/*
* 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.pdfparser;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.KeyStore;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Queue;
import java.util.Set;
import java.util.TreeMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pdfbox.cos.COSArray;
import org.apache.pdfbox.cos.COSBase;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSDocument;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.cos.COSNull;
import org.apache.pdfbox.cos.COSNumber;
import org.apache.pdfbox.cos.COSObject;
import org.apache.pdfbox.cos.COSStream;
import org.apache.pdfbox.cos.COSString;
import org.apache.pdfbox.exceptions.CryptographyException;
import org.apache.pdfbox.io.IOUtils;
import org.apache.pdfbox.io.PushBackInputStream;
import org.apache.pdfbox.io.RandomAccess;
import org.apache.pdfbox.io.RandomAccessBuffer;
import org.apache.pdfbox.io.RandomAccessBufferedFileInputStream;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.encryption.AccessPermission;
import org.apache.pdfbox.pdmodel.encryption.DecryptionMaterial;
import org.apache.pdfbox.pdmodel.encryption.PDEncryptionDictionary;
import org.apache.pdfbox.pdmodel.encryption.PublicKeyDecryptionMaterial;
import org.apache.pdfbox.pdmodel.encryption.SecurityHandler;
import org.apache.pdfbox.pdmodel.encryption.SecurityHandlersManager;
import org.apache.pdfbox.pdmodel.encryption.StandardDecryptionMaterial;
import org.apache.pdfbox.persistence.util.COSObjectKey;
/**
* PDFParser which first reads startxref and xref tables in order to know valid
* objects and parse only these objects. Thus it is closer to a conforming
* parser than the sequential reading of {@link PDFParser}.
*
* This class can be used as a {@link PDFParser} replacement. First
* {@link #parse()} must be called before page objects can be retrieved, e.g.
* {@link #getPDDocument()}.
*
* This class is a much enhanced version of <code>QuickParser</code> presented
* in <a
* href="https://issues.apache.org/jira/browse/PDFBOX-1104">PDFBOX-1104</a> by
* Jeremy Villalobos.
*/
public class NonSequentialPDFParser extends PDFParser
{
private static final byte[] XREF = new byte[] { 'x', 'r', 'e', 'f' };
private static final int E = 'e';
private static final int N = 'n';
private static final int X = 'x';
public static final String SYSPROP_PARSEMINIMAL = "org.apache.pdfbox.pdfparser.nonSequentialPDFParser.parseMinimal";
public static final String SYSPROP_EOFLOOKUPRANGE = "org.apache.pdfbox.pdfparser.nonSequentialPDFParser.eofLookupRange";
private static final InputStream EMPTY_INPUT_STREAM = new ByteArrayInputStream(new byte[0]);
protected static final int DEFAULT_TRAIL_BYTECOUNT = 2048;
/**
* EOF-marker.
*/
protected static final char[] EOF_MARKER = new char[] { '%', '%', 'E', 'O', 'F' };
/**
* StartXRef-marker.
*/
protected static final char[] STARTXREF_MARKER = new char[] { 's', 't', 'a', 'r', 't', 'x', 'r', 'e', 'f' };
/**
* obj-marker.
*/
protected static final char[] OBJ_MARKER = new char[] { 'o', 'b', 'j' };
private final File pdfFile;
private long fileLen;
private final RandomAccessBufferedFileInputStream raStream;
/**
* is parser using auto healing capacity ?
*/
private boolean isLenient = true;
/**
* The security handler.
*/
protected SecurityHandler securityHandler = null;
private String keyStoreFilename = null;
private String alias = null;
private String password = "";
private int readTrailBytes = DEFAULT_TRAIL_BYTECOUNT; // how many trailing
// bytes to read for
// EOF marker
/**
* If <code>true</code> object references in catalog are not followed; pro:
* page objects will be only parsed when needed; cons: some information of
* catalog might not be available (e.g. outline). Catalog parsing without
* pages is not an option since a number of entries will also refer to page
* objects (like OpenAction).
*/
private boolean parseMinimalCatalog = "true".equals(System.getProperty(SYSPROP_PARSEMINIMAL));
private boolean initialParseDone = false;
private boolean allPagesParsed = false;
private static final Log LOG = LogFactory.getLog(NonSequentialPDFParser.class);
/**
* <code>true</code> if the NonSequentialPDFParser is initialized by a
* InputStream, in this case a temporary file is created. At the end of the
* {@linkplain #parse()} method,the temporary file will be deleted.
*/
private boolean isTmpPDFFile = false;
public static final String TMP_FILE_PREFIX = "tmpPDF";
// ------------------------------------------------------------------------
/**
* Constructs parser for given file using memory buffer.
*
* @param filename the filename of the pdf to be parsed
*
* @throws IOException If something went wrong.
*/
public NonSequentialPDFParser(String filename) throws IOException
{
this(new File(filename), null);
}
/**
* Constructs parser for given file using given buffer for temporary
* storage.
*
* @param file the pdf to be parsed
* @param raBuf the buffer to be used for parsing
*
* @throws IOException If something went wrong.
*/
/**
* Constructs parser for given file using given buffer for temporary
* storage.
*
* @param file the pdf to be parsed
* @param raBuf the buffer to be used for parsing
*
* @throws IOException If something went wrong.
*/
public NonSequentialPDFParser(File file, RandomAccess raBuf) throws IOException
{
this(file, raBuf, "");
}
/**
* Constructs parser for given file using given buffer for temporary
* storage.
*
* @param file the pdf to be parsed
* @param raBuf the buffer to be used for parsing
*
* @throws IOException If something went wrong.
*/
/**
* Constructs parser for given file using given buffer for temporary
* storage.
*
* @param file the pdf to be parsed
* @param raBuf the buffer to be used for parsing
* @param decryptionPassword password to be used for decryption
*
* @throws IOException If something went wrong.
*/
public NonSequentialPDFParser(File file, RandomAccess raBuf, String decryptionPassword) throws IOException
{
super(EMPTY_INPUT_STREAM, null, false);
pdfFile = file;
raStream = new RandomAccessBufferedFileInputStream(pdfFile);
init(file, raBuf, decryptionPassword);
}
private void init(File file, RandomAccess raBuf, String decryptionPassword) throws IOException
{
String eofLookupRangeStr = System.getProperty(SYSPROP_EOFLOOKUPRANGE);
if (eofLookupRangeStr != null)
{
try
{
setEOFLookupRange(Integer.parseInt(eofLookupRangeStr));
}
catch (NumberFormatException nfe)
{
LOG.warn("System property " + SYSPROP_EOFLOOKUPRANGE + " does not contain an integer value, but: '"
+ eofLookupRangeStr + "'");
}
}
setDocument((raBuf == null) ? new COSDocument(new RandomAccessBuffer(), false) : new COSDocument(raBuf, false));
pdfSource = new PushBackInputStream(raStream, 4096);
password = decryptionPassword;
}
/**
* Constructor.
