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| Codec for the Quoted-Printable section of http://www.ietf.org/rfc/rfc1521.txt (RFC 1521) |
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/*
* Copyright 2001-2004 The Apache Software Foundation.
*
* Licensed 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.
*/
import java.io.ByteArrayOutputStream;
import java.io.UnsupportedEncodingException;
import java.util.BitSet;
/**
* <p>
* Codec for the Quoted-Printable section of <a href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521 </a>.
* </p>
* <p>
* The Quoted-Printable encoding is intended to represent data that largely consists of octets that correspond to
* printable characters in the ASCII character set. It encodes the data in such a way that the resulting octets are
* unlikely to be modified by mail transport. If the data being encoded are mostly ASCII text, the encoded form of the
* data remains largely recognizable by humans. A body which is entirely ASCII may also be encoded in Quoted-Printable
* to ensure the integrity of the data should the message pass through a character- translating, and/or line-wrapping
* gateway.
* </p>
*
* <p>
* Note:
* </p>
* <p>
* Rules #3, #4, and #5 of the quoted-printable spec are not implemented yet because the complete quoted-printable spec
* does not lend itself well into the byte[] oriented codec framework. Complete the codec once the steamable codec
* framework is ready. The motivation behind providing the codec in a partial form is that it can already come in handy
* for those applications that do not require quoted-printable line formatting (rules #3, #4, #5), for instance Q codec.
* </p>
*
* @see <a href="http://www.ietf.org/rfc/rfc1521.txt"> RFC 1521 MIME (Multipurpose Internet Mail Extensions) Part One:
* Mechanisms for Specifying and Describing the Format of Internet Message Bodies </a>
*
* @author Apache Software Foundation
* @since 1.3
* @version $Id: QuotedPrintableCodec.java,v 1.7 2004/04/09 22:21:07 ggregory Exp $
*/
public class QuotedPrintableCodec {
/**
* The default charset used for string decoding and encoding.
*/
private String charset = "UTF8";
/**
* BitSet of printable characters as defined in RFC 1521.
*/
private static final BitSet PRINTABLE_CHARS = new BitSet(256);
private static byte ESCAPE_CHAR = '=';
private static byte TAB = 9;
private static byte SPACE = 32;
// Static initializer for printable chars collection
static {
// alpha characters
for (int i = 33; i <= 60; i++) {
PRINTABLE_CHARS.set(i);
}
for (int i = 62; i <= 126; i++) {
PRINTABLE_CHARS.set(i);
}
PRINTABLE_CHARS.set(TAB);
PRINTABLE_CHARS.set(SPACE);
}
/**
* Default constructor.
*/
public QuotedPrintableCodec() {
super();
}
/**
* Constructor which allows for the selection of a default charset
*
* @param charset
* the default string charset to use.
*/
public QuotedPrintableCodec(String charset) {
super();
this.charset = charset;
}
/**
* Encodes byte into its quoted-printable representation.
*
* @param b
* byte to encode
* @param buffer
* the buffer to write to
*/
private static final void encodeQuotedPrintable(int b, ByteArrayOutputStream buffer) {
buffer.write(ESCAPE_CHAR);
char hex1 = Character.toUpperCase(Character.forDigit((b >> 4) & 0xF, 16));
char hex2 = Character.toUpperCase(Character.forDigit(b & 0xF, 16));
buffer.write(hex1);
buffer.write(hex2);
}
/**
* Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
*
* <p>
* This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
* RFC 1521 and is suitable for encoding binary data and unformatted text.
* </p>
*
* @param printable
* bitset of characters deemed quoted-printable
* @param bytes
* array of bytes to be encoded
* @return array of bytes containing quoted-printable data
*/
public static final byte[] encodeQuotedPrintable(BitSet printable, byte[] bytes) {
if (bytes == null) {
return null;
}
if (printable == null) {
printable = PRINTABLE_CHARS;
}
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
for (int i = 0; i < bytes.length; i++) {
int b = bytes[i];
if (b < 0) {
b = 256 + b;
}
if (printable.get(b)) {
buffer.write(b);
} else {
encodeQuotedPrintable(b, buffer);
}
}
return buffer.toByteArray();
}
/**
* Decodes an array quoted-printable characters into an array of original bytes. Escaped characters are converted
* back to their original representation.
*
* <p>
* This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
* RFC 1521.
* </p>
*
* @param bytes
* array of quoted-printable characters
* @return array of original bytes
* @throws DecoderException
* Thrown if quoted-printable decoding is unsuccessful
*/
public static final byte[] decodeQuotedPrintable(byte[] bytes) throws Exception {
if (bytes == null) {
return null;
}
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
for (int i = 0; i < bytes.length; i++) {
int b = bytes[i];
if (b == ESCAPE_CHAR) {
try {
int u = Character.digit((char) bytes[++i], 16);
int l = Character.digit((char) bytes[++i], 16);
if (u == -1 || l == -1) {
throw new RuntimeException("Invalid quoted-printable encoding");
}
buffer.write((char) ((u << 4) + l));
} catch (ArrayIndexOutOfBoundsException e) {
throw new RuntimeException("Invalid quoted-printable encoding");
}
} else {
buffer.write(b);
}
}
return buffer.toByteArray();
}
/**
* Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
*
* <p>
* This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
* RFC 1521 and is suitable for encoding binary data and unformatted text.
