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 * Implements Hex Interpreter. The Hex digits are stored in ASCII.
023 * 
024 * @author joconnor
025 * @version $Revision$ $Date$
026 */
027public class AsciiHexInterpreter implements BinaryInterpreter
028{
029    /** Public constructor; prefer {@link #INSTANCE} for repeated use. */
030    public AsciiHexInterpreter() {}
031    /** An instance of this Interpreter. Only one needed for the whole system */
032    public static final AsciiHexInterpreter INSTANCE = new AsciiHexInterpreter();
033
034    /** 0-15 to ASCII hex digit lookup table. */
035    private static final byte[] HEX_ASCII = new byte[] {
036              0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
037              0x38, 0x39, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46
038    };
039
040    /**
041     * Converts the binary data into ASCII hex digits.
042     */
043    public void interpret(byte[] data, byte[] b, int offset)
044    {
045        for (int i = 0; i < data.length; i++) {
046            b[offset + i * 2] = HEX_ASCII[(data[i] & 0xF0) >> 4];
047            b[offset + i * 2 + 1] = HEX_ASCII[data[i] & 0x0F];
048        }
049    }
050
051    /**
052     * Converts the ASCII hex digits into binary data.
053     */
054    public byte[] uninterpret(byte[] rawData, int offset, int length)
055    {
056        byte[] d = new byte[length];
057        for (int i=0; i<length*2; i++) {
058            int shift = i%2 == 1 ? 0 : 4;
059            d[i>>1] |= Character.digit((char) rawData[offset+i], 16) << shift;
060        }
061        return d;
062    }
063
064    /**
065     * Returns double nBytes because the hex representation of 1 byte needs 2 hex digits.
066     *
067     */
068    public int getPackedLength(int nBytes)
069    {
070        return nBytes * 2;
071    }
072}