*
* @param input input stream representing the pdf.
* @throws IOException If something went wrong.
*/
public NonSequentialPDFParser(InputStream input) throws IOException
{
this(input, null, "");
}
/**
* Constructor.
*
* @param input input stream representing the pdf.
* @param raBuf the buffer to be used for parsing
* @param decryptionPassword password to be used for decryption.
* @throws IOException If something went wrong.
*/
public NonSequentialPDFParser(InputStream input, RandomAccess raBuf, String decryptionPassword) throws IOException
{
super(EMPTY_INPUT_STREAM, null, false);
pdfFile = createTmpFile(input);
raStream = new RandomAccessBufferedFileInputStream(pdfFile);
init(pdfFile, raBuf, decryptionPassword);
}
/**
* Create a temporary file with the input stream. If the creation succeed,
* the {@linkplain #isTmpPDFFile} is set to true. This Temporary file will
* be deleted at end of the parse method
*
* @param input
* @return
* @throws IOException If something went wrong.
*/
private File createTmpFile(InputStream input) throws IOException
{
File tmpFile = null;
FileOutputStream fos = null;
try
{
tmpFile = File.createTempFile(TMP_FILE_PREFIX, ".pdf");
fos = new FileOutputStream(tmpFile);
IOUtils.copy(input, fos);
isTmpPDFFile = true;
return tmpFile;
}
finally
{
IOUtils.closeQuietly(input);
IOUtils.closeQuietly(fos);
}
}
// ------------------------------------------------------------------------
/**
* Sets how many trailing bytes of PDF file are searched for EOF marker and
* 'startxref' marker. If not set we use default value
* {@link #DEFAULT_TRAIL_BYTECOUNT}.
*
* <p<We check that new value is at least 16. However for practical use
* cases this value should not be lower than 1000; even 2000 was found to
* not be enough in some cases where some trailing garbage like HTML
* snippets followed the EOF marker.</p>
*
* <p>In case system property {@link #SYSPROP_EOFLOOKUPRANGE} is defined
* this value will be set on initialization but can be overwritten
* later.</p>
*
* @param byteCount number of trailing bytes
*/
public void setEOFLookupRange(int byteCount)
{
if (byteCount > 15)
{
readTrailBytes = byteCount;
}
}
// ------------------------------------------------------------------------
/**
* The initial parse will first parse only the trailer, the xrefstart and
* all xref tables to have a pointer (offset) to all the pdf's objects. It
* can handle linearized pdfs, which will have an xref at the end pointing
* to an xref at the beginning of the file. Last the root object is parsed.
*
* @throws IOException If something went wrong.
*/
protected void initialParse() throws IOException
{
// ---- parse startxref
setPdfSource(getStartxrefOffset());
parseStartXref();
long startXrefOffset = document.getStartXref();
// check the startxref offset
if (isLenient) {
startXrefOffset -= calculateFixingOffset(startXrefOffset);
document.setStartXref(startXrefOffset);
}
long prev = startXrefOffset;
// ---- parse whole chain of xref tables/object streams using PREV
// reference
while (prev > -1)
{
// seek to xref table
setPdfSource(prev);
// skip white spaces
skipSpaces();
// -- parse xref
if (pdfSource.peek() == X)
{
// xref table and trailer
// use existing parser to parse xref table
parseXrefTable(prev);
// parse the last trailer.
if (!parseTrailer())
{
throw new IOException("Expected trailer object at position: " + pdfSource.getOffset());
}
COSDictionary trailer = xrefTrailerResolver.getCurrentTrailer();
prev = trailer.getInt(COSName.PREV);
if (isLenient && prev > -1)
{
// check the xref table reference
long fixingOffset = calculateFixingOffset(prev);
if (fixingOffset != 0)
{
prev -= fixingOffset;
trailer.setLong(COSName.PREV, prev);
}
}
}
else
{
// parse xref stream
prev = parseXrefObjStream(prev);
if (isLenient && prev > -1)
{
// check the xref table reference
long fixingOffset = calculateFixingOffset(prev);
if (fixingOffset != 0)
{
prev -= fixingOffset;
COSDictionary trailer = xrefTrailerResolver.getCurrentTrailer();
trailer.setLong(COSName.PREV, prev);
}
}
}
}
// ---- build valid xrefs out of the xref chain
xrefTrailerResolver.setStartxref(startXrefOffset);
COSDictionary trailer = xrefTrailerResolver.getTrailer();
document.setTrailer(trailer);
// check the offsets of all referenced objects
if (isLenient) {
checkXrefOffsets();
}
// ---- prepare encryption if necessary
COSBase trailerEncryptItem = document.getTrailer().getItem(COSName.ENCRYPT);
if (trailerEncryptItem != null)
{
if (trailerEncryptItem instanceof COSObject)
{
COSObject trailerEncryptObj = (COSObject) trailerEncryptItem;
parseObjectDynamically(trailerEncryptObj, true);
}
try
{
PDEncryptionDictionary encParameters = new PDEncryptionDictionary(document.getEncryptionDictionary());
DecryptionMaterial decryptionMaterial = null;
if (keyStoreFilename != null)
{
KeyStore ks = KeyStore.getInstance("PKCS12");
ks.load(new FileInputStream(keyStoreFilename), password.toCharArray());
decryptionMaterial = new PublicKeyDecryptionMaterial(ks, alias, password);
}
else
{
decryptionMaterial = new StandardDecryptionMaterial(password);
}
securityHandler = SecurityHandlersManager.getInstance().getSecurityHandler(encParameters.getFilter());
securityHandler.prepareForDecryption(encParameters, document.getDocumentID(), decryptionMaterial);
AccessPermission permission = securityHandler.getCurrentAccessPermission();
if (!permission.canExtractContent())
{
LOG.warn("PDF file '" + pdfFile.getPath() + "' does not allow extracting content.");
}
}
catch (Exception e)
{
throw new IOException("Error (" + e.getClass().getSimpleName()
+ ") while creating security handler for decryption: " + e.getMessage() /*
* , e TODO: remove
* remark with Java 1.6
*/);
}
}
// PDFBOX-1557 - ensure that all COSObject are loaded in the trailer
// PDFBOX-1606 - after securityHandler has been instantiated
for (COSBase trailerEntry : trailer.getValues())
{
if (trailerEntry instanceof COSObject)
{
COSObject tmpObj = (COSObject) trailerEntry;
parseObjectDynamically(tmpObj, false);
}
}
// ---- parse catalog or root object
COSObject root = (COSObject) xrefTrailerResolver.getTrailer().getItem(COSName.ROOT);
if (root == null)
{
throw new IOException("Missing root object specification in trailer.");
}
parseObjectDynamically(root, false);
// ---- resolve all objects (including pages)
if (!parseMinimalCatalog)
{
COSObject catalogObj = document.getCatalog();
if (catalogObj != null)
{
if (catalogObj.getObject() instanceof COSDictionary)
{
parseDictObjects((COSDictionary) catalogObj.getObject(), (COSName[]) null);
allPagesParsed = true;
document.setDecrypted();
}
}
}
initialParseDone = true;
}
// ------------------------------------------------------------------------
/**
* Parses an xref object stream starting with indirect object id.
