Avoid unnecessary page labels creation. Another fix for PdfObject#release()

DEVSIX-480

Author: Snipx

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfCatalog.java

@@ -35,6 +35,7 @@ protected PdfCatalog(PdfDictionary pdfObject) {
         }
         ensureObjectIsAddedToDocument(pdfObject);
         getPdfObject().put(PdfName.Type, PdfName.Catalog);
+        setForbidRelease();
         pageTree = new PdfPagesTree(this);
     }
 
@@ -231,8 +232,8 @@ public PdfNameTree getNameTree(PdfName treeType) {
      * This method returns the NumberTree of Page Labels
      * @return
      */
-    public PdfNumTree getPageLabelsTree(){
-        if (pageLabels == null) {
+    public PdfNumTree getPageLabelsTree(boolean createIfNotExists) {
+        if (pageLabels == null && createIfNotExists) {
             pageLabels = new PdfNumTree(this, PdfName.PageLabels);
         }
 

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfDocument.java

@@ -1102,11 +1102,14 @@ public void addFileAttachment(String description, PdfFileSpec fs) {
      * @return
      */
     public String[] getPageLabels() {
-        String[] labelStrings = new String[getNumberOfPages()];
-        Map<Integer, PdfObject> pageLabels = catalog.getPageLabelsTree().getNumbers();
+        if (catalog.getPageLabelsTree(false) == null) {
+            return null;
+        }
+        Map<Integer, PdfObject> pageLabels = catalog.getPageLabelsTree(false).getNumbers();
         if (pageLabels.size() == 0) {
             return null;
         }
+        String[] labelStrings = new String[getNumberOfPages()];
         int pageCount = 1;
         String prefix = "";
         String type = "D";

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfPage.java

@@ -644,7 +644,7 @@ public PdfPage setPageLabel(PageLabelNumberingStyleConstants numberingStyle, Str
         if (firstPage != 1) {
             pageLabel.put(PdfName.St, new PdfNumber(firstPage));
         }
-        getDocument().getCatalog().getPageLabelsTree().addEntry(getDocument().getPageNumber(this) - 1, pageLabel);
+        getDocument().getCatalog().getPageLabelsTree(true).addEntry(getDocument().getPageNumber(this) - 1, pageLabel);
 
         return this;
     }

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfPages.java

@@ -27,6 +27,7 @@ public PdfPages(int from, PdfDocument pdfDocument) {
 
     public PdfPages(int from, int maxCount, PdfDictionary pdfObject, PdfPages parent) {
         super(pdfObject);
+        setForbidRelease();
         this.from = from;
         this.count = pdfObject.getAsNumber(PdfName.Count);
         this.parent = parent;

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfXrefTable.java

@@ -255,7 +255,6 @@ protected void writeXrefTableAndTrailer(PdfDocument document, PdfObject fileId,
                 trailer.put(PdfName.Prev, lastXref);
             }
             writer.write(document.getTrailer());
-
         }
 
         writer.writeString("\nstartxref\n").

kernel/src/main/java/com/itextpdf/kernel/pdf/canvas/PdfCanvas.java

@@ -1,18 +1,17 @@
 package com.itextpdf.kernel.pdf.canvas;
 
-import com.itextpdf.kernel.PdfException;
-import com.itextpdf.io.util.Utilities;
 import com.itextpdf.io.font.PdfEncodings;
 import com.itextpdf.io.font.otf.Glyph;
 import com.itextpdf.io.font.otf.GlyphLine;
-import com.itextpdf.kernel.geom.AffineTransform;
-import com.itextpdf.kernel.geom.Rectangle;
 import com.itextpdf.io.image.Image;
 import com.itextpdf.io.source.OutputStream;
-import com.itextpdf.kernel.pdf.canvas.wmf.WmfImageHelper;
+import com.itextpdf.io.util.Utilities;
+import com.itextpdf.kernel.PdfException;
 import com.itextpdf.kernel.color.Color;
 import com.itextpdf.kernel.color.PatternColor;
 import com.itextpdf.kernel.font.PdfFont;
+import com.itextpdf.kernel.geom.AffineTransform;
+import com.itextpdf.kernel.geom.Rectangle;
 import com.itextpdf.kernel.pdf.IsoKey;
 import com.itextpdf.kernel.pdf.PdfArray;
 import com.itextpdf.kernel.pdf.PdfDictionary;
@@ -25,6 +24,7 @@
 import com.itextpdf.kernel.pdf.PdfResources;
 import com.itextpdf.kernel.pdf.PdfStream;
 import com.itextpdf.kernel.pdf.PdfString;
+import com.itextpdf.kernel.pdf.canvas.wmf.WmfImageHelper;
 import com.itextpdf.kernel.pdf.colorspace.PdfColorSpace;
 import com.itextpdf.kernel.pdf.colorspace.PdfDeviceCs;
 import com.itextpdf.kernel.pdf.colorspace.PdfPattern;
@@ -45,8 +45,6 @@
 import java.util.Map;
 import java.util.Stack;
 
-import static java.lang.Math.*;
-
 /**
  * PdfCanvas class represents an algorithm for writing data into content stream.
  * To write into page content, create PdfCanvas from a page instance.