tsearch.c revision 1.6 
1/*	$NetBSD: tsearch.c,v 1.6 2011/05/18 19:36:36 dsl 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 1.6 2011/05/18 19:36:36 dsl 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)(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
37	if (rootp == NULL)
38		return NULL;
39
40	while (*rootp != NULL) {	/* Knuth's T1: */
41		int r;
42
43		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
44			return *rootp;		/* we found it! */
45
46		rootp = (r < 0) ?
47		    &(*rootp)->llink :		/* T3: follow left branch */
48		    &(*rootp)->rlink;		/* T4: follow right branch */
49	}
50
51	q = malloc(sizeof(node_t));		/* T5: key not found */
52	if (q != 0) {				/* make new node */
53		*rootp = q;			/* link new node to old */
54		q->key = __UNCONST(vkey);	/* initialize new node */
55		q->llink = q->rlink = NULL;
56	}
57	return q;
58}
59