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/*
* Copyright 2002-2008 by Paulo Soares.
*
* This code was originally released in 2001 by SUN (see class
* com.sun.media.imageioimpl.plugins.tiff.TIFFLZWDecompressor.java)
* using the BSD license in a specific wording. In a mail dating from
* January 23, 2008, Brian Burkhalter (@sun.com) gave us permission
* to use the code under the following version of the BSD license:
*
* Copyright (c) 2005 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistribution of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistribution in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any
* kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
* WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
* EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL
* NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
* USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
* ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
* CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
* REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
* INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed or intended for
* use in the design, construction, operation or maintenance of any
* nuclear facility.
*/
package com.aowagie.text.pdf;
import java.io.IOException;
import java.io.OutputStream;
import com.aowagie.text.ExceptionConverter;
/**
* A class for performing LZW decoding.
*
*
*/
class LZWDecoder {
private byte stringTable[][];
private byte data[] = null;
private OutputStream uncompData;
private int tableIndex, bitsToGet = 9;
private int bytePointer, bitPointer;
private int nextData = 0;
private int nextBits = 0;
private final int andTable[] = {
511,
1023,
2047,
4095
};
public LZWDecoder() {
}
/**
* Method to decode LZW compressed data.
*
* @param data The compressed data.
* @param uncompData Array to return the uncompressed data in.
*/
public void decode(final byte data[], final OutputStream uncompData) {
if(data[0] == (byte)0x00 && data[1] == (byte)0x01) {
throw new RuntimeException("LZW flavour not supported.");
}
initializeStringTable();
this.data = data;
this.uncompData = uncompData;
// Initialize pointers
this.bytePointer = 0;
this.bitPointer = 0;
this.nextData = 0;
this.nextBits = 0;
int code, oldCode = 0;
byte string[];
while ((code = getNextCode()) != 257) {
if (code == 256) {
initializeStringTable();
code = getNextCode();
if (code == 257) {
break;
}
writeString(this.stringTable[code]);
oldCode = code;
} else {
if (code < this.tableIndex) {
string = this.stringTable[code];
writeString(string);
addStringToTable(this.stringTable[oldCode], string[0]);
oldCode = code;
} else {
string = this.stringTable[oldCode];
string = composeString(string, string[0]);
writeString(string);
addStringToTable(string);
oldCode = code;
}
}
}
}
/**
* Initialize the string table.
*/
private void initializeStringTable() {
this.stringTable = new byte[8192][];
for (int i=0; i<256; i++) {
this.stringTable[i] = new byte[1];
this.stringTable[i][0] = (byte)i;
}
this.tableIndex = 258;
this.bitsToGet = 9;
}
/**
* Write out the string just uncompressed.
*/
private void writeString(final byte string[]) {
try {
this.uncompData.write(string);
}
catch (final IOException e) {
throw new ExceptionConverter(e);
}
}
/**
* Add a new string to the string table.
*/
private void addStringToTable(final byte oldString[], final byte newString) {
final int length = oldString.length;
final byte string[] = new byte[length + 1];
System.arraycopy(oldString, 0, string, 0, length);
string[length] = newString;
// Add this new String to the table
this.stringTable[this.tableIndex++] = string;
if (this.tableIndex == 511) {
this.bitsToGet = 10;
} else if (this.tableIndex == 1023) {
this.bitsToGet = 11;
} else if (this.tableIndex == 2047) {
this.bitsToGet = 12;
}
}
/**
* Add a new string to the string table.
*/
private void addStringToTable(final byte string[]) {
// Add this new String to the table
this.stringTable[this.tableIndex++] = string;
if (this.tableIndex == 511) {
this.bitsToGet = 10;
} else if (this.tableIndex == 1023) {
this.bitsToGet = 11;
} else if (this.tableIndex == 2047) {
this.bitsToGet = 12;
}
}
/**
* Append newString to the end of oldString.
*/
private byte[] composeString(final byte oldString[], final byte newString) {
final int length = oldString.length;
final byte string[] = new byte[length + 1];
System.arraycopy(oldString, 0, string, 0, length);
string[length] = newString;
return string;
}
// Returns the next 9, 10, 11 or 12 bits
public int getNextCode() {
// Attempt to get the next code. The exception is caught to make
// this robust to cases wherein the EndOfInformation code has been
// omitted from a strip. Examples of such cases have been observed
// in practice.
try {
this.nextData = this.nextData << 8 | this.data[this.bytePointer++] & 0xff;
this.nextBits += 8;
if (this.nextBits < this.bitsToGet) {
this.nextData = this.nextData << 8 | this.data[this.bytePointer++] & 0xff;
this.nextBits += 8;
}
final int code =
this.nextData >> this.nextBits - this.bitsToGet & this.andTable[this.bitsToGet-9];
this.nextBits -= this.bitsToGet;
return code;
} catch(final ArrayIndexOutOfBoundsException e) {
// Strip not terminated as expected: return EndOfInformation code.
return 257;
}
}
}
