Improve comparison of num trees by comparing leftover keys if any and logging a warning to indicate specification nonconformance if hanging keys are found

ITXT-CR-260

Author: Snipx

io/src/main/java/com/itextpdf/io/LogMessageConstant.java

@@ -84,6 +84,7 @@ public final class LogMessageConstant {
     public static final String MAKE_COPY_OF_CATALOG_DICTIONARY_IS_FORBIDDEN = "Make copy of Catalog dictionary is forbidden.";
     public static final String NAME_ALREADY_EXISTS_IN_THE_NAME_TREE = "Name \"{0}\" already exists in the name tree; old value will be replaced by the new one.";
     public static final String NOT_TAGGED_PAGES_IN_TAGGED_DOCUMENT = "Not tagged pages are copied to the tagged document. Destination document now may contain not tagged content.";
+    public static final String NUM_TREE_SHALL_NOT_END_WITH_KEY = "Number tree ends with a key which is invalid according to the PDF specification.";
     public static final String PDF_READER_CLOSING_FAILED = "PdfReader closing failed due to the error occurred!";
     public static final String PDF_WRITER_CLOSING_FAILED = "PdfWriter closing failed due to the error occurred!";
     public static final String POPUP_ENTRY_IS_NOT_POPUP_ANNOTATION = "Popup entry in the markup annotations refers not to the annotation with Popup subtype.";

kernel/src/main/java/com/itextpdf/kernel/utils/CompareTool.java

@@ -43,6 +43,7 @@ This file is part of the iText (R) project.
  */
 package com.itextpdf.kernel.utils;
 
+import com.itextpdf.io.LogMessageConstant;
 import com.itextpdf.io.font.PdfEncodings;
 import com.itextpdf.io.util.FileUtil;
 import com.itextpdf.io.util.SystemUtil;
@@ -71,6 +72,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.kernel.xmp.XMPMetaFactory;
 import com.itextpdf.kernel.xmp.XMPUtils;
 import com.itextpdf.kernel.xmp.options.SerializeOptions;
+import org.slf4j.LoggerFactory;
 import org.w3c.dom.Document;
 import org.w3c.dom.Element;
 import org.w3c.dom.Node;
@@ -1150,8 +1152,26 @@ private boolean compareDictionariesExtended(PdfDictionary outDict, PdfDictionary
                 PdfDictionary cmpNumTree = cmpDict.getAsDictionary(key);
                 LinkedList<PdfObject> outItems = new LinkedList<PdfObject>();
                 LinkedList<PdfObject> cmpItems = new LinkedList<PdfObject>();
-                flattenNumTree(outNumTree, null, outItems);
-                flattenNumTree(cmpNumTree, null, cmpItems);
+                PdfNumber outLeftover = flattenNumTree(outNumTree, null, outItems);
+                PdfNumber cmpLeftover = flattenNumTree(cmpNumTree, null, cmpItems);
+                if (outLeftover != null) {
+                    LoggerFactory.getLogger(CompareTool.class).warn(LogMessageConstant.NUM_TREE_SHALL_NOT_END_WITH_KEY);
+                    if (compareResult != null && cmpLeftover == null) {
+                        compareResult.addError(currentPath, "Number tree unexpectedly ends with a key");
+                    }
+                }
+                if (cmpLeftover != null) {
+                    LoggerFactory.getLogger(CompareTool.class).warn(LogMessageConstant.NUM_TREE_SHALL_NOT_END_WITH_KEY);
+                    if (compareResult != null && outLeftover == null) {
+                        compareResult.addError(currentPath, "Number tree was expected to end with a key (although it is invalid according to the specification), but ended with a value");
+                    }
+                }
+                if (outLeftover != null && cmpLeftover != null && !compareNumbers(outLeftover, cmpLeftover)) {
+                    if (compareResult != null) {
+                        compareResult.addError(currentPath, "Number tree was expected to end with a different key (although it is invalid according to the specification)");
+                    }
+                    return false;
+                }
                 PdfArray outArray = new PdfArray(outItems, outItems.size());
                 PdfArray cmpArray = new PdfArray(cmpItems, cmpItems.size());
                 if (!compareArraysExtended(outArray, cmpArray, currentPath, compareResult))