content: package io.jafka.jeos.util.ecc;
  
  public class Hex {
  
      /**
       * Used to build output as Hex
       */
      private static final char[] DIGITS_LOWER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
  
      /**
       * Used to build output as Hex
       */
      private static final char[] DIGITS_UPPER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
  
      public static char[] encodeHex(final byte[] data) {
          return encodeHex(data, true);
      }
  
      public static char[] encodeHex(final byte[] data, final boolean toLowerCase) {
          return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
      }
  
      protected static char[] encodeHex(final byte[] data, final char[] toDigits) {
          final int l = data.length;
          final char[] out = new char[l << 1];
          // two characters form the hex value.
          for (int i = 0, j = 0; i < l; i++) {
              out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
              out[j++] = toDigits[0x0F & data[i]];
          }
          return out;
      }
  
      public static byte[] toBytes(final char[] data) throws RuntimeException {
  
          final int len = data.length;
  
          if ((len & 0x01) != 0) {
              throw new RuntimeException("Odd number of characters.");
          }
  
          final byte[] out = new byte[len >> 1];
  
          // two characters form the hex value.
          for (int i = 0, j = 0; j < len; i++) {
              int f = toDigit(data[j], j) << 4;
              j++;
              f = f | toDigit(data[j], j);
              j++;
              out[i] = (byte) (f & 0xFF);
          }
  
          return out;
      }
  
      public static byte[] toBytes(String hex) {
          return toBytes(hex.toCharArray());
      }
  
      protected static int toDigit(final char ch, final int index) throws RuntimeException {
          final int digit = Character.digit(ch, 16);
          if (digit == -1) {
              throw new RuntimeException("Illegal hexadecimal character " + ch + " at index " + index);
          }
          return digit;
      }
  
      public static String toHex(final byte[] data) {
          return new String(encodeHex(data));
      }
  }
  