*
* @return value of PREV item in dictionary or <code>-1</code> if no such
* item exists
*/
private long parseXrefObjStream(long objByteOffset) throws IOException
{
// ---- parse indirect object head
readObjectNumber();
readGenerationNumber();
readPattern(OBJ_MARKER);
COSDictionary dict = parseCOSDictionary();
COSStream xrefStream = parseCOSStream(dict, getDocument().getScratchFile());
parseXrefStream(xrefStream, (int) objByteOffset);
return dict.getLong(COSName.PREV);
}
// ------------------------------------------------------------------------
/** Get current offset in file at which next byte would be read. */
private final long getPdfSourceOffset()
{
return pdfSource.getOffset();
}
/**
* Sets {@link #pdfSource} to start next parsing at given file offset.
*
* @param fileOffset file offset
* @throws IOException If something went wrong.
*/
protected final void setPdfSource(long fileOffset) throws IOException
{
pdfSource.seek(fileOffset);
// alternative using 'old fashioned' input stream
// if ( pdfSource != null )
// pdfSource.close();
//
// pdfSource = new PushBackInputStream(
// new BufferedInputStream(
// new FileInputStream( file ), 16384), 4096);
// pdfSource.skip( _fileOffset );
}
/**
* Enable handling of alternative pdfSource implementation.
* @throws IOException If something went wrong.
*/
protected final void releasePdfSourceInputStream() throws IOException
{
// if ( pdfSource != null )
// pdfSource.close();
}
private final void closeFileStream() throws IOException
{
if (pdfSource != null)
{
pdfSource.close();
}
}
// ------------------------------------------------------------------------
/**
* Looks for and parses startxref. We first look for last '%%EOF' marker
* (within last {@link #DEFAULT_TRAIL_BYTECOUNT} bytes (or range set via
* {@link #setEOFLookupRange(int)}) and go back to find
* <code>startxref</code>.
*
* @return the offset of StartXref
* @throws IOException If something went wrong.
*/
protected final long getStartxrefOffset() throws IOException
{
byte[] buf;
long skipBytes;
// ---- read trailing bytes into buffer
fileLen = pdfFile.length();
FileInputStream fIn = null;
try
{
fIn = new FileInputStream(pdfFile);
final int trailByteCount = (fileLen < readTrailBytes) ? (int) fileLen : readTrailBytes;
buf = new byte[trailByteCount];
fIn.skip(skipBytes = fileLen - trailByteCount);
int off = 0;
int readBytes;
while (off < trailByteCount)
{
readBytes = fIn.read(buf, off, trailByteCount - off);
// in order to not get stuck in a loop we check readBytes (this
// should never happen)
if (readBytes < 1)
{
throw new IOException("No more bytes to read for trailing buffer, but expected: "
+ (trailByteCount - off));
}
off += readBytes;
}
}
finally
{
if (fIn != null)
{
try
{
fIn.close();
}
catch (IOException ioe)
{
}
}
}
// ---- find last '%%EOF'
int bufOff = lastIndexOf(EOF_MARKER, buf, buf.length);
if (bufOff < 0)
{
throw new IOException("Missing end of file marker '" + (new String(EOF_MARKER)) + "'");
}
// ---- find last startxref preceding EOF marker
bufOff = lastIndexOf(STARTXREF_MARKER, buf, bufOff);
if (bufOff < 0)
{
throw new IOException("Missing 'startxref' marker.");
}
return skipBytes + bufOff;
}
// ------------------------------------------------------------------------
/**
* Searches last appearance of pattern within buffer. Lookup before _lastOff
* and goes back until 0.
*
* @param pattern pattern to search for
* @param buf buffer to search pattern in
* @param endOff offset (exclusive) where lookup starts at
*
* @return start offset of pattern within buffer or <code>-1</code> if
* pattern could not be found
*/
protected int lastIndexOf(final char[] pattern, final byte[] buf, final int endOff)
{
final int lastPatternChOff = pattern.length - 1;
int bufOff = endOff;
int patOff = lastPatternChOff;
char lookupCh = pattern[patOff];
while (--bufOff >= 0)
{
if (buf[bufOff] == lookupCh)
{
if (--patOff < 0)
{
// whole pattern matched
return bufOff;
}
// matched current char, advance to preceding one
lookupCh = pattern[patOff];
}
else if (patOff < lastPatternChOff)
{
// no char match but already matched some chars; reset
lookupCh = pattern[patOff = lastPatternChOff];
}
}
return -1;
}
// ------------------------------------------------------------------------
/**
* Reads given pattern from {@link #pdfSource}. Skipping whitespace at start
* and end.
*
* @param pattern pattern to be skipped
* @throws IOException if pattern could not be read
*/
protected final void readPattern(final char[] pattern) throws IOException
{
skipSpaces();
for (char c : pattern)
{
if (pdfSource.read() != c)
{
throw new IOException("Expected pattern '" + new String(pattern) + " but missed at character '" + c
+ "'");
}
}
skipSpaces();
}
// ------------------------------------------------------------------------
private COSDictionary pagesDictionary = null;
/**
* Returns PAGES {@link COSDictionary} object or throws {@link IOException}
* if PAGES dictionary does not exist.
