/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.pdfbox.filter;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
/**
* This is the used for the LZWDecode filter. This represents the dictionary mappings
* between codes and their values.
*
* @author <a href="mailto:ben@benlitchfield.com">Ben Litchfield</a>
* @version $Revision: 1.4 $
*/
class LZWDictionary
{
private Map codeToData = new HashMap();
private LZWNode root = new LZWNode();
private ByteArrayOutputStream buffer = new ByteArrayOutputStream();
private long nextCode = 258;
private int codeSize = 9;
/**
* constructor.
*/
public LZWDictionary()
{
for( long i=0; i<256; i++ )
{
LZWNode node = new LZWNode();
node.setCode( i );
root.setNode( (byte)i, node );
codeToData.put( new Long( i ), new byte[]{ (byte)i } );
}
}
/**
* This will get the value for the code. It will return null if the code is not
* defined.
*
* @param code The key to the data.
*
* @return The data that is mapped to the code.
*/
public byte[] getData( long code )
{
return (byte[])codeToData.get( new Long( code ) );
}
/**
* This will take a visit from a byte[]. This will create new code entries as
* necessary.
*
* @param data The byte to get a visit from.
*
* @throws IOException If there is an error visiting this data.
*/
public void visit( byte[] data ) throws IOException
{
for( int i=0; i<data.length; i++ )
{
visit( data[i] );
}
}
/**
* This will take a visit from a byte. This will create new code entries as
* necessary.
*
* @param data The byte to get a visit from.
*
* @throws IOException If there is an error visiting this data.
*/
public void visit( byte data ) throws IOException
{
buffer.write( data );
byte[] curBuffer = buffer.toByteArray();
LZWNode previous = null;
LZWNode current = root;
boolean createNewCode = false;
for( int i=0; i<curBuffer.length && current != null; i++ )
{
previous = current;
current = current.getNode( curBuffer[i] );
if( current == null )
{
createNewCode = true;
current = new LZWNode();
previous.setNode( curBuffer[i], current );
}
}
if( createNewCode )
{
long code = nextCode++;
current.setCode( code );
codeToData.put( new Long( code ), curBuffer );
/**
System.out.print( "Adding " + code + "='" );
for( int i=0; i<curBuffer.length; i++ )
{
String hex = Integer.toHexString( ((curBuffer[i]+256)%256) );
if( hex.length() <=1 )
{
hex = "0" + hex;
}
if( i != curBuffer.length -1 )
{
hex += " ";
}
System.out.print( hex.toUpperCase() );
}
System.out.println( "'" );
**/
buffer.reset();
buffer.write( data );
resetCodeSize();
}
}
/**
* This will get the next code that will be created.
*
* @return The next code to be created.
*/
public long getNextCode()
{
return nextCode;
}
/**
* This will get the size of the code in bits, 9, 10, or 11.
*
* @return The size of the code in bits.
*/
public int getCodeSize()
{
return codeSize;
}
/**
* This will determine the code size.
*/
private void resetCodeSize()
{
if( nextCode >= 2048 )
{
codeSize = 12;
}
else if( nextCode >= 1024 )
{
codeSize = 11;
}
else if( nextCode >= 512 )
{
codeSize = 10;
}
else
{
codeSize = 9;
}
}
/**
* This will crear the internal buffer that the dictionary uses.
*/
public void clear()
{
buffer.reset();
}
/**
* This will folow the path to the data node.
*
* @param data The path to the node.
*
* @return The node that resides at that path.
*/
public LZWNode getNode( byte[] data )
{
return root.getNode( data );
}
}