1/*	$NetBSD: tsearch.c,v 1.7 2012/06/25 22:32:45 abs 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: tsearch.c,v 1.7 2012/06/25 22:32:45 abs Exp $");
18#endif /* LIBC_SCCS and not lint */
19#endif
20__FBSDID("$FreeBSD$");
21
22#define _SEARCH_PRIVATE
23#include <search.h>
24#include <stdlib.h>
25
26/* find or insert datum into search tree */
27void *
28tsearch(const void *vkey, void **vrootp,
29    int (*compar)(const void *, const void *))
30{
31	node_t *q;
32	node_t **rootp = (node_t **)vrootp;
33
34	if (rootp == NULL)
35		return NULL;
36
37	while (*rootp != NULL) {	/* Knuth's T1: */
38		int r;
39
40		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
41			return *rootp;		/* we found it! */
42
43		rootp = (r < 0) ?
44		    &(*rootp)->llink :		/* T3: follow left branch */
45		    &(*rootp)->rlink;		/* T4: follow right branch */
46	}
47
48	q = malloc(sizeof(node_t));		/* T5: key not found */
49	if (q != 0) {				/* make new node */
50		*rootp = q;			/* link new node to old */
51		q->key = __DECONST(void *, vkey);/* initialize new node */
52		q->llink = q->rlink = NULL;
53	}
54	return q;
55}
56