Removed some bound checks for arr[0] indexing to get a reference

Author: gfoidl

src/ImageSharp/Compression/Zlib/DeflaterEngine.cs

@@ -3,6 +3,7 @@
 
 using System.Buffers;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Memory;
 
 namespace SixLabors.ImageSharp.Compression.Zlib;
@@ -426,8 +427,8 @@ private int InsertString()
     private void SlideWindow()
     {
         Unsafe.CopyBlockUnaligned(
-            ref this.window.Span[0],
-            ref this.window.Span[DeflaterConstants.WSIZE],
+            ref MemoryMarshal.GetReference(this.window.Span),
+            ref Unsafe.Add(ref MemoryMarshal.GetReference(this.window.Span), DeflaterConstants.WSIZE),
             DeflaterConstants.WSIZE);
 
         this.matchStart -= DeflaterConstants.WSIZE;

src/ImageSharp/Formats/Jpeg/Components/Decoder/ArithmeticScanDecoder.cs

@@ -53,7 +53,8 @@ internal class ArithmeticScanDecoder : IJpegScanDecoder
 
     private ArithmeticDecodingTable[] acDecodingTables;
 
-    private readonly byte[] fixedBin = { 113, 0, 0, 0 };
+    // Use C#'s optimization to refer to assembly's data segment, no allocation occurs.
+    private ReadOnlySpan<byte> fixedBin => new byte[] { 113, 0, 0, 0 };
 
     private readonly CancellationToken cancellationToken;
 
@@ -231,7 +232,7 @@ public void InitDecodingTables(List<ArithmeticDecodingTable> arithmeticDecodingT
         }
     }
 
-    private ref byte GetFixedBinReference() => ref this.fixedBin[0];
+    private ref byte GetFixedBinReference() => ref MemoryMarshal.GetReference(fixedBin);
 
     /// <summary>
     /// Decodes the entropy coded data.

src/ImageSharp/Formats/Jpeg/Components/Decoder/ArithmeticStatistics.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Runtime.InteropServices;
+
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder;
 
 internal class ArithmeticStatistics
@@ -18,7 +20,7 @@ public ArithmeticStatistics(bool dc, int identifier)
 
     public int Identifier { get; private set; }
 
-    public ref byte GetReference() => ref this.statistics[0];
+    public ref byte GetReference() => ref MemoryMarshal.GetArrayDataReference(this.statistics);
 
     public ref byte GetReference(int offset) => ref this.statistics[offset];
 

src/ImageSharp/Formats/Png/PngScanlineProcessor.cs

@@ -255,7 +255,7 @@ public static void ProcessPaletteScanline<TPixel>(
             // If the alpha palette is not null and has one or more entries, this means, that the image contains an alpha
             // channel and we should try to read it.
             Rgba32 rgba = default;
-            ref byte paletteAlphaRef = ref paletteAlpha[0];
+            ref byte paletteAlphaRef = ref MemoryMarshal.GetArrayDataReference(paletteAlpha);
 
             for (int x = 0; x < header.Width; x++)
             {
@@ -301,7 +301,7 @@ public static void ProcessInterlacedPaletteScanline<TPixel>(
             // If the alpha palette is not null and has one or more entries, this means, that the image contains an alpha
             // channel and we should try to read it.
             Rgba32 rgba = default;
-            ref byte paletteAlphaRef = ref paletteAlpha[0];
+            ref byte paletteAlphaRef = ref MemoryMarshal.GetArrayDataReference(paletteAlpha);
             for (int x = pixelOffset, o = 0; x < header.Width; x += increment, o++)
             {
                 int index = Unsafe.Add(ref scanlineSpanRef, (uint)o);

src/ImageSharp/Formats/Tga/TgaDecoderCore.cs

@@ -4,6 +4,7 @@
 using System.Buffers;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Metadata;
@@ -429,11 +430,11 @@ private void ReadBgra16<TPixel>(BufferedReadStream stream, int width, int height
 
                     if (this.fileHeader.ImageType == TgaImageType.BlackAndWhite)
                     {
-                        color.FromLa16(Unsafe.As<byte, La16>(ref this.scratchBuffer[0]));
+                        color.FromLa16(Unsafe.As<byte, La16>(ref MemoryMarshal.GetArrayDataReference(this.scratchBuffer)));
                     }
                     else
                     {
-                        color.FromBgra5551(Unsafe.As<byte, Bgra5551>(ref this.scratchBuffer[0]));
+                        color.FromBgra5551(Unsafe.As<byte, Bgra5551>(ref MemoryMarshal.GetArrayDataReference(this.scratchBuffer)));
                     }
 
                     pixelSpan[x] = color;
@@ -695,7 +696,7 @@ private void ReadBgr24Pixel<TPixel>(BufferedReadStream stream, TPixel color, int
             TgaThrowHelper.ThrowInvalidImageContentException("Not enough data to read a bgr pixel");
         }
 
-        color.FromBgr24(Unsafe.As<byte, Bgr24>(ref this.scratchBuffer[0]));
+        color.FromBgr24(Unsafe.As<byte, Bgr24>(ref MemoryMarshal.GetArrayDataReference(this.scratchBuffer)));
         pixelSpan[x] = color;
     }
 

src/ImageSharp/Processing/Processors/Convolution/BokehBlurProcessor.cs

@@ -133,7 +133,7 @@ public void Invoke(int y)
             // The target buffer is zeroed initially and then it accumulates the results
             // of each partial convolution, so we don't have to clear it here as well
             ref Vector4 targetBase = ref this.targetValues.GetElementUnsafe(boundsX, y);
-            ref Complex64 kernelStart = ref this.kernel[0];
+            ref Complex64 kernelStart = ref MemoryMarshal.GetArrayDataReference(this.kernel);
             ref Complex64 kernelEnd = ref Unsafe.Add(ref kernelStart, (uint)kernelSize);
 
