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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>
#else /* ! HAVE_STDDEF_H */
#define NULL ((void*)0)
#endif /* ! HAVE_STDDEF_H */
typedef struct node
{
const void *key;
struct node *llink;
struct node *rlink;
} node_t;
/* $NetBSD: tsearch.c,v 1.5 2005/11/29 03:12:00 christos Exp $ */
/* find or insert datum into search tree */
void *
tsearch (const void *vkey, /* key to be located */
void **vrootp, /* address of tree root */
int (*compar)(const void *, const void *))
{
node_t *q;
node_t **rootp = (node_t **) vrootp;
if (NULL == rootp)
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)
{ /* 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 1.5 2005/03/23 08:16:53 kleink Exp $ */
/* find a node, or return NULL */
void *
tfind (const void *vkey, /* key to be found */
void *const *vrootp, /* address of the tree root */
int (*compar)(const void *, const void *))
{
node_t *const *rootp = (node_t *const*) vrootp;
if (NULL == rootp)
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 1.2 1999/09/16 11:45:37 lukem Exp $ */
/*
* 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
*/
void *
tdelete (const void *__restrict vkey,
void **__restrict vrootp,
int (*compar)(const void *, const void *))
{
node_t **rootp = (node_t **) vrootp;
node_t *p;
node_t *q;
node_t *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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