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/*
* 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
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.zookeeper.server;
import java.nio.ByteBuffer;
import java.util.zip.CRC32;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.data.StatPersisted;
/**
* Defines how to calculate the digest for a given node.
*/
public class DigestCalculator {
// The hardcoded digest version, should bump up this version whenever
// we changed the digest method or fields.
private static final int DIGEST_VERSION = 2;
/**
* Calculate the digest based on the given params.
*
* Besides the path and data, the following stat fields are included in
* the digest calculation:
*
* - long czxid 8 bytes
* - long mzxid 8 bytes
* - long pzxid 8 bytes
* - long ctime 8 bytes
* - long mtime 8 bytes
* - int version 4 bytes
* - int cversion 4 bytes
* - int aversion 4 bytes
* - long ephemeralOwner 8 bytes
*
* @param path the path of the node
* @param data the data of the node
* @param stat the stat associated with the node
* @return the digest calculated from the given params
*/
long calculateDigest(String path, byte[] data, StatPersisted stat) {
if (!ZooKeeperServer.isDigestEnabled()) {
return 0;
}
// Quota nodes are updated locally, there is inconsistent issue
// when we tried to release digest feature at the beginning.
//
// Instead of taking time to fix that, we decided to disable digest
// check for all the nodes under /zookeeper/ first.
//
// We can enable this after fixing that inconsistent problem. The
// digest version in the protocol enables us to change the digest
// calculation without disrupting the system.
if (path.startsWith(ZooDefs.ZOOKEEPER_NODE_SUBTREE)) {
return 0;
}
// "" and "/" are aliases to each other, in DataTree when adding child
// under "/", it will use "" as the path, but when set data or change
// ACL on "/", it will use "/" as the path. Always mapping "/" to ""
// to avoid mismatch.
if (path.equals("/")) {
path = "";
}
// total = 8 * 6 + 4 * 3 = 60 bytes
byte[] b = new byte[60];
ByteBuffer bb = ByteBuffer.wrap(b);
bb.putLong(stat.getCzxid());
bb.putLong(stat.getMzxid());
bb.putLong(stat.getPzxid());
bb.putLong(stat.getCtime());
bb.putLong(stat.getMtime());
bb.putInt(stat.getVersion());
bb.putInt(stat.getCversion());
bb.putInt(stat.getAversion());
bb.putLong(stat.getEphemeralOwner());
CRC32 crc = new CRC32();
crc.update(path.getBytes());
if (data != null) {
crc.update(data);
}
crc.update(b);
return crc.getValue();
}
/**
* Calculate the digest based on the given path and data node.
*/
long calculateDigest(String path, DataNode node) {
if (!node.isDigestCached()) {
node.setDigest(calculateDigest(path, node.getData(), node.stat));
node.setDigestCached(true);
}
return node.getDigest();
}
/**
* Returns with the current digest version.
*/
int getDigestVersion() {
return DIGEST_VERSION;
}
}