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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.utils;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SeekableByteChannel;

/**
 * InputStream that delegates requests to the underlying SeekableByteChannel, making sure that only bytes from a certain range can be read.
 *
 * @ThreadSafe
 * @since 1.21
 */
public class BoundedSeekableByteChannelInputStream extends BoundedArchiveInputStream {

    private final SeekableByteChannel channel;

    /**
     * Constructs a bounded stream on the underlying {@link SeekableByteChannel}
     *
     * @param start     Position in the stream from where the reading of this bounded stream starts
     * @param remaining Amount of bytes which are allowed to read from the bounded stream
     * @param channel   Channel which the reads will be delegated to
     */
    public BoundedSeekableByteChannelInputStream(final long start, final long remaining, final SeekableByteChannel channel) {
        super(start, remaining);
        this.channel = channel;
    }

    @Override
    protected int read(final long pos, final ByteBuffer buf) throws IOException {
        int read;
        synchronized (channel) {
            channel.position(pos);
            read = channel.read(buf);
        }
        buf.flip();
        return read;
    }
}