genode/repos/base/include/util/avl_tree.h
Martin Stein abf9557bb5 AVL node/tree: make non-copyable
AVL trees can't be copied with the default copy constructor as the
parent pointer of the first item of both of the resulting trees would
point to the original tree. Copying an AVL node, however, generally
violates the integrity of the corresponding tree. The copy constructor
of Avl_tree is used in some places but in those places it can be
replaced easily. So, this commit deletes the copy constructor of
Avl_node_base which makes Avl_node and Avl_tree non-copyable.

Issue #2654
2018-02-09 13:34:23 +01:00

242 lines
5.4 KiB
C++

/*
* \brief AVL tree
* \author Norman Feske
* \date 2006-04-12
*/
/*
* Copyright (C) 2006-2017 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__UTIL__AVL_TREE_H_
#define _INCLUDE__UTIL__AVL_TREE_H_
#include <util/misc_math.h>
#include <util/noncopyable.h>
namespace Genode {
class Avl_node_base;
template <typename> class Avl_node;
template <typename> class Avl_tree;
}
class Genode::Avl_node_base : Noncopyable
{
protected:
/**
* Internal policy interface
*
* The implementation of this interface is provided by the AVL tree.
*/
struct Policy
{
virtual ~Policy() { }
/**
* Compare two nodes
*
* \retval false if n2 is lower than n1
* \retval true if n2 is higher than or equal to n1
*
* This method must be provided by the derived class.
* It determines the order of nodes inside the AVL tree.
*/
virtual bool higher(Avl_node_base *n1, Avl_node_base *n2) const = 0;
/**
* Node recomputation hook
*
* If a node gets rearranged, this method is called.
* It can be used to update AVL-tree-position dependent
* meta data.
*/
virtual void recompute(Avl_node_base *) { }
};
struct {
Avl_node_base *_child[2]; /* left and right subtrees */
Avl_node_base *_parent; /* parent of subtree */
unsigned char _depth; /* depth of subtree */
};
public:
typedef bool Side;
enum { LEFT = false, RIGHT = true };
private:
/**
* Determine depth of subtree
*/
inline int _child_depth(Side i) {
return _child[i] ? _child[i]->_depth : 0; }
/**
* Update depth of node
*/
void _recompute_depth(Policy &policy);
/**
* Determine left-right bias of both subtrees
*/
inline Side _bias() {
return (_child_depth(RIGHT) > _child_depth(LEFT)); }
/**
* Insert subtree into specified side of the node
*/
void _adopt(Avl_node_base *node, Side i, Policy &policy);
/**
* Rotate subtree
*
* \param side direction of rotate operation
* \param node subtree to rotate
*
* The local node_* variable names describe node locations for
* the left (default) rotation. For example, node_r_l is the
* left of the right of node.
*/
void _rotate_subtree(Avl_node_base *node, Side side, Policy &policy);
/**
* Rebalance subtree
*
* \param node immediate child that needs balancing
*
* 'this' is parent of the subtree to rebalance
*/
void _rebalance_subtree(Avl_node_base *node, Policy &policy);
public:
/**
* Constructor
*/
Avl_node_base();
/**
* Insert new node into subtree
*/
void insert(Avl_node_base *node, Policy &policy);
/**
* Remove node from tree
*/
void remove(Policy &policy);
};
/**
* AVL node
*
* \param NT type of the class derived from 'Avl_node'
*
* Each object to be stored in the AVL tree must be derived from 'Avl_node'.
* The type of the derived class is to be specified as template argument to
* enable 'Avl_node' to call virtual methods specific for the derived class.
*
* The NT class must implement a method called 'higher' that takes a pointer to
* another NT object as argument and returns a bool value. The bool value is
* true if the specified node is higher or equal in the tree order.
*/
template <typename NT>
struct Genode::Avl_node : Avl_node_base
{
/**
* Return child of specified side, or nullptr if there is no child
*
* This method can be called by the NT objects to traverse the tree.
*/
inline NT *child(Side i) const { return static_cast<NT *>(_child[i]); }
/**
* Default policy
*
* \noapi
*/
void recompute() { }
/**
* Apply a functor (read-only) to every node within this subtree
*
* \param functor function that takes a const NT reference
*/
template <typename FUNC>
void for_each(FUNC && functor) const
{
if (NT * l = child(Avl_node<NT>::LEFT)) l->for_each(functor);
functor(*static_cast<NT const *>(this));
if (NT * r = child(Avl_node<NT>::RIGHT)) r->for_each(functor);
}
};
/**
* Root node of the AVL tree
*
* The real nodes are always attached at the left branch of this root node.
*/
template <typename NT>
class Genode::Avl_tree : Avl_node<NT>
{
private:
/**
* Auto-generated policy class specific for NT
*/
class Policy : public Avl_node_base::Policy
{
bool higher(Avl_node_base *n1, Avl_node_base *n2) const
{
return static_cast<NT *>(n1)->higher(static_cast<NT *>(n2));
}
void recompute(Avl_node_base *node)
{
static_cast<NT *>(node)->recompute();
}
} _policy { };
public:
/**
* Insert node into AVL tree
*/
void insert(Avl_node<NT> *node) { Avl_node_base::insert(node, _policy); }
/**
* Remove node from AVL tree
*/
void remove(Avl_node<NT> *node) { node->remove(_policy); }
/**
* Request first node of the tree
*
* \return first node, or nullptr if the tree is empty
*/
inline NT *first() const { return this->child(Avl_node<NT>::LEFT); }
/**
* Apply a functor (read-only) to every node within the tree
*
* \param functor function that takes a const NT reference
*
* The iteration order corresponds to the order of the keys
*/
template <typename FUNC>
void for_each(FUNC && functor) const {
if (first()) first()->for_each(functor); }
};
#endif /* _INCLUDE__UTIL__AVL_TREE_H_ */