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

/**
 * 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);
    }

    @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 {
        final int r = in.read(b, off, len);
        if (r >= 0) {
            count(r);
        }
        return r;
    }
    /**
     * 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;
    }
}