Base16.java

package io.multibase;

public class Base16 {
  public static byte[] decode(String hex) {
    if (hex.length() % 2 == 1)
      throw new IllegalArgumentException(
          "Must have an even number of hex digits to convert to bytes!");
    byte[] res = new byte[hex.length() / 2];
    for (int i = 0; i < res.length; i++)
      res[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
    return res;
  }

  public static String encode(byte[] data) {
    return bytesToHex(data);
  }

  private static String[] HEX_DIGITS =
      new String[] {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
  private static String[] HEX = new String[256];

  static {
    for (int i = 0; i < 256; i++) HEX[i] = HEX_DIGITS[(i >> 4) & 0xF] + HEX_DIGITS[i & 0xF];
  }

  public static String byteToHex(byte b) {
    return HEX[b & 0xFF];
  }

  public static String bytesToHex(byte[] data) {
    StringBuilder s = new StringBuilder();
    for (byte b : data) s.append(byteToHex(b));
    return s.toString();
  }
}