Implement tests for special cases of free references handling

Autoported commit.
Original commit hash: [a9e869592]

Author: yulian-gaponenko

itext.tests/itext.kernel.tests/itext/kernel/pdf/FreeReferencesTest.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Generic;
+using System.Text;
 using iText.Test;
 
 namespace iText.Kernel.Pdf {
@@ -13,5 +15,143 @@ public class FreeReferencesTest : ExtendedITextTest {
         public static void BeforeClass() {
             CreateOrClearDestinationFolder(destinationFolder);
         }
+
+        /// <exception cref="System.IO.IOException"/>
+        [NUnit.Framework.Test]
+        public virtual void FreeReferencesTest01() {
+            String src = "freeRefsGapsAndMaxGen.pdf";
+            String @out = "freeReferencesTest01.pdf";
+            PdfDocument pdfDocument = new PdfDocument(new PdfReader(sourceFolder + src), new PdfWriter(destinationFolder
+                 + @out));
+            pdfDocument.Close();
+            String[] xrefString = ExtractXrefTableAsStrings(@out);
+            String[] expected = new String[] { "xref\n" + "0 4\n" + "0000000000 65535 f \n" + "0000000269 00000 n \n" 
+                + "0000000561 00000 n \n" + "0000000314 00000 n \n" + "12 3\n" + "0000000133 00000 n \n" + "0000000015 00000 n \n"
+                 + "0000000613 00000 n \n" };
+            // TODO first xref shall have no subsections
+            NUnit.Framework.Assert.AreEqual(expected, xrefString);
+        }
+
+        /// <exception cref="System.IO.IOException"/>
+        [NUnit.Framework.Test]
+        public virtual void FreeReferencesTest02() {
+            String src = "freeRefsGapsAndMaxGen.pdf";
+            String @out = "freeReferencesTest02.pdf";
+            PdfDocument pdfDocument = new PdfDocument(new PdfReader(sourceFolder + src), new PdfWriter(destinationFolder
+                 + @out), new StampingProperties().UseAppendMode());
+            pdfDocument.Close();
+            String[] xrefString = ExtractXrefTableAsStrings(@out);
+            String[] expected = new String[] { "xref\n" + "0 5\n" + "0000000010 65535 f \n" + "0000000269 00000 n \n" 
+                + "0000000569 00000 n \n" + "0000000314 00000 n \n" + "0000000000 65535 f \n" + "10 5\n" + "0000000011 00000 f \n"
+                 + "0000000000 00001 f \n" + "0000000133 00000 n \n" + "0000000015 00000 n \n" + "0000000480 00000 n \n"
+                , "xref\n" + "3 1\n" + "0000000995 00000 n \n" };
+            // Append mode, no possibility to fix subsections in first xref
+            NUnit.Framework.Assert.AreEqual(expected, xrefString);
+        }
+
+        /// <exception cref="System.IO.IOException"/>
+        [NUnit.Framework.Test]
+        public virtual void FreeReferencesTest03() {
+            String src = "freeRefsDeletedObj.pdf";
+            String @out = "freeReferencesTest03.pdf";
+            PdfDocument pdfDocument = new PdfDocument(new PdfReader(sourceFolder + src), new PdfWriter(destinationFolder
+                 + @out), new StampingProperties().UseAppendMode());
+            pdfDocument.AddNewPage();
+            pdfDocument.Close();
+            String[] xrefString = ExtractXrefTableAsStrings(@out);
+            String[] expected = new String[] { "xref\n" + "0 7\n" + "0000000000 65535 f \n" + "0000000265 00000 n \n" 
+                + "0000000564 00000 n \n" + "0000000310 00000 n \n" + "0000000132 00000 n \n" + "0000000015 00001 n \n"
+                 + "0000000476 00000 n \n", "xref\n" + "0 1\n" + "0000000005 65535 n \n" + "3 3\n" + "0000000923 00000 n \n"
+                 + "0000001170 00000 n \n" + "0000000000 00002 f \n" + "7 1\n" + "0000001303 00000 n \n", "xref\n" + "1 3\n"
+                 + "0000001706 00000 n \n" + "0000001998 00000 n \n" + "0000001751 00000 n \n" + "5 1\n" + "0000002055 00002 n \n"
+                 + "8 1\n" + "0000002156 00000 n \n" };
+            // TODO fifth object is no longer free, however zero obj not updated
+            NUnit.Framework.Assert.AreEqual(expected, xrefString);
+        }
+
+        /// <exception cref="System.IO.IOException"/>
+        [NUnit.Framework.Test]
+        public virtual void FreeReferencesTest04() {
+            String src = "simpleDoc.pdf";
+            String @out = "freeReferencesTest04.pdf";
+            PdfDocument pdfDocument = new PdfDocument(new PdfReader(sourceFolder + src), new PdfWriter(destinationFolder
+                 + @out));
+            PdfObject contentsObj = pdfDocument.GetPage(1).GetPdfObject().Remove(PdfName.Contents);
