src/java/org/apache/commons/codec/net/BCodec.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.codec.net;

import java.io.UnsupportedEncodingException;

import org.apache.commons.codec.CharEncoding;
import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.EncoderException;
import org.apache.commons.codec.StringDecoder;
import org.apache.commons.codec.StringEncoder;
import org.apache.commons.codec.binary.Base64;

/**
 * <p>
 * Identical to the Base64 encoding defined by <a href="http://www.ietf.org/rfc/rfc1521.txt">RFC
 * 1521</a> and allows a character set to be specified.
 * </p>
 * 
 * <p>
 * <a href="http://www.ietf.org/rfc/rfc1522.txt">RFC 1522</a> describes techniques to allow the encoding of non-ASCII
 * text in various portions of a RFC 822 [2] message header, in a manner which is unlikely to confuse existing message
 * handling software.
 * </p>
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc1522.txt">MIME (Multipurpose Internet Mail Extensions) Part Two: Message
 *          Header Extensions for Non-ASCII Text</a>
 * 
 * @author Apache Software Foundation
 * @since 1.3
 * @version $Id$
 */
public class BCodec extends RFC1522Codec implements StringEncoder, StringDecoder {
    /**
     * The default charset used for string decoding and encoding.
     */
    private final String charset;

    /**
     * Default constructor.
     */
    public BCodec() {
        this(CharEncoding.UTF_8);
    }

    /**
     * Constructor which allows for the selection of a default charset
     * 
     * @param charset
     *                  the default string charset to use.
     * 
     * @see <a href="http://download.oracle.com/javase/1.5.0/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
     */
    public BCodec(final String charset) {
        super();
        this.charset = charset;
    }

    @Override
    protected String getEncoding() {
        return "B";
    }

    @Override
    protected byte[] doEncoding(byte[] bytes) {
        if (bytes == null) {
            return null;
        }
        return Base64.encodeBase64(bytes);
    }

    @Override
    protected byte[] doDecoding(byte[] bytes) {
        if (bytes == null) {
            return null;
        }
        return Base64.decodeBase64(bytes);
    }

    /**
     * Encodes a string into its Base64 form using the specified charset. Unsafe characters are escaped.
     * 
     * @param value
     *                  string to convert to Base64 form
     * @param charset
     *                  the charset for <code>value</code>
     * @return Base64 string
     * 
     * @throws EncoderException
     *                  thrown if a failure condition is encountered during the encoding process.
     */
    public String encode(final String value, final String charset) throws EncoderException {
        if (value == null) {
            return null;
        }
        try {
            return encodeText(value, charset);
        } catch (UnsupportedEncodingException e) {
            throw new EncoderException(e.getMessage(), e);
        }
    }

    /**
     * Encodes a string into its Base64 form using the default charset. Unsafe characters are escaped.
     * 
     * @param value
     *                  string to convert to Base64 form
     * @return Base64 string
     * 
     * @throws EncoderException
     *                  thrown if a failure condition is encountered during the encoding process.
     */
    public String encode(String value) throws EncoderException {
        if (value == null) {
            return null;
        }
        return encode(value, getDefaultCharset());
    }

    /**
     * Decodes a Base64 string into its original form. Escaped characters are converted back to their original
     * representation.
     * 
     * @param value
     *            Base64 string to convert into its original form
     * @return original string
     * @throws DecoderException
     *             A decoder exception is thrown if a failure condition is encountered during the decode process.
     */
    public String decode(String value) throws DecoderException {
        if (value == null) {
            return null;
        }
        try {
            return decodeText(value);
        } catch (UnsupportedEncodingException e) {
            throw new DecoderException(e.getMessage(), e);
        }
    }

    /**
     * The default charset used for string decoding and encoding.
     * 
     * @return the default string charset.
     */
    public String getDefaultCharset() {
        return this.charset;
    }
}