blob: 47968a264a88b529681f07a5b70761f9f474ac73 [file] [log] [blame]
/* $NetBSD: tdelete.c,v 1.3 1999/09/20 04:39:43 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 <assert.h>
#define _SEARCH_PRIVATE
#include <search.h>
#include <stdlib.h>
#define _DIAGASSERT assert
/* delete node with given key */
void *
tdelete(const void *vkey, /* key to be deleted */
void **vrootp, /* 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;
_DIAGASSERT(compar != NULL);
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;
}