tdelete.c revision 101882 
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 101882 2002-08-14 21:16:41Z robert $");
21
22#include <assert.h>
23#define _SEARCH_PRIVATE
24#include <search.h>
25#include <stdlib.h>
26
27
28/*
29 * delete node with given key
30 *
31 * vkey:   key to be deleted
32 * vrootp: address of the root of the tree
33 * compar: function to carry out node comparisons
34 */
35void *
36tdelete(const void *__restrict vkey, void **__restrict vrootp,
37    int (*compar)(const void *, const void *))
38{
39	node_t **rootp = (node_t **)vrootp;
40	node_t *p, *q, *r;
41	int cmp;
42
43	if (rootp == NULL || (p = *rootp) == NULL)
44		return NULL;
45
46	while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
47		p = *rootp;
48		rootp = (cmp < 0) ?
49		    &(*rootp)->llink :		/* follow llink branch */
50		    &(*rootp)->rlink;		/* follow rlink branch */
51		if (*rootp == NULL)
52			return NULL;		/* key not found */
53	}
54	r = (*rootp)->rlink;			/* D1: */
55	if ((q = (*rootp)->llink) == NULL)	/* Left NULL? */
56		q = r;
57	else if (r != NULL) {			/* Right link is NULL? */
58		if (r->llink == NULL) {		/* D2: Find successor */
59			r->llink = q;
60			q = r;
61		} else {			/* D3: Find NULL link */
62			for (q = r->llink; q->llink != NULL; q = r->llink)
63				r = q;
64			r->llink = q->rlink;
65			q->llink = (*rootp)->llink;
66			q->rlink = (*rootp)->rlink;
67		}
68	}
69	free(*rootp);				/* D4: Free node */
70	*rootp = q;				/* link parent to new node */
71	return p;
72}
73