BASE64MailboxEncoderpublic class BASE64MailboxEncoder extends Object | 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 "-
").
Crispin Standards Track [Page 15]
RFC 2060 IMAP4rev1 December 1996
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 |
| Fields Summary |
|---|
| protected byte[] | buffer | | protected int | bufsize | | protected boolean | started | | protected Writer | out | | private static final char[] | pem_array |
| Constructors Summary |
|---|
public BASE64MailboxEncoder(Writer what)Create a BASE64 encoder
out = what;
|
| Methods Summary |
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| public static java.lang.String | encode(java.lang.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;
}
| | protected void | encode()
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];
}
| | 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();
}
| | 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();
}
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