234 lines
8.4 KiB
Java
234 lines
8.4 KiB
Java
/*
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* Copyright (c) 1995, 2000, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.misc;
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import java.io.OutputStream;
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import java.io.ByteArrayOutputStream;
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import java.io.PushbackInputStream;
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import java.io.PrintStream;
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import java.io.IOException;
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/**
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* This class implements a robust character decoder. The decoder will
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* converted encoded text into binary data.
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*
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* The basic encoding unit is a 3 character atom. It encodes two bytes
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* of data. Bytes are encoded into a 64 character set, the characters
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* were chosen specifically because they appear in all codesets.
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* We don't care what their numerical equivalent is because
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* we use a character array to map them. This is like UUencoding
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* with the dependency on ASCII removed.
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*
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* The three chars that make up an atom are encoded as follows:
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* <pre>
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* 00xxxyyy 00axxxxx 00byyyyy
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* 00 = leading zeros, all values are 0 - 63
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* xxxyyy - Top 3 bits of X, Top 3 bits of Y
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* axxxxx - a = X parity bit, xxxxx lower 5 bits of X
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* byyyyy - b = Y parity bit, yyyyy lower 5 bits of Y
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* </pre>
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*
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* The atoms are arranged into lines suitable for inclusion into an
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* email message or text file. The number of bytes that are encoded
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* per line is 48 which keeps the total line length under 80 chars)
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*
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* Each line has the form(
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* <pre>
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* *(LLSS)(DDDD)(DDDD)(DDDD)...(CRC)
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* Where each (xxx) represents a three character atom.
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* (LLSS) - 8 bit length (high byte), and sequence number
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* modulo 256;
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* (DDDD) - Data byte atoms, if length is odd, last data
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* atom has (DD00) (high byte data, low byte 0)
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* (CRC) - 16 bit CRC for the line, includes length,
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* sequence, and all data bytes. If there is a
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* zero pad byte (odd length) it is _NOT_
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* included in the CRC.
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* </pre>
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*
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* If an error is encountered during decoding this class throws a
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* CEFormatException. The specific detail messages are:
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*
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* <pre>
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* "UCDecoder: High byte parity error."
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* "UCDecoder: Low byte parity error."
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* "UCDecoder: Out of sequence line."
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* "UCDecoder: CRC check failed."
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* </pre>
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*
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* @author Chuck McManis
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* @see CharacterEncoder
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* @see UCEncoder
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*/
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public class UCDecoder extends CharacterDecoder {
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/** This class encodes two bytes per atom. */
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protected int bytesPerAtom() {
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return (2);
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}
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/** this class encodes 48 bytes per line */
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protected int bytesPerLine() {
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return (48);
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}
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/* this is the UCE mapping of 0-63 to characters .. */
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private final static byte map_array[] = {
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// 0 1 2 3 4 5 6 7
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(byte)'0',(byte)'1',(byte)'2',(byte)'3',(byte)'4',(byte)'5',(byte)'6',(byte)'7', // 0
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(byte)'8',(byte)'9',(byte)'A',(byte)'B',(byte)'C',(byte)'D',(byte)'E',(byte)'F', // 1
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(byte)'G',(byte)'H',(byte)'I',(byte)'J',(byte)'K',(byte)'L',(byte)'M',(byte)'N', // 2
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(byte)'O',(byte)'P',(byte)'Q',(byte)'R',(byte)'S',(byte)'T',(byte)'U',(byte)'V', // 3
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(byte)'W',(byte)'X',(byte)'Y',(byte)'Z',(byte)'a',(byte)'b',(byte)'c',(byte)'d', // 4
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(byte)'e',(byte)'f',(byte)'g',(byte)'h',(byte)'i',(byte)'j',(byte)'k',(byte)'l', // 5
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(byte)'m',(byte)'n',(byte)'o',(byte)'p',(byte)'q',(byte)'r',(byte)'s',(byte)'t', // 6
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(byte)'u',(byte)'v',(byte)'w',(byte)'x',(byte)'y',(byte)'z',(byte)'(',(byte)')' // 7
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};
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private int sequence;
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private byte tmp[] = new byte[2];
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private CRC16 crc = new CRC16();
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/**
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* Decode one atom - reads the characters from the input stream, decodes
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* them, and checks for valid parity.
