/src/main/java/com/solab/iso8583/util/Bcd.java

/*
 * j8583 A Java implementation of the ISO8583 protocol
 * Copyright (C) 2007 Enrique Zamudio Lopez
 *
 * 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 3 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */
package com.solab.iso8583.util;

import java.math.BigInteger;
import java.text.ParseException;

/**
 * Routines for Binary Coded Digits.
 *
 * @author Enrique Zamudio
 *         Date: 23/04/13 11:24
 */
public final class Bcd {

    private Bcd(){}

    /** Decodes a BCD-encoded number as a long.
     * @param buf The byte buffer containing the BCD data.
     * @param pos The starting position in the buffer.
     * @param length The number of DIGITS (not bytes) to read. */
    public static long decodeToLong(byte[] buf, int pos, int length)
            throws IndexOutOfBoundsException {
        if (length > 18) {
            throw new IndexOutOfBoundsException("Buffer too big to decode as long");
        }
        long l = 0;
        long power = 1L;
        for (int i = pos + (length / 2) + (length % 2) - 1; i >= pos; i--) {
            l += (buf[i] & 0x0f) * power;
            power *= 10L;
            l += ((buf[i] & 0xf0) >> 4) * power;
            power *= 10L;
        }
        return l;
    }

    public static long decodeRightPaddedToLong(byte[] buf, int pos, int length)
            throws IndexOutOfBoundsException {
        if (length > 18) {
            throw new IndexOutOfBoundsException("Buffer too big to decode as long");
        }
        long l = 0;
        long power = 1L;
        int end = pos + (length / 2) + (length % 2) - 1;
        if ((buf[end] & 0xf) == 0xf) {
            l += (buf[end] & 0xf0) >> 4;
            power *= 10L;
            end--;
        }
        for (int i = end; i >= pos; i--) {
            l += (buf[i] & 0x0f) * power;
            power *= 10L;
            l += ((buf[i] & 0xf0) >> 4) * power;
            power *= 10L;
        }
        return l;
    }

    /** Encode the value as BCD and put it in the buffer. The buffer must be big enough
   	 * to store the digits in the original value (half the length of the string). */
    public static void encode(String value, byte[] buf) {
        int charpos = 0; //char where we start
        int bufpos = 0;
        if (value.length() % 2 == 1) {
            //for odd lengths we encode just the first digit in the first byte
            buf[0] = (byte)(value.charAt(0) - 48);
            charpos = 1;
            bufpos = 1;
        }
        //encode the rest of the string
        while (charpos < value.length()) {
            buf[bufpos] = (byte)(((value.charAt(charpos) - 48) << 4)
                | (value.charAt(charpos + 1) - 48));
            charpos += 2;
            bufpos++;
        }
    }

    /** Encode the value as BCD and put it in the buffer. The buffer must be big enough
   	 * to store the digits in the original value (half the length of the string).
     * If the value contains an odd number of digits, the last one is stored in
     * its own byte at the end, padded with an F nibble. */
    public static void encodeRightPadded(String value, byte[] buf) {
        int bufpos = 0;
        int charpos = 0;
        int limit = value.length();
        if (limit % 2 == 1) {
            limit--;
        }
        //encode the rest of the string
        while (charpos < limit) {
            buf[bufpos] = (byte)(((value.charAt(charpos) - 48) << 4)
                | (value.charAt(charpos + 1) - 48));
            charpos += 2;
            bufpos++;
        }
        if (value.length() % 2 == 1) {
            buf[bufpos] = (byte)(((value.charAt(limit) - 48) << 4)
                | 0xf);
        }
    }

    /** Decodes a BCD-encoded number as a BigInteger.
     * @param buf The byte buffer containing the BCD data.
     * @param pos The starting position in the buffer.
     * @param length The number of DIGITS (not bytes) to read. */
    public static BigInteger decodeToBigInteger(byte[] buf, int pos, int length)
            throws IndexOutOfBoundsException {
        char[] digits = new char[length];
        int start = 0;
        int i = pos;
        if (length % 2 != 0) {
            digits[start++] = (char)((buf[i] & 0x0f) + 48);
            i++;
        }
        for (;i < pos + (length / 2) + (length % 2); i++) {
            digits[start++] = (char)(((buf[i] & 0xf0) >> 4) + 48);
            digits[start++] = (char)((buf[i] & 0x0f) + 48);
        }
        return new BigInteger(new String(digits));
    }

    /** Decodes a right-padded BCD-encoded number as a BigInteger.
     * @param buf The byte buffer containing the BCD data.
     * @param pos The starting position in the buffer.
     * @param length The number of DIGITS (not bytes) to read. */
    public static BigInteger decodeRightPaddedToBigInteger(byte[] buf, int pos, int length)
            throws IndexOutOfBoundsException {
        char[] digits = new char[length];
        int start = 0;
        int i = pos;
        int limit = pos + (length / 2) + (length % 2);
        for (;i < limit; i++) {
            digits[start++] = (char)(((buf[i] & 0xf0) >> 4) + 48);
            int r = buf[i] & 0xf;
            digits[start++] = r == 15 ? ' ' : (char)(r + 48);
        }
        return new BigInteger(new String(digits, 0, start).trim());
    }

    /** Convert two bytes of BCD length to an int,
     * e.g. 0x4521 into 4521, starting at the specified offset. */
    public static int parseBcdLength(byte b) {
        return (((b & 0xf0) >> 4) * 10) + (b & 0xf);
    }

    /** Convert two bytes of BCD length to an int,
     * e.g. 0x4521 into 4521, starting at the specified offset. */
    public static int parseBcdLength2bytes(byte[] b, int offset) {
        return (((b[offset] & 0xf0) >> 4) * 1000) + ((b[offset] & 0xf) * 100) +
               (((b[offset + 1] & 0xf0) >> 4) * 10) + (b[offset + 1] & 0xf);
    }
}