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Java library for Javascript Object Signing and Encryption (JOSE) and JSON Web Tokens (JWT)
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/*
 * nimbus-jose-jwt
 *
 * Copyright 2012-2016, Connect2id Ltd.
 *
 * 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 com.nimbusds.jose.util;


import java.io.ByteArrayOutputStream;
import java.io.IOException;


/**
 * Byte utilities.
 *
 * @author Vladimir Dzhuvinov
 * @version 2022-04-22
 */
public class ByteUtils {


	/**
	 * Concatenates the specified byte arrays.
	 *
	 * @param byteArrays The byte arrays to concatenate, may be
	 *                   {@code null}.
	 *
	 * @return The resulting byte array.
	 */
	public static byte[] concat(byte[]... byteArrays) {

		try {
			ByteArrayOutputStream baos = new ByteArrayOutputStream();

			for (byte[] bytes : byteArrays) {

				if (bytes == null) {
					continue; // skip
				}

				baos.write(bytes);
			}
			return baos.toByteArray();

		} catch (IOException e) {
			// Should never happen
			throw new IllegalStateException(e.getMessage(), e);
		}
	}


	/**
	 * Returns a portion of the specified byte array.
	 *
	 * @param byteArray  The byte array. Must not be {@code null}.
	 * @param beginIndex The beginning index, inclusive. Must be zero or
	 *                   positive.
	 * @param length     The length. Must be zero or positive.
	 *
	 * @return The byte array portion.
	 */
	public static byte[] subArray(byte[] byteArray, int beginIndex, int length) {

		byte[] subArray = new byte[length];
		System.arraycopy(byteArray, beginIndex, subArray, 0, subArray.length);
		return subArray;
	}


	/**
	 * Returns the bit length of the specified byte length.
	 *
	 * @param byteLength The byte length.
	 *
	 * @return The bit length.
	 */
	public static int bitLength(final int byteLength) {

		return byteLength * 8;
	}


	/**
	 * Returns the bit length of the specified byte length, preventing
	 * integer overflow.
	 *
	 * @param byteLength The byte length.
	 *
	 * @return The bit length.
	 *
	 * @throws IntegerOverflowException On a integer overflow.
	 */
	public static int safeBitLength(final int byteLength)
		throws IntegerOverflowException {
		
		long longResult = (long)byteLength * (long)8;
		if((long)((int)longResult) != longResult) {
			throw new IntegerOverflowException();
		} else {
			return (int)longResult;
		}
	}


	/**
	 * Returns the byte length of the specified byte array.
	 *
	 * @param byteArray The byte array. May be {@code null}.
	 *
	 * @return The bite length, zero if the array is {@code null}.
	 */
	public static int bitLength(final byte[] byteArray) {

		if (byteArray == null) {
			return 0;
		} else {
			return bitLength(byteArray.length);
		}
	}


	/**
	 * Returns the byte length of the specified byte array, preventing
	 * integer overflow.
	 *
	 * @param byteArray The byte array. May be {@code null}.
	 *
	 * @return The bite length, zero if the array is {@code null}.
	 *
	 * @throws IntegerOverflowException On a integer overflow.
	 */
	public static int safeBitLength(final byte[] byteArray)
		throws IntegerOverflowException {

		if (byteArray == null) {
			return 0;
		} else {
			return safeBitLength(byteArray.length);
		}
	}


	/**
	 * Returns the byte length of the specified bit length.
	 *
	 * @param bitLength The bit length.
	 *
	 * @return The byte byte length.
	 */
	public static int byteLength(final int bitLength) {

		return bitLength / 8;
	}
	
	
	/**
	 * Returns {@code true} if the specified byte array is zero filled.
	 *
	 * @param byteArray the byte array. Must not be {@code null}.
	 *
	 * @return {@code true} if zero filled, else {@code false}.
	 */
	public static boolean isZeroFilled(final byte[] byteArray) {
		
		for (final byte b : byteArray) {
			if (b != 0) {
				return false;
			}
		}
		return true;
	}
}