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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.sevenz;

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

class BoundedSeekableByteChannelInputStream extends InputStream {
    private static final int MAX_BUF_LEN = 8192;
    private final ByteBuffer buffer;
    private final SeekableByteChannel channel;
    private long bytesRemaining;

    public BoundedSeekableByteChannelInputStream(final SeekableByteChannel channel,
            final long size) {
        this.channel = channel;
        this.bytesRemaining = size;
        if (size < MAX_BUF_LEN && size > 0) {
            buffer = ByteBuffer.allocate((int) size);
        } else {
            buffer = ByteBuffer.allocate(MAX_BUF_LEN);
        }
    }

    @Override
    public int read() throws IOException {
        if (bytesRemaining > 0) {
            --bytesRemaining;
            int read = read(1);
            if (read < 0) {
                return read;
            }
            return buffer.get() & 0xff;
        }
        return -1;
    }

    @Override
    public int read(final byte[] b, final int off, final int len) throws IOException {
        if (bytesRemaining == 0) {
            return -1;
        }
        int bytesToRead = len;
        if (bytesToRead > bytesRemaining) {
            bytesToRead = (int) bytesRemaining;
        }
        int bytesRead;
        ByteBuffer buf;
        if (bytesToRead <= buffer.capacity()) {
            buf = buffer;
            bytesRead = read(bytesToRead);
        } else {
            buf = ByteBuffer.allocate(bytesToRead);
            bytesRead = channel.read(buf);
            buf.flip();
        }
        if (bytesRead >= 0) {
            buf.get(b, off, bytesRead);
            bytesRemaining -= bytesRead;
        }
        return bytesRead;
    }

    private int read(int len) throws IOException {
        buffer.rewind().limit(len);
        int read = channel.read(buffer);
        buffer.flip();
        return read;
    }

    @Override
    public void close() {
        // the nested channel is controlled externally
    }
}