/****************************************************************************
* Copyright (C) 2012 ecsec GmbH.
* All rights reserved.
* Contact: ecsec GmbH (info@ecsec.de)
*
* This file is part of the Open eCard App.
*
* GNU General Public License Usage
* This file may be used under the terms of the GNU General Public
* License version 3.0 as published by the Free Software Foundation
* and appearing in the file LICENSE.GPL included in the packaging of
* this file. Please review the following information to ensure the
* GNU General Public License version 3.0 requirements will be met:
* http://www.gnu.org/copyleft/gpl.html.
*
* Other Usage
* Alternatively, this file may be used in accordance with the terms
* and conditions contained in a signed written agreement between
* you and ecsec GmbH.
*
***************************************************************************/
package org.openecard.common.util;
/**
* A set of utility functions for long integers.
*
* @author Tobias Wich <tobias.wich@ecsec.de>
*/
public class LongUtils {
/**
* Convert a long integer to a byte array.
*
* @param value long integer to be converted
* @return byte[]
*/
public static byte[] toByteArray(long value) {
return toByteArray(value, 8);
}
/**
* Convert a long integer to a byte array with a given bit size per byte.
*
* @param value - long integer to be converted
* @param numBits Number of bits to use per byte.
* @return byte[]
*/
public static byte[] toByteArray(long value, int numBits) {
return toByteArray(value, numBits, true);
}
/**
* Convert a long integer to a byte array with a given bit size per byte.
*
* @param value Long integer to be converted.
* @param numBits Number of bits to use per byte.
* @param bigEndian {@code true} when output should be in Big Endian, {@code false} for Little Endian.
* @return byte[]
* @throws IllegalArgumentException Thrown in case the numBits value is not within the permitted range.
*/
public static byte[] toByteArray(long value, int numBits, boolean bigEndian) {
if (numBits <= 0 || numBits > 8) {
throw new IllegalArgumentException("Numbits must be between 0 and 8.");
}
if (value == 0) {
return new byte[1];
}
byte[] buffer = null;
int numBytesInBuffer = 64 / numBits;
int restBits = 64 - (numBytesInBuffer * numBits);
int j = 0;
for (int i = numBytesInBuffer - ((restBits > 0) ? 0 : 1); i >= 0; i--) {
byte b;
// first chunk which has uneven number of bits?
if (i == numBytesInBuffer) {
byte mask = numBitsToMask((byte) restBits);
b = (byte) ((byte) (value >> (((i - 1) * numBits) + restBits)) & mask);
} else {
byte mask = numBitsToMask((byte) numBits);
b = (byte) ((value >> (i * numBits)) & mask);
}
if (buffer == null && b != 0) {
buffer = new byte[i + 1];
} else if (buffer == null) {
continue;
}
buffer[j] = b;
j++;
}
// when emitting little endian, reverse the array
if (! bigEndian) {
buffer = ByteUtils.reverse(buffer);
}
return buffer;
}
private static byte numBitsToMask(byte numBits) {
byte result = 0;
for (byte i = 0; i < numBits; i++) {
result = (byte) ((result << 1) | 1);
}
return result;
}
/**
* Convert a long integer to a byte array.
* If the resulting array contains less bytes than 8 bytes, 0 bytes are prepended if the flag is set.
*
* @param value long integer to be converted
* @param padArrayToTypeLength
* @return byte[]
*/
public static byte[] toByteArray(long value, boolean padArrayToTypeLength) {
return toByteArray(value, padArrayToTypeLength, true);
}
/**
* Convert a long integer to a byte array.
* If the resulting array contains less bytes than 8 bytes, 0 bytes are prepended if the flag is set.
*
* @param value long integer to be converted
* @param padArrayToTypeLength
* @param bigEndian {@code true} when output should be in Big Endian, {@code false} for Little Endian.
* @return byte[]
*/
public static byte[] toByteArray(long value, boolean padArrayToTypeLength, boolean bigEndian) {
byte[] result = toByteArray(value, 8, bigEndian);
if (padArrayToTypeLength && result.length < 8) {
result = ByteUtils.concatenate(new byte[8 - result.length], result);
}
return result;
}
}