CpioUtil.java

/*
 * Copyright (C) 2014 Jörg Prante
 *
 * 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.xbib.io.archive.cpio;

/**
 * Package private utility class for Cpio
 */
class CpioUtil {
    /**
     * Converts a byte array to a long. Halfwords can be swapped by setting
     * swapHalfWord=true.
     *
     * @param number       An array of bytes containing a number
     * @param swapHalfWord Swap halfwords ([0][1][2][3]->[1][0][3][2])
     * @return The long value
     * @throws UnsupportedOperationException if number length is not a multiple of 2
     */
    static long byteArray2long(final byte[] number, final boolean swapHalfWord) {
        if (number.length % 2 != 0) {
            throw new UnsupportedOperationException();
        }

        long ret = 0;
        int pos = 0;
        byte tmp_number[] = new byte[number.length];
        System.arraycopy(number, 0, tmp_number, 0, number.length);

        if (!swapHalfWord) {
            byte tmp = 0;
            for (pos = 0; pos < tmp_number.length; pos++) {
                tmp = tmp_number[pos];
                tmp_number[pos++] = tmp_number[pos];
                tmp_number[pos] = tmp;
            }
        }

        ret = tmp_number[0] & 0xFF;
        for (pos = 1; pos < tmp_number.length; pos++) {
            ret <<= 8;
            ret |= tmp_number[pos] & 0xFF;
        }
        return ret;
    }

    /**
     * Converts a long number to a byte array
     * Halfwords can be swapped by setting swapHalfWord=true.
     *
     * @param number       the input long number to be converted
     * @param length       The length of the returned array
     * @param swapHalfWord Swap halfwords ([0][1][2][3]->[1][0][3][2])
     * @return The long value
     * @throws UnsupportedOperationException if the length is not a positive multiple of two
     */
    static byte[] long2byteArray(final long number, final int length,
                                 final boolean swapHalfWord) {
        byte[] ret = new byte[length];
        int pos = 0;
        long tmp_number = 0;

        if (length % 2 != 0 || length < 2) {
            throw new UnsupportedOperationException();
        }

        tmp_number = number;
        for (pos = length - 1; pos >= 0; pos--) {
            ret[pos] = (byte) (tmp_number & 0xFF);
            tmp_number >>= 8;
        }

        if (!swapHalfWord) {
            byte tmp = 0;
            for (pos = 0; pos < length; pos++) {
                tmp = ret[pos];
                ret[pos++] = ret[pos];
                ret[pos] = tmp;
            }
        }

        return ret;
    }
}