org.apache.pdfbox.filter.RunLengthDecodeFilter Maven / Gradle / Ivy
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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.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pdfbox.cos.COSDictionary;
/**
* Decompresses data encoded using a byte-oriented run-length encoding algorithm,
* reproducing the original text or binary data
*
* @author Ben Litchfield
*/
final class RunLengthDecodeFilter extends Filter
{
private static final Log LOG = LogFactory.getLog(RunLengthDecodeFilter.class);
private static final int RUN_LENGTH_EOD = 128;
@Override
public DecodeResult decode(InputStream encoded, OutputStream decoded,
COSDictionary parameters, int index) throws IOException
{
int dupAmount;
byte[] buffer = new byte[128];
while ((dupAmount = encoded.read()) != -1 && dupAmount != RUN_LENGTH_EOD)
{
if (dupAmount <= 127)
{
int amountToCopy = dupAmount + 1;
int compressedRead;
while (amountToCopy > 0)
{
compressedRead = encoded.read(buffer, 0, amountToCopy);
// EOF reached?
if (compressedRead == -1)
{
break;
}
decoded.write(buffer, 0, compressedRead);
amountToCopy -= compressedRead;
}
}
else
{
int dupByte = encoded.read();
// EOF reached?
if (dupByte == -1)
{
break;
}
for (int i = 0; i < 257 - dupAmount; i++)
{
decoded.write(dupByte);
}
}
}
return new DecodeResult(parameters);
}
@Override
protected void encode(InputStream input, OutputStream encoded, COSDictionary parameters)
throws IOException
{
LOG.warn("RunLengthDecodeFilter.encode is not implemented yet, skipping this stream.");
}
}