/*
 *  BIP39 library, a Java implementation of BIP39
 *  Copyright (C) 2017-2019 Alan Evans, NovaCrypto
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 *  Original source: https://github.com/NovaCrypto/BIP39
 *  You can contact the authors via github issues.
 */

package io.github.novacrypto.bip39;

final class ByteUtils {

    static int next11Bits(byte[] bytes, int offset) {
        final int skip = offset / 8;
        final int lowerBitsToRemove = (3 * 8 - 11) - (offset % 8);
        return (((int) bytes[skip] & 0xff) << 16 |
                ((int) bytes[skip + 1] & 0xff) << 8 |
                (lowerBitsToRemove < 8
                        ? ((int) bytes[skip + 2] & 0xff)
                        : 0)) >> lowerBitsToRemove & (1 << 11) - 1;
    }

    static void writeNext11(byte[] bytes, int value, int offset) {
        int skip = offset / 8;
        int bitSkip = offset % 8;
        {//byte 0
            byte firstValue = bytes[skip];
            byte toWrite = (byte) (value >> (3 + bitSkip));
            bytes[skip] = (byte) (firstValue | toWrite);
        }

        {//byte 1
            byte valueInByte = bytes[skip + 1];
            final int i = 5 - bitSkip;
            byte toWrite = (byte) (i > 0 ? (value << i) : (value >> -i));
            bytes[skip + 1] = (byte) (valueInByte | toWrite);
        }

        if (bitSkip >= 6) {//byte 2
            byte valueInByte = bytes[skip + 2];
            byte toWrite = (byte) (value << 13 - bitSkip);
            bytes[skip + 2] = (byte) (valueInByte | toWrite);
        }
    }
}