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/*
* 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.DecoderException;
import org.apache.commons.codec.EncoderException;
import org.apache.commons.codec.binary.StringUtils;
/**
*
* Implements methods common to all codecs defined in RFC 1522.
*
*
*
* RFC 1522
* 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.
*
* @see
* MIME (Multipurpose Internet Mail Extensions) Part Two:
* Message Header Extensions for Non-ASCII Text
*
*
* @author Apache Software Foundation
* @since 1.3
* @version $Id: RFC1522Codec.java 1170351 2011-09-13 21:09:09Z ggregory $
*/
abstract class RFC1522Codec {
/**
* Separator.
*/
protected static final char SEP = '?';
/**
* Prefix
*/
protected static final String POSTFIX = "?=";
/**
* Postfix
*/
protected static final String PREFIX = "=?";
/**
* Applies an RFC 1522 compliant encoding scheme to the given string of text with the
* given charset. This method constructs the "encoded-word" header common to all the
* RFC 1522 codecs and then invokes {@link #doEncoding(byte [])} method of a concrete
* class to perform the specific encoding.
*
* @param text a string to encode
* @param charset a charset to be used
*
* @return RFC 1522 compliant "encoded-word"
*
* @throws EncoderException thrown if there is an error condition during the Encoding
* process.
* @throws UnsupportedEncodingException thrown if charset is not supported
*
* @see Standard charsets
*/
protected String encodeText(final String text, final String charset)
throws EncoderException, UnsupportedEncodingException
{
if (text == null) {
return null;
}
StringBuffer buffer = new StringBuffer();
buffer.append(PREFIX);
buffer.append(charset);
buffer.append(SEP);
buffer.append(getEncoding());
buffer.append(SEP);
byte [] rawdata = doEncoding(text.getBytes(charset));
buffer.append(StringUtils.newStringUsAscii(rawdata));
buffer.append(POSTFIX);
return buffer.toString();
}
/**
* Applies an RFC 1522 compliant decoding scheme to the given string of text. This method
* processes the "encoded-word" header common to all the RFC 1522 codecs and then invokes
* {@link #doEncoding(byte [])} method of a concrete class to perform the specific decoding.
*
* @param text a string to decode
* @return A new decoded String or null if the input is null.
*
* @throws DecoderException thrown if there is an error condition during the decoding
* process.
* @throws UnsupportedEncodingException thrown if charset specified in the "encoded-word"
* header is not supported
*/
protected String decodeText(final String text)
throws DecoderException, UnsupportedEncodingException
{
if (text == null) {
return null;
}
if ((!text.startsWith(PREFIX)) || (!text.endsWith(POSTFIX))) {
throw new DecoderException("RFC 1522 violation: malformed encoded content");
}
int terminator = text.length() - 2;
int from = 2;
int to = text.indexOf(SEP, from);
if (to == terminator) {
throw new DecoderException("RFC 1522 violation: charset token not found");
}
String charset = text.substring(from, to);
if (charset.equals("")) {
throw new DecoderException("RFC 1522 violation: charset not specified");
}
from = to + 1;
to = text.indexOf(SEP, from);
if (to == terminator) {
throw new DecoderException("RFC 1522 violation: encoding token not found");
}
String encoding = text.substring(from, to);
if (!getEncoding().equalsIgnoreCase(encoding)) {
throw new DecoderException("This codec cannot decode " +
encoding + " encoded content");
}
from = to + 1;
to = text.indexOf(SEP, from);
byte[] data = StringUtils.getBytesUsAscii(text.substring(from, to));
data = doDecoding(data);
return new String(data, charset);
}
/**
* Returns the codec name (referred to as encoding in the RFC 1522)
*
* @return name of the codec
*/
protected abstract String getEncoding();
/**
* Encodes an array of bytes using the defined encoding scheme
*
* @param bytes Data to be encoded
*
* @return A byte array containing the encoded data
*
* @throws EncoderException thrown if the Encoder encounters a failure condition
* during the encoding process.
*/
protected abstract byte[] doEncoding(byte[] bytes) throws EncoderException;
/**
* Decodes an array of bytes using the defined encoding scheme
*
* @param bytes Data to be decoded
*
* @return a byte array that contains decoded data
*
* @throws DecoderException A decoder exception is thrown if a Decoder encounters a
* failure condition during the decode process.
*/
protected abstract byte[] doDecoding(byte[] bytes) throws DecoderException;
}