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The Apache PDFBox library is an open source Java tool for working with PDF documents.
/*
* 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.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.zip.DataFormatException;
import java.util.zip.DeflaterOutputStream;
import java.util.zip.Inflater;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSName;
/**
* Decompresses data encoded using the zlib/deflate compression method,
* reproducing the original text or binary data.
*
* @author Ben Litchfield
* @author Marcel Kammer
*/
final class FlateFilter extends Filter
{
private static final Log LOG = LogFactory.getLog(FlateFilter.class);
private static final int BUFFER_SIZE = 16348;
@Override
public DecodeResult decode(InputStream encoded, OutputStream decoded,
COSDictionary parameters, int index) throws IOException
{
int predictor = -1;
final COSDictionary decodeParams = getDecodeParams(parameters, index);
if (decodeParams != null)
{
predictor = decodeParams.getInt(COSName.PREDICTOR);
}
try
{
if (predictor > 1)
{
int colors = Math.min(decodeParams.getInt(COSName.COLORS, 1), 32);
int bitsPerPixel = decodeParams.getInt(COSName.BITS_PER_COMPONENT, 8);
int columns = decodeParams.getInt(COSName.COLUMNS, 1);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
decompress(encoded, baos);
ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
Predictor.decodePredictor(predictor, colors, bitsPerPixel, columns, bais, decoded);
decoded.flush();
baos.reset();
bais.reset();
}
else
{
decompress(encoded, decoded);
}
}
catch (DataFormatException e)
{
// if the stream is corrupt a DataFormatException may occur
LOG.error("FlateFilter: stop reading corrupt stream due to a DataFormatException");
// re-throw the exception
throw new IOException(e);
}
return new DecodeResult(parameters);
}
// Use Inflater instead of InflateInputStream to avoid an EOFException due to a probably
// missing Z_STREAM_END, see PDFBOX-1232 for details
private void decompress(InputStream in, OutputStream out) throws IOException, DataFormatException
{
byte[] buf = new byte[2048];
// skip zlib header
in.read(buf,0,2);
int read = in.read(buf);
if (read > 0)
{
// use nowrap mode to bypass zlib-header and checksum to avoid a DataFormatException
Inflater inflater = new Inflater(true);
inflater.setInput(buf,0,read);
byte[] res = new byte[1024];
boolean dataWritten = false;
while (true)
{
int resRead = 0;
try
{
resRead = inflater.inflate(res);
}
catch(DataFormatException exception)
{
if (dataWritten)
{
// some data could be read -> don't throw an exception
LOG.warn("FlateFilter: premature end of stream due to a DataFormatException");
break;
}
else
{
// nothing could be read -> re-throw exception
throw exception;
}
}
if (resRead != 0)
{
out.write(res,0,resRead);
dataWritten = true;
continue;
}
if (inflater.finished() || inflater.needsDictionary() || in.available() == 0)
{
break;
}
read = in.read(buf);
inflater.setInput(buf,0,read);
}
}
out.flush();
}
@Override
protected void encode(InputStream input, OutputStream encoded, COSDictionary parameters)
throws IOException
{
DeflaterOutputStream out = new DeflaterOutputStream(encoded);
int amountRead;
int mayRead = input.available();
if (mayRead > 0)
{
byte[] buffer = new byte[Math.min(mayRead,BUFFER_SIZE)];
while ((amountRead = input.read(buffer, 0, Math.min(mayRead,BUFFER_SIZE))) != -1)
{
out.write(buffer, 0, amountRead);
}
}
out.close();
encoded.flush();
}
}