xref: /src/lib/libc/stdlib/tsearch.c

/*	$NetBSD: tsearch.c,v 1.1 1999/02/22 10:33:16 christos Exp $	*/

/*
 * Tree search generalized from Knuth (6.2.2) Algorithm T just like
 * the AT&T man page says.
 *
 * The node_t structure is for internal use only, lint doesn't grok it.
 *
 * Written by reading the System V Interface Definition, not the code.
 *
 * Totally public domain.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: tsearch.c,v 1.1 1999/02/22 10:33:16 christos Exp $");
#endif /* LIBC_SCCS and not lint */

#define _SEARCH_PRIVATE
#include <search.h>
#include <stdlib.h>

/* find or insert datum into search tree */
void *
tsearch(vkey, vrootp, compar)
	const void *vkey;		/* key to be located */
	void **vrootp;			/* address of tree root */
	int (*compar) __P((const void *, const void *));
{
	node_t *q;
	node_t **rootp = (node_t **)vrootp;

	if (rootp == NULL)
		return NULL;

	while (*rootp != NULL) {	/* Knuth's T1: */
		int r;

		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
			return *rootp;		/* we found it! */

		rootp = (r < 0) ?
		    &(*rootp)->llink :		/* T3: follow left branch */
		    &(*rootp)->rlink;		/* T4: follow right branch */
	}

	q = malloc(sizeof(node_t));		/* T5: key not found */
	if (q != 0) {				/* make new node */
		*rootp = q;			/* link new node to old */
		q->key = (void *)vkey;		/* initialize new node */
		q->llink = q->rlink = NULL;
	}
	return q;
}