Rand.java example

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Lucee-master
/**
 *
 * Copyright (c) 2014, the Railo Company Ltd. 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.
 * 
 * You should have received a copy of the GNU Lesser General Public 
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 * 
 **/
/**
 * Implements the CFML Function rand
 */
package lucee.runtime.functions.math;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Map;
import java.util.Random;

import lucee.commons.collection.HashMapPro;
import lucee.runtime.PageContext;
import lucee.runtime.crypt.CFMXCompat;
import lucee.runtime.exp.ExpressionException;
import lucee.runtime.ext.function.Function;

public final class Rand implements Function {

    private static Map<String, Random> randoms = new HashMapPro<String, Random>();

	public static double call(PageContext pc ) throws ExpressionException {

		return getRandom( CFMXCompat.ALGORITHM_NAME, Double.NaN ).nextDouble();
	}

	public static double call(PageContext pc, String algorithm) throws ExpressionException {

        return getRandom( algorithm, Double.NaN ).nextDouble();
	}

    static synchronized Random getRandom(String algorithm, Double seed) throws ExpressionException {

        algorithm = algorithm.toLowerCase();

        Random result = randoms.get( algorithm );

        if ( result == null || !seed.isNaN() ) {
            if (CFMXCompat.ALGORITHM_NAME.equalsIgnoreCase( algorithm )) {

                result = new Random();
            }
            else {

                try {

                    result = SecureRandom.getInstance( algorithm );
                }
                catch (NoSuchAlgorithmException e) {
                    throw new ExpressionException("random algorithm ["+algorithm+"] is not installed on the system",e.getMessage());
                }
            }

            if ( !seed.isNaN() )
                result.setSeed( seed.longValue() );

            randoms.put( algorithm, result );
        }

        return result;
    }
}