126236Swpaul/*	$NetBSD: tsearch.c,v 1.6 2011/05/18 19:36:36 dsl Exp $	*/
226236Swpaul
326236Swpaul/*
426236Swpaul * Tree search generalized from Knuth (6.2.2) Algorithm T just like
526236Swpaul * the AT&T man page says.
626236Swpaul *
726236Swpaul * The node_t structure is for internal use only, lint doesn't grok it.
826236Swpaul *
926236Swpaul * Written by reading the System V Interface Definition, not the code.
1026236Swpaul *
1150479Speter * Totally public domain.
1226236Swpaul */
1326236Swpaul
1426236Swpaul#include <sys/cdefs.h>
1526236Swpaul#if defined(LIBC_SCCS) && !defined(lint)
1626236Swpaul__RCSID("$NetBSD: tsearch.c,v 1.6 2011/05/18 19:36:36 dsl Exp $");
1726236Swpaul#endif /* LIBC_SCCS and not lint */
1826236Swpaul
1926236Swpaul#include <assert.h>
2026236Swpaul#define _SEARCH_PRIVATE
2126236Swpaul#include <search.h>
2226236Swpaul#include <stdlib.h>
2326236Swpaul
2426236Swpaul/* find or insert datum into search tree */
2526236Swpaulvoid *
2626236Swpaultsearch(const void *vkey, void **vrootp,
2726236Swpaul    int (*compar)(const void *, const void *))
2826236Swpaul{
2926236Swpaul	node_t *q;
3026236Swpaul	node_t **rootp = (node_t **)vrootp;
3126236Swpaul
3226236Swpaul	_DIAGASSERT(vkey != NULL);
3326236Swpaul	_DIAGASSERT(compar != NULL);
34
35	if (rootp == NULL)
36		return NULL;
37
38	while (*rootp != NULL) {	/* Knuth's T1: */
39		int r;
40
41		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
42			return *rootp;		/* we found it! */
43
44		rootp = (r < 0) ?
45		    &(*rootp)->llink :		/* T3: follow left branch */
46		    &(*rootp)->rlink;		/* T4: follow right branch */
47	}
48
49	q = malloc(sizeof(node_t));		/* T5: key not found */
50	if (q != 0) {				/* make new node */
51		*rootp = q;			/* link new node to old */
52		q->key = __UNCONST(vkey);	/* initialize new node */
53		q->llink = q->rlink = NULL;
54	}
55	return q;
56}
57