1/*	$NetBSD: tsearch.c,v 1.2 2017/01/28 21:31:50 christos 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 * NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp
14 * NetBSD: twalk.c,v 1.1 1999/02/22 10:33:16 christos Exp
15 * NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp
16 * NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 lukem Exp
17 */
18
19#include <config.h>
20#include <krb5/roken.h>
21#include "search.h"
22#include <stdlib.h>
23
24typedef struct node {
25  char         *key;
26  struct node  *llink, *rlink;
27} node_t;
28
29#ifndef __DECONST
30#define __DECONST(type, var)    ((type)(uintptr_t)(const void *)(var))
31#endif
32
33/*
34 * find or insert datum into search tree
35 *
36 * Parameters:
37 *	vkey:	key to be located
38 *	vrootp:	address of tree root
39 */
40
41ROKEN_LIB_FUNCTION void *
42rk_tsearch(const void *vkey, void **vrootp,
43	int (*compar)(const void *, const void *))
44{
45	node_t *q;
46	node_t **rootp = (node_t **)vrootp;
47
48	if (rootp == NULL)
49		return NULL;
50
51	while (*rootp != NULL) {	/* Knuth's T1: */
52		int r;
53
54		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
55			return *rootp;		/* we found it! */
56
57		rootp = (r < 0) ?
58		    &(*rootp)->llink :		/* T3: follow left branch */
59		    &(*rootp)->rlink;		/* T4: follow right branch */
60	}
61
62	q = malloc(sizeof(node_t));		/* T5: key not found */
63	if (q != 0) {				/* make new node */
64		*rootp = q;			/* link new node to old */
65		/* LINTED const castaway ok */
66		q->key = __DECONST(void *, vkey); /* initialize new node */
67		q->llink = q->rlink = NULL;
68	}
69	return q;
70}
71
72/*
73 * Walk the nodes of a tree
74 *
75 * Parameters:
76 *	root:	Root of the tree to be walked
77 */
78static void
79trecurse(const node_t *root, void (*action)(const void *, VISIT, int),
80	 int level)
81{
82
83	if (root->llink == NULL && root->rlink == NULL)
84		(*action)(root, leaf, level);
85	else {
86		(*action)(root, preorder, level);
87		if (root->llink != NULL)
88			trecurse(root->llink, action, level + 1);
89		(*action)(root, postorder, level);
90		if (root->rlink != NULL)
91			trecurse(root->rlink, action, level + 1);
92		(*action)(root, endorder, level);
93	}
94}
95
96/*
97 * Walk the nodes of a tree
98 *
99 * Parameters:
100 *	vroot:	Root of the tree to be walked
101 */
102ROKEN_LIB_FUNCTION void
103rk_twalk(const void *vroot,
104      void (*action)(const void *, VISIT, int))
105{
106	if (vroot != NULL && action != NULL)
107		trecurse(vroot, action, 0);
108}
109
110/*
111 * delete node with given key
112 *
113 * vkey:   key to be deleted
114 * vrootp: address of the root of the tree
115 * compar: function to carry out node comparisons
116 */
117ROKEN_LIB_FUNCTION void *
118rk_tdelete(const void * vkey, void ** vrootp,
119	int (*compar)(const void *, const void *))
120{
121	node_t **rootp = (node_t **)vrootp;
122	node_t *q, *r;
123	int cmp;
124
125	if (rootp == NULL || *rootp == NULL)
126		return NULL;
127
128	while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
129		rootp = (cmp < 0) ?
130		    &(*rootp)->llink :		/* follow llink branch */
131		    &(*rootp)->rlink;		/* follow rlink branch */
132		if (*rootp == NULL)
133			return NULL;		/* key not found */
134	}
135	r = (*rootp)->rlink;			/* D1: */
136	if ((q = (*rootp)->llink) == NULL)	/* Left NULL? */
137		q = r;
138	else if (r != NULL) {			/* Right link is NULL? */
139		if (r->llink == NULL) {		/* D2: Find successor */
140			r->llink = q;
141			q = r;
142		} else {			/* D3: Find NULL link */
143			for (q = r->llink; q->llink != NULL; q = r->llink)
144				r = q;
145			r->llink = q->rlink;
146			q->llink = (*rootp)->llink;
147			q->rlink = (*rootp)->rlink;
148		}
149	}
150	free(*rootp);				/* D4: Free node */
151	*rootp = q;				/* link parent to new node */
152	return *rootp;
153}
154
155/*
156 * find a node, or return 0
157 *
158 * Parameters:
159 *	vkey:	key to be found
160 *	vrootp:	address of the tree root
161 */
162ROKEN_LIB_FUNCTION void *
163rk_tfind(const void *vkey, void * const *vrootp,
164      int (*compar)(const void *, const void *))
165{
166	node_t **rootp = (node_t **)vrootp;
167
168	if (rootp == NULL)
169		return NULL;
170
171	while (*rootp != NULL) {		/* T1: */
172		int r;
173
174		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
175			return *rootp;		/* key found */
176		rootp = (r < 0) ?
177		    &(*rootp)->llink :		/* T3: follow left branch */
178		    &(*rootp)->rlink;		/* T4: follow right branch */
179	}
180	return NULL;
181}
182