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	/*
	* Copyright (c) 1995, 1997, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* 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).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	package sun.misc;

	import java.io.OutputStream;
	import java.io.InputStream;
	import java.io.PrintStream;
	import java.io.IOException;

	/**
	* This class implements a robust character encoder. The encoder is designed
	* to convert binary data into printable characters. The characters are
	* assumed to exist but they are not assumed to be ASCII, the complete set
	* is 0-9, A-Z, a-z, "(", and ")".
	*
	* 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>
	*
	* @author Chuck McManis
	* @see CharacterEncoder
	* @see UCDecoder
	*/
	public class UCEncoder extends CharacterEncoder {

	/** this clase 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();

	/**
	* encodeAtom - take two bytes and encode them into the correct
	* three characters. If only one byte is to be encoded, the other
	* must be zero. The padding byte is not included in the CRC computation.
	*/
	protected void encodeAtom(OutputStream outStream, byte data[], int offset, int len) throws IOException
	{
	int i;
	int p1, p2; // parity bits
	byte a, b;

	a = data[offset];
	if (len == 2) {
	b = data[offset+1];
	} else {
	b = 0;
	}
	crc.update(a);
	if (len == 2) {
	crc.update(b);
	}
	outStream.write(map_array[((a >>> 2) & 0x38) + ((b >>> 5) & 0x7)]);
	p1 = 0; p2 = 0;
	for (i = 1; i < 256; i = i * 2) {
	if ((a & i) != 0) {
	p1++;
	}
	if ((b & i) != 0) {
	p2++;
	}
	}
	p1 = (p1 & 1) * 32;
	p2 = (p2 & 1) * 32;
	outStream.write(map_array[(a & 31) + p1]);
	outStream.write(map_array[(b & 31) + p2]);
	return;
	}

	/**
	* Each UCE encoded line starts with a prefix of '*[XXX]', where
	* the sequence number and the length are encoded in the first
	* atom.
	*/
	protected void encodeLinePrefix(OutputStream outStream, int length) throws IOException {
	outStream.write('*');
	crc.value = 0;
	tmp[0] = (byte) length;
	tmp[1] = (byte) sequence;
	sequence = (sequence + 1) & 0xff;
	encodeAtom(outStream, tmp, 0, 2);
	}


	/**
	* each UCE encoded line ends with YYY and encoded version of the
	* 16 bit checksum. The most significant byte of the check sum
	* is always encoded FIRST.
	*/
	protected void encodeLineSuffix(OutputStream outStream) throws IOException {
	tmp[0] = (byte) ((crc.value >>> 8) & 0xff);
	tmp[1] = (byte) (crc.value & 0xff);
	encodeAtom(outStream, tmp, 0, 2);
	super.pStream.println();
	}

	/**
	* The buffer prefix code is used to initialize the sequence number
	* to zero.
	*/
	protected void encodeBufferPrefix(OutputStream a) throws IOException {
	sequence = 0;
	super.encodeBufferPrefix(a);
	}
	}

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