package org.bouncycastle.util.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * An input stream which copies anything read through it to another stream.
 */
public class TeeInputStream
    extends InputStream
{
    private final InputStream input;
    private final OutputStream output;

    /**
     * Base constructor.
     *
     * @param input input stream to be wrapped.
     * @param output output stream to copy any input read to.
     */
    public TeeInputStream(InputStream input, OutputStream output)
    {
        this.input = input;
        this.output = output;
    }

    public int read(byte[] buf)
        throws IOException
    {
        return read(buf, 0, buf.length);
    }

    public int read(byte[] buf, int off, int len)
        throws IOException
    {
        int i = input.read(buf, off, len);

        if (i > 0)
        {
            output.write(buf, off, i);
        }

        return i;
    }

    public int read()
        throws IOException
    {
        int i = input.read();

        if (i >= 0)
        {
            output.write(i);
        }

        return i;
    }

    public void close()
        throws IOException
    {
        this.input.close();
        this.output.close();
    }

    public OutputStream getOutputStream()
    {
        return output;
    }
}

package org.bouncycastle.util.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * An input stream which copies anything read through it to another stream.
 */
public class TeeInputStream
    extends InputStream
{
    private final InputStream input;
    private final OutputStream output;

    /**
     * Base constructor.
     *
     * @param input input stream to be wrapped.
     * @param output output stream to copy any input read to.
     */
    public TeeInputStream(InputStream input, OutputStream output)
    {
        this.input = input;
        this.output = output;
    }

    public int available() throws IOException
    {
        return input.available();
    }

    public int read(byte[] buf)
        throws IOException
    {
        return read(buf, 0, buf.length);
    }

    public int read(byte[] buf, int off, int len)
        throws IOException
    {
        int i = input.read(buf, off, len);

        if (i > 0)
        {
            output.write(buf, off, i);
        }

        return i;
    }

    public int read()
        throws IOException
    {
        int i = input.read();

        if (i >= 0)
        {
            output.write(i);
        }

        return i;
    }

    public void close()
        throws IOException
    {
        this.input.close();
        this.output.close();
    }

    public OutputStream getOutputStream()
    {
        return output;
    }
}

Implement available()