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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.
*/
#include "mhd_options.h"
#include "tsearch.h"
#ifdef HAVE_STDDEF_H
#include <stddef.h>
#endif /* HAVE_STDDEF_H */
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif /* HAVE_STDLIB_H */
typedef struct node
{
const void *key;
struct node *llink, *rlink;
} node_t;
/* $NetBSD: tsearch.c,v 1.7 2012/06/25 22:32:45 abs Exp $ */
/* find or insert datum into search tree */
void *
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 != NULL) /* make new node */
{
*rootp = q; /* link new node to old */
q->key = vkey; /* initialize new node */
q->llink = q->rlink = NULL;
}
return q;
}
/* $NetBSD: tfind.c,v 1.7 2012/06/25 22:32:45 abs Exp $ */
/* find a node by key "vkey" in tree "vrootp", or return 0 */
void *
tfind (const void *vkey, void * const *vrootp,
int (*compar)(const void *, const void *))
{
node_t * const *rootp = (node_t * const *) 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;
}
/* $NetBSD: tdelete.c,v 1.8 2016/01/20 20:47:41 christos Exp $ */
/* find a node with key "vkey" in tree "vrootp" */
void *
tdelete (const void *vkey, void **vrootp,
int (*compar)(const void *, const void *))
{
node_t **rootp = (node_t **) vrootp;
node_t *p, *q, *r;
int cmp;
if ((rootp == NULL) || ((p = *rootp) == NULL) )
return NULL;
while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0)
{
p = *rootp;
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 p;
}
/* end of tsearch.c */
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