jgit/org.eclipse.jgit.storage.dht/src/org/eclipse/jgit/storage/dht/RecentInfoCache.java

/*
 * Copyright (C) 2011, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
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 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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package org.eclipse.jgit.storage.dht;

import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.ObjectId;

final class RecentInfoCache {
	private final Map<ObjectId, List<ObjectInfo>> infoCache;

	RecentInfoCache(DhtReaderOptions options) {
		final int sz = options.getRecentInfoCacheSize();
		infoCache = new LinkedHashMap<ObjectId, List<ObjectInfo>>(sz, 0.75f, true) {
			private static final long serialVersionUID = 1L;

			@Override
			protected boolean removeEldestEntry(Entry<ObjectId, List<ObjectInfo>> e) {
				return sz < size();
			}
		};
	}

	List<ObjectInfo> get(AnyObjectId id) {
		return infoCache.get(id);
	}

	void put(AnyObjectId id, List<ObjectInfo> info) {
		infoCache.put(id.copy(), copyList(info));
	}

	private static List<ObjectInfo> copyList(List<ObjectInfo> info) {
		int cnt = info.size();
		if (cnt == 1)
			return Collections.singletonList(info.get(0));

		ObjectInfo[] tmp = info.toArray(new ObjectInfo[cnt]);
		return Collections.unmodifiableList(Arrays.asList(tmp));
	}

	void clear() {
		infoCache.clear();
	}
}