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/*      $NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem 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 0

#if defined(LIBC_SCCS) && !defined(lint)

__RCSID("$NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $");

#endif /* LIBC_SCCS and not lint */

#endif

#include <assert.h>

#define _SEARCH_PRIVATE

#include <search.h>

#include <stdlib.h>

/* find or insert datum into search tree */

void *

_DEFUN(tsearch, (vkey, vrootp, compar),

        const void *vkey _AND           /* key to be located */

        void **vrootp _AND              /* address of tree root */

        int (*compar)(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 */

                /* LINTED const castaway ok */

                q->key = (void *)vkey;          /* initialize new node */

                q->llink = q->rlink = NULL;

        }

        return q;

}