1 /* $NetBSD: tdelete.c,v 1.8 2016/01/20 20:47:41 christos 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 defined(LIBC_SCCS) && !defined(lint)
16 __RCSID("$NetBSD: tdelete.c,v 1.8 2016/01/20 20:47:41 christos Exp $");
17 #endif /* LIBC_SCCS and not lint */
18
19 #include <assert.h>
20 #define _SEARCH_PRIVATE
21 #include <search.h>
22 #include <stdlib.h>
23
24
25 /* find a node with key "vkey" in tree "vrootp" */
26 void *
tdelete(const void * vkey,void ** vrootp,int (* compar)(const void *,const void *))27 tdelete(const void *vkey, void **vrootp,
28 int (*compar)(const void *, const void *))
29 {
30 node_t **rootp = (node_t **)vrootp;
31 node_t *p, *q, *r;
32 int cmp;
33
34 _DIAGASSERT(vkey != NULL);
35 _DIAGASSERT(compar != NULL);
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