+            NUnit.Framework.Assert.IsTrue(contentsObj is PdfIndirectReference);
+            PdfIndirectReference contentsRef = (PdfIndirectReference)contentsObj;
+            contentsRef.SetFree();
+            PdfObject freedContentsRefRefersTo = contentsRef.GetRefersTo();
+            NUnit.Framework.Assert.IsNull(freedContentsRefRefersTo);
+            pdfDocument.Close();
+        }
+
+        /// <exception cref="System.IO.IOException"/>
+        [NUnit.Framework.Test]
+        public virtual void FreeReferencesTest05() {
+            String src = "simpleDocWithSubsections.pdf";
+            String @out = "freeReferencesTest05.pdf";
+            PdfDocument pdfDocument = new PdfDocument(new PdfReader(sourceFolder + src), new PdfWriter(destinationFolder
+                 + @out));
+            pdfDocument.Close();
+            String[] xrefString = ExtractXrefTableAsStrings(@out);
+            String[] expected = new String[] { "xref\n" + "0 4\n" + "0000000000 65535 f \n" + "0000000269 00000 n \n" 
+                + "0000000561 00000 n \n" + "0000000314 00000 n \n" + "11 3\n" + "0000000133 00000 n \n" + "0000000015 00000 n \n"
+                 + "0000000613 00000 n \n" };
+            // TODO first xref shall have no subsections
+            NUnit.Framework.Assert.AreEqual(expected, xrefString);
+        }
+
+        /// <exception cref="System.IO.IOException"/>
+        [NUnit.Framework.Test]
+        public virtual void FreeReferencesTest06() {
+            String src = "simpleDocWithSubsections.pdf";
+            String @out = "freeReferencesTest06.pdf";
+            PdfDocument pdfDocument = new PdfDocument(new PdfReader(sourceFolder + src), new PdfWriter(destinationFolder
+                 + @out), new StampingProperties().UseAppendMode());
+            pdfDocument.Close();
+            String[] xrefString = ExtractXrefTableAsStrings(@out);
+            String[] expected = new String[] { "xref\n" + "0 4\n" + "0000000000 65535 f \n" + "0000000269 00000 n \n" 
+                + "0000000569 00000 n \n" + "0000000314 00000 n \n" + "11 3\n" + "0000000133 00000 n \n" + "0000000015 00000 n \n"
+                 + "0000000480 00000 n \n", "xref\n" + "3 1\n" + "0000000935 00000 n \n" };
+            // Append mode, no possibility to fix subsections in first xref
+            NUnit.Framework.Assert.AreEqual(expected, xrefString);
+        }
+
+        /// <exception cref="System.IO.IOException"/>
+        [NUnit.Framework.Test]
+        public virtual void FreeReferencesTest07() {
+            String @out = "freeReferencesTest07.pdf";
+            PdfDocument pdfDocument = new PdfDocument(new PdfWriter(destinationFolder + @out));
+            pdfDocument.CreateNextIndirectReference();
+            pdfDocument.AddNewPage();
+            pdfDocument.Close();
+            String[] xrefString = ExtractXrefTableAsStrings(@out);
+            String[] expected = new String[] { "xref\n" + "0 4\n" + "0000000000 65535 f \n" + "0000000203 00000 n \n" 
+                + "0000000414 00000 n \n" + "0000000248 00000 n \n" + "5 2\n" + "0000000088 00000 n \n" + "0000000015 00000 n \n"
+                 };
+            // TODO first xref shall have no subsections
+            NUnit.Framework.Assert.AreEqual(expected, xrefString);
+        }
+
+        /// <exception cref="System.IO.IOException"/>
+        private String[] ExtractXrefTableAsStrings(String @out) {
+            byte[] outPdfBytes = ReadFile(destinationFolder + @out);
+            String outPdfContent = iText.IO.Util.JavaUtil.GetStringForBytes(outPdfBytes, Encoding.ASCII);
+            String xrefStr = "\nxref";
+            String trailerStr = "trailer";
+            int xrefInd = outPdfContent.IndexOf(xrefStr, StringComparison.Ordinal);
+            int trailerInd = outPdfContent.IndexOf(trailerStr, StringComparison.Ordinal);
+            int lastXrefInd = outPdfContent.LastIndexOf(xrefStr);
+            IList<String> xrefs = new List<String>();
+            while (true) {
+                xrefs.Add(outPdfContent.JSubstring(xrefInd + 1, trailerInd));
+                if (xrefInd == lastXrefInd) {
+                    break;
+                }
+                xrefInd = outPdfContent.IndexOf(xrefStr, xrefInd + 1);
+                trailerInd = outPdfContent.IndexOf(trailerStr, trailerInd + 1);
+            }
+            return xrefs.ToArray(new String[xrefs.Count]);
+        }
     }
 }

itext.tests/itext.kernel.tests/resources/itext/kernel/pdf/FreeReferencesTest/freeRefsDeletedObj.pdf

@@ -1 +1 @@
-2d9b063944b0f10315f8c60a7a6b599e5187f500
+a9e869592c56bb12a0afe24aff383a3f590da3fb