com.liferay.portal.kernel.util.DeterminateKeyGenerator.java Source code

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Here is the source code for com.liferay.portal.kernel.util.DeterminateKeyGenerator.java

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/**
 * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 */

package com.liferay.portal.kernel.util;

import com.liferay.petra.lang.CentralizedThreadLocal;

import java.util.HashMap;
import java.util.Map;

/**
 * <p>
 * See https://issues.liferay.com/browse/LPS-6872.
 * </p>
 *
 * @author Shuyang Zhou
 * @author Brian Wing Shun Chan
 */
public class DeterminateKeyGenerator {

    public static String generate(String input) {
        return generate(input, _DEFAULT_LENGTH);
    }

    public static String generate(String input, int length) {
        if (input == null) {
            throw new IllegalArgumentException("Input is null");
        }

        if (length <= 0) {
            throw new IllegalArgumentException("Length is less than or equal to 0");
        }

        Map<String, Integer> seedMap = _seedMap.get();

        Integer previousSeed = seedMap.get(input);

        int seed = 0;

        if (previousSeed == null) {
            seed = input.hashCode();
        } else {
            seed = previousSeed;
        }

        StringBuilder sb = new StringBuilder(length);

        for (int i = 0; i < length; i++) {
            int index = 0;

            if (seed > 0) {
                index = seed % 26;
            } else {
                index = -seed % 26;
            }

            sb.append(_CHARACTERS[index]);

            seed = _nextRandom(seed);
        }

        seedMap.put(input, seed);

        return sb.toString();
    }

    public static void reset() {
        Map<String, Integer> seedMap = _seedMap.get();

        seedMap.clear();
    }

    public static void reset(String key) {
        Map<String, Integer> seedMap = _seedMap.get();

        seedMap.remove(key);
    }

    private static int _nextRandom(int seed) {
        return (seed % 127773) * 16807 - (seed / 127773) * 2836;
    }

    private static final char[] _CHARACTERS = "abcdefghijklmnopqrstuvwxyz".toCharArray();

    private static final int _DEFAULT_LENGTH = 4;

    private static final ThreadLocal<Map<String, Integer>> _seedMap = new CentralizedThreadLocal<>(
            DeterminateKeyGenerator.class + "._seedMap", HashMap::new);

}