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tsearch.c
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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
17 #define _SEARCH_PRIVATE
18 #include "tsearch.h"
19 #include <stdlib.h>
20 
21 /* find or insert datum into search tree */
22 void *
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 *
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 *
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 */
void ** vrootp
Definition: tsearch.c:25
__BEGIN_DECLS void * tdelete(const void *__restrict, void **__restrict, int(*)(const void *, const void *))
int(* compar)(const void *, const void *)
Definition: tsearch.c:26
return NULL
Definition: tsearch.c:32
void *const void * vkey
Definition: tsearch.c:24
if((r=(*compar)(vkey,(*rootp) ->key))==0)
Definition: tsearch.c:37
node_t ** rootp
Definition: tsearch.c:29
void * tfind(const void *, void *const *, int(*)(const void *, const void *))
return q
Definition: tsearch.c:52
void * tsearch(const void *, void **, int(*)(const void *, const void *))