org.codelibs.elasticsearch.taste.model.AbstractIDMigrator Maven / Gradle / Ivy

Go to download
/**
 * 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.codelibs.elasticsearch.taste.model;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Collection;

import org.codelibs.elasticsearch.taste.common.Refreshable;

import com.google.common.base.Charsets;

public abstract class AbstractIDMigrator implements IDMigrator {

    private final MessageDigest md5Digest;

    protected AbstractIDMigrator() {
        try {
            md5Digest = MessageDigest.getInstance("MD5");
        } catch (final NoSuchAlgorithmException nsae) {
            // Can't happen
            throw new IllegalStateException(nsae);
        }
    }

    /**
     * @return most significant 8 bytes of the MD5 hash of the string, as a long
     */
    protected final long hash(final String value) {
        byte[] md5hash;
        synchronized (md5Digest) {
            md5hash = md5Digest.digest(value.getBytes(Charsets.UTF_8));
            md5Digest.reset();
        }
        long hash = 0L;
        for (int i = 0; i < 8; i++) {
            hash = hash << 8 | md5hash[i] & 0x00000000000000FFL;
        }
        return hash;
    }

    @Override
    public long toLongID(final String stringID) {
        return hash(stringID);
    }

    @Override
    public void refresh(final Collection alreadyRefreshed) {
    }

}