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68 lines
1.7 KiB
C
68 lines
1.7 KiB
C
/* $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $ */
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/*
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* Tree search generalized from Knuth (6.2.2) Algorithm T just like
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* the AT&T man page says.
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*
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* The node_t structure is for internal use only, lint doesn't grok it.
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*
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* Written by reading the System V Interface Definition, not the code.
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*
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* Totally public domain.
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*/
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#include <sys/cdefs.h>
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#if 0
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#if defined(LIBC_SCCS) && !defined(lint)
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__RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $");
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#endif /* LIBC_SCCS and not lint */
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#endif
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#include <assert.h>
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#define _SEARCH_PRIVATE
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#include <search.h>
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#include <stdlib.h>
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/* delete node with given key */
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void *
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_DEFUN(tdelete, (vkey, vrootp, compar),
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const void *vkey _AND /* key to be deleted */
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void **vrootp _AND /* address of the root of tree */
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int (*compar)(const void *, const void *))
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{
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node_t **rootp = (node_t **)vrootp;
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node_t *p, *q, *r;
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int cmp;
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if (rootp == NULL || (p = *rootp) == NULL)
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return NULL;
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while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
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p = *rootp;
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rootp = (cmp < 0) ?
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&(*rootp)->llink : /* follow llink branch */
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&(*rootp)->rlink; /* follow rlink branch */
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if (*rootp == NULL)
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return NULL; /* key not found */
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}
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r = (*rootp)->rlink; /* D1: */
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if ((q = (*rootp)->llink) == NULL) /* Left NULL? */
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q = r;
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else if (r != NULL) { /* Right link is NULL? */
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if (r->llink == NULL) { /* D2: Find successor */
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r->llink = q;
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q = r;
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} else { /* D3: Find NULL link */
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for (q = r->llink; q->llink != NULL; q = r->llink)
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r = q;
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r->llink = q->rlink;
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q->llink = (*rootp)->llink;
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q->rlink = (*rootp)->rlink;
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}
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}
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free(*rootp); /* D4: Free node */
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*rootp = q; /* link parent to new node */
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return p;
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}
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