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/*
* Copyright 2003-2012 by Paulo Soares.
*
* This code was originally released in 2001 by SUN (see class
* com.sun.media.imageio.plugins.tiff.TIFFDirectory.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.
*
* $Revision$
* $Date$
* $State: Exp $
*/
package com.itextpdf.text.pdf.codec;
import java.io.IOException;
import java.io.OutputStream;
/**
* Modified from original LZWCompressor to change interface to passing a
* buffer of data to be compressed.
* @since 5.0.2
*/
public class LZWCompressor
{
/** base underlying code size of data being compressed 8 for TIFF, 1 to 8 for GIF **/
int codeSize_;
/** reserved clear code based on code size **/
int clearCode_;
/** reserved end of data code based on code size **/
int endOfInfo_;
/** current number bits output for each code **/
int numBits_;
/** limit at which current number of bits code size has to be increased **/
int limit_;
/** the prefix code which represents the predecessor string to current input point **/
short prefix_;
/** output destination for bit codes **/
BitFile bf_;
/** general purpose LZW string table **/
LZWStringTable lzss_;
/** modify the limits of the code values in LZW encoding due to TIFF bug / feature **/
boolean tiffFudge_;
/**
* @param out destination for compressed data
* @param codeSize the initial code size for the LZW compressor
* @param TIFF flag indicating that TIFF lzw fudge needs to be applied
* @exception IOException if underlying output stream error
**/
public LZWCompressor(OutputStream out, int codeSize, boolean TIFF) throws IOException
{
bf_ = new BitFile(out, !TIFF); // set flag for GIF as NOT tiff
codeSize_ = codeSize;
tiffFudge_ = TIFF;
clearCode_ = 1 << codeSize_;
endOfInfo_ = clearCode_ + 1;
numBits_ = codeSize_ + 1;
limit_ = (1 << numBits_) - 1;
if (tiffFudge_)
--limit_;
prefix_ = (short)0xFFFF;
lzss_ = new LZWStringTable();
lzss_.ClearTable(codeSize_);
bf_.writeBits(clearCode_, numBits_);
}
/**
* @param buf data to be compressed to output stream
* @exception IOException if underlying output stream error
**/
public void compress(byte[] buf, int offset, int length)
throws IOException
{
int idx;
byte c;
short index;
int maxOffset = offset + length;
for (idx = offset; idx < maxOffset; ++idx)
{
c = buf[idx];
if ((index = lzss_.FindCharString(prefix_, c)) != -1)
prefix_ = index;
else
{
bf_.writeBits(prefix_, numBits_);
if (lzss_.AddCharString(prefix_, c) > limit_)
{
if (numBits_ == 12)
{
bf_.writeBits(clearCode_, numBits_);
lzss_.ClearTable(codeSize_);
numBits_ = codeSize_ + 1;
}
else
++numBits_;
limit_ = (1 << numBits_) - 1;
if (tiffFudge_)
--limit_;
}
prefix_ = (short)((short)c & 0xFF);
}
}
}
/**
* Indicate to compressor that no more data to go so write out
* any remaining buffered data.
*
* @exception IOException if underlying output stream error
**/
public void flush() throws IOException
{
if (prefix_ != -1)
bf_.writeBits(prefix_, numBits_);
bf_.writeBits(endOfInfo_, numBits_);
bf_.flush();
}
}
