PDFBOX-6200: Link the document state to substructures without recursion

pdfbox/src/main/java/org/apache/pdfbox/cos/COSUpdateState.java

@@ -16,6 +16,9 @@
  */
 package org.apache.pdfbox.cos;
 
+import java.util.ArrayDeque;
+import java.util.Deque;
+
 /**
  * A {@link COSUpdateState} instance manages update states for a {@link COSUpdateInfo}. Such states are used to create
  * a {@link COSIncrement} for the incremental saving of a {@link COSDocument}.
@@ -117,51 +120,71 @@ public void setOriginDocumentState(COSDocumentState originDocumentState)
      */
     private void setOriginDocumentState(COSDocumentState originDocumentState, boolean dereferencing)
     {
-        if(this.originDocumentState != null || originDocumentState == null)
+        if (originDocumentState == null)
         {
             return;
         }
-        this.originDocumentState = originDocumentState;
-        if(!dereferencing)
+        // The structure is traversed with an explicit stack instead of recursion, as it may be
+        // nested deeper than the call stack allows (PDFBOX-6200).
+        Deque<COSUpdateState> pending = new ArrayDeque<>();
+        pending.push(this);
+        while (!pending.isEmpty())
         {
-            update();
+            COSUpdateState state = pending.pop();
+            if (state.originDocumentState != null)
+            {
+                continue;
+            }
+            state.originDocumentState = originDocumentState;
+            if (!dereferencing)
+            {
+                state.update();
+            }
+            state.pushSubstructures(pending);
         }
-
-        if(updateInfo instanceof COSDictionary)
+    }
+
+    /**
+     * Pushes the {@link COSUpdateState}s of the substructures directly contained by the managed
+     * {@link #updateInfo} onto the given stack.
+     *
+     * @param pending The stack of {@link COSUpdateState}s that still have to be processed.
+     */
+    private void pushSubstructures(Deque<COSUpdateState> pending)
+    {
+        if (updateInfo instanceof COSDictionary)
         {
             COSDictionary dictionary = (COSDictionary) updateInfo;
-            for(COSBase entry : dictionary.getValues())
+            for (COSBase entry : dictionary.getValues())
             {
-                if (entry instanceof COSUpdateInfo)
-                {
-                    ((COSUpdateInfo) entry).getUpdateState().setOriginDocumentState(originDocumentState, dereferencing);
-                }
+                pushUpdateState(pending, entry);
             }
         }
-        else if(updateInfo instanceof COSArray)
+        else if (updateInfo instanceof COSArray)
         {
             COSArray array = (COSArray) updateInfo;
-            for(COSBase entry : array)
+            for (COSBase entry : array)
             {
-                if (entry instanceof COSUpdateInfo)
-                {
-                    ((COSUpdateInfo) entry).getUpdateState().setOriginDocumentState(originDocumentState, dereferencing);
-                }
+                pushUpdateState(pending, entry);
             }
         }
-        else if(updateInfo instanceof COSObject)
+        else if (updateInfo instanceof COSObject)
         {
             COSObject object = (COSObject) updateInfo;
             if (object.isDereferenced())
             {
-                COSBase reference = object.getObject();
-                if (reference instanceof COSUpdateInfo)
-                {
-                    ((COSUpdateInfo) reference).getUpdateState().setOriginDocumentState(originDocumentState, dereferencing);
-                }
+                pushUpdateState(pending, object.getObject());
             }
         }
     }
+
+    private static void pushUpdateState(Deque<COSUpdateState> pending, COSBase base)
+    {
+        if (base instanceof COSUpdateInfo)
+        {
+            pending.push(((COSUpdateInfo) base).getUpdateState());
+        }
+    }
 
     /**
      * <p>

pdfbox/src/test/java/org/apache/pdfbox/cos/TestCOSUpdateInfo.java

@@ -17,6 +17,7 @@
 
 package org.apache.pdfbox.cos;
 
+import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 
@@ -58,4 +59,46 @@ void testIsSetNeedToBeUpdate()
         assertFalse(testCOSObject.isNeedToBeUpdated());
     }
 
+
+    /**
+     * PDFBOX-6200: linking a document state to a deeply nested structure must not overflow the
+     * stack.
+     */
+    @Test
+    void testSetOriginDocumentStateOfDeeplyNestedStructure()
+    {
+        COSDocumentState origin = new COSDocumentState();
+        origin.setParsing(false);
+
+        // a chain of dictionaries, arrays and dereferenced indirect objects, built from the end
+        COSDictionary deepest = new COSDictionary();
+        COSBase current = deepest;
+        for (int i = 0; i < 50_000; i++)
+        {
+            switch (i % 3)
+            {
+                case 0:
+                    COSDictionary dictionary = new COSDictionary();
+                    dictionary.setItem(COSName.getPDFName("Next"), current);
+                    current = dictionary;
+                    break;
+                case 1:
+                    COSArray array = new COSArray();
+                    array.add(current);
+                    current = array;
+                    break;
+                default:
+                    current = new COSObject(current);
+                    break;
+            }
+        }
+        COSUpdateInfo root = (COSUpdateInfo) current;
+
+        root.getUpdateState().setOriginDocumentState(origin);
+
+        assertSame(origin, deepest.getUpdateState().getOriginDocumentState());
+        assertTrue(root.isNeedToBeUpdated());
+        assertTrue(deepest.isNeedToBeUpdated());
+    }
+
 }