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id codec
There is a newer version: 1.1.7
/*
 * Copyright 2012 Jin Kwon .
 *
 * Licensed 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 com.github.jinahya.codec;


import java.util.UUID;


/**
 * A class for decoding identifiers.
 *
 * @author Jin Kwon <jinahya_at_gmail.com>
 */
public class IdDecoder extends IdCodecBase {


    @Override
    public IdDecoder scale(int scale) {

        return super.scale(scale);
    }


    @Override
    public IdDecoder radix(int radix) {

        return super.radix(radix);
    }


    /**
     * Decodes a single block.
     *
     * @param encoded the block to decode
     * @param radix the radix
     * @param scale the scale
     *
     * @return decoded output
     */
    private long block(final String encoded) {

        final StringBuilder builder = new StringBuilder(
            Long.toString(Long.parseLong(encoded, getRadix())));

        builder.reverse();

        builder.delete(builder.length() - getScale(), builder.length());

        return Long.parseLong(builder.toString());
    }


    /**
     * Decodes given value.
     *
     * @param encoded the value to decode.
     *
     * @return decoded value
     */
    public long decode(final String encoded) {

        final int index = encoded.indexOf('-');

        return (block(encoded.substring(0, index)) << Integer.SIZE)
               | (block(encoded.substring(index + 1)));
    }


    /**
     * Decodes given value.
     *
     * @param encoded the value to decode.
     *
     * @return decoded value
     */
    public UUID decodeUuid(final String encoded) {

        final int first = encoded.indexOf('-');
        final int second = encoded.indexOf('-', first + 1);
        final long mostSignificantBits = decode(encoded.substring(0, second));
        final long leastSignificantBits = decode(encoded.substring(second + 1));

        return new UUID(mostSignificantBits, leastSignificantBits);
    }

}