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*/
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protected void decodeAtom(PushbackInputStream inStream, OutputStream outStream, int l) throws IOException {
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int i, p1, p2, np1, np2;
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byte a = -1, b = -1, c = -1;
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byte high_byte, low_byte;
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byte tmp[] = new byte[3];
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i = inStream.read(tmp);
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if (i != 3) {
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throw new CEStreamExhausted();
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}
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for (i = 0; (i < 64) && ((a == -1) || (b == -1) || (c == -1)); i++) {
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if (tmp[0] == map_array[i]) {
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a = (byte) i;
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}
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if (tmp[1] == map_array[i]) {
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b = (byte) i;
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}
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if (tmp[2] == map_array[i]) {
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c = (byte) i;
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}
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}
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high_byte = (byte) (((a & 0x38) << 2) + (b & 0x1f));
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low_byte = (byte) (((a & 0x7) << 5) + (c & 0x1f));
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p1 = 0;
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p2 = 0;
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for (i = 1; i < 256; i = i * 2) {
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if ((high_byte & i) != 0)
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p1++;
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if ((low_byte & i) != 0)
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p2++;
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}
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np1 = (b & 32) / 32;
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np2 = (c & 32) / 32;
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if ((p1 & 1) != np1) {
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throw new CEFormatException("UCDecoder: High byte parity error.");
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}
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if ((p2 & 1) != np2) {
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throw new CEFormatException("UCDecoder: Low byte parity error.");
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}
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outStream.write(high_byte);
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crc.update(high_byte);
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if (l == 2) {
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outStream.write(low_byte);
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crc.update(low_byte);
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}
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}
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private ByteArrayOutputStream lineAndSeq = new ByteArrayOutputStream(2);
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/**
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* decodeBufferPrefix initializes the sequence number to zero.
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*/
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protected void decodeBufferPrefix(PushbackInputStream inStream, OutputStream outStream) {
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sequence = 0;
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}
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/**
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* decodeLinePrefix reads the sequence number and the number of
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* encoded bytes from the line. If the sequence number is not the
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* previous sequence number + 1 then an exception is thrown.
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* UCE lines are line terminator immune, they all start with *
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* so the other thing this method does is scan for the next line
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* by looking for the * character.
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*
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* @exception CEFormatException out of sequence lines detected.
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*/
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protected int decodeLinePrefix(PushbackInputStream inStream, OutputStream outStream) throws IOException {
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int i;
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int nLen, nSeq;
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byte xtmp[];
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int c;
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crc.value = 0;
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while (true) {
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c = inStream.read(tmp, 0, 1);
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if (c == -1) {
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throw new CEStreamExhausted();
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}
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if (tmp[0] == '*') {
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break;
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}
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}
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lineAndSeq.reset();
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decodeAtom(inStream, lineAndSeq, 2);
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xtmp = lineAndSeq.toByteArray();
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nLen = xtmp[0] & 0xff;
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nSeq = xtmp[1] & 0xff;
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if (nSeq != sequence) {
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throw new CEFormatException("UCDecoder: Out of sequence line.");
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}
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sequence = (sequence + 1) & 0xff;
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return (nLen);
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}
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/**
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* this method reads the CRC that is at the end of every line and
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* verifies that it matches the computed CRC.
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*
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* @exception CEFormatException if CRC check fails.
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*/
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protected void decodeLineSuffix(PushbackInputStream inStream, OutputStream outStream) throws IOException {
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int i;
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int lineCRC = crc.value;
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int readCRC;
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byte tmp[];
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lineAndSeq.reset();
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decodeAtom(inStream, lineAndSeq, 2);
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tmp = lineAndSeq.toByteArray();
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readCRC = ((tmp[0] << 8) & 0xFF00) + (tmp[1] & 0xff);
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if (readCRC != lineCRC) {
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throw new CEFormatException("UCDecoder: CRC check failed.");
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}
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}
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}
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