*/
private COSDictionary getPagesObject() throws IOException
{
if (pagesDictionary != null)
{
return pagesDictionary;
}
COSObject pages = (COSObject) document.getCatalog().getItem(COSName.PAGES);
if (pages == null)
{
throw new IOException("Missing PAGES entry in document catalog.");
}
COSBase object = parseObjectDynamically(pages, false);
if (!(object instanceof COSDictionary))
{
throw new IOException("PAGES not a dictionary object, but: " + object.getClass().getSimpleName());
}
pagesDictionary = (COSDictionary) object;
return pagesDictionary;
}
// ------------------------------------------------------------------------
/** Parses all objects needed by pages and closes input stream. */
/**
* {@inheritDoc}
*/
@Override
public void parse() throws IOException
{
boolean exceptionOccurred = true; // set to false if all is processed
try
{
if (!initialParseDone)
{
initialParse();
}
final int pageCount = getPageNumber();
if (!allPagesParsed)
{
for (int pNr = 0; pNr < pageCount; pNr++)
{
getPage(pNr);
}
allPagesParsed = true;
document.setDecrypted();
}
exceptionOccurred = false;
}
finally
{
try
{
closeFileStream();
}
catch (IOException ioe)
{
}
deleteTempFile();
if (exceptionOccurred && (document != null))
{
try
{
document.close();
document = null;
}
catch (IOException ioe)
{
}
}
}
}
/**
* Return the pdf file.
*
* @return the pdf file
*/
protected File getPdfFile()
{
return this.pdfFile;
}
/**
* Return true if parser is lenient. Meaning auto healing capacity of the parser are used.
*
* @return true if parser is lenient
*/
public boolean isLenient () {
return isLenient;
}
/**
* Change the parser leniency flag.
*
* This method can only be called before the parsing of the file.
*
* @param lenient
*
* @throws IllegalArgumentException if the method is called after parsing.
*/
public void setLenient (boolean lenient) throws IllegalArgumentException {
if (initialParseDone) {
throw new IllegalArgumentException("Cannot change leniency after parsing");
}
this.isLenient = lenient;
}
/**
* Remove the temporary file. A temporary file is created if this class is
* instantiated with an InputStream
*/
protected void deleteTempFile()
{
if (isTmpPDFFile)
{
try
{
if (!pdfFile.delete())
{
LOG.warn("Temporary file '" + pdfFile.getName() + "' can't be deleted");
}
}
catch (SecurityException e)
{
LOG.warn("Temporary file '" + pdfFile.getName() + "' can't be deleted", e);
}
}
}
// ------------------------------------------------------------------------
/**
* Returns security handler of the document or <code>null</code> if document
* is not encrypted or {@link #parse()} wasn't called before.
*
* @return the security handler.
*/
public SecurityHandler getSecurityHandler()
{
return securityHandler;
}
// ------------------------------------------------------------------------
/**
* This will get the PD document that was parsed. When you are done with
* this document you must call close() on it to release resources.
*
* Overwriting super method was necessary in order to set security handler.
*
* @return The document at the PD layer.
*
* @throws IOException If there is an error getting the document.
*/
@Override
public PDDocument getPDDocument() throws IOException
{
PDDocument pdDocument = super.getPDDocument();
if (securityHandler != null)
{
pdDocument.setSecurityHandler(securityHandler);
}
return pdDocument;
}
// ------------------------------------------------------------------------
/**
* Returns the number of pages in a document.
*
* @return the number of pages.
*
* @throws IOException if PAGES or other needed object is missing
*/
public int getPageNumber() throws IOException
{
int pageCount = getPagesObject().getInt(COSName.COUNT);
if (pageCount < 0)
{
throw new IOException("No page number specified.");
}
return pageCount;
}
// ------------------------------------------------------------------------
/**
* Returns the page requested with all the objects loaded into it.
*
* @param pageNr starts from 0 to the number of pages.
* @return the page with the given pagenumber.
* @throws IOException If something went wrong.
*/
public PDPage getPage(int pageNr) throws IOException
{
getPagesObject();
// ---- get list of top level pages
COSArray kids = (COSArray) pagesDictionary.getDictionaryObject(COSName.KIDS);
if (kids == null)
{
throw new IOException("Missing 'Kids' entry in pages dictionary.");
}
// ---- get page we are looking for (possibly going recursively into
// subpages)
COSObject pageObj = getPageObject(pageNr, kids, 0);
if (pageObj == null)
{
throw new IOException("Page " + pageNr + " not found.");
}
// ---- parse all objects necessary to load page.
COSDictionary pageDict = (COSDictionary) pageObj.getObject();
if (parseMinimalCatalog && (!allPagesParsed))
{
// parse page resources since we did not do this on start
COSDictionary resDict = (COSDictionary) pageDict.getDictionaryObject(COSName.RESOURCES);
parseDictObjects(resDict);
}
return new PDPage(pageDict);
}
/**
* Returns the object for a specific page. The page tree is made up of kids.
* The kids have COSArray with COSObjects inside of them. The COSObject can
* be parsed using the dynamic parsing method We want to only parse the
* minimum COSObjects and still return a complete page. ready to be used.
*
* @param num the requested page number; numbering starts with 0
* @param startKids Kids array to start with looking up page number
* @param startPageCount
*
* @return page object or <code>null</code> if no such page exists
*
* @throws IOException
*/
private COSObject getPageObject(int num, COSArray startKids, int startPageCount) throws IOException
{
int curPageCount = startPageCount;
Iterator<COSBase> kidsIter = startKids.iterator();
while (kidsIter.hasNext())
{
COSObject obj = (COSObject) kidsIter.next();
COSBase base = obj.getObject();
if (base == null)
{
base = parseObjectDynamically(obj, false);
obj.setObject(base);
}
COSDictionary dic = (COSDictionary) base;
int count = dic.getInt(COSName.COUNT);
if (count >= 0)
{
// skip this branch if requested page comes later
if ((curPageCount + count) <= num)
{
curPageCount += count;
continue;
}
}
COSArray kids = (COSArray) dic.getDictionaryObject(COSName.KIDS);
if (kids != null)
{
// recursively scan subpages
COSObject ans = getPageObject(num, kids, curPageCount);
// if ans is not null, we got what we were looking for
if (ans != null)
{
return ans;
}
}
else
{
// found page?
if (curPageCount == num)
{
return obj;
}
// page has no kids and it is not the page we are looking for
curPageCount++;
}
}
return null;
}
/**
* Creates a unique object id using object number and object generation
* number. (requires object number < 2^31))
*/
private final long getObjectId(final COSObject obj)
{
return (obj.getObjectNumber().longValue() << 32) | obj.getGenerationNumber().longValue();
}
/**
* Adds all from newObjects to toBeParsedList if it is not an COSObject or
* we didn't add this COSObject already (checked via addedObjects).
