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Devin Jankowski
2023-06-21 12:46:23 -04:00
commit c70248a520
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iTechSharp/iTextSharp/text/pdf/LZWDecoder.cs Normal file
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using System;
using System.IO;
using System.Collections;
/*
* 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.
*/
namespace iTextSharp.text.pdf {
/**
* A class for performing LZW decoding.
*
*
*/
public class LZWDecoder {
byte[][] stringTable;
byte[] data = null;
Stream uncompData;
int tableIndex, bitsToGet = 9;
int bytePointer;
int nextData = 0;
int nextBits = 0;
internal 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, Stream uncompData) {
if (data[0] == (byte)0x00 && data[1] == (byte)0x01) {
throw new Exception("LZW flavour not supported.");
}
InitializeStringTable();
this.data = data;
this.uncompData = uncompData;
// Initialize pointers
bytePointer = 0;
nextData = 0;
nextBits = 0;
int code, oldCode = 0;
byte[] str;
while ((code = this.NextCode) != 257) {
if (code == 256) {
InitializeStringTable();
code = NextCode;
if (code == 257) {
break;
}
WriteString(stringTable[code]);
oldCode = code;
} else {
if (code < tableIndex) {
str = stringTable[code];
WriteString(str);
AddStringToTable(stringTable[oldCode], str[0]);
oldCode = code;
} else {
str = stringTable[oldCode];
str = ComposeString(str, str[0]);
WriteString(str);
AddStringToTable(str);
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[] str) {
uncompData.Write(str, 0, str.Length);
}
/**
* Add a new string to the string table.
*/
public void AddStringToTable(byte[] oldstring, byte newstring) {
int length = oldstring.Length;
byte[] str = new byte[length + 1];
Array.Copy(oldstring, 0, str, 0, length);
str[length] = newstring;
// Add this new string to the table
stringTable[tableIndex++] = str;
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[] str) {
// Add this new string to the table
stringTable[tableIndex++] = str;
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[] str = new byte[length + 1];
Array.Copy(oldstring, 0, str, 0, length);
str[length] = newstring;
return str;
}
// Returns the next 9, 10, 11 or 12 bits
public int NextCode {
get {
// 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 {
// Strip not terminated as expected: return EndOfInformation code.
return 257;
}
}
}
}
}