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/*      $NetBSD: tdelete.c,v 1.2 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: tdelete.c,v 1.2 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>

/* delete node with given key */

void *

_DEFUN(tdelete, (vkey, vrootp, compar),

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

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

        int       (*compar)(const void *, const void *))

{

        node_t **rootp = (node_t **)vrootp;

        node_t *p, *q, *r;

        int  cmp;

        if (rootp == NULL || (p = *rootp) == NULL)

                return NULL;

        while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {

                p = *rootp;

                rootp = (cmp < 0) ?

                    &(*rootp)->llink :          /* follow llink branch */

                    &(*rootp)->rlink;           /* follow rlink branch */

                if (*rootp == NULL)

                        return NULL;            /* key not found */

        }

        r = (*rootp)->rlink;                    /* D1: */

        if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */

                q = r;

        else if (r != NULL) {                   /* Right link is NULL? */

                if (r->llink == NULL) {         /* D2: Find successor */

                        r->llink = q;

                        q = r;

                } else {                        /* D3: Find NULL link */

                        for (q = r->llink; q->llink != NULL; q = r->llink)

                                r = q;

                        r->llink = q->rlink;

                        q->llink = (*rootp)->llink;

                        q->rlink = (*rootp)->rlink;

                }

        }

        free(*rootp);                           /* D4: Free node */

        *rootp = q;                             /* link parent to new node */

        return p;

}