xref: /freebsd/lib/libc/stdlib/tsearch.c (revision ae83180158c4c937f170e31eff311b18c0286a93)
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$");
21 
22 #include <assert.h>
23 #define _SEARCH_PRIVATE
24 #include <search.h>
25 #include <stdlib.h>
26 
27 /* find or insert datum into search tree */
28 void *
29 tsearch(vkey, vrootp, compar)
30 	const void *vkey;		/* key to be located */
31 	void **vrootp;			/* address of tree root */
32 	int (*compar)(const void *, const void *);
33 {
34 	node_t *q;
35 	node_t **rootp = (node_t **)vrootp;
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 		/* LINTED const castaway ok */
55 		q->key = (void *)vkey;		/* initialize new node */
56 		q->llink = q->rlink = NULL;
57 	}
58 	return q;
59 }
60