*/
private final void addNewToList(final Queue<COSBase> toBeParsedList, final Collection<COSBase> newObjects,
final Set<Long> addedObjects)
{
for (COSBase newObject : newObjects)
{
if (newObject instanceof COSObject)
{
final long objId = getObjectId((COSObject) newObject);
if (!addedObjects.add(objId))
{
continue;
}
}
toBeParsedList.add(newObject);
}
}
/**
* Adds newObject to toBeParsedList if it is not an COSObject or we didn't
* add this COSObject already (checked via addedObjects).
*/
private final void addNewToList(final Queue<COSBase> toBeParsedList, final COSBase newObject,
final Set<Long> addedObjects)
{
if (newObject instanceof COSObject)
{
final long objId = getObjectId((COSObject) newObject);
if (!addedObjects.add(objId))
{
return;
}
}
toBeParsedList.add(newObject);
}
/**
* Will parse every object necessary to load a single page from the pdf
* document. We try our best to order objects according to offset in file
* before reading to minimize seek operations.
*
* @param dict the COSObject from the parent pages.
* @param excludeObjects dictionary object reference entries with these
* names will not be parsed
*
* @throws IOException
*/
private void parseDictObjects(COSDictionary dict, COSName... excludeObjects) throws IOException
{
// ---- create queue for objects waiting for further parsing
final Queue<COSBase> toBeParsedList = new LinkedList<COSBase>();
// offset ordered object map
final TreeMap<Long, List<COSObject>> objToBeParsed = new TreeMap<Long, List<COSObject>>();
// in case of compressed objects offset points to stmObj
final Set<Long> parsedObjects = new HashSet<Long>();
final Set<Long> addedObjects = new HashSet<Long>();
// ---- add objects not to be parsed to list of already parsed objects
if (excludeObjects != null)
{
for (COSName objName : excludeObjects)
{
COSBase baseObj = dict.getItem(objName);
if (baseObj instanceof COSObject)
{
parsedObjects.add(getObjectId((COSObject) baseObj));
}
}
}
addNewToList(toBeParsedList, dict.getValues(), addedObjects);
// ---- go through objects to be parsed
while (!(toBeParsedList.isEmpty() && objToBeParsed.isEmpty()))
{
// -- first get all COSObject from other kind of objects and
// put them in objToBeParsed; afterwards toBeParsedList is empty
COSBase baseObj;
while ((baseObj = toBeParsedList.poll()) != null)
{
if (baseObj instanceof COSStream)
{
addNewToList(toBeParsedList, ((COSStream) baseObj).getValues(), addedObjects);
}
else if (baseObj instanceof COSDictionary)
{
addNewToList(toBeParsedList, ((COSDictionary) baseObj).getValues(), addedObjects);
}
else if (baseObj instanceof COSArray)
{
final Iterator<COSBase> arrIter = ((COSArray) baseObj).iterator();
while (arrIter.hasNext())
{
addNewToList(toBeParsedList, arrIter.next(), addedObjects);
}
}
else if (baseObj instanceof COSObject)
{
COSObject obj = (COSObject) baseObj;
long objId = getObjectId(obj);
COSObjectKey objKey = new COSObjectKey(obj.getObjectNumber().intValue(), obj.getGenerationNumber()
.intValue());
if (!(parsedObjects.contains(objId) /*
* || document.hasObjectInPool ( objKey )
*/))
{
Long fileOffset = xrefTrailerResolver.getXrefTable().get(objKey);
// it is allowed that object references point to null,
// thus we have to test
if (fileOffset != null)
{
if (fileOffset > 0)
{
objToBeParsed.put(fileOffset, Collections.singletonList(obj));
}
else
{
// negative offset means we have a compressed
// object within object stream;
// get offset of object stream
fileOffset = xrefTrailerResolver.getXrefTable().get(new COSObjectKey(-fileOffset, 0));
if ((fileOffset == null) || (fileOffset <= 0))
{
throw new IOException("Invalid object stream xref object reference: " + fileOffset);
}
List<COSObject> stmObjects = objToBeParsed.get(fileOffset);
if (stmObjects == null)
{
objToBeParsed.put(fileOffset, stmObjects = new ArrayList<COSObject>());
}
stmObjects.add(obj);
}
}
else
{
// NULL object
COSObject pdfObject = document.getObjectFromPool(objKey);
pdfObject.setObject(COSNull.NULL);
}
}
}
}
// ---- read first COSObject with smallest offset;
// resulting object will be added to toBeParsedList
if (objToBeParsed.isEmpty())
{
break;
}
for (COSObject obj : objToBeParsed.remove(objToBeParsed.firstKey()))
{
COSBase parsedObj = parseObjectDynamically(obj, false);
obj.setObject(parsedObj);
addNewToList(toBeParsedList, parsedObj, addedObjects);
parsedObjects.add(getObjectId(obj));
}
}
}
/**
* This will parse the next object from the stream and add it to the local
* state. This is taken from {@link PDFParser} and reduced to parsing an
* indirect object.
*
* @param obj object to be parsed (we only take object number and generation
* number for lookup start offset)
* @param requireExistingNotCompressedObj if <code>true</code> object to be
* parsed must not be contained within compressed stream
* @return the parsed object (which is also added to document object)
*
* @throws IOException If an IO error occurs.
*/
protected final COSBase parseObjectDynamically(COSObject obj, boolean requireExistingNotCompressedObj)
throws IOException
{
return parseObjectDynamically(obj.getObjectNumber().intValue(), obj.getGenerationNumber().intValue(),
requireExistingNotCompressedObj);
}
/**
* This will parse the next object from the stream and add it to the local
* state. This is taken from {@link PDFParser} and reduced to parsing an
* indirect object.
*
* @param objNr object number of object to be parsed
* @param objGenNr object generation number of object to be parsed
* @param requireExistingNotCompressedObj if <code>true</code> the object to
* be parsed must be defined in xref (comment: null objects may
* be missing from xref) and it must not be a compressed object
* within object stream (this is used to circumvent being stuck
* in a loop in a malicious PDF)
*
* @return the parsed object (which is also added to document object)
*
* @throws IOException If an IO error occurs.
