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	/*
	* Copyright (c) 1995, 2000, 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.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.");
	}
	}
	}

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