fix: don't clobber objects that are overridden in a trailer when reading compressed objects

ascott18 · ascott18 · commit c4277dac7b2a · 2024-08-21T19:39:38.000-07:00
diff --git a/PdfSharpCore/Pdf.IO/PdfReader.cs b/PdfSharpCore/Pdf.IO/PdfReader.cs
@@ -499,6 +499,13 @@ public static PdfDocument Open(Stream stream, string password, PdfDocumentOpenMo
                             // Is type xref to compressed object?
                             if (item.Type == 2)
                             {
+                                if (document._irefTable.ObjectTable.TryGetValue(new PdfObjectID(idx2), out var irefToRead) && irefToRead.Position > 0)
+                                {
+                                    // The object has been overridden by a trailer with a specific position.
+                                    // Don't read from compressed objects. Continue on later to "read all indirect objects"
+                                    continue;
+                                }
+
                                 PdfReference irefNew = parser.ReadCompressedObject(new PdfObjectID((int)item.Field2),
                                     (int)item.Field3);
                                 Debug.Assert(document._irefTable.Contains(iref.ObjectID));
