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Apache Commons Compress defines an API for working with compression and archive formats. These include bzip2, gzip, pack200, LZMA, XZ, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4, Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.commons.compress.archivers.cpio;

/**
 * Package private utility class for Cpio
 * 
 * @Immutable
 */
class CpioUtil {

    /**
     * Extracts the file type bits from a mode.
     */
    static long fileType(final long mode) {
        return mode & CpioConstants.S_IFMT;
    }

    /**
     * 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;
        final 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) {
        final 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;
    }
}