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.zip.blockreader;

import java.io.IOException;
import java.io.InputStream;
import net.multiphasicapps.io.CRC32Calculator;
import net.multiphasicapps.zip.ZipCRCConstants;

/**
 * This is used to check that the CRC is valid.
 *
 * @since 2017/01/03
 */
class __CRCInputStream__
    extends InputStream
{
    /** The stream to source from. */
    protected final InputStream in;
    
    /** The final resulting CRC to use. */
    protected final int crc;
    
    /** CRC calculation. */
    protected final CRC32Calculator crccalc =
        new CRC32Calculator(ZipCRCConstants.CRC_REFLECT_DATA,
            ZipCRCConstants.CRC_REFLECT_REMAINDER,
            ZipCRCConstants.CRC_POLYNOMIAL, ZipCRCConstants.CRC_REMAINDER,
            ZipCRCConstants.CRC_FINALXOR);
    
    /** The number of read bytes. */
    private volatile int _count;
    
    /**
     * Calcualtes the CRC of another given input stream.
     *
     * @param __in The stream to read from.
     * @param __crc The final CRC to calculate.
     * @throws NullPointerException On null arguments.
     * @since 2017/01/03
     */
    __CRCInputStream__(InputStream __in, int __crc)
        throws NullPointerException
    {
        // Check
        if (__in == null)
            throw new NullPointerException("NARG");
        
        // Set
        this.in = __in;
        this.crc = __crc;
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/01/03
     */
    @Override
    public int available()
        throws IOException
    {
        // Forward as it may be calculable
        return this.in.available();
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/01/03
     */
    @Override
    public void close()
        throws IOException
    {
        // Forward
        this.in.close();
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/01/03
     */
    @Override
    public int read()
        throws IOException
    {
        // Read in
        int rv = this.in.read();
        
        // EOF? Check CRC value
        CRC32Calculator crccalc = this.crccalc;
        if (rv < 0)
        {
            /* {@squirreljme.error BF0s CRC mismatch. (The expected CRC; The
            calculated CRC; The number of read bytes)} */
            int thiscrc = crccalc.checksum(), wantcrc = this.crc;
            if (thiscrc != wantcrc)
                throw new IOException(String.format("BF0s %08x %08x %d",
                    wantcrc, thiscrc, this._count));
            
            // EOF
            return -1;
        }
        
        // Calculate
        crccalc.offer((byte)rv);
        this._count += 1;
        
        // Return
        return rv;
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/01/03
     */
    @Override
    public int read(byte[] __b, int __o, int __l)
        throws ArrayIndexOutOfBoundsException, IOException,
            NullPointerException
    {
        // Check
        if (__b == null)
            throw new NullPointerException("NARG");
        if (__o < 0 || __l < 0 || (__o + __l) < 0 || (__o + __l) > __b.length)
            throw new ArrayIndexOutOfBoundsException("AIOB");
        
        // Read in
        int rv = this.in.read(__b, __o, __l);
        
        // EOF? Check CRC value
        CRC32Calculator crccalc = this.crccalc;
        if (rv < 0)
        {
            /* {@squirreljme.error BF0t CRC mismatch. (The expected CRC; The
            calculated CRC; The number of read bytes)} */
            int thiscrc = crccalc.checksum(), wantcrc = this.crc;
            if (thiscrc != wantcrc)
                throw new IOException(String.format("BF0t %08x %08x %d",
                    wantcrc, thiscrc, this._count));
            
            // EOF
            return -1;
        }
        
        // Calculate
        crccalc.offer(__b, __o, rv);
        this._count += rv;
        
        // Return
        return rv;
    }
}