tsearch.c revision 62321 
1/*	$NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $	*/
2/* $FreeBSD: head/lib/libc/stdlib/tsearch.c 62321 2000-07-01 06:55:11Z alfred $ */
3
4/*
5 * Tree search generalized from Knuth (6.2.2) Algorithm T just like
6 * the AT&T man page says.
7 *
8 * The node_t structure is for internal use only, lint doesn't grok it.
9 *
10 * Written by reading the System V Interface Definition, not the code.
11 *
12 * Totally public domain.
13 */
14
15#include <sys/cdefs.h>
16#if defined(LIBC_SCCS) && !defined(lint)
17__RCSID("$NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $");
18#endif /* LIBC_SCCS and not lint */
19
20#include <assert.h>
21#define _SEARCH_PRIVATE
22#include <search.h>
23#include <stdlib.h>
24
25/* find or insert datum into search tree */
26void *
27tsearch(vkey, vrootp, compar)
28	const void *vkey;		/* key to be located */
29	void **vrootp;			/* address of tree root */
30	int (*compar) __P((const void *, const void *));
31{
32	node_t *q;
33	node_t **rootp = (node_t **)vrootp;
34
35	if (rootp == NULL)
36		return NULL;
37
38	while (*rootp != NULL) {	/* Knuth's T1: */
39		int r;
40
41		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
42			return *rootp;		/* we found it! */
43
44		rootp = (r < 0) ?
45		    &(*rootp)->llink :		/* T3: follow left branch */
46		    &(*rootp)->rlink;		/* T4: follow right branch */
47	}
48
49	q = malloc(sizeof(node_t));		/* T5: key not found */
50	if (q != 0) {				/* make new node */
51		*rootp = q;			/* link new node to old */
52		/* LINTED const castaway ok */
53		q->key = (void *)vkey;		/* initialize new node */
54		q->llink = q->rlink = NULL;
55	}
56	return q;
57}
58