/*
 * Copyright 2020 Signal Messenger, LLC
 * SPDX-License-Identifier: AGPL-3.0-only
 */

package org.signal.storageservice.s3;


public class Base16Lower {

  private final static char[] HEX = new char[]{
      '0', '1', '2', '3', '4', '5', '6', '7',
      '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

  /**
   * Convert bytes to a base16 string.
   */
  public static String encode(byte[] byteArray) {
    StringBuffer hexBuffer = new StringBuffer(byteArray.length * 2);
    for (int i = 0; i < byteArray.length; i++)
      for (int j = 1; j >= 0; j--)
        hexBuffer.append(HEX[(byteArray[i] >> (j * 4)) & 0xF]);
    return hexBuffer.toString();
  }

  /**
   * Convert a base16 string into a byte array.
   */
  public static byte[] decode(String s) {
    int len = s.length();
    byte[] r = new byte[len / 2];
    for (int i = 0; i < r.length; i++) {
      int digit1 = s.charAt(i * 2), digit2 = s.charAt(i * 2 + 1);
      if (digit1 >= '0' && digit1 <= '9')
        digit1 -= '0';
      else if (digit1 >= 'A' && digit1 <= 'F')
        digit1 -= 'A' - 10;
      if (digit2 >= '0' && digit2 <= '9')
        digit2 -= '0';
      else if (digit2 >= 'A' && digit2 <= 'F')
        digit2 -= 'A' - 10;

      r[i] = (byte) ((digit1 << 4) + digit2);
    }
    return r;
  }
}