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package com.jcohy.security.AsymmetricAlgorithm;

/**
 * BCD码（Binary-Coded Decimal‎）亦称二进码十进数或二-十进制代码

 * BCD码这种编码形式利用了四个位元来储存一个十进制的数码，使二进制和十进制之间的转换得以快捷的进行

 * see http://blog.chinaunix.net/uid-21273878-id-4733738.html
 *
 * @author Looly
 */
public class BCD {
    /**
     * 字符串转BCD码
     *
     * @param asc ASCII字符串
     * @return BCD
     */
    public static byte[] strToBcd(String asc) {
        int len = asc.length();
        int mod = len % 2;
        if (mod != 0) {
            asc = "0" + asc;
            len = asc.length();
        }
        byte abt[] = new byte[len];
        if (len >= 2) {
            len = len / 2;
        }
        byte bbt[] = new byte[len];
        abt = asc.getBytes();
        int j, k;
        for (int p = 0; p < asc.length() / 2; p++) {
            if ((abt[2 * p] >= '0') && (abt[2 * p] <= '9')) {
                j = abt[2 * p] - '0';
            } else if ((abt[2 * p] >= 'a') && (abt[2 * p] <= 'z')) {
                j = abt[2 * p] - 'a' + 0x0a;
            } else {
                j = abt[2 * p] - 'A' + 0x0a;
            }
            if ((abt[2 * p + 1] >= '0') && (abt[2 * p + 1] <= '9')) {
                k = abt[2 * p + 1] - '0';
            } else if ((abt[2 * p + 1] >= 'a') && (abt[2 * p + 1] <= 'z')) {
                k = abt[2 * p + 1] - 'a' + 0x0a;
            } else {
                k = abt[2 * p + 1] - 'A' + 0x0a;
            }
            int a = (j << 4) + k;
            byte b = (byte) a;
            bbt[p] = b;
            System.out.format("%02X\n", bbt[p]);
        }
        return bbt;
    }

    /**
     * ASCII转BCD
     *
     * @param ascii ASCII byte数组
     * @return BCD
     */
    public static byte[] ascToBcd(byte[] ascii) {
        return ascToBcd(ascii, ascii.length);
    }

    /**
     * ASCII转BCD
     *
     * @param ascii     ASCII byte数组
     * @param ascLength 长度
     * @return BCD
     */
    public static byte[] ascToBcd(byte[] ascii, int ascLength) {
        byte[] bcd = new byte[ascLength / 2];
        int j = 0;
        for (int i = 0; i < (ascLength + 1) / 2; i++) {
            bcd[i] = ascToBcd(ascii[j++]);
            bcd[i] = (byte) (((j >= ascLength) ? 0x00 : ascToBcd(ascii[j++])) + (bcd[i] << 4));
//            System.out.format("%02X\n", bcd[i]);
        }
        return bcd;
    }

    /**
     * BCD转ASCII字符串
     *
     * @param bytes BCD byte数组
     * @return ASCII字符串
     */
    public static String bcdToStr(byte[] bytes) {
        char temp[] = new char[bytes.length * 2], val;

        for (int i = 0; i < bytes.length; i++) {
            val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);
            temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');

            val = (char) (bytes[i] & 0x0f);
            temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');
        }
        return new String(temp);
    }

    /**
     * 转换单个byte为BCD
     *
     * @param asc ACSII
     * @return BCD
     */
    private static byte ascToBcd(byte asc) {
        byte bcd;

        if ((asc >= '0') && (asc <= '9'))
            bcd = (byte) (asc - '0');
        else if ((asc >= 'A') && (asc <= 'F'))
            bcd = (byte) (asc - 'A' + 10);
        else if ((asc >= 'a') && (asc <= 'f'))
            bcd = (byte) (asc - 'a' + 10);
        else
            bcd = (byte) (asc - 48);
        return bcd;
    }
}