/*
* Copyright (c) 2004-2005, 2007, 2009-2015
* Todd C. Miller <Todd.Miller@courtesan.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* Adapted from the following code written by Emin Martinian:
* http://web.mit.edu/~emin/www/source_code/red_black_tree/index.html
*
* Copyright (c) 2001 Emin Martinian
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that neither the name of Emin
* Martinian nor the names of any contributors are be used to endorse or
* promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT
* OWNER 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 <config.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include "sudoers.h"
#include "redblack.h"
static void rbrepair(struct rbtree *, struct rbnode *);
static void rotate_left(struct rbtree *, struct rbnode *);
static void rotate_right(struct rbtree *, struct rbnode *);
static void rbdestroy_int(struct rbtree *, struct rbnode *, void (*)(void *));
/*
* Red-Black tree, see http://en.wikipedia.org/wiki/Red-black_tree
*
* A red-black tree is a binary search tree where each node has a color
* attribute, the value of which is either red or black. Essentially, it
* is just a convenient way to express a 2-3-4 binary search tree where
* the color indicates whether the node is part of a 3-node or a 4-node.
* In addition to the ordinary requirements imposed on binary search
* trees, we make the following additional requirements of any valid
* red-black tree:
* 1) Every node is either red or black.
* 2) The root is black.
* 3) All leaves are black.
* 4) Both children of each red node are black.
* 5) The paths from each leaf up to the root each contain the same
* number of black nodes.
*/
/*
* Create a red black tree struct using the specified compare routine.
* Allocates and returns the initialized (empty) tree or NULL if
* memory cannot be allocated.
*/
struct rbtree *
rbcreate(int (*compar)(const void *, const void*))
{
struct rbtree *tree;
debug_decl(rbcreate, SUDOERS_DEBUG_RBTREE)
if ((tree = malloc(sizeof(*tree))) == NULL) {
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
"unable to allocate memory");
debug_return_ptr(NULL);
}
tree->compar = compar;
/*
* We use a self-referencing sentinel node called nil to simplify the
* code by avoiding the need to check for NULL pointers.
*/
tree->nil.left = tree->nil.right = tree->nil.parent = &tree->nil;
tree->nil.color = black;
tree->nil.data = NULL;
/*
* Similarly, the fake root node keeps us from having to worry
* about splitting the root.
*/
tree->root.left = tree->root.right = tree->root.parent = &tree->nil;
tree->root.color = black;
tree->root.data = NULL;
debug_return_ptr(tree);
}
/*
* Perform a left rotation starting at node.
*/
static void
rotate_left(struct rbtree *tree, struct rbnode *node)
{
struct rbnode *child;
debug_decl(rotate_left, SUDOERS_DEBUG_RBTREE)
child = node->right;
node->right = child->left;
if (child->left != rbnil(tree))
child->left->parent = node;
child->parent = node->parent;
if (node == node->parent->left)
node->parent->left = child;
else
node->parent->right = child;
child->left = node;
node->parent = child;
debug_return;
}
/*
* Perform a right rotation starting at node.
*/
static void
rotate_right(struct rbtree *tree, struct rbnode *node)
{
struct rbnode *child;
debug_decl(rotate_right, SUDOERS_DEBUG_RBTREE)
child = node->left;
node->left = child->right;
if (child->right != rbnil(tree))
child->right->parent = node;
child->parent = node->parent;
if (node == node->parent->left)
node->parent->left = child;
else
node->parent->right = child;
child->right = node;
node->parent = child;
debug_return;
}
/*
* Insert data pointer into a redblack tree.
* Returns a 0 on success, 1 if a node matching "data" already exists
* (filling in "existing" if not NULL), or -1 on malloc() failure.
