Java BigInteger Calculate unsignedBigIntergerToByteArray(BigInteger bigInteger)

Description

Convert a BigInteger to a byte-array, but treat the byte-array given from the BigInteger as unsigned and removing any leading zero bytes; e.g.

License

Open Source License

Parameter

Parameter	Description
bigInteger	The BigInteger to convert.

Return

The byte-array representation of the BigInterger without signum-bit. null, if the BigInteger is null.

Declaration

public static byte[] unsignedBigIntergerToByteArray(BigInteger bigInteger)

Method Source Code


//package com.java2s;
/* Copyright  (c) 2002 Graz University of Technology. All rights reserved.
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 *  //from   w ww  .j a v  a2  s .  c o  m
 * 3. The end-user documentation included with the redistribution, if any, must
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 *    "This product includes software developed by IAIK of Graz University of
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 * 4. The names "Graz University of Technology" and "IAIK of Graz University of
 *    Technology" must not be used to endorse or promote products derived from 
 *    this software without prior written permission.
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import java.math.BigInteger;

public class Main {
    /**
     * Convert a BigInteger to a byte-array, but treat the byte-array given from
     * the BigInteger as unsigned and removing any leading zero bytes; e.g. a
     * 1024 bit integer with its highest bit set will result in an 128 byte
     * array.
     *
     * @param bigInteger The BigInteger to convert.
     * @return The byte-array representation of the BigInterger without
     *         signum-bit. null, if the BigInteger is null.
     * @preconditions
     * @postconditions
     */
    public static byte[] unsignedBigIntergerToByteArray(BigInteger bigInteger) {
        if (bigInteger == null) {
            return null;
        }
        byte[] integerBytes = bigInteger.toByteArray();
        byte[] unsignedIntegerBytes;
        if ((integerBytes.length > 0) && (integerBytes[0] == 0x00)) {
            unsignedIntegerBytes = new byte[integerBytes.length - 1];
            for (int i = 0; i < unsignedIntegerBytes.length; i++) {
                unsignedIntegerBytes[i] = integerBytes[i + 1];
            }
        } else {
            unsignedIntegerBytes = integerBytes;
        }

        return unsignedIntegerBytes;
    }
}