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An Apache PDFBox fork intended to be used as PDF processor for Sejda and PDFsam
related projects
/*
* 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.sejda.sambox.output;
import static java.util.Objects.nonNull;
import static org.sejda.commons.util.RequireUtils.requireNotNullArg;
import static org.sejda.sambox.util.SpecVersionUtils.PDF_HEADER;
import java.io.Closeable;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.Optional;
import org.sejda.commons.util.IOUtils;
import org.sejda.sambox.cos.COSDictionary;
import org.sejda.sambox.cos.COSInteger;
import org.sejda.sambox.cos.COSName;
import org.sejda.sambox.cos.DirectCOSObject;
import org.sejda.sambox.cos.IndirectCOSObjectReference;
import org.sejda.sambox.xref.XrefEntry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Default PDF writer that writes part of the pdf document using the given {@link IndirectObjectsWriter}.
*
* @author Andrea Vacondio
*/
class DefaultPDFWriter implements Closeable
{
private static final Logger LOG = LoggerFactory.getLogger(DefaultPDFWriter.class);
byte COMMENT = '%';
byte[] GARBAGE = new byte[] { (byte) 0xA7, (byte) 0xE3, (byte) 0xF1, (byte) 0xF1 };
private final IndirectObjectsWriter writer;
public DefaultPDFWriter(IndirectObjectsWriter writer)
{
requireNotNullArg(writer, "Cannot write to a null COSWriter");
this.writer = writer;
}
public void writeHeader(String version) throws IOException
{
LOG.debug("Writing header " + version);
writer().write(PDF_HEADER);
writer().write(version);
writer().writeEOL();
writer().write(COMMENT);
writer().write(GARBAGE);
writer().writeEOL();
}
/**
* writes the xref table
*
* @return the startxref value
* @throws IOException
*/
public long writeXrefTable() throws IOException
{
long startxref = writer().offset();
LOG.debug("Writing xref table at offset " + startxref);
if (nonNull(writer.context().addWritten(XrefEntry.DEFAULT_FREE_ENTRY)))
{
LOG.warn("Reserved object number 0 has been overwritten with the expected free entry");
}
writer().write("xref");
writer().writeEOL();
for (List continuos : writer.context().getWrittenContiguousGroups())
{
writer().write(continuos.get(0).toString() + " " + continuos.size());
writer().writeEOL();
for (long key : continuos)
{
writer().write(Optional.ofNullable(writer.context().getWritten(key))
.orElse(XrefEntry.DEFAULT_FREE_ENTRY).toXrefTableEntry());
}
}
return startxref;
}
/**
* Writes the given trailer setting startxref to the given offsets
*
* @param trailer
* @param startxref
* @throws IOException
*/
public void writeTrailer(COSDictionary trailer, long startxref) throws IOException
{
writeTrailer(trailer, startxref, -1);
}
/**
* Writes the given trailer setting the /Prev entry and startxref to the given offsets
*
* @param trailer
* @param startxref
* @param prev prev offset, written only if != -1
* @throws IOException
*/
public void writeTrailer(COSDictionary trailer, long startxref, long prev) throws IOException
{
LOG.trace("Writing trailer");
sanitizeTrailer(trailer, prev);
trailer.setItem(COSName.SIZE, DirectCOSObject
.asDirectObject(COSInteger.get(writer.context().highestObjectNumber() + 1)));
writer.write("trailer".getBytes(StandardCharsets.US_ASCII));
writer.writeEOL();
trailer.getCOSObject().accept(writer.writer());
writeXrefFooter(startxref);
}
/**
* Writes an xref stream using the given trailer
*
* @param trailer
* @throws IOException
*/
public void writeXrefStream(COSDictionary trailer) throws IOException
{
if (nonNull(writer.context().addWritten(XrefEntry.DEFAULT_FREE_ENTRY)))
{
LOG.warn("Reserved object number 0 has been overwritten with the expected free entry");
}
writeXrefStream(trailer, -1);
}
/**
* Writes an xref stream using the given trailer and setting the /Prev entry to the given offset
*
* @param trailer
* @param prev
* @throws IOException
*/
public void writeXrefStream(COSDictionary trailer, long prev) throws IOException
{
long startxref = writer().offset();
LOG.debug("Writing xref stream at offset " + startxref);
sanitizeTrailer(trailer, prev);
XrefEntry entry = XrefEntry.inUseEntry(writer.context().highestObjectNumber() + 1,
startxref, 0);
writer.context().addWritten(entry);
writer.writeObject(new IndirectCOSObjectReference(entry.getObjectNumber(),
entry.getGenerationNumber(), new XrefStream(trailer, writer.context())));
writeXrefFooter(startxref);
}
private static void sanitizeTrailer(COSDictionary trailer, long prev)
{
trailer.removeItem(COSName.PREV);
trailer.removeItem(COSName.XREF_STM);
trailer.removeItem(COSName.DOC_CHECKSUM);
trailer.removeItem(COSName.DECODE_PARMS);
trailer.removeItem(COSName.FILTER);
trailer.removeItem(COSName.F_DECODE_PARMS);
trailer.removeItem(COSName.F_FILTER);
trailer.removeItem(COSName.F);
trailer.removeItem(COSName.LENGTH);
trailer.removeItem(COSName.W);
trailer.removeItem(COSName.DL);
trailer.removeItem(COSName.TYPE);
trailer.removeItem(COSName.INDEX);
if (prev != -1)
{
trailer.setLong(COSName.PREV, prev);
}
}
private void writeXrefFooter(long startxref) throws IOException
{
writer.write("startxref".getBytes(StandardCharsets.US_ASCII));
writer.writeEOL();
writer.write(Long.toString(startxref));
writer.writeEOL();
writer.write("%%EOF".getBytes(StandardCharsets.US_ASCII));
writer.writeEOL();
}
IndirectObjectsWriter writer()
{
return writer;
}
@Override
public void close() throws IOException
{
IOUtils.close(writer);
}
}