Skip creating IndirectReference in CrossReferenceTablePartBuilder when generationNumber is more than 65,535

Author: BobLd

src/UglyToad.PdfPig.Core/IndirectReference.cs

@@ -39,9 +39,10 @@
         [DebuggerStepThrough]
         public IndirectReference(long objectNumber, int generation)
         {
-            if (generation < 0 || generation > ushort.MaxValue)
+            if (generation < 0)
             {
-               throw new ArgumentOutOfRangeException(nameof(generation), "Generation number must not be a negative value, and less or equal to 65,535.");
+                // Note: We do not check generation for max value and let it overflow
+                throw new ArgumentOutOfRangeException(nameof(generation), "Generation number must not be a negative value.");
             }
 
             if (objectNumber < -MAX_OBJECT_NUMBER || objectNumber > MAX_OBJECT_NUMBER)

src/UglyToad.PdfPig.Tests/ContentStream/IndirectReferenceTests.cs

@@ -63,9 +63,20 @@ public void IndirectReferenceHashTest()
             Assert.StartsWith("Object number must be between -140,737,488,355,327 and 140,737,488,355,327.", ex1.Message);
 
             var ex2 = Assert.Throws<ArgumentOutOfRangeException>(() => new IndirectReference(1574, -1));
-            Assert.StartsWith("Generation number must not be a negative value, and less or equal to 65,535.", ex2.Message);
-            var ex3 = Assert.Throws<ArgumentOutOfRangeException>(() => new IndirectReference(1574, ushort.MaxValue + 1));
-            Assert.StartsWith("Generation number must not be a negative value, and less or equal to 65,535.", ex3.Message);
+            Assert.StartsWith("Generation number must not be a negative value.", ex2.Message);
+            
+            // We make sure object number is still correct even if generation is not
+            var reference6 = new IndirectReference(1574, int.MaxValue);
+            Assert.Equal(1574, reference6.ObjectNumber);
+            
+            var reference7 = new IndirectReference(-1574, ushort.MaxValue + 10);
+            Assert.Equal(-1574, reference7.ObjectNumber);
+
+            var reference9 = new IndirectReference(-140737488355327, ushort.MaxValue + 10);
+            Assert.Equal(-140737488355327, reference9.ObjectNumber);
+
+            var reference10 = new IndirectReference(140737488355327, ushort.MaxValue * 10);
+            Assert.Equal(140737488355327, reference10.ObjectNumber);
         }
 
         [Fact]

src/UglyToad.PdfPig.Tests/Integration/IndirectReferenceTests.cs

@@ -0,0 +1,27 @@
+namespace UglyToad.PdfPig.Tests.Integration
+{
+    using DocumentLayoutAnalysis.WordExtractor;
+    using System.Linq;
+
+    public class IndirectReferenceTests
+    {
+        [Fact]
+        public void Generation65536()
+        {
+            using (var document = PdfDocument.Open(IntegrationHelpers.GetSpecificTestDocumentPath("93101_1.pdf")))
+            {
+                var page = document.GetPage(1);
+                var words = NearestNeighbourWordExtractor.Instance.GetWords(page.Letters).ToArray();
+                Assert.NotEmpty(words);
+                
+                Assert.Equal("Railway", words[0].Text);
+
+                for (int p = 2; p <= document.NumberOfPages; ++p)
+                {
+                    page = document.GetPage(p);
+                    Assert.NotEmpty(page.Letters);
+                }
+            }
+        }
+    }
+}

src/UglyToad.PdfPig.Tests/Integration/SpecificTestDocuments/93101_1.pdf

@@ -20,6 +20,12 @@ internal class CrossReferenceTablePartBuilder
 
         public void Add(long objectId, int generationNumber, long offset)
         {
+            if (generationNumber > ushort.MaxValue)
+            {
+                // We skip invalid generation number
+                return;
+            }
+
             IndirectReference objKey = new IndirectReference(objectId, generationNumber);
 
             if (!objects.ContainsKey(objKey))

src/UglyToad.PdfPig/CrossReference/CrossReferenceTablePartBuilder.cs

@@ -745,6 +745,7 @@ public void DeregisterCustomTokenizer(ITokenizer tokenizer)
 
             if (offset == 0 && reference.Generation > ushort.MaxValue)
             {
+                // TODO - To remove as should not happen anymore
                 return new ObjectToken(offset, reference, NullToken.Instance);
             }