1 /*
2 * Tree search generalized from Knuth (6.2.2) Algorithm T just like
3 * the AT&T man page says.
4 *
5 * The node_t structure is for internal use only, lint doesn't grok it.
6 *
7 * Written by reading the System V Interface Definition, not the code.
8 *
9 * Totally public domain.
10 *
11 * $NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $
12 * $FreeBSD: src/lib/libc/stdlib/tsearch.c,v 1.4 2003/01/05 02:43:18 tjr Exp $
13 */
14
15 #define _SEARCH_PRIVATE
16 #include <search.h>
17 #include <stdlib.h>
18
19 /*
20 * find or insert datum into search tree
21 *
22 * Parameters:
23 * vkey: key to be located
24 * vrootp: address of tree root
25 */
26
27 void *
tsearch(const void * vkey,void ** vrootp,int (* compar)(const void *,const void *))28 tsearch(const void *vkey, void **vrootp,
29 int (*compar)(const void *, const void *))
30 {
31 node_t *q;
32 node_t **rootp = (node_t **)vrootp;
33
34 if (rootp == NULL)
35 return NULL;
36
37 while (*rootp != NULL) { /* Knuth's T1: */
38 int r;
39
40 if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */
41 return *rootp; /* we found it! */
42
43 rootp = (r < 0) ?
44 &(*rootp)->llink : /* T3: follow left branch */
45 &(*rootp)->rlink; /* T4: follow right branch */
46 }
47
48 q = malloc(sizeof(node_t)); /* T5: key not found */
49 if (q != NULL) { /* make new node */
50 *rootp = q; /* link new node to old */
51 /* LINTED const castaway ok */
52 q->key = __DECONST(void *, vkey); /* initialize new node */
53 q->llink = q->rlink = NULL;
54 }
55 return q;
56 }
57