org.eclipse.jgit.storage.dht/src/org/eclipse/jgit/storage/dht/spi/cache/CacheRepositoryIndexTable.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.
 *
 * - 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
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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package org.eclipse.jgit.storage.dht.spi.cache;

import static java.util.Collections.emptyMap;
import static java.util.Collections.singleton;

import java.util.Map;
import java.util.concurrent.TimeoutException;

import org.eclipse.jgit.storage.dht.DhtException;
import org.eclipse.jgit.storage.dht.RepositoryKey;
import org.eclipse.jgit.storage.dht.RepositoryName;
import org.eclipse.jgit.storage.dht.Sync;
import org.eclipse.jgit.storage.dht.spi.RepositoryIndexTable;
import org.eclipse.jgit.storage.dht.spi.cache.CacheService.Change;

/** Cache wrapper around RepositoryIndexTable. */
public class CacheRepositoryIndexTable implements RepositoryIndexTable {
	private final RepositoryIndexTable db;

	private final CacheService client;

	private final CacheOptions options;

	private final Namespace ns;

	private final Sync<Void> none;

	/**
	 * Initialize a new wrapper.
	 *
	 * @param dbTable
	 *            the underlying database's corresponding table.
	 * @param cacheDatabase
	 *            the cache database.
	 */
	public CacheRepositoryIndexTable(RepositoryIndexTable dbTable,
			CacheDatabase cacheDatabase) {
		this.db = dbTable;
		this.client = cacheDatabase.getClient();
		this.options = cacheDatabase.getOptions();
		this.ns = Namespace.REPOSITORY_INDEX;
		this.none = Sync.none();
	}

	public RepositoryKey get(RepositoryName name) throws DhtException,
			TimeoutException {
		CacheKey memKey = ns.key(name);
		Sync<Map<CacheKey, byte[]>> sync = Sync.create();
		client.get(singleton(memKey), sync);

		Map<CacheKey, byte[]> result;
		try {
			result = sync.get(options.getTimeout());
		} catch (InterruptedException e) {
			throw new TimeoutException();
		} catch (TimeoutException timeout) {
			// Fall through and read the database directly.
			result = emptyMap();
		}

		byte[] data = result.get(memKey);
		if (data != null) {
			if (data.length == 0)
				return null;
			return RepositoryKey.fromBytes(data);
		}

		RepositoryKey key = db.get(name);
		data = key != null ? key.asBytes() : new byte[0];
		client.modify(singleton(Change.put(memKey, data)), none);
		return key;
	}

	public void putUnique(RepositoryName name, RepositoryKey key)
			throws DhtException, TimeoutException {
		db.putUnique(name, key);

		Sync<Void> sync = Sync.create();
		CacheKey memKey = ns.key(name);
		byte[] data = key.asBytes();
		client.modify(singleton(Change.put(memKey, data)), sync);
		try {
			sync.get(options.getTimeout());
		} catch (InterruptedException e) {
			throw new TimeoutException();
		}
	}

	public void remove(RepositoryName name, RepositoryKey key)
			throws DhtException, TimeoutException {
		db.remove(name, key);

		Sync<Void> sync = Sync.create();
		CacheKey memKey = ns.key(name);
		client.modify(singleton(Change.remove(memKey)), sync);
		try {
			sync.get(options.getTimeout());
		} catch (InterruptedException e) {
			throw new TimeoutException();
		}
	}
}