scummvm/common/map.h
2002-11-13 13:42:05 +00:00

258 lines
5.5 KiB
C++

/* ScummVM - Scumm Interpreter
* Copyright (C) 2002 The ScummVM project
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* $Header$
*/
#ifndef COMMON_MAP_H
#define COMMON_MAP_H
#include "scummsys.h"
namespace ScummVM {
template <class Key, class Value>
class Map {
protected:
struct Node {
Node *_parent;
Node *_left, *_right;
Key _key;
Value _value;
Node() : _parent(0), _left(0), _right(0) {}
Node(const Key &key, Node *parent) : _parent(parent), _left(0), _right(0), _key(key) {}
};
Node *_root;
Node *_header;
public:
class Iterator {
protected:
Node *_node;
public:
Iterator(Node *node = 0) : _node(node) {}
Node &operator *() { assert(_node != 0); return *_node; }
const Node &operator *() const { assert(_node != 0); return *_node; }
const Node *operator->() const { assert(_node != 0); return _node; }
bool operator !=(const Iterator &iter) const { return _node != iter._node; }
void operator ++()
{
if (!_node)
return;
if (_node->_right) {
_node = _node->_right;
while (_node->_left)
_node = _node->_left;
} else {
Node *parent = _node->_parent;
while (_node == parent->_right) {
_node = parent;
parent = _node->_parent;
}
if (_node->_right != parent)
_node = parent;
}
if (_node->_parent == 0)
_node = 0;
}
};
public:
Map<Key, Value>() : _root(0)
{
_header = new Node();
_header->_right = _header->_left = _header;
}
~Map<Key, Value>()
{
clearNodes(_root);
delete _header;
_root = _header = 0;
}
/*
* Return the object for the given key. If no match is found, a new entry
* with the given key and the default data value is inserted.
*/
Value &operator [](const Key &key)
{
Node *node;
if (!_root)
node = _root = new Node(key, _header);
else
node = createNode(_root, key);
return node->_value;
}
const Value &operator [](const Key &key) const
{
Node *node = findNode(_root, key);
assert(node != 0);
return node->_value;
}
bool contains(const Key &key) const
{
return (findNode(_root, key) != 0);
}
void clear()
{
clearNodes(_root);
_root = 0;
}
bool isEmpty() const
{
return (_root == 0);
}
void remove(const Key &key)
{
// TODO - implement efficiently. Indeed, maybe switch to using red-black trees?
// For now, just a lame, bad remove algorithm. Rule: don't remove elements
// from one of our maps if you need to be efficient :-)
Node *node = findNode(_root, key);
if (!node)
return;
// Now we have to remove 'node'. There are two simple cases and one hard.
Node *parent = node->_parent;
Node *rep;
if (!node->_left) {
rep = node->_right;
} else if (!node->_right) {
rep = node->_left;
} else {
// We have to do it the hard way since both children are present.
Node *n2;
n2 = rep = node->_right;
// Now insert the left child leftmost into our right child
while (n2->_left)
n2 = n2->_left;
n2->_left = node->_left;
n2->_left->_parent = n2;
}
// Replace this node with node 'rep'
if (rep)
rep->_parent = parent;
if (parent == _header) // Root node?
_root = rep;
else if (parent->_left == node)
parent->_left = rep;
else
parent->_right = rep;
// Finally free the allocated memory
delete node;
}
void merge(const Map<Key, Value> &map)
{
// FIXME - this is a very bad algorithm.
// Right now we insert the items from 'map' using the default iterator,
// which gives us the objects ordered, leading to an unbalanced tree.
// This could be fixed by switching to a red black tree, or by using a
// different walk order (infix comes to mind).
if (map.isEmpty())
return;
Iterator x(map.begin()), e(map.end());
for (; x != e; ++x) {
(*this)[x->_key] = x->_value;
}
}
Iterator begin() const
{
Node *node = _root;
if (node) {
while (node->_left)
node = node->_left;
}
return Iterator(node);
}
Iterator end() const
{
return Iterator();
}
protected:
// Find the node matching the given key, if any
Node *findNode(Node *node, const Key &key) const
{
while (node && (key != node->_key)) {
if (key < node->_key) {
node = node->_left;
} else {
node = node->_right;
}
}
return node;
}
Node *createNode(Node *node, const Key &key)
{
Node *prevNode = 0;
bool left = true;
while (node) {
prevNode = node;
if (key == node->_key) {
return node;
} else if (key < node->_key) {
left = true;
node = node->_left;
} else {
left = false;
node = node->_right;
}
}
node = new Node(key, prevNode);
if (left) {
prevNode->_left = node;
} else {
prevNode->_right = node;
}
return node;
}
void clearNodes(Node *node)
{
if (!node)
return;
clearNodes(node->_left);
clearNodes(node->_right);
delete node;
}
};
class String;
typedef Map<String, String> StringMap;
}; // End of namespace ScummVM
#endif