// Crib'd from cryptix -jis

/*
 * Copyright (c) 1997 Systemics Ltd
 * on behalf of the Cryptix Development Team.  All rights reserved.
 *
 * Derived partly from code Copyright (c) 1996 Type & Graphics Pty
 * Limited.  All rights reserved.
 */

package mit.cipher;

import java.io.PrintWriter;

/**
 * Static methods for converting to and from hexadecimal strings.
 * <p>
 *
 * <b>Copyright</b> &copy; 1995-1997
 * <a href="http://www.systemics.com/">Systemics Ltd</a> on behalf of the
 * <a href="http://www.systemics.com/docs/cryptix/">Cryptix Development Team</a>.
 * <br>All rights reserved.
 *
 * <p><b>$Revision: 1.1 $</b>
 * @author  David Hopwood
 * @author  Raif Naffah
 * @author  Systemics Ltd
 * @since   Cryptix 2.2.0a, 2.2.2
 */
public class Hex
{
    private Hex() {} // static methods only

    private static final char[] hexDigits = {
        '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'
    };

    /**
     * Returns a string of hexadecimal digits from a byte array. Each
     * byte is converted to 2 hex symbols.
     * <p>
     * If offset and length are omitted, the whole array is used.
     */
    public static String toString(byte[] ba, int offset, int length) {
        char[] buf = new char[length * 2];
        int j = 0;
        int k;

        for (int i = offset; i < offset + length; i++) {
            k = ba[i];
            buf[j++] = hexDigits[(k >>> 4) & 0x0F];
            buf[j++] = hexDigits[ k        & 0x0F];
        }
        return new String(buf);
    }

    public static String toString(byte[] ba) {
        return toString(ba, 0, ba.length);
    }

    /**
     * Returns a string of hexadecimal digits from an integer array. Each
     * int is converted to 4 hex symbols.
     * <p>
     * If offset and length are omitted, the whole array is used.
     */
    public static String toString(int[] ia, int offset, int length) {
        char[] buf = new char[length * 8];
        int j = 0;
        int k;

        for (int i = offset; i < offset + length; i++) {
            k = ia[i];
            buf[j++] = hexDigits[(k >>> 28) & 0x0F];
            buf[j++] = hexDigits[(k >>> 24) & 0x0F];
            buf[j++] = hexDigits[(k >>> 20) & 0x0F];
            buf[j++] = hexDigits[(k >>> 16) & 0x0F];
            buf[j++] = hexDigits[(k >>> 12) & 0x0F];
            buf[j++] = hexDigits[(k >>>  8) & 0x0F];
            buf[j++] = hexDigits[(k >>>  4) & 0x0F];
            buf[j++] = hexDigits[ k         & 0x0F];
        }
        return new String(buf);
    }

    public static String toString(int[] ia) {
        return toString(ia, 0, ia.length);
    }

    /**
     * Returns a string of hexadecimal digits in reverse order from a byte array
     * (i.e. the least significant byte is first, but within each byte the
     * most significant hex digit is before the least significant hex digit).
     * <p>
     * If offset and length are omitted, the whole array is used.
     */
    public static String toReversedString(byte[] b, int offset, int length) {
        char[] buf = new char[length * 2];
        int j = 0;

        for (int i = offset + length - 1; i >= offset; i--) {
            buf[j++] = hexDigits[(b[i] >>> 4) & 0x0F];
            buf[j++] = hexDigits[ b[i]        & 0x0F];
        }
        return new String(buf);
    }

    public static String toReversedString(byte[] b) {
        return toReversedString(b, 0, b.length);
    }

    /**
     * Returns a byte array from a string of hexadecimal digits.
     */
    public static byte[] fromString(String hex) {
        int len = hex.length();
        byte[] buf = new byte[((len + 1) / 2)];

        int i = 0, j = 0;
        if ((len % 2) == 1)
            buf[j++] = (byte) fromDigit(hex.charAt(i++));

        while (i < len) {
            buf[j++] = (byte) ((fromDigit(hex.charAt(i++)) << 4) |
                                fromDigit(hex.charAt(i++)));
        }
        return buf;
    }

