diff options
Diffstat (limited to 'ridljar/com/sun/star/lib/uno/protocols/urp/Cache.java')
-rw-r--r-- | ridljar/com/sun/star/lib/uno/protocols/urp/Cache.java | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/ridljar/com/sun/star/lib/uno/protocols/urp/Cache.java b/ridljar/com/sun/star/lib/uno/protocols/urp/Cache.java new file mode 100644 index 000000000..26c2d449d --- /dev/null +++ b/ridljar/com/sun/star/lib/uno/protocols/urp/Cache.java @@ -0,0 +1,114 @@ +/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ +/* + * This file is part of the LibreOffice project. + * + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. + * + * This file incorporates work covered by the following license notice: + * + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed + * with this work for additional information regarding copyright + * ownership. The ASF licenses this file to you under the Apache + * License, Version 2.0 (the "License"); you may not use this file + * except in compliance with the License. You may obtain a copy of + * the License at http://www.apache.org/licenses/LICENSE-2.0 . + */ + +package com.sun.star.lib.uno.protocols.urp; + +import java.util.HashMap; + +/** + * An LRU cache for arbitrary objects. + * + * <p>This class is not synchronized, as any necessary synchronization will already + * take place in the client.</p> + */ +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 = 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(), null, first); + 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<Object, Entry> map = new HashMap<Object, Entry>(); // from Object to Entry + private Entry first = null; + private Entry last = null; +} + +/* vim:set shiftwidth=4 softtabstop=4 expandtab: */ |