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/*
* Tree search generalized from Knuth (6.2.2) Algorithm T just like
* the AT&T man page says.
*
* The node_t structure is for internal use only, lint doesn't grok it.
*
* Written by reading the System V Interface Definition, not the code.
*
* Totally public domain.
*
* $NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $
* $NetBSD: twalk.c,v 1.1 1999/02/22 10:33:16 christos Exp $
* $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
* $NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
*/
#include <config.h>
#include "roken.h"
#include "search.h"
#include <stdlib.h>
typedef struct node {
char *key;
struct node *llink, *rlink;
} node_t;
/*
* find or insert datum into search tree
*
* Parameters:
* vkey: key to be located
* vrootp: address of tree root
*/
ROKEN_LIB_FUNCTION void *
rk_tsearch(const void *vkey, void **vrootp,
int (*compar)(const void *, const void *))
{
node_t *q;
node_t **rootp = (node_t **)vrootp;
if (rootp == NULL)
return NULL;
while (*rootp != NULL) { /* Knuth's T1: */
int r;
if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */
return *rootp; /* we found it! */
rootp = (r < 0) ?
&(*rootp)->llink : /* T3: follow left branch */
&(*rootp)->rlink; /* T4: follow right branch */
}
q = malloc(sizeof(node_t)); /* T5: key not found */
if (q != 0) { /* make new node */
*rootp = q; /* link new node to old */
/* LINTED const castaway ok */
q->key = rk_UNCONST(vkey); /* initialize new node */
q->llink = q->rlink = NULL;
}
return q;
}
/*
* Walk the nodes of a tree
*
* Parameters:
* root: Root of the tree to be walked
*/
static void
trecurse(const node_t *root, void (*action)(const void *, VISIT, int),
int level)
{
if (root->llink == NULL && root->rlink == NULL)
(*action)(root, leaf, level);
else {
(*action)(root, preorder, level);
if (root->llink != NULL)
trecurse(root->llink, action, level + 1);
(*action)(root, postorder, level);
if (root->rlink != NULL)
trecurse(root->rlink, action, level + 1);
(*action)(root, endorder, level);
}
}
/*
* Walk the nodes of a tree
*
* Parameters:
* vroot: Root of the tree to be walked
*/
ROKEN_LIB_FUNCTION void
rk_twalk(const void *vroot,
void (*action)(const void *, VISIT, int))
{
if (vroot != NULL && action != NULL)
trecurse(vroot, action, 0);
}
/*
* delete node with given key
*
* vkey: key to be deleted
* vrootp: address of the root of the tree
* compar: function to carry out node comparisons
*/
ROKEN_LIB_FUNCTION void *
rk_tdelete(const void * vkey, void ** vrootp,
int (*compar)(const void *, const void *))
{
node_t **rootp = (node_t **)vrootp;
node_t *q, *r;
int cmp;
if (rootp == NULL || *rootp == NULL)
return NULL;
while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
rootp = (cmp < 0) ?
&(*rootp)->llink : /* follow llink branch */
&(*rootp)->rlink; /* follow rlink branch */
if (*rootp == NULL)
return NULL; /* key not found */
}
r = (*rootp)->rlink; /* D1: */
if ((q = (*rootp)->llink) == NULL) /* Left NULL? */
q = r;
else if (r != NULL) { /* Right link is NULL? */
if (r->llink == NULL) { /* D2: Find successor */
r->llink = q;
q = r;
} else { /* D3: Find NULL link */
for (q = r->llink; q->llink != NULL; q = r->llink)
r = q;
r->llink = q->rlink;
q->llink = (*rootp)->llink;
q->rlink = (*rootp)->rlink;
}
}
free(*rootp); /* D4: Free node */
*rootp = q; /* link parent to new node */
return *rootp;
}
/*
* find a node, or return 0
*
* Parameters:
* vkey: key to be found
* vrootp: address of the tree root
*/
ROKEN_LIB_FUNCTION void *
rk_tfind(const void *vkey, void * const *vrootp,
int (*compar)(const void *, const void *))
{
node_t **rootp = (node_t **)vrootp;
if (rootp == NULL)
return NULL;
while (*rootp != NULL) { /* T1: */
int r;
if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */
return *rootp; /* key found */
rootp = (r < 0) ?
&(*rootp)->llink : /* T3: follow left branch */
&(*rootp)->rlink; /* T4: follow right branch */
}
return NULL;
}
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