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/*************************************************************************
*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* Copyright 2008 by Sun Microsystems, Inc.
*
* OpenOffice.org - a multi-platform office productivity suite
*
* $RCSfile: Cache.java,v $
* $Revision: 1.4 $
*
* This file is part of OpenOffice.org.
*
* OpenOffice.org is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 3
* only, as published by the Free Software Foundation.
*
* OpenOffice.org 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 Lesser General Public License version 3 for more details
* (a copy is included in the LICENSE file that accompanied this code).
*
* You should have received a copy of the GNU Lesser General Public License
* version 3 along with OpenOffice.org. If not, see
* <http://www.openoffice.org/license.html>
* for a copy of the LGPLv3 License.
*
************************************************************************/
package com.sun.star.lib.uno.protocols.urp;
import java.util.HashMap;
/**
An LRU cache for arbitrary objects.
This class is not synchronized, as any necessary synchronization will already
take place in the client.
*/
final class Cache {
/**
Create a cache.
@param size the maximum cache size, must be between 0, inclusive, and
NOT_CACHED, exclusive
*/
public Cache(int size) {
maxSize = size;
}
public int add(boolean[] found, Object content) {
Entry e = (Entry) map.get(content);
found[0] = e != null;
if (e == null) {
if (map.size() < maxSize) {
// There is still room for a new entry at the front:
e = new Entry(content, map.size(), last, null);
if (first == null) {
last = e;
} else {
first.prev = e;
}
first = e;
} else if (last != null) {
// Take last entry out and recycle as new front:
map.remove(last.content);
e = last;
e.content = content;
if (first != last) {
// Reached only if maxSize > 1:
last = last.prev;
last.next = null;
e.prev = null;
e.next = first;
first.prev = e;
first = e;
}
} else {
// Reached iff maxSize == 0:
return NOT_CACHED;
}
map.put(content, e);
} else if (e != first) {
// Move to front (reached only if maxSize > 1):
e.prev.next = e.next;
if (e.next == null) {
last = e.prev;
} else {
e.next.prev = e.prev;
}
e.prev = null;
e.next = first;
first.prev = e;
first = e;
}
return e.index;
}
public static final int NOT_CACHED = 0xFFFF;
private static final class Entry {
public Entry(Object content, int index, Entry prev, Entry next) {
this.content = content;
this.index = index;
this.prev = prev;
this.next = next;
}
public Object content;
public int index;
public Entry prev;
public Entry next;
}
// first/last form a list of 0 to maxSize entries, most recently used first;
// map contains the same entries; each entry has a unique index in the range
// 0 to maxSize - 1
private final int maxSize;
private final HashMap map = new HashMap(); // from Object to Entry
private Entry first = null;
private Entry last = null;
}
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