             while (Unsafe.IsAddressLessThan(ref kernelStart, ref kernelEnd))

src/ImageSharp/Processing/Processors/Convolution/BokehBlurProcessor{TPixel}.cs

@@ -244,7 +244,7 @@ public void Invoke(int y, Span<Vector4> span)
             ref Vector4 sourceBase = ref MemoryMarshal.GetReference(span);
             ref ComplexVector4 targetStart = ref MemoryMarshal.GetReference(targetBuffer);
             ref ComplexVector4 targetEnd = ref Unsafe.Add(ref targetStart, (uint)span.Length);
-            ref Complex64 kernelBase = ref this.kernel[0];
+            ref Complex64 kernelBase = ref MemoryMarshal.GetArrayDataReference(this.kernel);
             ref Complex64 kernelEnd = ref Unsafe.Add(ref kernelBase, (uint)kernelSize);
             ref int sampleColumnBase = ref MemoryMarshal.GetReference(this.map.GetColumnOffsetSpan());
 

src/ImageSharp/Processing/Processors/Convolution/Convolution2PassProcessor{TPixel}.cs

@@ -179,7 +179,7 @@ private void Convolve3(int y, Span<Vector4> span)
             ref Vector4 sourceBase = ref MemoryMarshal.GetReference(sourceBuffer);
             ref Vector4 targetStart = ref MemoryMarshal.GetReference(targetBuffer);
             ref Vector4 targetEnd = ref Unsafe.Add(ref targetStart, (uint)sourceBuffer.Length);
-            ref float kernelBase = ref this.kernel[0];
+            ref float kernelBase = ref MemoryMarshal.GetArrayDataReference(this.kernel);
             ref float kernelEnd = ref Unsafe.Add(ref kernelBase, (uint)kernelSize);
             ref int sampleColumnBase = ref MemoryMarshal.GetReference(this.map.GetColumnOffsetSpan());
 
@@ -243,7 +243,7 @@ private void Convolve4(int y, Span<Vector4> span)
             ref Vector4 sourceBase = ref MemoryMarshal.GetReference(sourceBuffer);
             ref Vector4 targetStart = ref MemoryMarshal.GetReference(targetBuffer);
             ref Vector4 targetEnd = ref Unsafe.Add(ref targetStart, (uint)sourceBuffer.Length);
-            ref float kernelBase = ref this.kernel[0];
+            ref float kernelBase = ref MemoryMarshal.GetArrayDataReference(this.kernel);
             ref float kernelEnd = ref Unsafe.Add(ref kernelBase, (uint)kernelSize);
             ref int sampleColumnBase = ref MemoryMarshal.GetReference(this.map.GetColumnOffsetSpan());
 
@@ -341,7 +341,7 @@ private void Convolve3(int y, Span<Vector4> span)
             targetBuffer.Clear();
 
             ref Vector4 targetBase = ref MemoryMarshal.GetReference(targetBuffer);
-            ref float kernelStart = ref this.kernel[0];
+            ref float kernelStart = ref MemoryMarshal.GetArrayDataReference(this.kernel);
             ref float kernelEnd = ref Unsafe.Add(ref kernelStart, (uint)kernelSize);
 
             Span<TPixel> sourceRow;
@@ -406,7 +406,7 @@ private void Convolve4(int y, Span<Vector4> span)
             targetBuffer.Clear();
 
             ref Vector4 targetBase = ref MemoryMarshal.GetReference(targetBuffer);
-            ref float kernelStart = ref this.kernel[0];
+            ref float kernelStart = ref MemoryMarshal.GetArrayDataReference(this.kernel);
             ref float kernelEnd = ref Unsafe.Add(ref kernelStart, (uint)kernelSize);
 
             Span<TPixel> sourceRow;

src/ImageSharp/Processing/Processors/Convolution/Parameters/BokehBlurKernelDataProvider.cs

@@ -192,7 +192,7 @@ private static void NormalizeKernels(Complex64[][] kernels, Vector4[] kernelPara
         {
             ref Complex64[] kernelRef = ref Unsafe.Add(ref baseKernelsRef, (uint)i);
             int length = kernelRef.Length;
-            ref Complex64 valueRef = ref kernelRef[0];
+            ref Complex64 valueRef = ref MemoryMarshal.GetArrayDataReference(kernelRef);
             ref Vector4 paramsRef = ref Unsafe.Add(ref baseParamsRef, (uint)i);
 
             for (int j = 0; j < length; j++)
@@ -214,7 +214,7 @@ private static void NormalizeKernels(Complex64[][] kernels, Vector4[] kernelPara
         {
             ref Complex64[] kernelsRef = ref Unsafe.Add(ref baseKernelsRef, (uint)i);
             int length = kernelsRef.Length;
-            ref Complex64 valueRef = ref kernelsRef[0];
+            ref Complex64 valueRef = ref MemoryMarshal.GetArrayDataReference(kernelsRef);
 
             for (int j = 0; j < length; j++)
             {

src/ImageSharp/Processing/Processors/Quantization/WuQuantizer{TPixel}.cs

@@ -684,7 +684,7 @@ private void BuildCube()
         using IMemoryOwner<double> vvOwner = this.Configuration.MemoryAllocator.Allocate<double>(this.maxColors);
         Span<double> vv = vvOwner.GetSpan();
 
-        ref Box cube = ref this.colorCube[0];
+        ref Box cube = ref MemoryMarshal.GetArrayDataReference(this.colorCube);
         cube.RMin = cube.GMin = cube.BMin = cube.AMin = 0;
         cube.RMax = cube.GMax = cube.BMax = IndexCount - 1;
         cube.AMax = IndexAlphaCount - 1;