michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.sync.jpake;
michael@0: 
michael@0: import java.math.BigInteger;
michael@0: 
michael@0: public class BigIntegerHelper {
michael@0: 
michael@0:   public static byte[] BigIntegerToByteArrayWithoutSign(BigInteger value) {
michael@0:     byte[] bytes = value.toByteArray();
michael@0:     if (bytes[0] == (byte) 0) {
michael@0:       bytes = copyArray(bytes, 1, bytes.length - 1);
michael@0:     }
michael@0:     return bytes;
michael@0:   }
michael@0: 
michael@0:   private static byte[] copyArray(byte[] original, int start, int length) {
michael@0:     byte[] copy = new byte[length];
michael@0:     System.arraycopy(original, start, copy, 0,
michael@0:         Math.min(original.length - start, length));
michael@0:     return copy;
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Convert an array of bytes to a non-negative big integer.
michael@0:    */
michael@0:   public static BigInteger ByteArrayToBigIntegerWithoutSign(byte[] array) {
michael@0:     return new BigInteger(1, array);
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Convert a big integer into hex string. If the length is not even, add an
michael@0:    * '0' character in the beginning to make it even.
michael@0:    */
michael@0:   public static String toEvenLengthHex(BigInteger value) {
michael@0:     String result = value.toString(16);
michael@0:     if (result.length() % 2 != 0) {
michael@0:       result = "0" + result;
michael@0:     }
michael@0:     return result;
michael@0:   }
michael@0: }