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/*
* Copyright (c) 1997, 2023 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package org.eclipse.angus.mail.imap.protocol;
import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.Writer;
/**
* From RFC2060:
*
*
*
* 5.1.3. Mailbox International Naming Convention
*
* By convention, international mailbox names are specified using a
* modified version of the UTF-7 encoding described in [UTF-7]. The
* purpose of these modifications is to correct the following problems
* with UTF-7:
*
* 1) UTF-7 uses the "+" character for shifting; this conflicts with
* the common use of "+" in mailbox names, in particular USENET
* newsgroup names.
*
* 2) UTF-7's encoding is BASE64 which uses the "/" character; this
* conflicts with the use of "/" as a popular hierarchy delimiter.
*
* 3) UTF-7 prohibits the unencoded usage of "\"; this conflicts with
* the use of "\" as a popular hierarchy delimiter.
*
* 4) UTF-7 prohibits the unencoded usage of "~"; this conflicts with
* the use of "~" in some servers as a home directory indicator.
*
* 5) UTF-7 permits multiple alternate forms to represent the same
* string; in particular, printable US-ASCII chararacters can be
* represented in encoded form.
*
* In modified UTF-7, printable US-ASCII characters except for "&"
* represent themselves; that is, characters with octet values 0x20-0x25
* and 0x27-0x7e. The character "&" (0x26) is represented by the two-
* octet sequence "&-".
*
* All other characters (octet values 0x00-0x1f, 0x7f-0xff, and all
* Unicode 16-bit octets) are represented in modified BASE64, with a
* further modification from [UTF-7] that "," is used instead of "/".
* Modified BASE64 MUST NOT be used to represent any printing US-ASCII
* character which can represent itself.
*
* "&" is used to shift to modified BASE64 and "-" to shift back to US-
* ASCII. All names start in US-ASCII, and MUST end in US-ASCII (that
* is, a name that ends with a Unicode 16-bit octet MUST end with a "-
* ").
*
* For example, here is a mailbox name which mixes English, Japanese,
* and Chinese text: ~peter/mail/&ZeVnLIqe-/&U,BTFw-
*
*
*
* This class will do the correct Encoding for the IMAP mailboxes.
*
* @author Christopher Cotton
*/
public class BASE64MailboxEncoder {
protected byte[] buffer = new byte[4];
protected int bufsize = 0;
protected boolean started = false;
protected Writer out = null;
public static String encode(String original) {
BASE64MailboxEncoder base64stream = null;
char[] origchars = original.toCharArray();
int length = origchars.length;
boolean changedString = false;
CharArrayWriter writer = new CharArrayWriter(length);
// loop over all the chars
for (int index = 0; index < length; index++) {
char current = origchars[index];
// octets in the range 0x20-0x25,0x27-0x7e are themselves
// 0x26 "&" is represented as "&-"
if (current >= 0x20 && current <= 0x7e) {
if (base64stream != null) {
base64stream.flush();
}
if (current == '&') {
changedString = true;
writer.write('&');
writer.write('-');
} else {
writer.write(current);
}
} else {
// use a B64MailboxEncoder to write out the other bytes
// as a modified BASE64. The stream will write out
// the beginning '&' and the ending '-' which is part
// of every encoding.
if (base64stream == null) {
base64stream = new BASE64MailboxEncoder(writer);
changedString = true;
}
base64stream.write(current);
}
}
if (base64stream != null) {
base64stream.flush();
}
if (changedString) {
return writer.toString();
} else {
return original;
}
}
/**
* Create a BASE64 encoder
*
* @param what where to write the encoded name
*/
public BASE64MailboxEncoder(Writer what) {
out = what;
}
public void write(int c) {
try {
// write out the initial character if this is the first time
if (!started) {
started = true;
out.write('&');
}
// we write each character as a 2 byte unicode character
buffer[bufsize++] = (byte) (c >> 8);
buffer[bufsize++] = (byte) (c & 0xff);
if (bufsize >= 3) {
encode();
bufsize -= 3;
}
} catch (IOException e) {
//e.printStackTrace();
}
}
public void flush() {
try {
// flush any bytes we have
if (bufsize > 0) {
encode();
bufsize = 0;
}
// write the terminating character of the encoding
if (started) {
out.write('-');
started = false;
}
} catch (IOException e) {
//e.printStackTrace();
}
}
protected void encode() throws IOException {
byte a, b, c;
if (bufsize == 1) {
a = buffer[0];
b = 0;
c = 0;
out.write(pem_array[(a >>> 2) & 0x3F]);
out.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
// no padding characters are written
} else if (bufsize == 2) {
a = buffer[0];
b = buffer[1];
c = 0;
out.write(pem_array[(a >>> 2) & 0x3F]);
out.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
out.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
// no padding characters are written
} else {
a = buffer[0];
b = buffer[1];
c = buffer[2];
out.write(pem_array[(a >>> 2) & 0x3F]);
out.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
out.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
out.write(pem_array[c & 0x3F]);
// copy back the extra byte
if (bufsize == 4)
buffer[0] = buffer[3];
}
}
private final static char[] pem_array = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', // 0
'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 1
'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 2
'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', // 3
'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 4
'o', 'p', 'q', 'r', 's', 't', 'u', 'v', // 5
'w', 'x', 'y', 'z', '0', '1', '2', '3', // 6
'4', '5', '6', '7', '8', '9', '+', ',' // 7
};
}