tsearch.c revision 1.1 
1/*	$NetBSD: tsearch.c,v 1.1 1999/02/22 10:33:16 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: tsearch.c,v 1.1 1999/02/22 10:33:16 christos Exp $");
17#endif /* LIBC_SCCS and not lint */
18
19#define _SEARCH_PRIVATE
20#include <search.h>
21#include <stdlib.h>
22
23/* find or insert datum into search tree */
24void *
25tsearch(vkey, vrootp, compar)
26	const void *vkey;		/* key to be located */
27	void **vrootp;			/* address of tree root */
28	int (*compar) __P((const void *, const void *));
29{
30	node_t *q;
31	node_t **rootp = (node_t **)vrootp;
32
33	if (rootp == NULL)
34		return NULL;
35
36	while (*rootp != NULL) {	/* Knuth's T1: */
37		int r;
38
39		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
40			return *rootp;		/* we found it! */
41
42		rootp = (r < 0) ?
43		    &(*rootp)->llink :		/* T3: follow left branch */
44		    &(*rootp)->rlink;		/* T4: follow right branch */
45	}
46
47	q = malloc(sizeof(node_t));		/* T5: key not found */
48	if (q != 0) {				/* make new node */
49		*rootp = q;			/* link new node to old */
50		q->key = (void *)vkey;		/* initialize new node */
51		q->llink = q->rlink = NULL;
52	}
53	return q;
54}
55