tsearch.c revision 108694 
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 0
16#if defined(LIBC_SCCS) && !defined(lint)
17__RCSID("$NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $");
18#endif /* LIBC_SCCS and not lint */
19#endif
20__FBSDID("$FreeBSD: head/lib/libc/stdlib/tsearch.c 108694 2003-01-05 02:43:18Z tjr $");
21
22#define _SEARCH_PRIVATE
23#include <search.h>
24#include <stdlib.h>
25
26/* find or insert datum into search tree */
27void *
28tsearch(vkey, vrootp, compar)
29	const void *vkey;		/* key to be located */
30	void **vrootp;			/* address of tree root */
31	int (*compar)(const void *, const void *);
32{
33	node_t *q;
34	node_t **rootp = (node_t **)vrootp;
35
36	if (rootp == NULL)
37		return NULL;
38
39	while (*rootp != NULL) {	/* Knuth's T1: */
40		int r;
41
42		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
43			return *rootp;		/* we found it! */
44
45		rootp = (r < 0) ?
46		    &(*rootp)->llink :		/* T3: follow left branch */
47		    &(*rootp)->rlink;		/* T4: follow right branch */
48	}
49
50	q = malloc(sizeof(node_t));		/* T5: key not found */
51	if (q != 0) {				/* make new node */
52		*rootp = q;			/* link new node to old */
53		/* LINTED const castaway ok */
54		q->key = (void *)vkey;		/* initialize new node */
55		q->llink = q->rlink = NULL;
56	}
57	return q;
58}
59