public class: UCDecoder
This class implements a robust character decoder. The decoder will
converted encoded text into binary data.
The basic encoding unit is a 3 character atom. It encodes two bytes
of data. Bytes are encoded into a 64 character set, the characters
were chosen specifically because they appear in all codesets.
We don't care what their numerical equivalent is because
we use a character array to map them. This is like UUencoding
with the dependency on ASCII removed.
The three chars that make up an atom are encoded as follows:
00xxxyyy 00axxxxx 00byyyyy
00 = leading zeros, all values are 0 - 63
xxxyyy - Top 3 bits of X, Top 3 bits of Y
axxxxx - a = X parity bit, xxxxx lower 5 bits of X
byyyyy - b = Y parity bit, yyyyy lower 5 bits of Y
The atoms are arranged into lines suitable for inclusion into an
email message or text file. The number of bytes that are encoded
per line is 48 which keeps the total line length under 80 chars)
Each line has the form(
Where each (xxx) represents a three character atom.
(LLSS) - 8 bit length (high byte), and sequence number
(DDDD) - Data byte atoms, if length is odd, last data
atom has (DD00) (high byte data, low byte 0)
(CRC) - 16 bit CRC for the line, includes length,
sequence, and all data bytes. If there is a
zero pad byte (odd length) it is _NOT_
included in the CRC.
If an error is encountered during decoding this class throws a
CEFormatException. The specific detail messages are:
"UCDecoder: High byte parity error."
"UCDecoder: Low byte parity error."
"UCDecoder: Out of sequence line."
"UCDecoder: CRC check failed."
|Methods from sun.misc.CharacterDecoder:|
bytesPerAtom, bytesPerLine, decodeAtom, decodeBuffer, decodeBuffer, decodeBuffer, decodeBufferPrefix, decodeBufferSuffix, decodeBufferToByteBuffer, decodeBufferToByteBuffer, decodeLinePrefix, decodeLineSuffix, readFully|
|Methods from java.lang.Object:|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait|