tdelete.c revision 92905 
1/*	$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $	*/
2/* $FreeBSD: head/lib/libc/stdlib/tdelete.c 92905 2002-03-21 22:49:10Z obrien $ */
3
4/*
5 * Tree search generalized from Knuth (6.2.2) Algorithm T just like
6 * the AT&T man page says.
7 *
8 * The node_t structure is for internal use only, lint doesn't grok it.
9 *
10 * Written by reading the System V Interface Definition, not the code.
11 *
12 * Totally public domain.
13 */
14
15#include <sys/cdefs.h>
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
20#include <assert.h>
21#define _SEARCH_PRIVATE
22#include <search.h>
23#include <stdlib.h>
24
25
26/* delete node with given key */
27void *
28tdelete(vkey, vrootp, compar)
29	const void *vkey;	/* key to be deleted */
30	void      **vrootp;	/* address of the root of tree */
31	int       (*compar)(const void *, const void *);
32{
33	node_t **rootp = (node_t **)vrootp;
34	node_t *p, *q, *r;
35	int  cmp;
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