/****************************************************************
* 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.james.mime4j.decoder;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.james.mime4j.util.CharsetUtil;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
/**
* Static methods for decoding strings, byte arrays and encoded words.
*
*
* @version $Id: DecoderUtil.java,v 1.3 2005/02/07 15:33:59 ntherning Exp $
*/
public class DecoderUtil {
private static Log log = LogFactory.getLog(DecoderUtil.class);
/**
* Decodes a string containing quoted-printable encoded data.
*
* @param s the string to decode.
* @return the decoded bytes.
*/
public static byte[] decodeBaseQuotedPrintable(String s) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
byte[] bytes = s.getBytes("US-ASCII");
QuotedPrintableInputStream is = new QuotedPrintableInputStream(
new ByteArrayInputStream(bytes));
int b = 0;
while ((b = is.read()) != -1) {
baos.write(b);
}
} catch (IOException e) {
/*
* This should never happen!
*/
log.error(e);
}
return baos.toByteArray();
}
/**
* Decodes a string containing base64 encoded data.
*
* @param s the string to decode.
* @return the decoded bytes.
*/
public static byte[] decodeBase64(String s) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
byte[] bytes = s.getBytes("US-ASCII");
Base64InputStream is = new Base64InputStream(
new ByteArrayInputStream(bytes));
int b = 0;
while ((b = is.read()) != -1) {
baos.write(b);
}
} catch (IOException e) {
/*
* This should never happen!
*/
log.error(e);
}
return baos.toByteArray();
}
/**
* Decodes an encoded word encoded with the 'B' encoding (described in
* RFC 2047) found in a header field body.
*
* @param encodedWord the encoded word to decode.
* @param charset the Java charset to use.
* @return the decoded string.
* @throws UnsupportedEncodingException if the given Java charset isn't
* supported.
*/
public static String decodeB(String encodedWord, String charset)
throws UnsupportedEncodingException {
return new String(decodeBase64(encodedWord), charset);
}
/**
* Decodes an encoded word encoded with the 'Q' encoding (described in
* RFC 2047) found in a header field body.
*
* @param encodedWord the encoded word to decode.
* @param charset the Java charset to use.
* @return the decoded string.
* @throws UnsupportedEncodingException if the given Java charset isn't
* supported.
*/
public static String decodeQ(String encodedWord, String charset)
throws UnsupportedEncodingException {
/*
* Replace _ with =20
*/
StringBuffer sb = new StringBuffer();
for (int i = 0; i < encodedWord.length(); i++) {
char c = encodedWord.charAt(i);
if (c == '_') {
sb.append("=20");
} else {
sb.append(c);
}
}
return new String(decodeBaseQuotedPrintable(sb.toString()), charset);
}
/**
* Decodes a string containing encoded words as defined by RFC 2047.
* Encoded words in have the form
* =?charset?enc?Encoded word?= where enc is either 'Q' or 'q' for
* quoted-printable and 'B' or 'b' for Base64.
*
* ANDROID: COPIED FROM A NEWER VERSION OF MIME4J
*
* @param body the string to decode.
* @return the decoded string.
*/
public static String decodeEncodedWords(String body) {
// ANDROID: Most strings will not include "=?" so a quick test can prevent unneeded
// object creation. This could also be handled via lazy creation of the StringBuilder.
if (body.indexOf("=?") == -1) {
return body;
}
int previousEnd = 0;
boolean previousWasEncoded = false;
StringBuilder sb = new StringBuilder();
while (true) {
int begin = body.indexOf("=?", previousEnd);
// ANDROID: The mime4j original version has an error here. It gets confused if
// the encoded string begins with an '=' (just after "?Q?"). This patch seeks forward
// to find the two '?' in the "header", before looking for the final "?=".
int endScan = begin + 2;
if (begin != -1) {
int qm1 = body.indexOf('?', endScan + 2);
int qm2 = body.indexOf('?', qm1 + 1);
if (qm2 != -1) {
endScan = qm2 + 1;
}
}
int end = begin == -1 ? -1 : body.indexOf("?=", endScan);
if (end == -1) {
if (previousEnd == 0)
return body;
sb.append(body.substring(previousEnd));
return sb.toString();
}
end += 2;
String sep = body.substring(previousEnd, begin);
String decoded = decodeEncodedWord(body, begin, end);
if (decoded == null) {
sb.append(sep);
sb.append(body.substring(begin, end));
} else {
if (!previousWasEncoded || !CharsetUtil.isWhitespace(sep)) {
sb.append(sep);
}
sb.append(decoded);
}
previousEnd = end;
previousWasEncoded = decoded != null;
}
}
// return null on error
private static String decodeEncodedWord(String body, int begin, int end) {
int qm1 = body.indexOf('?', begin + 2);
if (qm1 == end - 2)
return null;
int qm2 = body.indexOf('?', qm1 + 1);
if (qm2 == end - 2)
return null;
String mimeCharset = body.substring(begin + 2, qm1);
String encoding = body.substring(qm1 + 1, qm2);
String encodedText = body.substring(qm2 + 1, end - 2);
String charset = CharsetUtil.toJavaCharset(mimeCharset);
if (charset == null) {
if (log.isWarnEnabled()) {
log.warn("MIME charset '" + mimeCharset + "' in encoded word '"
+ body.substring(begin, end) + "' doesn't have a "
+ "corresponding Java charset");
}
return null;
} else if (!CharsetUtil.isDecodingSupported(charset)) {
if (log.isWarnEnabled()) {
log.warn("Current JDK doesn't support decoding of charset '"
+ charset + "' (MIME charset '" + mimeCharset
+ "' in encoded word '" + body.substring(begin, end)
+ "')");
}
return null;
}
if (encodedText.length() == 0) {
if (log.isWarnEnabled()) {
log.warn("Missing encoded text in encoded word: '"
+ body.substring(begin, end) + "'");
}
return null;
}
try {
if (encoding.equalsIgnoreCase("Q")) {
return DecoderUtil.decodeQ(encodedText, charset);
} else if (encoding.equalsIgnoreCase("B")) {
return DecoderUtil.decodeB(encodedText, charset);
} else {
if (log.isWarnEnabled()) {
log.warn("Warning: Unknown encoding in encoded word '"
+ body.substring(begin, end) + "'");
}
return null;
}
} catch (UnsupportedEncodingException e) {
// should not happen because of isDecodingSupported check above
if (log.isWarnEnabled()) {
log.warn("Unsupported encoding in encoded word '"
+ body.substring(begin, end) + "'", e);
}
return null;
} catch (RuntimeException e) {
if (log.isWarnEnabled()) {
log.warn("Could not decode encoded word '"
+ body.substring(begin, end) + "'", e);
}
return null;
}
}
}
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