openscad/src/cache.h

/****************************************************************************
**
** OpenSCAD (www.openscad.org)
** Copyright (C) 2009-2011 Clifford Wolf <clifford@clifford.at> and
**                         Marius Kintel <marius@kintel.net>
** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
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** General Public License version 2.1 as published by the Free Software
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#pragma once

#include <boost/unordered_map.hpp>
#include <boost/format.hpp>
#include "printutils.h"

template <class Key, class T>
class Cache
{
	struct Node {
		inline Node() : keyPtr(0) {}
		inline Node(T *data, int cost)
			: keyPtr(0), t(data), c(cost), p(0), n(0) {}
		const Key *keyPtr; T *t; int c; Node *p,*n;
	};
	typedef typename boost::unordered_map<Key, Node> map_type;
	typedef typename map_type::iterator iterator_type;
	typedef typename map_type::value_type value_type;

	boost::unordered_map<Key, Node> hash;
	Node *f, *l;
	void *unused;
	int mx, total;

	inline void unlink(Node &n) {
		if (n.p) n.p->n = n.n;
		if (n.n) n.n->p = n.p;
		if (l == &n) l = n.p;
		if (f == &n) f = n.n;
		total -= n.c;
		T *obj = n.t;
		hash.erase(*n.keyPtr);
		delete obj;
	}
	inline T *relink(const Key &key) {
		iterator_type i = hash.find(key);
		if (i == hash.end()) return 0;

		Node &n = i->second;
		if (f != &n) {
			if (n.p) n.p->n = n.n;
			if (n.n) n.n->p = n.p;
			if (l == &n) l = n.p;
			n.p = 0;
			n.n = f;
			f->p = &n;
			f = &n;
		}
		return n.t;
	}

public:
	inline explicit Cache(int maxCost = 100)
		: f(0), l(0), unused(0), mx(maxCost), total(0) { }
	inline ~Cache() { clear(); }

	inline int maxCost() const { return mx; }
	void setMaxCost(int m) { mx = m; trim(mx); }
	inline int totalCost() const { return total; }

	inline int size() const { return hash.size(); }
	inline bool empty() const { return hash.empty(); }

	void clear() {
		while (f) { delete f->t; f = f->n; }
		hash.clear(); l = 0; total = 0;
	}

	bool insert(const Key &key, T *object, int cost = 1);
	T *object(const Key &key) const { return const_cast<Cache<Key,T>*>(this)->relink(key); }
	inline bool contains(const Key &key) const { return hash.find(key) != hash.end(); }
	T *operator[](const Key &key) const { return object(key); }

	bool remove(const Key &key);
	T *take(const Key &key);

private:
	void trim(int m);
};

template <class Key, class T>
inline bool Cache<Key,T>::remove(const Key &key)
{
	iterator_type i = hash.find(key);
	if (i == hash.end()) {
		return false;
	} else {
		unlink(i->second);
		return true;
	}
}

template <class Key, class T>
inline T *Cache<Key,T>::take(const Key &key)
{
	iterator_type i = hash.find(key);
	if (i == hash.end()) return 0;

	Node &n = *i;
	T *t = n.t;
	n.t = 0;
	unlink(n);
	return t;
}

template <class Key, class T>
bool Cache<Key,T>::insert(const Key &akey, T *aobject, int acost)
{
	remove(akey);
	if (acost > mx) {
		delete aobject;
		return false;
	}
	trim(mx - acost);
	Node node(aobject, acost);
	hash[akey] = node;
	iterator_type i = hash.find(akey);
	total += acost;
	Node *n = &i->second;
	n->keyPtr = &i->first;
	if (f) f->p = n;
	n->n = f;
	f = n;
	if (!l) l = f;
	return true;
}

template <class Key, class T>
void Cache<Key,T>::trim(int m)
{
	Node *n = l;
	while (n && total > m) {
		Node *u = n;
		n = n->p;
#ifdef DEBUG
		PRINTB("Trimming cache: %1% (%2% bytes)", u->keyPtr->substr(0, 40) % u->c);
#endif
		unlink(*u);
	}
}