Add test image and use constants

src/ImageSharp/Formats/Jpeg/Components/ZigZag.cs

@@ -17,17 +17,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
     internal unsafe struct ZigZag
     {
         /// <summary>
-        /// Copy of <see cref="Unzig"/> in a value type
-        /// </summary>
-        public fixed byte Data[64 + 16];
-
-        /// <summary>
-        /// <para>
-        /// Unzig maps from the zigzag ordering to the natural ordering. For example,
-        /// unzig[3] is the column and row of the fourth element in zigzag order. The
-        /// value is 16, which means first column (16%8 == 0) and third row (16/8 == 2).
-        /// </para>
-        /// <para>
         /// When reading corrupted data, the Huffman decoders could attempt
         /// to reference an entry beyond the end of this array (if the decoded
         /// zero run length reaches past the end of the block).  To prevent
@@ -36,9 +25,21 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
         /// to be stored in location 63 of the block, not somewhere random.
         /// The worst case would be a run-length of 15, which means we need 16
         /// fake entries.
-        /// </para>
+        /// </summary>
+        private const int Size = 64 + 16;
+
+        /// <summary>
+        /// Copy of <see cref="Unzig"/> in a value type
+        /// </summary>
+        public fixed byte Data[Size];
+
+        /// <summary>
+        /// Unzig maps from the zigzag ordering to the natural ordering. For example,
+        /// unzig[3] is the column and row of the fourth element in zigzag order. The
+        /// value is 16, which means first column (16%8 == 0) and third row (16/8 == 2).
         /// </summary>
         private static readonly byte[] Unzig =
+        new byte[Size]
         {
             0,  1,  8, 16,  9,  2,  3, 10,
             17, 24, 32, 25, 18, 11,  4,  5,
@@ -75,7 +76,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
         {
             ZigZag result = default;
             byte* unzigPtr = result.Data;
-            Marshal.Copy(Unzig, 0, (IntPtr)unzigPtr, 64 + 16);
+            Marshal.Copy(Unzig, 0, (IntPtr)unzigPtr, Size);
             return result;
         }
 
@@ -86,7 +87,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
         {
             Block8x8F result = default;
 
-            for (int i = 0; i < 64; i++)
+            for (int i = 0; i < Block8x8F.Size; i++)
             {
                 result[Unzig[i]] = qt[i];
             }

tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Images.cs

@@ -17,6 +17,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
 
                 // BUG: The following image has a high difference compared to the expected output:
                 // TestImages.Jpeg.Baseline.Jpeg420Small,
+                // TestImages.Jpeg.Issues.Fuzz.AccessViolationException922,
 
                 TestImages.Jpeg.Baseline.Jpeg444,
                 TestImages.Jpeg.Baseline.Bad.BadEOF,
@@ -106,4 +107,4 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                 [TestImages.Jpeg.Progressive.Bad.ExifUndefType] = 0.011f / 100,
             };
     }
-}
+}

tests/ImageSharp.Tests/TestImages.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors and contributors.
+// Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
 using System.Linq;
@@ -202,6 +202,7 @@ namespace SixLabors.ImageSharp.Tests
                     public const string ArgumentException826C = "Jpg/issues/fuzz/Issue826-ArgumentException-C.jpg";
                     public const string AccessViolationException827 = "Jpg/issues/fuzz/Issue827-AccessViolationException.jpg";
                     public const string ExecutionEngineException839 = "Jpg/issues/fuzz/Issue839-ExecutionEngineException.jpg";
+                    public const string AccessViolationException922 = "Jpg/issues/fuzz/Issue922-AccessViolationException.jpg";
                 }
             }