*/
protected COSBase parseObjectDynamically(int objNr, int objGenNr, boolean requireExistingNotCompressedObj)
throws IOException
{
// ---- create object key and get object (container) from pool
final COSObjectKey objKey = new COSObjectKey(objNr, objGenNr);
final COSObject pdfObject = document.getObjectFromPool(objKey);
if (pdfObject.getObject() == null)
{
// not previously parsed
// ---- read offset or object stream object number from xref table
Long offsetOrObjstmObNr = xrefTrailerResolver.getXrefTable().get(objKey);
// sanity test to circumvent loops with broken documents
if (requireExistingNotCompressedObj && ((offsetOrObjstmObNr == null) || (offsetOrObjstmObNr <= 0)))
{
throw new IOException("Object must be defined and must not be compressed object: " + objKey.getNumber()
+ ":" + objKey.getGeneration());
}
if (offsetOrObjstmObNr == null)
{
// not defined object -> NULL object (Spec. 1.7, chap. 3.2.9)
pdfObject.setObject(COSNull.NULL);
}
else if (offsetOrObjstmObNr > 0)
{
// offset of indirect object in file
// ---- go to object start
setPdfSource(offsetOrObjstmObNr);
// ---- we must have an indirect object
final long readObjNr = readObjectNumber();
final long readObjGen = readGenerationNumber();
readPattern(OBJ_MARKER);
// ---- consistency check
if ((readObjNr != objKey.getNumber()) || (readObjGen != objKey.getGeneration()))
{
throw new IOException("XREF for " + objKey.getNumber() + ":" + objKey.getGeneration()
+ " points to wrong object: " + readObjNr + ":" + readObjGen);
}
skipSpaces();
COSBase pb = parseDirObject();
String endObjectKey = readString();
if (endObjectKey.equals("stream"))
{
pdfSource.unread(endObjectKey.getBytes("ISO-8859-1"));
pdfSource.unread(' ');
if (pb instanceof COSDictionary)
{
COSStream stream = parseCOSStream((COSDictionary) pb, getDocument().getScratchFile());
if (securityHandler != null)
{
try
{
securityHandler.decryptStream(stream, objNr, objGenNr);
}
catch (CryptographyException ce)
{
throw new IOException("Error decrypting stream object " + objNr + ": "
+ ce.getMessage()
/* , ce // TODO: remove remark with Java 1.6 */);
}
}
pb = stream;
}
else
{
// this is not legal
// the combination of a dict and the stream/endstream
// forms a complete stream object
throw new IOException("Stream not preceded by dictionary (offset: " + offsetOrObjstmObNr + ").");
}
skipSpaces();
endObjectKey = readLine();
// we have case with a second 'endstream' before endobj
if (!endObjectKey.startsWith("endobj"))
{
if (endObjectKey.startsWith("endstream"))
{
endObjectKey = endObjectKey.substring(9).trim();
if (endObjectKey.length() == 0)
{
// no other characters in extra endstream line
endObjectKey = readLine(); // read next line
}
}
}
}
else if (securityHandler != null)
{
// decrypt
if (pb instanceof COSString)
{
decrypt((COSString) pb, objNr, objGenNr);
}
else if (pb instanceof COSDictionary)
{
for (Entry<COSName, COSBase> entry : ((COSDictionary) pb).entrySet())
{
// TODO: specially handle 'Contents' entry of
// signature dictionary like in
// SecurityHandler#decryptDictionary
if (entry.getValue() instanceof COSString)
{
decrypt((COSString) entry.getValue(), objNr, objGenNr);
}
}
}
else if (pb instanceof COSArray)
{
final COSArray array = (COSArray) pb;
for (int aIdx = 0, len = array.size(); aIdx < len; aIdx++)
{
if (array.get(aIdx) instanceof COSString)
{
decrypt((COSString) array.get(aIdx), objNr, objGenNr);
}
}
}
}
pdfObject.setObject(pb);
if (!endObjectKey.startsWith("endobj"))
{
if (endObjectKey.endsWith(" obj") && isLenient)
{
LOG.warn("Object (" + readObjNr + ":" + readObjGen + ") at offset "
+ offsetOrObjstmObNr + " does not end with 'endobj' but with '" + endObjectKey + "'");
}
else
{
throw new IOException("Object (" + readObjNr + ":" + readObjGen + ") at offset "
+ offsetOrObjstmObNr + " does not end with 'endobj' but with '" + endObjectKey + "'");
}
}
releasePdfSourceInputStream();
}
else
{
// xref value is object nr of object stream containing object to
// be parsed;
// since our object was not found it means object stream was not
// parsed so far
final int objstmObjNr = (int) (-offsetOrObjstmObNr);
final COSBase objstmBaseObj = parseObjectDynamically(objstmObjNr, 0, true);
if (objstmBaseObj instanceof COSStream)
{
// parse object stream
PDFObjectStreamParser parser = new PDFObjectStreamParser((COSStream) objstmBaseObj, document,
forceParsing);
parser.parse();
// get set of object numbers referenced for this object
// stream
final Set<Long> refObjNrs = xrefTrailerResolver.getContainedObjectNumbers(objstmObjNr);
// register all objects which are referenced to be contained
// in object stream
for (COSObject next : parser.getObjects())
{
COSObjectKey stmObjKey = new COSObjectKey(next);
if (refObjNrs.contains(stmObjKey.getNumber()))
{
COSObject stmObj = document.getObjectFromPool(stmObjKey);
stmObj.setObject(next.getObject());
}
}
}
}
}
return pdfObject.getObject();
}
// ------------------------------------------------------------------------
/**
* Decrypts given COSString.
