tdelete.c revision 92986 
1/*	$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 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 <sys/cdefs.h>
15#if 0
16#if defined(LIBC_SCCS) && !defined(lint)
17__RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $");
18#endif /* LIBC_SCCS and not lint */
19#endif
20__FBSDID("$FreeBSD: head/lib/libc/stdlib/tdelete.c 92986 2002-03-22 21:53:29Z obrien $");
21
22#include <assert.h>
23#define _SEARCH_PRIVATE
24#include <search.h>
25#include <stdlib.h>
26
27
28/* delete node with given key */
29void *
30tdelete(vkey, vrootp, compar)
31	const void *vkey;	/* key to be deleted */
32	void      **vrootp;	/* address of the root of tree */
33	int       (*compar)(const void *, const void *);
34{
35	node_t **rootp = (node_t **)vrootp;
36	node_t *p, *q, *r;
37	int  cmp;
38
39	if (rootp == NULL || (p = *rootp) == NULL)
40		return NULL;
41
42	while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
43		p = *rootp;
44		rootp = (cmp < 0) ?
45		    &(*rootp)->llink :		/* follow llink branch */
46		    &(*rootp)->rlink;		/* follow rlink branch */
47		if (*rootp == NULL)
48			return NULL;		/* key not found */
49	}
50	r = (*rootp)->rlink;			/* D1: */
51	if ((q = (*rootp)->llink) == NULL)	/* Left NULL? */
52		q = r;
53	else if (r != NULL) {			/* Right link is NULL? */
54		if (r->llink == NULL) {		/* D2: Find successor */
55			r->llink = q;
56			q = r;
57		} else {			/* D3: Find NULL link */
58			for (q = r->llink; q->llink != NULL; q = r->llink)
59				r = q;
60			r->llink = q->rlink;
61			q->llink = (*rootp)->llink;
62			q->rlink = (*rootp)->rlink;
63		}
64	}
65	free(*rootp);				/* D4: Free node */
66	*rootp = q;				/* link parent to new node */
67	return p;
68}
69