ByteUtils.java

/**
 * This program 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 3 of the License, or
 * (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * @author Arne Kepp, The Open Planning Project, Copyright 2008
 */
package org.geowebcache.util;

public class ByteUtils {
    
    /**
     * Converts an unsigned 32 bit integer, stored in a long, into an array of bytes.
     *
     * @param j a long
     * @return byte[4] representing the unsigned integer, most significant bit first.
     */
    public static byte[] uIntLongToByteWord(long j) {
        int i = (int) j;
        byte[] byteWord = new byte[4];
        byteWord[0] = (byte) ((i >>> 24) & 0x000000FF);
        byteWord[1] = (byte) ((i >> 16) & 0x000000FF);
        byteWord[2] = (byte) ((i >> 8) & 0x000000FF);
        byteWord[3] = (byte) (i & 0x00FF);
        return byteWord;
    }
    
    /**
     * Combines four bytes (most significant bit first) into a 32 bit unsigned integer.
     *
     * @param bytes
     * @param index of most significant byte
     * @return long with the 32 bit unsigned integer
     */
    public static long bytesToUIntLong(byte[] bytes, int index) {
        long accum = 0;
        int i = 3;
        for (int shiftBy = 0; shiftBy < 32; shiftBy += 8 ) {
            accum |= ( (long)( bytes[index + i] & 0xff ) ) << shiftBy;
            i--;
        }
        return accum;
    }
}