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/*
 * Copyright (c) 2013-2018, João Vitor Verona Biazibetti - All Rights Reserved
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see .
 *
 * https://www.github.com/BloodShura
 */

package com.github.bloodshura.x.cryptography.impl.twoway;

import com.github.bloodshura.x.cryptography.Twoway;
import com.github.bloodshura.x.cryptography.exception.CryptoException;

import javax.annotation.Nonnull;

public class Bytaway implements Twoway {
	private int level;
	private int modifier;

	public Bytaway() {
		this(15, 12);
	}

	public Bytaway(int level, int modifier) {
		this.level = level;
		this.modifier = modifier;
	}

	@Nonnull
	@Override
	public byte[] decrypt(@Nonnull byte[] data) {
		int level = getLevel() + 1;
		byte[] result = new byte[data.length / level];

		for (int i = 0; i < result.length; i++) {
			int offset = i * level;
			byte bit = data[offset];
			short s = bit;

			if ((offset + 1) < data.length) {
				byte bit2 = data[offset + 1];

				s = (short) ((bit) + (bit2 << 8));
			}

			result[i] = (byte) (s + getModifier());
		}

		return result;
	}

	@Nonnull
	@Override
	public byte[] encrypt(@Nonnull byte[] data) {
		int level = getLevel() + 1;
		byte[] result = new byte[(data.length * level) + 1];

		for (int i = 0; i < data.length; i++) {
			for (int j = 0; j < level; j++) {
				int offset = (i * level) + j;
				short bit = (short) (data[i] - getModifier() * (j + 1));

				result[offset] = (byte) (bit & 0xFF);
				result[offset + 1] = (byte) ((bit >>> 8) & 0xFF);
			}
		}

		return result;
	}

	public int getLevel() {
		return level;
	}

	public int getModifier() {
		return modifier;
	}

	public boolean needsSalt() {
		return false;
	}

	public void setLevel(int level) throws CryptoException {
		if (level <= 0) {
			throw new CryptoException("Level must be higher than zero");
		}

		this.level = level;
	}

	public void setModifier(int modifier) throws CryptoException {
		if (modifier > Short.MAX_VALUE - Byte.MAX_VALUE || modifier < Short.MIN_VALUE + Byte.MIN_VALUE) {
			throw new CryptoException("Modifier out of Short bounds.");
		}

		this.modifier = modifier;
	}
}




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