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/*
 * Copyright 2012-2017 Brian Campbell
 *
 * 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 org.jose4j.lang;


import org.jose4j.base64url.Base64Url;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.security.SecureRandom;
import java.util.Arrays;

public class ByteUtil
{
    public static final byte[] EMPTY_BYTES = new byte[0];

    private static final int MAX_BYTE_LENGTH = Integer.MAX_VALUE / 8;

    public static byte[] convertUnsignedToSignedTwosComp(int[] ints)
    {
        byte[] bytes = new byte[ints.length];
        for (int idx = 0; idx < ints.length; idx++)
        {
            bytes[idx] = ByteUtil.getByte(ints[idx]);
        }
        return bytes;
    }

    public static int[] convertSignedTwosCompToUnsigned(byte[] bytes)
    {
        int[] ints = new int[bytes.length];
        for (int idx = 0; idx < bytes.length; idx++)
        {
            ints[idx] = ByteUtil.getInt(bytes[idx]);
        }
        return ints;
    }

    public static byte getByte(int intValue)
    {
        byte[] bytes = getBytes(intValue);
        if (bytes[0] != 0 || bytes[1] != 0 || bytes[2] != 0)
        {
            throw new IllegalArgumentException("Integer value (" + intValue + ") too large to stuff into one byte.");
        }
        return bytes[3];
    }

    public static byte[] getBytes(int intValue)
    {
        ByteBuffer byteBuffer = ByteBuffer.allocate(4);
        byteBuffer.putInt(intValue);
        return byteBuffer.array();
    }

    public static byte[] getBytes(long longValue)
    {
         ByteBuffer byteBuffer = ByteBuffer.allocate(8);
         byteBuffer.putLong(longValue);
         return byteBuffer.array();
    }

    public static int getInt(byte b)
    {
        return (b >= 0) ? (int) b : 256 - (~(b - 1));
    }

    public static boolean secureEquals(byte[] bytes1, byte[] bytes2)
    {
        bytes1 = (bytes1 == null) ? EMPTY_BYTES : bytes1;
        bytes2 = (bytes2 == null) ? EMPTY_BYTES : bytes2;

        int shortest = Math.min(bytes1.length, bytes2.length);
        int longest = Math.max(bytes1.length, bytes2.length);

        int result = 0;

        // should be a time-constant comparison with respect to the length
        for (int i = 0; i < shortest; i++)
        {
            result |= bytes1[i] ^ bytes2[i];
        }

        return (result == 0) && (shortest == longest) ;
    }

    public static byte[] concat(byte[]... byteArrays)
    {
        try
        {
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            for (byte[] bytes : byteArrays)
            {
                byteArrayOutputStream.write(bytes);
            }
            return byteArrayOutputStream.toByteArray();
        }
        catch (IOException e)
        {
            throw new IllegalStateException("IOEx from ByteArrayOutputStream?!", e);
        }
    }

    public static byte[] subArray(byte[] inputBytes, int startPos, int length)
    {
        byte[] subArray = new byte[length];
        System.arraycopy(inputBytes, startPos, subArray, 0, subArray.length);
        return subArray;
    }

    public static byte[] leftHalf(byte[] inputBytes)
    {
        return subArray(inputBytes, 0, (inputBytes.length / 2));
    }

    public static byte[] rightHalf(byte[] inputBytes)
    {
        int half = inputBytes.length / 2;
        return subArray(inputBytes, half, half);
    }

    public static int bitLength(byte[] bytes)
    {
        return bitLength(bytes.length);
    }

    public static int bitLength(int byteLength)
    {
        // prevent integer overflow and negative values
        if (byteLength > MAX_BYTE_LENGTH || (byteLength < 0))
        {
            throw new UncheckedJoseException("Invalid byte length ("+byteLength+") for converting to bit length");
        }
        return byteLength * 8;
    }

    public static byte[] reverse(byte[] in)
    {
        if (in == null)
        {
            return null;
        }

        byte[] reversed = new byte[in.length];
        for (int i = 0; i < in.length; i++)
        {
            reversed[reversed.length - 1 - i] = in[i];
        }

        return reversed;
    }

    public static int byteLength(int numberOfBits)
    {
        return numberOfBits / 8;
    }

    public static byte[] randomBytes(int length, SecureRandom secureRandom)
    {
        secureRandom = (secureRandom == null) ? new SecureRandom() : secureRandom;
        byte[] bytes = new byte[length];
        secureRandom.nextBytes(bytes);
        return bytes;
    }

    public static byte[] randomBytes(int length)
    {
        return randomBytes(length, null);
    }

    public static String toDebugString(byte[] bytes)
    {
        Base64Url base64Url = new Base64Url();
        String s = base64Url.base64UrlEncode(bytes);
        int[] ints = convertSignedTwosCompToUnsigned(bytes);
        return Arrays.toString(ints) + "("+ints.length+"bytes/"+bitLength(ints.length)+"bits) | base64url encoded: " + s;
    }

}