* </p>
*
* @param bytes
* array of bytes to be encoded
* @return array of bytes containing quoted-printable data
*/
public byte[] encode(byte[] bytes) {
return encodeQuotedPrintable(PRINTABLE_CHARS, bytes);
}
/**
* Decodes an array of quoted-printable characters into an array of original bytes. Escaped characters are converted
* back to their original representation.
*
* <p>
* This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
* RFC 1521.
* </p>
*
* @param bytes
* array of quoted-printable characters
* @return array of original bytes
* @throws DecoderException
* Thrown if quoted-printable decoding is unsuccessful
*/
public byte[] decode(byte[] bytes) throws Exception {
return decodeQuotedPrintable(bytes);
}
/**
* Encodes a string into its quoted-printable form using the default string charset. Unsafe characters are escaped.
*
* <p>
* This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
* RFC 1521 and is suitable for encoding binary data.
* </p>
*
* @param pString
* string to convert to quoted-printable form
* @return quoted-printable string
*
* @throws EncoderException
* Thrown if quoted-printable encoding is unsuccessful
*
* @see #getDefaultCharset()
*/
public String encode(String pString) throws Exception {
if (pString == null) {
return null;
}
try {
return encode(pString, getDefaultCharset());
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e.getMessage());
}
}
/**
* Decodes a quoted-printable string into its original form using the specified string charset. Escaped characters
* are converted back to their original representation.
*
* @param pString
* quoted-printable string to convert into its original form
* @param charset
* the original string charset
* @return original string
* @throws DecoderException
* Thrown if quoted-printable decoding is unsuccessful
* @throws UnsupportedEncodingException
* Thrown if charset is not supported
*/
public String decode(String pString, String charset) throws Exception, UnsupportedEncodingException {
if (pString == null) {
return null;
}
return new String(decode(pString.getBytes("US-ASCII")), charset);
}
/**
* Decodes a quoted-printable string into its original form using the default string charset. Escaped characters are
* converted back to their original representation.
*
* @param pString
* quoted-printable string to convert into its original form
* @return original string
* @throws DecoderException
* Thrown if quoted-printable decoding is unsuccessful
* @throws UnsupportedEncodingException
* Thrown if charset is not supported
* @see #getDefaultCharset()
*/
public String decode(String pString) throws Exception {
if (pString == null) {
return null;
}
try {
return decode(pString, getDefaultCharset());
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e.getMessage());
}
}
/**
* Encodes an object into its quoted-printable safe form. Unsafe characters are escaped.
*
* @param pObject
* string to convert to a quoted-printable form
* @return quoted-printable object
* @throws EncoderException
* Thrown if quoted-printable encoding is not applicable to objects of this type or if encoding is
* unsuccessful
*/
public Object encode(Object pObject) throws Exception {
if (pObject == null) {
return null;
} else if (pObject instanceof byte[]) {
return encode((byte[]) pObject);
} else if (pObject instanceof String) {
return encode((String) pObject);
} else {
throw new RuntimeException("Objects of type "
+ pObject.getClass().getName()
+ " cannot be quoted-printable encoded");
}
}
/**
* Decodes a quoted-printable object into its original form. Escaped characters are converted back to their original
* representation.
*
* @param pObject
* quoted-printable object to convert into its original form
* @return original object
* @throws DecoderException
* Thrown if quoted-printable decoding is not applicable to objects of this type if decoding is
* unsuccessful
*/
public Object decode(Object pObject) throws Exception {
if (pObject == null) {
return null;
} else if (pObject instanceof byte[]) {
return decode((byte[]) pObject);
} else if (pObject instanceof String) {
return decode((String) pObject);
} else {
throw new RuntimeException("Objects of type "
+ pObject.getClass().getName()
+ " cannot be quoted-printable decoded");
}
}
/**
* Returns the default charset used for string decoding and encoding.
*
* @return the default string charset.
*/
public String getDefaultCharset() {
return this.charset;
}
/**
* Encodes a string into its quoted-printable form using the specified charset. Unsafe characters are escaped.
*
* <p>
* This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
* RFC 1521 and is suitable for encoding binary data and unformatted text.
* </p>
*
* @param pString
* string to convert to quoted-printable form
* @param charset
* the charset for pString
* @return quoted-printable string
*
* @throws UnsupportedEncodingException
* Thrown if the charset is not supported
*/
public String encode(String pString, String charset) throws UnsupportedEncodingException {
if (pString == null) {
return null;
}
return new String(encode(pString.getBytes(charset)), "US-ASCII");
}
}
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