/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Android Sync Client.
 *
 * The Initial Developer of the Original Code is
 * the Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2011
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Chenxia Liu <liuche@mozilla.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.gecko.sync.jpake;

import java.math.BigInteger;

public class BigIntegerHelper {

  public static byte[] BigIntegerToByteArrayWithoutSign(BigInteger value) {
    byte[] bytes = value.toByteArray();
    if (bytes[0] == (byte) 0) {
      bytes = copyArray(bytes, 1, bytes.length - 1);
    }
    return bytes;
  }

  private static byte[] copyArray(byte[] original, int start, int length) {
    byte[] copy = new byte[length];
    System.arraycopy(original, start, copy, 0,
        Math.min(original.length - start, length));
    return copy;
  }

  /**
   * Convert an array of bytes to a non-negative big integer.
   */
  public static BigInteger ByteArrayToBigIntegerWithoutSign(byte[] array) {
    return new BigInteger(1, array);
  }

  /**
   * Convert a big integer into hex string. If the length is not even, add an
   * '0' character in the beginning to make it even.
   */
  public static String toEvenLengthHex(BigInteger value) {
    String result = value.toString(16);
    if (result.length() % 2 != 0) {
      result = "0" + result;
    }
    return result;
  }
}
