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tdelete.c revision 1.2 
      1 /*	$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $	*/
      2 
      3 /*
      4  * Tree search generalized from Knuth (6.2.2) Algorithm T just like
      5  * the AT&T man page says.
      6  *
      7  * The node_t structure is for internal use only, lint doesn't grok it.
      8  *
      9  * Written by reading the System V Interface Definition, not the code.
     10  *
     11  * Totally public domain.
     12  */
     13 
     14 #include <sys/cdefs.h>
     15 #if defined(LIBC_SCCS) && !defined(lint)
     16 __RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $");
     17 #endif /* LIBC_SCCS and not lint */
     18 
     19 #include <assert.h>
     20 #define _SEARCH_PRIVATE
     21 #include <search.h>
     22 #include <stdlib.h>
     23 
     24 
     25 /* delete node with given key */
     26 void *
     27 tdelete(vkey, vrootp, compar)
     28 	const void *vkey;	/* key to be deleted */
     29 	void      **vrootp;	/* address of the root of tree */
     30 	int       (*compar) __P((const void *, const void *));
     31 {
     32 	node_t **rootp = (node_t **)vrootp;
     33 	node_t *p, *q, *r;
     34 	int  cmp;
     35 
     36 	_DIAGASSERT(vkey != NULL);
     37 	_DIAGASSERT(compar != NULL);
     38 #ifdef _DIAGNOSTIC
     39 	if (vkey == NULL || compar == NULL)
     40 		return (NULL);
     41 #endif
     42 
     43 	if (rootp == NULL || (p = *rootp) == NULL)
     44 		return NULL;
     45 
     46 	while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
     47 		p = *rootp;
     48 		rootp = (cmp < 0) ?
     49 		    &(*rootp)->llink :		/* follow llink branch */
     50 		    &(*rootp)->rlink;		/* follow rlink branch */
     51 		if (*rootp == NULL)
     52 			return NULL;		/* key not found */
     53 	}
     54 	r = (*rootp)->rlink;			/* D1: */
     55 	if ((q = (*rootp)->llink) == NULL)	/* Left NULL? */
     56 		q = r;
     57 	else if (r != NULL) {			/* Right link is NULL? */
     58 		if (r->llink == NULL) {		/* D2: Find successor */
     59 			r->llink = q;
     60 			q = r;
     61 		} else {			/* D3: Find NULL link */
     62 			for (q = r->llink; q->llink != NULL; q = r->llink)
     63 				r = q;
     64 			r->llink = q->rlink;
     65 			q->llink = (*rootp)->llink;
     66 			q->rlink = (*rootp)->rlink;
     67 		}
     68 	}
     69 	free(*rootp);				/* D4: Free node */
     70 	*rootp = q;				/* link parent to new node */
     71 	return p;
     72 }
     73