Author: lehmi
Date: Sat Nov 22 10:08:53 2025
New Revision: 1929915
Log:
PDFBOX-6036: replace recursive algorithm with an iterative one to avoid a
StackOverflowException
Added:
pdfbox/trunk/pdfbox/src/test/java/org/apache/pdfbox/pdfwriter/COSWriterCompressionPoolTest.java
(contents, props changed)
Modified:
pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdfwriter/compress/COSWriterCompressionPool.java
Modified:
pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdfwriter/compress/COSWriterCompressionPool.java
==============================================================================
---
pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdfwriter/compress/COSWriterCompressionPool.java
Sat Nov 22 10:05:39 2025 (r1929914)
+++
pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdfwriter/compress/COSWriterCompressionPool.java
Sat Nov 22 10:08:53 2025 (r1929915)
@@ -18,9 +18,9 @@ package org.apache.pdfbox.pdfwriter.comp
import java.io.IOException;
import java.util.ArrayList;
+import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
-import java.util.Iterator;
import java.util.List;
import java.util.Set;
@@ -29,7 +29,6 @@ import org.apache.pdfbox.pdmodel.PDDocum
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.COSObject;
import org.apache.pdfbox.cos.COSObjectKey;
@@ -79,11 +78,23 @@ public class COSWriterCompressionPool
objectPool = new
COSObjectPool(document.getDocument().getHighestXRefObjectNumber());
// Initialize object pool.
- COSDocument cosDocument = document.getDocument();
-
- COSDictionary trailer = cosDocument.getTrailer();
- addStructure(trailer.getItem(COSName.ROOT));
- addStructure(trailer.getItem(COSName.INFO));
+ COSDictionary trailer = document.getDocument().getTrailer();
+ List<COSBase> cosBaseList = new ArrayList<>();
+ COSDictionary root = trailer.getCOSDictionary(COSName.ROOT);
+ if (root != null)
+ {
+ cosBaseList.add(root);
+ }
+ COSDictionary info = trailer.getCOSDictionary(COSName.INFO);
+ if (info != null)
+ {
+ cosBaseList.add(info);
+ }
+ while (!cosBaseList.isEmpty())
+ {
+ cosBaseList = addStructure(cosBaseList);
+ }
+ allDirectObjects.clear();
Collections.sort(objectStreamObjects);
Collections.sort(topLevelObjects);
@@ -159,10 +170,27 @@ public class COSWriterCompressionPool
/**
* Attempts to find yet unregistered streams and dictionaries in the given
structure.
*
+ * @param cosBaseList A list of objects to be added for compressing.
+ * @throws IOException Shall be thrown, if adding failed.
+ */
+ private List<COSBase> addStructure(List<COSBase> cosBaseList) throws
IOException
+ {
+ List<COSBase> cosBaseListNext = new ArrayList<>();
+ for (COSBase cosBase : cosBaseList)
+ {
+ cosBaseListNext.addAll(addStructure(cosBase));
+ }
+ cosBaseList.clear();
+ return cosBaseListNext;
+ }
+
+ /**
+ * Attempts to find yet unregistered streams and dictionaries in the given
structure.
+ *
* @param current The object to be added for compressing.
* @throws IOException Shall be thrown, if compressing the object failed.
*/
- private void addStructure(COSBase current) throws IOException
+ private List<COSBase> addStructure(COSBase current) throws IOException
{
COSBase base = current;
if (current instanceof COSStream
@@ -182,45 +210,63 @@ public class COSWriterCompressionPool
}
if (base instanceof COSArray)
{
- addElements(((COSArray) base).iterator());
+ return getElements(((COSArray) base).toList());
}
else if (base instanceof COSDictionary)
{
- addElements(((COSDictionary) base).getValues().iterator());
+ return getElements(((COSDictionary) base).getValues());
}
+ return Collections.emptyList();
}
- private void addElements(Iterator<COSBase> elements) throws IOException
+ /**
+ * Collect all relevant objects from a COSDictionary/COSArray.
+ *
+ * @param elements collection of all elements of a COSDictionary/COSArray.
