Fix type 4 function Copy() stack operator and fix #724

UglyToad · Nov 12, 2023 · 1bc0ee7 · 1bc0ee7
1 parent 62bc32a
commit 1bc0ee7
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Showing 3 changed files with 29 additions and 4 deletions.
diff --git a/src/UglyToad.PdfPig.Tests/Integration/ColorSpaceTests.cs b/src/UglyToad.PdfPig.Tests/Integration/ColorSpaceTests.cs
@@ -331,6 +331,23 @@ public void SeparationIccColorSpacesWithForm()
             }
         }
 
+        [Fact]
+        public void Issue724()
+        {
+            // 11194059_2017-11_de_s
+            var path = IntegrationHelpers.GetDocumentPath("11194059_2017-11_de_s.pdf");
+            using (var document = PdfDocument.Open(path))
+            {
+                // Should not throw an exception.
+                // Fixed an issue in the Type 4 function Copy() StackOperators
+                Page page1 = document.GetPage(1);
+                Assert.NotNull(page1);
+
+                Page page2 = document.GetPage(2);
+                Assert.NotNull(page2);
+            }
+        }
+
         private static byte ConvertToByte(double componentValue)
         {
             var rounded = Math.Round(componentValue * 255, MidpointRounding.AwayFromZero);

diff --git a/src/UglyToad.PdfPig.Tests/Integration/Documents/11194059_2017-11_de_s.pdf b/src/UglyToad.PdfPig.Tests/Integration/Documents/11194059_2017-11_de_s.pdf
diff --git a/src/UglyToad.PdfPig/Functions/Type4/StackOperators.cs b/src/UglyToad.PdfPig/Functions/Type4/StackOperators.cs
@@ -21,13 +21,21 @@ internal sealed class Copy : Operator
         {
             public void Execute(ExecutionContext context)
             {
-                int n = ((int)context.Stack.Pop());
+                // Duplicate top n stack items
+                int n = (int)context.Stack.Pop();
                 if (n > 0)
                 {
-                    int size = context.Stack.Count;
                     // Need to copy to a new list to avoid ConcurrentModificationException
-                    List<object> copy = context.Stack.ToList().GetRange(size - n - 1, n);
-                    context.AddAllToStack(copy);
+                    context.AddAllToStack(context.Stack.ToList().Take(n));
+
+                    /* For reference, the PdfBox code:
+                     * https://github.com/apache/pdfbox/blob/18a1931bae5b8c1766cd4976d0fb0e28649190b5/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/common/function/type4/StackOperators.java#L41C1-L50C14
+                     * int size = stack.size();
+                       //Need to copy to a new list to avoid ConcurrentModificationException
+                       List<Object> copy = new java.util.ArrayList<>(
+                       stack.subList(size - n, size));
+                       stack.addAll(copy);
+                     */
                 }
             }
         }