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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package sun.misc;
import java.io.OutputStream;
import java.io.ByteArrayOutputStream;
import java.io.PushbackInputStream;
import java.io.PrintStream;
import java.io.IOException;
/**
* 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:
* <pre>
* 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
* </pre>
*
* 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(
* <pre>
* *(LLSS)(DDDD)(DDDD)(DDDD)...(CRC)
* Where each (xxx) represents a three character atom.
* (LLSS) - 8 bit length (high byte), and sequence number
* modulo 256;
* (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.
* </pre>
*
* If an error is encountered during decoding this class throws a
* CEFormatException. The specific detail messages are:
*
* <pre>
* "UCDecoder: High byte parity error."
* "UCDecoder: Low byte parity error."
* "UCDecoder: Out of sequence line."
* "UCDecoder: CRC check failed."
* </pre>
*
* @author Chuck McManis
* @see CharacterEncoder
* @see UCEncoder
*/
public class UCDecoder extends CharacterDecoder {
/** This class encodes two bytes per atom. */
protected int bytesPerAtom() {
return (2);
}
/** this class encodes 48 bytes per line */
protected int bytesPerLine() {
return (48);
}
/* this is the UCE mapping of 0-63 to characters .. */
private final static byte map_array[] = {
// 0 1 2 3 4 5 6 7
(byte)'0',(byte)'1',(byte)'2',(byte)'3',(byte)'4',(byte)'5',(byte)'6',(byte)'7', // 0
(byte)'8',(byte)'9',(byte)'A',(byte)'B',(byte)'C',(byte)'D',(byte)'E',(byte)'F', // 1
(byte)'G',(byte)'H',(byte)'I',(byte)'J',(byte)'K',(byte)'L',(byte)'M',(byte)'N', // 2
(byte)'O',(byte)'P',(byte)'Q',(byte)'R',(byte)'S',(byte)'T',(byte)'U',(byte)'V', // 3
(byte)'W',(byte)'X',(byte)'Y',(byte)'Z',(byte)'a',(byte)'b',(byte)'c',(byte)'d', // 4
(byte)'e',(byte)'f',(byte)'g',(byte)'h',(byte)'i',(byte)'j',(byte)'k',(byte)'l', // 5
(byte)'m',(byte)'n',(byte)'o',(byte)'p',(byte)'q',(byte)'r',(byte)'s',(byte)'t', // 6
(byte)'u',(byte)'v',(byte)'w',(byte)'x',(byte)'y',(byte)'z',(byte)'(',(byte)')' // 7
};
private int sequence;
private byte tmp[] = new byte[2];
private CRC16 crc = new CRC16();
/**
* Decode one atom - reads the characters from the input stream, decodes
* them, and checks for valid parity.
*/
protected void decodeAtom(PushbackInputStream inStream, OutputStream outStream, int l) throws IOException {
int i, p1, p2, np1, np2;
byte a = -1, b = -1, c = -1;
byte high_byte, low_byte;
byte tmp[] = new byte[3];
i = inStream.read(tmp);
if (i != 3) {
throw new CEStreamExhausted();
}
for (i = 0; (i < 64) && ((a == -1) || (b == -1) || (c == -1)); i++) {
if (tmp[0] == map_array[i]) {
a = (byte) i;
}
if (tmp[1] == map_array[i]) {
b = (byte) i;
}
if (tmp[2] == map_array[i]) {
c = (byte) i;
}
}
high_byte = (byte) (((a & 0x38) << 2) + (b & 0x1f));
low_byte = (byte) (((a & 0x7) << 5) + (c & 0x1f));
p1 = 0;
p2 = 0;
for (i = 1; i < 256; i = i * 2) {
if ((high_byte & i) != 0)
p1++;
if ((low_byte & i) != 0)
p2++;
}
np1 = (b & 32) / 32;
np2 = (c & 32) / 32;
if ((p1 & 1) != np1) {
throw new CEFormatException("UCDecoder: High byte parity error.");
}
if ((p2 & 1) != np2) {
throw new CEFormatException("UCDecoder: Low byte parity error.");
}
outStream.write(high_byte);
crc.update(high_byte);
if (l == 2) {
outStream.write(low_byte);
crc.update(low_byte);
}
}
private ByteArrayOutputStream lineAndSeq = new ByteArrayOutputStream(2);
/**
* decodeBufferPrefix initializes the sequence number to zero.
*/
protected void decodeBufferPrefix(PushbackInputStream inStream, OutputStream outStream) {
sequence = 0;
}
/**
* decodeLinePrefix reads the sequence number and the number of
* encoded bytes from the line. If the sequence number is not the
* previous sequence number + 1 then an exception is thrown.
* UCE lines are line terminator immune, they all start with *
* so the other thing this method does is scan for the next line
* by looking for the * character.
*
* @exception CEFormatException out of sequence lines detected.
*/
protected int decodeLinePrefix(PushbackInputStream inStream, OutputStream outStream) throws IOException {
int i;
int nLen, nSeq;
byte xtmp[];
int c;
crc.value = 0;
while (true) {
c = inStream.read(tmp, 0, 1);
if (c == -1) {
throw new CEStreamExhausted();
}
if (tmp[0] == '*') {
break;
}
}
lineAndSeq.reset();
decodeAtom(inStream, lineAndSeq, 2);
xtmp = lineAndSeq.toByteArray();
nLen = xtmp[0] & 0xff;
nSeq = xtmp[1] & 0xff;
if (nSeq != sequence) {
throw new CEFormatException("UCDecoder: Out of sequence line.");
}
sequence = (sequence + 1) & 0xff;
return (nLen);
}
/**
* this method reads the CRC that is at the end of every line and
* verifies that it matches the computed CRC.
*
* @exception CEFormatException if CRC check fails.
*/
protected void decodeLineSuffix(PushbackInputStream inStream, OutputStream outStream) throws IOException {
int i;
int lineCRC = crc.value;
int readCRC;
byte tmp[];
lineAndSeq.reset();
decodeAtom(inStream, lineAndSeq, 2);
tmp = lineAndSeq.toByteArray();
readCRC = ((tmp[0] << 8) & 0xFF00) + (tmp[1] & 0xff);
if (readCRC != lineCRC) {
throw new CEFormatException("UCDecoder: CRC check failed.");
}
}
}