+ *
+ * @return a collection containing the relevant objects within the given
Collection.
+ * @throws IOException if something went wrong.
+ */
+ private List<COSBase> getElements(Collection<? extends COSBase> elements)
throws IOException
{
- while (elements.hasNext())
+ List<COSBase> relevantElements = new ArrayList<>();
+ for (COSBase element : elements)
{
- COSBase value = elements.next();
- if (value instanceof COSArray
- || (value instanceof COSDictionary
- && !allDirectObjects.contains(value)))
+ if (filterElement(element))
{
- allDirectObjects.add(value);
- addStructure(value);
+ relevantElements.add(element);
}
- else if (value instanceof COSObject)
+ }
+ return relevantElements;
+ }
+
+ private boolean filterElement(COSBase element) throws IOException
+ {
+ if (element instanceof COSObject)
+ {
+ COSObject cosObject = (COSObject) element;
+ if (cosObject.getKey() != null &&
objectPool.contains(cosObject.getKey()))
{
- COSObject cosObject = (COSObject) value;
- if (cosObject.getKey() != null &&
objectPool.contains(cosObject.getKey()))
- {
- // check if the stored object matches the referenced
object otherwise replace the key with a new one
- // there may differences if some imported content uses the
same object numbers than the target pdf
- if
(objectPool.getObject(cosObject.getKey()).equals(cosObject.getObject()))
- {
- continue;
- }
- cosObject.setKey(null);
- }
- if (cosObject.getObject() != null)
+ // check if the stored object matches the referenced object
otherwise replace the key with a new one
+ // there may differences if some imported content uses the
same object numbers than the target pdf
+ if
(objectPool.getObject(cosObject.getKey()).equals(cosObject.getObject()))
{
- addStructure(value);
+ return false;
}
+ cosObject.setKey(null);
}
+ if (cosObject.getObject() != null)
+ {
+ return true;
+ }
+ }
+ else if (element instanceof COSArray
+ || (element instanceof COSDictionary &&
!allDirectObjects.contains(element)))
+ {
+ allDirectObjects.add(element);
+ return true;
}
+ return false;
}
/**
Added:
pdfbox/trunk/pdfbox/src/test/java/org/apache/pdfbox/pdfwriter/COSWriterCompressionPoolTest.java
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++
pdfbox/trunk/pdfbox/src/test/java/org/apache/pdfbox/pdfwriter/COSWriterCompressionPoolTest.java
Sat Nov 22 10:08:53 2025 (r1929915)
@@ -0,0 +1,56 @@
+/*
+ * 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.pdfwriter;
+
+import java.io.IOException;
+
+import org.apache.pdfbox.pdfwriter.compress.COSWriterCompressionPool;
+import org.apache.pdfbox.pdfwriter.compress.CompressParameters;
+import org.apache.pdfbox.pdmodel.PDDocument;
+import
org.apache.pdfbox.pdmodel.interactive.documentnavigation.outline.PDDocumentOutline;
+import
org.apache.pdfbox.pdmodel.interactive.documentnavigation.outline.PDOutlineItem;
+import org.junit.jupiter.api.Test;
+
+class COSWriterCompressionPoolTest
+{
+ /**
+ * The old implementation may run into a stack overflow whenever the
recursion depth gets too deep to be processed
+ * when collecting the objects to be compressed.
+ *
+ * The new solution replaces the recursion with an iteration.
+ *
+ * @throws IOException
+ */
+ @Test
+ void testPDFBox6036() throws IOException
+ {
+ for (int i = 1; i <= 222_222; i *= 2)
+ {
+ try (PDDocument document = new PDDocument())
+ {
+ PDDocumentOutline outline = new PDDocumentOutline();
+ document.getDocumentCatalog().setDocumentOutline(outline);
+ for (int j = 0; j < i; j++)
+ {
+ outline.addLast(new PDOutlineItem());
+ }
+ new COSWriterCompressionPool(document,
CompressParameters.DEFAULT_COMPRESSION);
+ }
+ }
+ }
+
+}
