001/*
002 * jPOS Project [http://jpos.org]
003 * Copyright (C) 2000-2026 jPOS Software SRL
004 *
005 * This program is free software: you can redistribute it and/or modify
006 * it under the terms of the GNU Affero General Public License as
007 * published by the Free Software Foundation, either version 3 of the
008 * License, or (at your option) any later version.
009 *
010 * This program is distributed in the hope that it will be useful,
011 * but WITHOUT ANY WARRANTY; without even the implied warranty of
012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
013 * GNU Affero General Public License for more details.
014 *
015 * You should have received a copy of the GNU Affero General Public License
016 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
017 */
018
019package org.jpos.iso;
020
021/**
022 * BinaryPrefixer constructs a prefix storing the length in binary.
023 * 
024 * @author joconnor
025 * @version $Revision$ $Date$
026 */
027public class BinaryPrefixer implements Prefixer
028{
029    /**
030         * A length prefixer for up to 255 chars. The length is encoded with 1 unsigned byte.
031         */
032    public static final BinaryPrefixer B = new BinaryPrefixer(1);
033
034    /**
035     * A length prefixer for up to 65535 chars. The length is encoded with 2 unsigned bytes.
036     */
037    public static final BinaryPrefixer BB = new BinaryPrefixer(2);
038
039    /** The number of digits allowed to express the length */
040    private int nBytes;
041
042    public BinaryPrefixer(int nBytes)
043    {
044        this.nBytes = nBytes;
045    }
046
047
048    @Override
049    public void encodeLength(int length, byte[] b)
050    {
051        for (int i = nBytes - 1; i >= 0; i--) {
052            b[i] = (byte)(length & 0xFF);
053            length >>= 8;
054        }
055    }
056
057    @Override
058    public int decodeLength(byte[] b, int offset)
059    {
060        int len = 0;
061        for (int i = 0; i < nBytes; i++)
062        {
063            len = 256 * len + (b[offset + i] & 0xFF);
064        }
065        return len;
066    }
067
068
069    @Override
070    public int getPackedLength()
071    {
072        return nBytes;
073    }
074}