    /**
     * Returns a byte array from a string of hexadecimal digits in reverse
     * order (i.e. the least significant byte is first, but within each byte the
     * most significant hex digit is before the least significant hex digit).
     * The string must have an even number of digits.
     * <p>
     * This is not really either little nor big-endian; it's just obscure. It is
     * here because it is the format used for the SPEED certification data.
     */
    public static byte[] fromReversedString(String hex) {
        int len = hex.length();
        byte[] buf = new byte[((len + 1) / 2)];

        int j = 0;
        if ((len % 2) == 1) throw new IllegalArgumentException(
            "string must have an even number of digits");

        while (len > 0) {
            buf[j++] = (byte) (fromDigit(hex.charAt(--len)) |
                              (fromDigit(hex.charAt(--len)) << 4));
        }
        return buf;
    }

    /**
     * Returns the hex digit corresponding to a number <i>n</i>, from 0 to 15.
     */
    public static char toDigit(int n) {
        try {
            return hexDigits[n];
        } catch (ArrayIndexOutOfBoundsException e) {
            throw new IllegalArgumentException(n +
                " is out of range for a hex digit");
        }
    }

    /**
     * Returns the number from 0 to 15 corresponding to the hex digit <i>ch</i>.
     */
    public static int fromDigit(char ch) {
        if (ch >= '0' && ch <= '9')
            return ch - '0';
        if (ch >= 'A' && ch <= 'F')
            return ch - 'A' + 10;
        if (ch >= 'a' && ch <= 'f')
            return ch - 'a' + 10;

        throw new IllegalArgumentException("invalid hex digit '" + ch + "'");
    }

    /**
     * Returns a string of 2 hexadecimal digits (most significant digit first)
     * corresponding to the lowest 8 bits of <i>n</i>.
     */
    public static String byteToString(int n) {
        char[] buf = { hexDigits[(n >>> 4) & 0x0F], hexDigits[n & 0x0F] };
        return new String(buf);
    }

    /**
     * Returns a string of 4 hexadecimal digits (most significant digit first)
     * corresponding to the lowest 16 bits of <i>n</i>.
     */
    public static String shortToString(int n) {
        char[] buf = { hexDigits[(n >>> 12) & 0x0F], hexDigits[(n >>> 8) & 0x0F],
                       hexDigits[(n >>> 4)  & 0x0F], hexDigits[ n        & 0x0F] };
        return new String(buf);
    }

    /**
     * Returns a string of 8 hexadecimal digits (most significant digit first)
     * corresponding to the integer <i>n</i>, which is treated as unsigned.
     */
    public static String intToString(int n) {
        char[] buf = new char[8];
            
        for (int i = 7; i >= 0; i--) {
            buf[i] = hexDigits[n & 0x0F];
            n >>>= 4;
        }
        return new String(buf);
    }

    /**
     * Returns a string of 16 hexadecimal digits (most significant digit first)
     * corresponding to the long <i>n</i>, which is treated as unsigned.
     */
    public static String longToString(long n) {
        char[] buf = new char[16];
            
        for (int i = 15; i >= 0; i--) {
            buf[i] = hexDigits[(int)n & 0x0F];
            n >>>= 4;
        }
        return new String(buf);
    }

    /**
     * Dump a byte array as a string, in a format that is easy to read for
     * debugging. The string <i>m</i> is prepended to the start of each line.
     * <p>
     * If offset and length are omitted, the whole array is used. If m is
     * omitted, nothing is prepended to each line.
     *
     * @param  data     the byte array to be dumped
     * @param  offset   the offset within <i>data</i> to start from
     * @param  length   the number of bytes to dump
     * @param  m        a string to be prepended to each line
     * @return a String containing the dump.
     */
    public static String dumpString(byte[] data, int offset, int length, String m) {
        if (data == null) return m + "null\n";

