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/**
 * As of "https://github.com/dfish3r/vt-crypt2 "CRYPT" (vt-crypt2) the source
 * code below the package "edu.vt.middleware.crypt" is dual licensed under both
 * the LGPL and Apache 2 license. As REFCODES.ORG source codes are also licensed
 * under the Apache License, v2.0 ("http://www.apache.org/licenses/TEXT-2.0"),
 * the according Apache 2 license principles are to be applied: "... The Apache
 * License is permissive; unlike copyleft licenses, it does not require a
 * derivative work of the software, or modifications to the original, to be
 * distributed using the same license. It still requires application of the same
 * license to all unmodified parts. In every licensed file, original copyright,
 * patent, trademark, and attribution notices must be preserved (excluding
 * notices that do not pertain to any part of the derivative works.) In every
 * licensed file changed, a notification must be added stating that changes have
 * been made to that file..." ("https://en.wikipedia.org/wiki/Apache_License")
 * 
 * "Software can be freely used, modified and distributed in any environment
 * under this license."
 * 
"A copy of the license must be included in the package." (→ see
 * refcodes-licensing dependency)
 * 
"Changes to the source code of the software under the Apache license do
 * not have to be sent back to the licensor."
 * 
"Own software that uses software under the Apache license does not have
 * to be under the Apache license."
 * 
"Your own software may only be called Apache if the Apache Foundation has
 * given written permission."
 * 
 * (freely translated from "https://de.wikipedia.org/wiki/Apache_License")
 */

/*
 * $Id: AbstractEncodingConverter.java 2744 2013-06-25 20:20:29Z dfisher $
 * 
 * Copyright (C) 2003-2013 Virginia Tech. All rights reserved.
 * 
 * SEE TEXT FOR MORE INFORMATION
 * 
 * Author: Middleware Services Email: [email protected] Version: $Revision: 2744
 * $ Updated: $Date: 2013-06-25 16:20:29 -0400 (Tue, 25 Jun 2013) $
 */
package edu.vt.middleware.crypt.util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import org.bouncycastle.util.encoders.Encoder;

/**
 * Abstract base class for all converters that perform encoding with a BC
 * {@link org.bouncycastle.util.encoders.Encoder} class.
 *
 * @author Middleware Services
 * 
 * @version $Revision: 2744 $
 */
public abstract class AbstractEncodingConverter implements Converter {

	/** {@inheritDoc} */
	@Override
	public String fromBytes( final byte[] input ) {
		return fromBytes( input, 0, input.length );
	}

	/** {@inheritDoc} */
	@Override
	public String fromBytes( final byte[] input, final int offset, final int length ) {
		final ByteArrayOutputStream out = new ByteArrayOutputStream();
		try {
			getEncoder().encode( input, offset, length, out );
		}
		catch ( IOException e ) {
			throw new IllegalArgumentException( e.getMessage() );
		}
		try {
			return out.toString( Convert.ASCII_CHARSET.name() );
		}
		catch ( UnsupportedEncodingException e ) {
			throw new IllegalStateException( "ASCII character set not available." );
		}
	}

	/** {@inheritDoc} */
	@Override
	public byte[] toBytes( final String input ) {
		final ByteArrayOutputStream out = new ByteArrayOutputStream();
		try {
			getEncoder().decode( input, out );
		}
		catch ( IOException e ) {
			throw new IllegalArgumentException( e.getMessage() );
		}
		return out.toByteArray();
	}

	/**
	 * Gets the encoder instance that does the work of byte-char/char-byte
	 * encoding.
	 *
	 * @return Encoder instance.
	 */
	protected abstract Encoder getEncoder();
}