/*      $NetBSD: tsearch.c,v 1.7 2012/06/25 22:32:45 abs 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 1.7 2012/06/25 22:32:45 abs Exp $");
#endif /* LIBC_SCCS and not lint */

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

/* find or insert datum into search tree */
void *
tsearch(const void *vkey, void **vrootp,
    int (*compar)(const void *, const void *))
{
        node_t *q;
        node_t **rootp = (node_t **)vrootp;

        _DIAGASSERT(vkey != NULL);
        _DIAGASSERT(compar != NULL);

        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 = __UNCONST(vkey);       /* initialize new node */
                q->llink = q->rlink = NULL;
        }
        return q;
}