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/*-
* Copyright (c) 2015 Nuxi, https://nuxi.nl/
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#define _SEARCH_PRIVATE
#include <search.h>
#include <stdlib.h>
#include "tsearch_path.h"
posix_tnode *
tsearch(const void *key, posix_tnode **rootp,
int (*compar)(const void *, const void *))
{
struct path path;
posix_tnode **leaf, *result, *n, *x, *y, *z;
int cmp;
/* POSIX requires that tsearch() returns NULL if rootp is NULL. */
if (rootp == NULL)
return (NULL);
/*
* Find the leaf where the new key needs to be inserted. Return
* if we've found an existing entry. Keep track of the path that
* is taken to get to the node, as we will need it to adjust the
* balances.
*/
path_init(&path);
leaf = rootp;
while (*leaf != NULL) {
if ((*leaf)->balance != 0) {
/*
* If we reach a node that has a non-zero
* balance on the way, we know that we won't
* need to perform any rotations above this
* point. In this case rotations are always
* capable of keeping the subtree in balance.
* Make this the root node and reset the path.
*/
rootp = leaf;
path_init(&path);
}
cmp = compar(key, (*leaf)->key);
if (cmp < 0) {
path_taking_left(&path);
leaf = &(*leaf)->llink;
} else if (cmp > 0) {
path_taking_right(&path);
leaf = &(*leaf)->rlink;
} else {
return (*leaf);
}
}
/* Did not find a matching key in the tree. Insert a new node. */
result = *leaf = malloc(sizeof(**leaf));
if (result == NULL)
return (NULL);
result->key = (void *)key;
result->llink = NULL;
result->rlink = NULL;
result->balance = 0;
/*
* Walk along the same path a second time and adjust the
* balances. Except for the first node, all of these nodes must
* have a balance of zero, meaning that these nodes will not get
* out of balance.
*/
for (n = *rootp; n != *leaf;) {
if (path_took_left(&path)) {
n->balance += 1;
n = n->llink;
} else {
n->balance -= 1;
n = n->rlink;
}
}
/*
* Adjusting the balances may have pushed the balance of the
* root node out of range. Perform a rotation to bring the
* balance back in range.
*/
x = *rootp;
if (x->balance > 1) {
y = x->llink;
if (y->balance < 0) {
/*
* Left-right case.
*
* x
* / \ z
* y D / \
* / \ --> y x
* A z /| |\
* / \ A B C D
* B C
*/
z = y->rlink;
y->rlink = z->llink;
z->llink = y;
x->llink = z->rlink;
z->rlink = x;
*rootp = z;
x->balance = z->balance > 0 ? -1 : 0;
y->balance = z->balance < 0 ? 1 : 0;
z->balance = 0;
} else {
/*
* Left-left case.
*
* x y
* / \ / \
* y C --> A x
* / \ / \
* A B B C
*/
x->llink = y->rlink;
y->rlink = x;
*rootp = y;
x->balance = 0;
y->balance = 0;
}
} else if (x->balance < -1) {
y = x->rlink;
if (y->balance > 0) {
/*
* Right-left case.
*
* x
* / \ z
* A y / \
* / \ --> x y
* z D /| |\
* / \ A B C D
* B C
*/
posix_tnode *z = y->llink;
x->rlink = z->llink;
z->llink = x;
y->llink = z->rlink;
z->rlink = y;
*rootp = z;
x->balance = z->balance < 0 ? 1 : 0;
y->balance = z->balance > 0 ? -1 : 0;
z->balance = 0;
} else {
/*
* Right-right case.
*
* x y
* / \ / \
* A y --> x C
* / \ / \
* B C A B
*/
x->rlink = y->llink;
y->llink = x;
*rootp = y;
x->balance = 0;
y->balance = 0;
}
}
/* Return the new entry. */
return (result);
}
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