/*
* Copyright (c) 2001 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:
*
* -Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduct 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 AND ITS LICENSORS SHALL NOT BE
* LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
* OR DISTRIBUTING THE 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 SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that Software is not designed,licensed or intended for use in
* the design, construction, operation or maintenance of any nuclear facility.
*
* Adapted from the JAI codecs TIFFLZWDecoder.
*/
package org.apache.poi.hdgf.other_lzw;
import java.io.IOException;
import java.io.OutputStream;
/**
* A class for performing LZW decoding.
*
*
*/
public class LZWDecoder {
byte stringTable[][];
byte data[] = null;
OutputStream uncompData;
int tableIndex, bitsToGet = 9;
int bytePointer, bitPointer;
int nextData = 0;
int nextBits = 0;
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(byte data[], OutputStream uncompData) throws IOException {
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
bytePointer = 0;
bitPointer = 0;
nextData = 0;
nextBits = 0;
int code, oldCode = 0;
byte string[];
while ((code = getNextCode()) != 257) {
if (code == 256) {
initializeStringTable();
code = getNextCode();
if (code == 257) {
break;
}
writeString(stringTable[code]);
oldCode = code;
} else {
if (code < tableIndex) {
string = stringTable[code];
writeString(string);
addStringToTable(stringTable[oldCode], string[0]);
oldCode = code;
} else {
string = stringTable[oldCode];
string = composeString(string, string[0]);
writeString(string);
addStringToTable(string);
oldCode = code;
}
}
}
}
/**
* Initialize the string table.
*/
public void initializeStringTable() {
stringTable = new byte[8192][];
for (int i=0; i<256; i++) {
stringTable[i] = new byte[1];
stringTable[i][0] = (byte)i;
}
tableIndex = 258;
bitsToGet = 9;
}
/**
* Write out the string just uncompressed.
*/
public void writeString(byte string[]) throws IOException {
uncompData.write(string);
}
/**
* Add a new string to the string table.
*/
public void addStringToTable(byte oldString[], byte newString) {
int length = oldString.length;
byte string[] = new byte[length + 1];
System.arraycopy(oldString, 0, string, 0, length);
string[length] = newString;
// Add this new String to the table
stringTable[tableIndex++] = string;
if (tableIndex == 511) {
bitsToGet = 10;
} else if (tableIndex == 1023) {
bitsToGet = 11;
} else if (tableIndex == 2047) {
bitsToGet = 12;
}
}
/**
* Add a new string to the string table.
*/
public void addStringToTable(byte string[]) {
// Add this new String to the table
stringTable[tableIndex++] = string;
if (tableIndex == 511) {
bitsToGet = 10;
} else if (tableIndex == 1023) {
bitsToGet = 11;
} else if (tableIndex == 2047) {
bitsToGet = 12;
}
}
/**
* Append <code>newString</code> to the end of <code>oldString</code>.
*/
public byte[] composeString(byte oldString[], byte newString) {
int length = oldString.length;
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 {
nextData = (nextData << 8) | (data[bytePointer++] & 0xff);
nextBits += 8;
if (nextBits < bitsToGet) {
nextData = (nextData << 8) | (data[bytePointer++] & 0xff);
nextBits += 8;
}
int code =
(nextData >> (nextBits - bitsToGet)) & andTable[bitsToGet-9];
nextBits -= bitsToGet;
return code;
} catch(ArrayIndexOutOfBoundsException e) {
// Strip not terminated as expected: return EndOfInformation code.
return 257;
}
}
}
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