*/
int
rbinsert(struct rbtree *tree, void *data, struct rbnode **existing)
{
struct rbnode *node = rbfirst(tree);
struct rbnode *parent = rbroot(tree);
int res;
debug_decl(rbinsert, SUDOERS_DEBUG_RBTREE)
/* Find correct insertion point. */
while (node != rbnil(tree)) {
parent = node;
if ((res = tree->compar(data, node->data)) == 0) {
if (existing != NULL)
*existing = node;
debug_return_int(1);
}
node = res < 0 ? node->left : node->right;
}
node = malloc(sizeof(*node));
if (node == NULL) {
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
"unable to allocate memory");
debug_return_int(-1);
}
node->data = data;
node->left = node->right = rbnil(tree);
node->parent = parent;
if (parent == rbroot(tree) || tree->compar(data, parent->data) < 0)
parent->left = node;
else
parent->right = node;
node->color = red;
/*
* If the parent node is black we are all set, if it is red we have
* the following possible cases to deal with. We iterate through
* the rest of the tree to make sure none of the required properties
* is violated.
*
* 1) The uncle is red. We repaint both the parent and uncle black
* and repaint the grandparent node red.
*
* 2) The uncle is black and the new node is the right child of its
* parent, and the parent in turn is the left child of its parent.
* We do a left rotation to switch the roles of the parent and
* child, relying on further iterations to fixup the old parent.
*
* 3) The uncle is black and the new node is the left child of its
* parent, and the parent in turn is the left child of its parent.
* We switch the colors of the parent and grandparent and perform
* a right rotation around the grandparent. This makes the former
* parent the parent of the new node and the former grandparent.
*
* Note that because we use a sentinel for the root node we never
* need to worry about replacing the root.
*/
while (node->parent->color == red) {
struct rbnode *uncle;
if (node->parent == node->parent->parent->left) {
uncle = node->parent->parent->right;
if (uncle->color == red) {
node->parent->color = black;
uncle->color = black;
node->parent->parent->color = red;
node = node->parent->parent;
} else /* if (uncle->color == black) */ {
if (node == node->parent->right) {
node = node->parent;
rotate_left(tree, node);
}
node->parent->color = black;
node->parent->parent->color = red;
rotate_right(tree, node->parent->parent);
}
} else { /* if (node->parent == node->parent->parent->right) */
uncle = node->parent->parent->left;
if (uncle->color == red) {
node->parent->color = black;
uncle->color = black;
node->parent->parent->color = red;
node = node->parent->parent;
} else /* if (uncle->color == black) */ {
if (node == node->parent->left) {
node = node->parent;
rotate_right(tree, node);
}
node->parent->color = black;
node->parent->parent->color = red;
rotate_left(tree, node->parent->parent);
}
}
}
rbfirst(tree)->color = black; /* first node is always black */
debug_return_int(0);
}
/*
* Look for a node matching key in tree.
* Returns a pointer to the node if found, else NULL.
*/
struct rbnode *
rbfind(struct rbtree *tree, void *key)
{
struct rbnode *node = rbfirst(tree);
int res;
debug_decl(rbfind, SUDOERS_DEBUG_RBTREE)
while (node != rbnil(tree)) {
if ((res = tree->compar(key, node->data)) == 0)
debug_return_ptr(node);
node = res < 0 ? node->left : node->right;
}
debug_return_ptr(NULL);
}
/*
* Call func() for each node, passing it the node data and a cookie;
* If func() returns non-zero for a node, the traversal stops and the
* error value is returned. Returns 0 on successful traversal.
*/
int
rbapply_node(struct rbtree *tree, struct rbnode *node,
int (*func)(void *, void *), void *cookie, enum rbtraversal order)
{
int error;
debug_decl(rbapply_node, SUDOERS_DEBUG_RBTREE)
if (node != rbnil(tree)) {
if (order == preorder)
if ((error = func(node->data, cookie)) != 0)
debug_return_int(error);
if ((error = rbapply_node(tree, node->left, func, cookie, order)) != 0)
debug_return_int(error);
if (order == inorder)
if ((error = func(node->data, cookie)) != 0)
debug_return_int(error);
if ((error = rbapply_node(tree, node->right, func, cookie, order)) != 0)
debug_return_int(error);
if (order == postorder)
if ((error = func(node->data, cookie)) != 0)
debug_return_int(error);
}
debug_return_int(0);
}
/*
* Returns the successor of node, or nil if there is none.
