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.
// For more information see license.mkd.
// ---------------------------------------------------------------------------

package net.multiphasicapps.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;

/**
 * This reads a stream of hexadecimal characters and converts it to a binary
 * input.
 *
 * @since 2016/05/15
 */
public class HexInputStream
    extends InputStream
{
    /** The source stream. */
    protected final Reader source;
    
    /** EOF? */
    private volatile boolean _eof;
    
    /**
     * Initializes the hex based input stream.
     *
     * @param __s The source hex bytes.
     * @throws NullPointerException On null arguments.
     * @since 2016/05/15
     */
    public HexInputStream(Reader __s)
        throws NullPointerException
    {
        // Check
        if (__s == null)
            throw new NullPointerException("NARG");
        
        // Set
        this.source = __s;
    }
    
    /**
     * Initializes the hex based input stream.
     *
     * @param __is The source hex bytes.
     * @throws NullPointerException On null arguments.
     * @since 2017/02/25
     */
    public HexInputStream(InputStream __is)
        throws NullPointerException
    {
        this(new InputStreamReader(__is));
    }
    
    /**
     * Initializes the hex based input stream.
     *
     * @param __is The source hex bytes.
     * @param __cs The character set used.
     * @throws IOException If the character set is not valid.
     * @throws NullPointerException On null arguments.
     * @since 2017/02/25
     */
    public HexInputStream(InputStream __is, String __cs)
        throws IOException, NullPointerException
    {
        this(new InputStreamReader(__is, __cs));
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/05/15
     */
    @Override
    public void close()
        throws IOException
    {
        // Always set EOF
        this._eof = true;
        
        // Close it
        this.source.close();
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/05/15
     */
    @Override
    public int read()
        throws IOException
    {
        // EOF?
        if (this._eof)
            return -1;
        
        // Read the high value
        int hi = -1;
        while (hi < 0)
        {
            // Read 
            int c = this.source.read();
            
            // EOF?
            if (c < 0)
                return -1;
            
            // Try a digit
            hi = Character.digit((char)c, 16);
        }
        
        // Read the low value
        int lo = -1;
        while (lo < 0)
        {
            // Read 
            int c = this.source.read();
            
            // EOF?
            if (c < 0)
                return -1;
            
            // Try a digit
            lo = Character.digit((char)c, 16);
        }
        
        // Merge together
        return (hi << 4) | lo;
    }
}