tsearch.c revision 1.3 
1/*	$NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 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 <sys/cdefs.h>
15#if defined(LIBC_SCCS) && !defined(lint)
16__RCSID("$NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem 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/* find or insert datum into search tree */
25void *
26tsearch(vkey, vrootp, compar)
27	const void *vkey;		/* key to be located */
28	void **vrootp;			/* address of tree root */
29	int (*compar) __P((const void *, const void *));
30{
31	node_t *q;
32	node_t **rootp = (node_t **)vrootp;
33
34	_DIAGASSERT(vkey != NULL);
35	_DIAGASSERT(compar != NULL);
36#ifdef _DIAGNOSTIC
37	if (vkey == NULL || compar == NULL)
38		return (NULL);
39#endif
40
41	if (rootp == NULL)
42		return NULL;
43
44	while (*rootp != NULL) {	/* Knuth's T1: */
45		int r;
46
47		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
48			return *rootp;		/* we found it! */
49
50		rootp = (r < 0) ?
51		    &(*rootp)->llink :		/* T3: follow left branch */
52		    &(*rootp)->rlink;		/* T4: follow right branch */
53	}
54
55	q = malloc(sizeof(node_t));		/* T5: key not found */
56	if (q != 0) {				/* make new node */
57		*rootp = q;			/* link new node to old */
58		/* LINTED const castaway ok */
59		q->key = (void *)vkey;		/* initialize new node */
60		q->llink = q->rlink = NULL;
61	}
62	return q;
63}
64