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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.utils;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Input stream that tracks the number of bytes read.
 * @since 1.3
 * @NotThreadSafe
 */
public class CountingInputStream extends FilterInputStream {
    private long bytesRead;

    public CountingInputStream(final InputStream in) {
        super(in);
    }

    /**
     * Increments the counter of already read bytes.
     * Doesn't increment if the EOF has been hit (read == -1)
     *
     * @param read the number of bytes read
     */
    protected final void count(final long read) {
        if (read != -1) {
            bytesRead += read;
        }
    }

    /**
     * Returns the current number of bytes read from this stream.
     * @return the number of read bytes
     */
    public long getBytesRead() {
        return bytesRead;
    }

    @Override
    public int read() throws IOException {
        final int r = in.read();
        if (r >= 0) {
            count(1);
        }
        return r;
    }

    @Override
    public int read(final byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    @Override
    public int read(final byte[] b, final int off, final int len) throws IOException {
        if (len == 0) {
            return 0;
        }
        final int r = in.read(b, off, len);
        if (r >= 0) {
            count(r);
        }
        return r;
    }
}