63 lines
2.4 KiB
Java
63 lines
2.4 KiB
Java
// $Id$
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/*
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* This file is a part of WorldGuard.
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* Copyright (c) sk89q <http://www.sk89q.com>
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* Copyright (c) the WorldGuard team and contributors
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*
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* This program is free software: you can redistribute it and/or modify it under the
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* terms of the GNU Lesser General Public License as published by the Free Software
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License along with
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* this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package com.sk89q.worldguard.protection;
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import java.util.WeakHashMap;
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/**
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* To facilitate performing regions-containing-point lookups from multiple stack frames
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* but within the same context (the same event), a cache is important in preventing the
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* need for redundant lookups made for the same point. This class serves as such a cache.
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* <p>
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* A key needs to be selected to store cache entries against. The best key is one that
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* is highly temporal, and would represent a certain "snapshot in time," such as
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* an event object. The event objects are indexed in this class using weak references,
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* and they will be removed by the garbage collector automatically. Because it
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* <em>is</em> a weak reference, the key object needs to be held somewhere with a strong
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* reference until the "snapshot" ends.
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* <p>
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* This class is abstract because implementing class should provide methods to check
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* against a standard key object. This cache itself is thread-safe.
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*/
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public abstract class RegionQueryCache {
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private final WeakHashMap<Object, RegionQueryCacheEntry> cache =
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new WeakHashMap<Object, RegionQueryCacheEntry>();
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public RegionQueryCache() {
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}
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/**
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* Get the {@link RegionQueryCacheEntry} object that will cache the
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* {@link ApplicableRegionSet}s for this context.
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*
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* @param key a standard key to store by
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* @return an existing QueryCacheEntry or a new one
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*/
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protected synchronized RegionQueryCacheEntry get(Object key) {
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RegionQueryCacheEntry entry = cache.get(key);
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if (entry == null) {
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entry = new RegionQueryCacheEntry();
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cache.put(key, entry);
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}
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return entry;
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}
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}
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