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/*
 * Copyright (C) 2006-2013 Bitronix Software (http://www.bitronix.be)
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package bitronix.tm.utils;

/**
 * Number to byte array and byte array to number encoder.
 *
 * @author Ludovic Orban
 */
public class Encoder
{
	private Encoder()
	{
		//Nope
	}

	/**
	 * Method longToBytes ...
	 *
	 * @param aLong
	 * 		of type long
	 *
	 * @return byte[]
	 */
	public static byte[] longToBytes(long aLong)
	{
		byte[] array = new byte[8];

		array[7] = (byte) (aLong & 0xff);
		array[6] = (byte) ((aLong >> 8) & 0xff);
		array[5] = (byte) ((aLong >> 16) & 0xff);
		array[4] = (byte) ((aLong >> 24) & 0xff);
		array[3] = (byte) ((aLong >> 32) & 0xff);
		array[2] = (byte) ((aLong >> 40) & 0xff);
		array[1] = (byte) ((aLong >> 48) & 0xff);
		array[0] = (byte) ((aLong >> 56) & 0xff);

		return array;
	}

	/**
	 * Method intToBytes ...
	 *
	 * @param anInt
	 * 		of type int
	 *
	 * @return byte[]
	 */
	public static byte[] intToBytes(int anInt)
	{
		byte[] array = new byte[4];

		array[3] = (byte) (anInt & 0xff);
		array[2] = (byte) ((anInt >> 8) & 0xff);
		array[1] = (byte) ((anInt >> 16) & 0xff);
		array[0] = (byte) ((anInt >> 24) & 0xff);

		return array;
	}

	/**
	 * Method shortToBytes ...
	 *
	 * @param aShort
	 * 		of type short
	 *
	 * @return byte[]
	 */
	public static byte[] shortToBytes(short aShort)
	{
		byte[] array = new byte[2];

		array[1] = (byte) (aShort & 0xff);
		array[0] = (byte) ((aShort >> 8) & 0xff);

		return array;
	}

	/**
	 * Method bytesToLong ...
	 *
	 * @param bytes
	 * 		of type byte[]
	 * @param pos
	 * 		of type int
	 *
	 * @return long
	 */
	public static long bytesToLong(byte[] bytes, int pos)
	{
		if (bytes.length + pos < 8)
		{
			throw new IllegalArgumentException(
					"a long can only be decoded from 8 bytes of an array (got a " + bytes.length + " byte(s) array, must start at position " + pos + ")");
		}

		long result = 0;

		for (int i = 0; i < 8; i++)
		{
			result <<= 8;
			result ^= (long) bytes[i + pos] & 0xFF;
		}

		return result;
	}

	/**
	 * Method bytesToInt ...
	 *
	 * @param bytes
	 * 		of type byte[]
	 * @param pos
	 * 		of type int
	 *
	 * @return int
	 */
	public static int bytesToInt(byte[] bytes, int pos)
	{
		if (bytes.length + pos < 4)
		{
			throw new IllegalArgumentException(
					"an integer can only be decoded from 4 bytes of an array (got a " + bytes.length + " byte(s) array, must start at position " + pos + ")");
		}

		int result = 0;

		for (int i = 0; i < 4; i++)
		{
			result <<= 8;
			result ^= (int) bytes[i + pos] & 0xFF;
		}

		return result;
	}
}