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Apache Commons Compress software 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.sevenz;

import java.io.IOException;
import java.util.Collections;
import java.util.LinkedList;

/**
 * The unit of solid compression.
 */
class Folder {
    static final Folder[] EMPTY_FOLDER_ARRAY = {};
    /// List of coders used in this folder, e.g. one for compression, one for encryption.
    Coder[] coders;
    /// Total number of input streams across all coders.
    /// this field is currently unused but technically part of the 7z API
    long totalInputStreams;
    /// Total number of output streams across all coders.
    long totalOutputStreams;
    /// Mapping between input and output streams.
    BindPair[] bindPairs;
    /// Indeces of input streams, one per input stream not listed in bindPairs.
    long[] packedStreams;
    /// Unpack sizes, per each output stream.
    long[] unpackSizes;
    /// Whether the folder has a CRC.
    boolean hasCrc;
    /// The CRC, if present.
    long crc;
    /// The number of unpack substreams, product of the number of
    /// output streams and the number of non-empty files in this
    /// folder.
    int numUnpackSubStreams;

    int findBindPairForInStream(final int index) {
        if (bindPairs != null) {
            for (int i = 0; i < bindPairs.length; i++) {
                if (bindPairs[i].inIndex == index) {
                    return i;
                }
            }
        }
        return -1;
    }

    int findBindPairForOutStream(final int index) {
        if (bindPairs != null) {
            for (int i = 0; i < bindPairs.length; i++) {
                if (bindPairs[i].outIndex == index) {
                    return i;
                }
            }
        }
        return -1;
    }

    /**
     * Sorts Coders using bind pairs.
     * The first coder reads from the packed stream (we currently
     * only support single input stream decoders), the second reads
     * from the output of the first and so on.
     */
    Iterable getOrderedCoders() throws IOException {
        if (packedStreams == null || coders == null || packedStreams.length == 0 || coders.length == 0) {
            return Collections.emptyList();
        }
        final LinkedList l = new LinkedList<>();
        int current = (int) packedStreams[0]; // more that 2^31 coders?
        while (current >= 0 && current < coders.length) {
            if (l.contains(coders[current])) {
                throw new IOException("folder uses the same coder more than once in coder chain");
            }
            l.addLast(coders[current]);
            final int pair = findBindPairForOutStream(current);
            current = pair != -1 ? (int) bindPairs[pair].inIndex : -1;
        }
        return l;
    }

    long getUnpackSize() {
        if (totalOutputStreams == 0) {
            return 0;
        }
        for (int i = ((int) totalOutputStreams) - 1; i >= 0; i--) {
            if (findBindPairForOutStream(i) < 0) {
                return unpackSizes[i];
            }
        }
        return 0;
    }

    long getUnpackSizeForCoder(final Coder coder) {
        if (coders != null) {
            for (int i = 0; i < coders.length; i++) {
                if (coders[i] == coder) {
                    return unpackSizes[i];
                }
            }
        }
        return 0;
    }

    @Override
    public String toString() {
        return "Folder with " + coders.length + " coders, " + totalInputStreams
            + " input streams, " + totalOutputStreams + " output streams, "
            + bindPairs.length + " bind pairs, " + packedStreams.length
            + " packed streams, " + unpackSizes.length + " unpack sizes, "
            + (hasCrc ? "with CRC " + crc : "without CRC")
            + " and " + numUnpackSubStreams + " unpack streams";
    }
}