*
* @param str the string to be decrypted
* @param objNr the object number
* @param objGenNr the object generation number
* @throws IOException ff something went wrong
*/
protected final void decrypt(COSString str, long objNr, long objGenNr) throws IOException
{
try
{
securityHandler.decryptString(str, objNr, objGenNr);
}
catch (CryptographyException ce)
{
throw new IOException("Error decrypting string: " + ce.getMessage()
/* , ce // TODO: remove remark with Java 1.6 */);
}
}
// ------------------------------------------------------------------------
private boolean inGetLength = false;
/** Returns length value referred to or defined in given object. */
private COSNumber getLength(final COSBase lengthBaseObj) throws IOException
{
if (lengthBaseObj == null)
{
return null;
}
if (inGetLength)
{
throw new IOException("Loop while reading length from " + lengthBaseObj);
}
COSNumber retVal = null;
try
{
inGetLength = true;
// ---- maybe length was given directly
if (lengthBaseObj instanceof COSNumber)
{
retVal = (COSNumber) lengthBaseObj;
}
// ---- length in referenced object
else if (lengthBaseObj instanceof COSObject)
{
COSObject lengthObj = (COSObject) lengthBaseObj;
if (lengthObj.getObject() == null)
{
// not read so far
// keep current stream position
final long curFileOffset = getPdfSourceOffset();
releasePdfSourceInputStream();
parseObjectDynamically(lengthObj, true);
// reset current stream position
setPdfSource(curFileOffset);
if (lengthObj.getObject() == null)
{
throw new IOException("Length object content was not read.");
}
}
if (!(lengthObj.getObject() instanceof COSNumber))
{
throw new IOException("Wrong type of referenced length object " + lengthObj + ": "
+ lengthObj.getObject().getClass().getSimpleName());
}
retVal = (COSNumber) lengthObj.getObject();
}
else
{
throw new IOException("Wrong type of length object: " + lengthBaseObj.getClass().getSimpleName());
}
}
finally
{
inGetLength = false;
}
return retVal;
}
// ------------------------------------------------------------------------
private final int streamCopyBufLen = 8192;
private final byte[] streamCopyBuf = new byte[streamCopyBufLen];
/**
* This will read a COSStream from the input stream using length attribute
* within dictionary. If length attribute is a indirect reference it is
* first resolved to get the stream length. This means we copy stream data
* without testing for 'endstream' or 'endobj' and thus it is no problem if
* these keywords occur within stream. We require 'endstream' to be found
* after stream data is read.
*
* @param dic dictionary that goes with this stream.
* @param file file to write the stream to when reading.
*
* @return parsed pdf stream.
*
* @throws IOException if an error occurred reading the stream, like
* problems with reading length attribute, stream does not end
* with 'endstream' after data read, stream too short etc.
*/
@Override
protected COSStream parseCOSStream(COSDictionary dic, RandomAccess file) throws IOException
{
final COSStream stream = new COSStream(dic, file);
OutputStream out = null;
try
{
readString(); // read 'stream'; this was already tested in
// parseObjectsDynamically()
// ---- skip whitespaces before start of data
// PDF Ref 1.7, chap. 3.2.7:
// 'stream' should be followed by either a CRLF (0x0d 0x0a) or LF
// but nothing else.
{
int whitespace = pdfSource.read();
// see brother_scan_cover.pdf, it adds whitespaces
// after the stream but before the start of the
// data, so just read those first
while (whitespace == 0x20)
{
whitespace = pdfSource.read();
}
if (whitespace == 0x0D)
{
whitespace = pdfSource.read();
if (whitespace != 0x0A)
{
// the spec says this is invalid but it happens in the
// real
// world so we must support it
pdfSource.unread(whitespace);
}
}
else if (whitespace != 0x0A)
{
// no whitespace after 'stream'; PDF ref. says 'should' so
// that is ok
pdfSource.unread(whitespace);
}
}
/*
* This needs to be dic.getItem because when we are parsing, the underlying object might still be null.
*/
COSNumber streamLengthObj = getLength(dic.getItem(COSName.LENGTH));
if (streamLengthObj == null)
{
throw new IOException("Missing length for stream.");
}
boolean useReadUntilEnd = false;
// ---- get output stream to copy data to
if (validateStreamLength(streamLengthObj.longValue()))
{
out = stream.createFilteredStream(streamLengthObj);
long remainBytes = streamLengthObj.longValue();
int bytesRead = 0;
while (remainBytes > 0)
{
final int readBytes = pdfSource.read(streamCopyBuf, 0,
(remainBytes > streamCopyBufLen) ? streamCopyBufLen : (int) remainBytes);
if (readBytes <= 0)
{
useReadUntilEnd = true;
out.close();
pdfSource.unread(bytesRead);
break;
}
out.write(streamCopyBuf, 0, readBytes);
remainBytes -= readBytes;
bytesRead += readBytes;
}
}
else
{
useReadUntilEnd = true;
}
if (useReadUntilEnd)
{
out = stream.createFilteredStream(streamLengthObj);
readUntilEndStream(out);
}
String endStream = readString();
if (!endStream.equals("endstream"))
{
throw new IOException("Error reading stream using length value. Expected='endstream' actual='"
+ endStream + "' ");
}
}
finally
{
if (out != null)
{
out.close();
}
}
return stream;
}
private boolean validateStreamLength(long streamLength) throws IOException
{
boolean streamLengthIsValid = true;
long originOffset = pdfSource.getOffset();
long expectedEndOfStream = originOffset + streamLength;
if (expectedEndOfStream > fileLen)
{
streamLengthIsValid = false;
LOG.error("The end of the stream is out of range, using workaround to read the stream");
}
else
{
pdfSource.seek(expectedEndOfStream);
skipSpaces();
if (!checkBytesAtOffset("endstream".getBytes("ISO-8859-1")))
{
streamLengthIsValid = false;
LOG.error("The end of the stream doesn't point to the correct offset, using workaround to read the stream");
}
pdfSource.seek(originOffset);
}
return streamLengthIsValid;
}
private void readUntilEndStream(final OutputStream out) throws IOException
{
int bufSize;
int charMatchCount = 0;
byte[] keyw = ENDSTREAM;
final int quickTestOffset = 5; // last character position of shortest
// keyword ('endobj')
// read next chunk into buffer; already matched chars are added to
// beginning of buffer
while ((bufSize = pdfSource.read(streamCopyBuf, charMatchCount, streamCopyBufLen - charMatchCount)) > 0)
{
// number of already matching chars
int startingMatchCount = charMatchCount;
int bIdx = charMatchCount;
int quickTestIdx;
// iterate over buffer, trying to find keyword match
for (int maxQuicktestIdx = bufSize - quickTestOffset; bIdx < bufSize; bIdx++)
{
// reduce compare operations by first test last character we
// would have to
// match if current one matches; if it is not a character from
// keywords
// we can move behind the test character;
// this shortcut is inspired by Boyer–Moore string search
// algorithm
// and can reduce parsing time by approx. 20%
if ((charMatchCount == 0) && ((quickTestIdx = bIdx + quickTestOffset) < maxQuicktestIdx))
{
final byte ch = streamCopyBuf[quickTestIdx];
if ((ch > 't') || (ch < 'a'))
{
// last character we would have to match if current
// character would match
// is not a character from keywords -> jump behind and
// start over
bIdx = quickTestIdx;
continue;
}
}
final byte ch = streamCopyBuf[bIdx]; // could be negative - but
// we only compare to ASCII
if (ch == keyw[charMatchCount])
{
if (++charMatchCount == keyw.length)
{
// match found
bIdx++;
break;
}
}
else
{
if ((charMatchCount == 3) && (ch == ENDOBJ[charMatchCount]))
{
// maybe ENDSTREAM is missing but we could have ENDOBJ
keyw = ENDOBJ;
charMatchCount++;
}
else
{
// no match; incrementing match start by 1 would be dumb
// since we already know matched chars
// depending on current char read we may already have
// beginning of a new match:
// 'e': first char matched;
// 'n': if we are at match position idx 7 we already
// read 'e' thus 2 chars matched
// for each other char we have to start matching first
// keyword char beginning with next
// read position
charMatchCount = (ch == E) ? 1 : ((ch == N) && (charMatchCount == 7)) ? 2 : 0;
// search again for 'endstream'
keyw = ENDSTREAM;
}
}
} // for
int contentBytes = Math.max(0, bIdx - charMatchCount);
// write buffer content until first matched char to output stream
if (contentBytes > 0)
{
out.write(streamCopyBuf, 0, contentBytes);
}
if (charMatchCount == keyw.length)
{
// keyword matched;
// unread matched keyword (endstream/endobj) and following buffered content
pdfSource.unread(streamCopyBuf, contentBytes, bufSize - contentBytes - keyw.length + startingMatchCount);
break;
}
else
{
// copy matched chars at start of buffer
System.arraycopy(keyw, 0, streamCopyBuf, 0, charMatchCount);
}
} // while
}
/**
*
* @param startXRefOffset
* @return
* @throws IOException
*/
private long calculateFixingOffset(long startXRefOffset) throws IOException
{
// TODO check offset for XRef stream objects
setPdfSource(startXRefOffset);
if (pdfSource.peek() == X && calculateFixingOffset(startXRefOffset, XREF) == 0)
{
return 0;
}
long fixingOffset = calculateFixingOffset(startXRefOffset, XREF);
return fixingOffset;
}
/**
* Try to dereference the given object at the given offset and calculate a new
* offset if necessary.
