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}