        StringBuffer sb = new StringBuffer(length * 3);
        if (length > 32)
            sb.append(m).append("Hexadecimal dump of ").append(length)
              .append(" bytes...\n");

        // each line will list 32 bytes in 4 groups of 8 each
        int end = offset + length;
        String s;
        int l = Integer.toString(length).length();
        if (l < 4) l = 4;
        for (; offset < end; offset += 32) {
            if (length > 32) {
                s = "         " + offset;
                sb.append(m).append(s.substring(s.length()-l)).append(": ");
            }
            int i = 0;
            for (; i < 32 && offset + i + 7 < end; i += 8)
                sb.append(toString(data, offset + i, 8)).append(' ');

            if (i < 32) {
                for (; i < 32 && offset + i < end; i++)
                    sb.append(byteToString(data[offset + i]));
            }
            sb.append('\n');
        }
        return sb.toString();
    }

    public static String dumpString(byte[] data) {
        return (data == null) ? "null\n"
                              : dumpString(data, 0, data.length, "");
    }

    public static String dumpString(byte[] data, String m) {
        return (data == null) ? "null\n"
                              : dumpString(data, 0, data.length, m);
    }

    public static String dumpString(byte[] data, int offset, int length) {
        return dumpString(data, offset, length, "");
    }

    /**
     * Dump an int array as a string, in a format that is easy to read for
     * debugging. The string <i>m</i> is prepended to the start of each line.
     * <p>
     * If offset and length are omitted, the whole array is used. If m is
     * omitted, nothing is prepended to each line.
     *
     * @param  data     The int[] to dump
     * @param  offset   The offset within <i>data</i> to start from
     * @param  length   The number of ints to dump
     * @param  m        A string to prepend to each line
     * @return A String containing the dump.
     */
    public static String dumpString(int[] data, int offset, int length, String m)
    {
        if (data == null) return m + "null\n";

        StringBuffer sb = new StringBuffer(length * 3);
        if (length > 8)
            sb.append(m).append("Hexadecimal dump of ").append(length)
              .append(" integers...\n");

        // each line will list 32 bytes in 8 groups of 4 each (1 int)
        int end = offset + length;
        String s;
        int x = Integer.toString(length).length();
        if (x < 8) x = 8;
        for ( ; offset < end; ) {
            if (length > 8) {
                s = "         " + offset;
                sb.append(m).append(s.substring(s.length()-x)).append(": ");
            }
            for (int i = 0; i < 8 && offset < end; i++)
                sb.append(intToString(data[offset++])).append(' ');
            sb.append('\n');
        }
        return sb.toString();
    }

    public static String dumpString(int[] data) {
        return dumpString(data, 0, data.length, "");
    }

    public static String dumpString(int[] data, String m) {
        return dumpString(data, 0, data.length, m);
    }

    public static String dumpString(int[] data, int offset, int length) {
        return dumpString(data, offset, length, "");
    }


// Test methods
//...........................................................................

    public static void main(String[] args) {
        self_test(new PrintWriter(System.out, true));
    }

    public static void self_test(PrintWriter out) {
        String test = "Hello. This is a test string with more than 32 characters.";
        byte[] buf = new byte[test.length()];
        for (int i = 0; i < test.length(); i++) {
            buf[i] = (byte) test.charAt(i);
        }
        String s;
        byte[] buf2;

        s = toString(buf);
        out.println("Hex.toString(buf) = " + s);
        buf2 = fromString(s);
        if (!ArrayUtil.areEqual(buf, buf2))
            System.out.println("buf != buf2");

        s = toReversedString(buf);
        out.println("Hex.toReversedString(buf) = " + s);
        buf2 = fromReversedString(s);
        if (!ArrayUtil.areEqual(buf, buf2))
            out.println("buf != buf2");

        out.print("Hex.dumpString(buf, 0, 28) =\n" + dumpString(buf, 0, 28));
        out.print("Hex.dumpString(null) =\n" + dumpString((byte[]) null));
        out.print(dumpString(buf, "+++"));

        out.flush();
    }
}