*
* @param objectOffset the offset where to look at
* @param objectID the object ID
* @param genID the generation number
* @return the difference to the origin offset
* @throws IOException if something went wrong
*/
private long calculateFixingOffset(long objectOffset, long objectID, long genID) throws IOException
{
String objString = Long.toString(objectID) + " " + Long.toString(genID)+ " obj";
return calculateFixingOffset(objectOffset, objString.getBytes("ISO-8859-1"));
}
/**
* Check if the given bytes can be found at the current offset.
*
* @param string the bytes to look for
* @return true if the bytes are in place, false if not
* @throws IOException if something went wrong
*/
private boolean checkBytesAtOffset(byte[] string) throws IOException
{
boolean bytesMatching = false;
if (pdfSource.peek() == string[0])
{
int length = string.length;
byte[] bytesRead = new byte[length];
int numberOfBytes = pdfSource.read(bytesRead, 0, length);
while (numberOfBytes < length)
{
int readMore = pdfSource.read(bytesRead, numberOfBytes, length-numberOfBytes);
if (readMore < 0)
{
break;
}
numberOfBytes += readMore;
}
if (Arrays.equals(string, bytesRead))
{
bytesMatching = true;
}
pdfSource.unread(bytesRead, 0, numberOfBytes);
}
return bytesMatching;
}
/**
* Check if the given bytes can be found at the given offset.
* The method seeks 200 bytes backward/forward if the given string
* can't be found at the given offset and returns the difference
* of the new offset to the origin one.
*
* @param objectOffset the given offset where to look at
* @param string the bytes to look for
* @return the difference to the origin one
* @throws IOException if something went wrong
*/
private long calculateFixingOffset(long objectOffset, byte[] string) throws IOException
{
if (objectOffset < 0)
{
LOG.error("Invalid object offset " + objectOffset + " for object " + new String(string));
return 0;
}
long originOffset = pdfSource.getOffset();
pdfSource.seek(objectOffset);
// most likely the object can be found at the given offset
if (checkBytesAtOffset(string))
{
pdfSource.seek(originOffset);
return 0;
}
// the offset seems to be wrong -> seek backward to find the object we are looking for
long currentOffset = objectOffset;
for (int i=1; i<20;i++)
{
currentOffset = objectOffset - (i*10);
if (currentOffset > 0)
{
pdfSource.seek(currentOffset);
for (int j=0; j<10;j++)
{
if (checkBytesAtOffset(string))
{
pdfSource.seek(originOffset);
LOG.debug("Fixed reference for object "+new String(string)+" "+objectOffset + " -> "+(objectOffset - currentOffset));
return objectOffset - currentOffset;
}
else
{
currentOffset++;
pdfSource.read();
}
}
}
}
// no luck by seeking backward -> seek forward to find the object we are looking for
pdfSource.seek(objectOffset);
currentOffset = objectOffset;
do
{
if (checkBytesAtOffset(string))
{
pdfSource.seek(originOffset);
if (currentOffset != 0)
{
LOG.debug("Fixed reference for object "+new String(string)+" "+objectOffset + " -> "+(objectOffset - currentOffset));
}
return objectOffset - currentOffset;
}
else
{
// next byte
currentOffset++;
if (pdfSource.read() == -1)
{
throw new IOException("Premature end of file while dereferencing object "+ new String(string) + " at offset " + objectOffset);
}
}
}
while(currentOffset < objectOffset+200);
pdfSource.seek(originOffset);
LOG.error("Can't find the object " + new String(string) + " at offset " + objectOffset);
return 0;
}
/**
* Check the XRef table by dereferencing all objects and fixing
* the offset if necessary.
*
* @throws IOException if something went wrong.
*/
private void checkXrefOffsets() throws IOException
{
Map<COSObjectKey, Long>xrefOffset = xrefTrailerResolver.getXrefTable();
if (xrefOffset != null)
{
for (COSObjectKey objectKey : xrefOffset.keySet())
{
Long objectOffset = xrefOffset.get(objectKey);
// a negative offset number represents a object number itself
// see type 2 entry in xref stream
if (objectOffset != null && objectOffset > 0)
{
long objectNr = objectKey.getNumber();
long objectGen = objectKey.getGeneration();
long fixingOffset = calculateFixingOffset(objectOffset, objectNr, objectGen);
if (fixingOffset != 0)
{
long newOffset = objectOffset - fixingOffset;
xrefOffset.put(objectKey, newOffset);
LOG.debug("Fixed reference for object "+objectNr+" "+objectGen+" "+objectOffset + " -> "+newOffset);
}
}
}
}
}
}