1 /* $NetBSD: tsearch.c,v 1.3 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 #ifndef _MSC_FULL_VER
15 #include <sys/cdefs.h>
16 #endif //! _MSC_FULL_VER
17 #define _SEARCH_PRIVATE
18 #include "tsearch.h"
19 #include <stdlib.h>
20
21 /* find or insert datum into search tree */
22 void *
tsearch(vkey,vrootp,compar)23 tsearch(vkey, vrootp, compar)
24 const void *vkey; /* key to be located */
25 void **vrootp; /* address of tree root */
26 int (*compar)(const void *, const void *);
27 {
28 node_t *q;
29 node_t **rootp = (node_t **)vrootp;
30
31 if (rootp == NULL)
32 return NULL;
33
34 while (*rootp != NULL) { /* Knuth's T1: */
35 int r;
36
37 if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */
38 return *rootp; /* we found it! */
39
40 rootp = (r < 0) ?
41 &(*rootp)->llink : /* T3: follow left branch */
42 &(*rootp)->rlink; /* T4: follow right branch */
43 }
44
45 q = malloc(sizeof(node_t)); /* T5: key not found */
46 if (q != 0) { /* make new node */
47 *rootp = q; /* link new node to old */
48 /* LINTED const castaway ok */
49 q->key = (void *)vkey; /* initialize new node */
50 q->llink = q->rlink = NULL;
51 }
52 return q;
53 }
54
55 /* find a node, or return 0 */
56 void *
tfind(vkey,vrootp,compar)57 tfind(vkey, vrootp, compar)
58 const void *vkey; /* key to be found */
59 void * const *vrootp; /* address of the tree root */
60 int (*compar)(const void *, const void *);
61 {
62 node_t **rootp = (node_t **)vrootp;
63
64 if (rootp == NULL)
65 return NULL;
66
67 while (*rootp != NULL) { /* T1: */
68 int r;
69
70 if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */
71 return *rootp; /* key found */
72 rootp = (r < 0) ?
73 &(*rootp)->llink : /* T3: follow left branch */
74 &(*rootp)->rlink; /* T4: follow right branch */
75 }
76 return NULL;
77 }
78
79 /*
80 * delete node with given key
81 *
82 * vkey: key to be deleted
83 * vrootp: address of the root of the tree
84 * compar: function to carry out node comparisons
85 */
86 void *
tdelete(const void * __restrict vkey,void ** __restrict vrootp,int (* compar)(const void *,const void *))87 tdelete(const void * __restrict vkey, void ** __restrict vrootp,
88 int (*compar)(const void *, const void *))
89 {
90 node_t **rootp = (node_t **)vrootp;
91 node_t *p, *q, *r;
92 int cmp;
93
94 if (rootp == NULL || (p = *rootp) == NULL)
95 return NULL;
96
97 while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
98 p = *rootp;
99 rootp = (cmp < 0) ?
100 &(*rootp)->llink : /* follow llink branch */
101 &(*rootp)->rlink; /* follow rlink branch */
102 if (*rootp == NULL)
103 return NULL; /* key not found */
104 }
105 r = (*rootp)->rlink; /* D1: */
106 if ((q = (*rootp)->llink) == NULL) /* Left NULL? */
107 q = r;
108 else if (r != NULL) { /* Right link is NULL? */
109 if (r->llink == NULL) { /* D2: Find successor */
110 r->llink = q;
111 q = r;
112 } else { /* D3: Find NULL link */
113 for (q = r->llink; q->llink != NULL; q = r->llink)
114 r = q;
115 r->llink = q->rlink;
116 q->llink = (*rootp)->llink;
117 q->rlink = (*rootp)->rlink;
118 }
119 }
120 free(*rootp); /* D4: Free node */
121 *rootp = q; /* link parent to new node */
122 return p;
123 }
124
125 /* end of tsearch.c */
126