45	}
46	r = (*rootp)->rlink;			/* D1: */
47	if ((q = (*rootp)->llink) == NULL)	/* Left NULL? */
48		q = r;
49	else if (r != NULL) {			/* Right link is NULL? */
50		if (r->llink == NULL) {		/* D2: Find successor */
51			r->llink = q;
52			q = r;
53		} else {			/* D3: Find NULL link */
54			for (q = r->llink; q->llink != NULL; q = r->llink)
55				r = q;
56			r->llink = q->rlink;
57			q->llink = (*rootp)->llink;
58			q->rlink = (*rootp)->rlink;
59		}
60	}
61	free(*rootp);				/* D4: Free node */
62	*rootp = q;				/* link parent to new node */
63	return p;
64}