Merge pull request #197 from Poltuu/fix_undefined_references

FIX : undefined references is a valid use case.

src/UglyToad.PdfPig.Tests/Tokenization/Scanner/PdfTokenScannerTests.cs

@@ -50,6 +50,36 @@ endobj";
             Assert.Equal(new IndirectReference(12, 7), reference.Data);
         }
 
+        [Fact]
+        public void ReadsObjectWithUndefinedIndirectReference()
+        {
+            const string s = @"
+5 0 obj
+<<
+/XObject <<
+/Pic1 7 0 R
+>>
+/ProcSet [/PDF /Text /ImageC ]
+/Font <<
+/F0 8 0 R
+/F1 9 0 R
+/F2 10 0 R
+/F3 0 0 R
+>>
+>>
+endobj";
+
+            var scanner = GetScanner(s);
+
+            ReadToEnd(scanner);
+
+            var token = scanner.Get(new IndirectReference(5, 0));
+            Assert.NotNull(token);
+
+            token = scanner.Get(new IndirectReference(0, 0));
+            Assert.Null(token);
+        }
+
         [Fact]
         public void ReadsNumericObjectWithComment()
         {

src/UglyToad.PdfPig/AcroForms/AcroFormFactory.cs

@@ -162,6 +162,10 @@
                     }
 
                     var kidObject = tokenScanner.Get(kidReferenceToken.Data);
+                    if (kidObject is null)
+                    {
+                        throw new InvalidOperationException($"Could not find the object with reference: {kidReferenceToken.Data}.");
+                    }
 
                     if (kidObject.Data is DictionaryToken kidDictionaryToken)
                     {

src/UglyToad.PdfPig/Content/ResourceStore.cs

@@ -148,7 +148,8 @@
 
                     if (fontObject == null)
                     {
-                        throw new InvalidOperationException($"Could not retrieve the font with name: {pair.Key} which should have been object {objectKey}");
+                        //This is a valid use case
+                        continue;
                     }
 
                     loadedFonts[reference] = fontFactory.Get(fontObject);

src/UglyToad.PdfPig/Parser/Parts/DirectObjectFinder.cs

@@ -43,9 +43,13 @@
             return false;
         }
 
-        public static T Get<T>(IndirectReference reference, IPdfTokenScanner scanner) where T : IToken
+        public static T Get<T>(IndirectReference reference, IPdfTokenScanner scanner) where T : class, IToken
         {
             var temp = scanner.Get(reference);
+            if (temp is null)
+            {
+                return null;
+            }
 
             if (temp.Data is T locatedResult)
             {
@@ -75,7 +79,7 @@
             throw new PdfDocumentFormatException($"Could not find the object number {reference} with type {typeof(T).Name}.");
         }
 
-        public static T Get<T>(IToken token, IPdfTokenScanner scanner) where T : IToken
+        public static T Get<T>(IToken token, IPdfTokenScanner scanner) where T : class, IToken
         {
             if (token is T result)
             {
@@ -84,32 +88,7 @@
 
             if (token is IndirectReferenceToken reference)
             {
-                var temp = scanner.Get(reference.Data);
-
-                if (temp.Data is T locatedResult)
-                {
-                    return locatedResult;
-                }
-
-                if (temp.Data is IndirectReferenceToken nestedReference)
-                {
-                    return Get<T>(nestedReference, scanner);
-                }
-
-                if (temp.Data is ArrayToken array && array.Data.Count == 1)
-                {
-                    var arrayElement = array.Data[0];
-
-                    if (arrayElement is IndirectReferenceToken arrayReference)
-                    {
-                        return Get<T>(arrayReference, scanner);
-                    }
-
-                    if (arrayElement is T arrayToken)
-                    {
-                        return arrayToken;
-                    }
-                }
+                return Get<T>(reference.Data, scanner);
             }
 
             throw new PdfDocumentFormatException($"Could not find the object {token} with type {typeof(T).Name}.");

src/UglyToad.PdfPig/PdfExtensions.cs

@@ -32,7 +32,7 @@
             return true;
         }
 
-        internal static T Get<T>(this DictionaryToken dictionary, NameToken name, IPdfTokenScanner scanner) where T : IToken
+        internal static T Get<T>(this DictionaryToken dictionary, NameToken name, IPdfTokenScanner scanner) where T : class, IToken
         {
             if (!dictionary.TryGet(name, out var token) || !(token is T typedToken))
             {

src/UglyToad.PdfPig/PdfFonts/Parser/Handlers/Type1FontHandler.cs

@@ -138,7 +138,7 @@
 
             try
             {
-                if (!(pdfScanner.Get(descriptor.FontFile.ObjectKey.Data).Data is StreamToken stream))
+                if (!(pdfScanner.Get(descriptor.FontFile.ObjectKey.Data)?.Data is StreamToken stream))
                 {
                     return null;
                 }

src/UglyToad.PdfPig/Structure.cs

@@ -45,7 +45,7 @@
         /// <returns>The tokenized PDF object from the file.</returns>
         public ObjectToken GetObject(IndirectReference reference)
         {
-            return TokenScanner.Get(reference);
+            return TokenScanner.Get(reference) ?? throw new InvalidOperationException($"Could not find the object with reference: {reference}.");
         }
     }
 }

src/UglyToad.PdfPig/Tokenization/Scanner/IPdfTokenScanner.cs

@@ -11,6 +11,7 @@
     {
         /// <summary>
         /// Tokenize the object with a given object number.
+        /// May return null when the reference is undefined
         /// </summary>
         /// <param name="reference">The object number for the object to tokenize.</param>
         /// <returns>The tokenized object.</returns>

src/UglyToad.PdfPig/Tokenization/Scanner/PdfTokenScanner.cs

@@ -664,7 +664,7 @@
 
             if (!objectLocationProvider.TryGetOffset(reference, out var offset))
             {
-                throw new InvalidOperationException($"Could not find the object with reference: {reference}.");
+                return null;
             }
 
             // Negative offsets refer to a stream with that number.