*/
static struct rbnode *
rbsuccessor(struct rbtree *tree, struct rbnode *node)
{
struct rbnode *succ;
debug_decl(rbsuccessor, SUDOERS_DEBUG_RBTREE)
if ((succ = node->right) != rbnil(tree)) {
while (succ->left != rbnil(tree))
succ = succ->left;
} else {
/* No right child, move up until we find it or hit the root */
for (succ = node->parent; node == succ->right; succ = succ->parent)
node = succ;
if (succ == rbroot(tree))
succ = rbnil(tree);
}
debug_return_ptr(succ);
}
/*
* Recursive portion of rbdestroy().
*/
static void
rbdestroy_int(struct rbtree *tree, struct rbnode *node, void (*destroy)(void *))
{
debug_decl(rbdestroy_int, SUDOERS_DEBUG_RBTREE)
if (node != rbnil(tree)) {
rbdestroy_int(tree, node->left, destroy);
rbdestroy_int(tree, node->right, destroy);
if (destroy != NULL)
destroy(node->data);
free(node);
}
debug_return;
}
/*
* Destroy the specified tree, calling the destructor "destroy"
* for each node and then freeing the tree itself.
*/
void
rbdestroy(struct rbtree *tree, void (*destroy)(void *))
{
debug_decl(rbdestroy, SUDOERS_DEBUG_RBTREE)
rbdestroy_int(tree, rbfirst(tree), destroy);
free(tree);
debug_return;
}
/*
* Delete node 'z' from the tree and return its data pointer.
*/
void *rbdelete(struct rbtree *tree, struct rbnode *z)
{
struct rbnode *x, *y;
void *data = z->data;
debug_decl(rbdelete, SUDOERS_DEBUG_RBTREE)
if (z->left == rbnil(tree) || z->right == rbnil(tree))
y = z;
else
y = rbsuccessor(tree, z);
x = (y->left == rbnil(tree)) ? y->right : y->left;
if ((x->parent = y->parent) == rbroot(tree)) {
rbfirst(tree) = x;
} else {
if (y == y->parent->left)
y->parent->left = x;
else
y->parent->right = x;
}
if (y->color == black)
rbrepair(tree, x);
if (y != z) {
y->left = z->left;
y->right = z->right;
y->parent = z->parent;
y->color = z->color;
z->left->parent = z->right->parent = y;
if (z == z->parent->left)
z->parent->left = y;
else
z->parent->right = y;
}
free(z);
debug_return_ptr(data);
}
/*
* Repair the tree after a node has been deleted by rotating and repainting
* colors to restore the 4 properties inherent in red-black trees.
*/
static void
rbrepair(struct rbtree *tree, struct rbnode *node)
{
struct rbnode *sibling;
debug_decl(rbrepair, SUDOERS_DEBUG_RBTREE)
while (node->color == black && node != rbfirst(tree)) {
if (node == node->parent->left) {
sibling = node->parent->right;
if (sibling->color == red) {
sibling->color = black;
node->parent->color = red;
rotate_left(tree, node->parent);
sibling = node->parent->right;
}
if (sibling->right->color == black && sibling->left->color == black) {
sibling->color = red;
node = node->parent;
} else {
if (sibling->right->color == black) {
sibling->left->color = black;
sibling->color = red;
rotate_right(tree, sibling);
sibling = node->parent->right;
}
sibling->color = node->parent->color;
node->parent->color = black;
sibling->right->color = black;
rotate_left(tree, node->parent);
node = rbfirst(tree); /* exit loop */
}
} else { /* if (node == node->parent->right) */
sibling = node->parent->left;
if (sibling->color == red) {
sibling->color = black;
node->parent->color = red;
rotate_right(tree, node->parent);
sibling = node->parent->left;
}
if (sibling->right->color == black && sibling->left->color == black) {
sibling->color = red;
node = node->parent;
} else {
if (sibling->left->color == black) {
sibling->right->color = black;
sibling->color = red;
rotate_left(tree, sibling);
sibling = node->parent->left;
}
sibling->color = node->parent->color;
node->parent->color = black;
sibling->left->color = black;
rotate_right(tree, node->parent);
node = rbfirst(tree); /* exit loop */
}
}
}
node->color = black;
debug_return;
}