SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package net.multiphasicapps.io;

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

/**
 * The forwards data from an input stream and calculates the checksum for that
 * data stream.
 *
 * @since 2017/03/05
 */
public class ChecksumInputStream
    extends InputStream
{
    /** The checksum Calculator used. */
    protected final Checksum checksum;
    
    /** Input stream. */
    protected final InputStream in;
    
    /**
     * Initializes the calculator.
     *
     * @param __calc The checksum calculator to write to.
     * @param __in The stream to read from.
     * @throws NullPointerException On null arguments.
     * @since 2017/02/28
     */
    public ChecksumInputStream(Checksum __calc, InputStream __in)
        throws NullPointerException
    {
        // Check
        if (__calc == null || __in == null)
            throw new NullPointerException("NARG");
        
        // Set
        this.checksum = __calc;
        this.in = __in;
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/02/28
     */
    @Override
    public int available()
        throws IOException
    {
        return this.in.available();
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/02/28
     */
    @Override
    public void close()
        throws IOException
    {
        this.in.close();
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/02/28
     */
    @Override
    public int read()
        throws IOException
    {
        int rv = this.in.read();
        
        // EOF?
        if (rv < 0)
            return rv;
        
        // Calculate checksum
        this.checksum.offer((byte)rv);
        
        // Return
        return rv;
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/02/28
     */
    @Override
    public int read(byte[] __b, int __o, int __l)
        throws IOException
    {
        // Read data
        int rv = this.in.read(__b, __o, __l);
        
        // EOF?
        if (rv < 0)
            return rv;
        
        // Calculate checksum
        this.checksum.offer(__b, __o, rv);
        
        // Read count
        return rv;
    }
}