Add WriteByte and optimize ReadByte

src/ImageSharp/IO/ChunkedMemoryStream.cs

@@ -4,6 +4,7 @@
 using System.Buffers;
 using System.Collections;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Memory;
 
 namespace SixLabors.ImageSharp.IO;
@@ -13,11 +14,10 @@ namespace SixLabors.ImageSharp.IO;
 /// Chunks are allocated by the <see cref="MemoryAllocator"/> assigned via the constructor
 /// and is designed to take advantage of buffer pooling when available.
 /// </summary>
-/// <summary>Provides an in-memory stream composed of non-contiguous chunks.</summary>
 public class ChunkedMemoryStream : Stream
 {
     private readonly MemoryChunkBuffer memoryChunkBuffer;
-    private readonly byte[] singleReadBuffer = new byte[1];
+    private readonly byte[] singleByteBuffer = new byte[1];
 
     private long length;
     private long position;
@@ -101,8 +101,8 @@ public override int ReadByte()
             return -1;
         }
 
-        _ = this.Read(this.singleReadBuffer, 0, 1);
-        return this.singleReadBuffer[^1];
+        _ = this.Read(this.singleByteBuffer, 0, 1);
+        return MemoryMarshal.GetReference<byte>(this.singleByteBuffer);
     }
 
     /// <inheritdoc/>
@@ -129,17 +129,17 @@ public override int Read(Span<byte> buffer)
         int count = buffer.Length;
 
         long remaining = this.length - this.position;
-        if (remaining > count)
-        {
-            remaining = count;
-        }
-
         if (remaining <= 0)
         {
             // Already at the end of the stream, nothing to read
             return 0;
         }
 
+        if (remaining > count)
+        {
+            remaining = count;
+        }
+
         int bytesToRead = (int)remaining;
         int bytesRead = 0;
         while (bytesToRead != 0 && this.currentChunk != this.memoryChunkBuffer.Length)
@@ -175,6 +175,14 @@ public override int Read(Span<byte> buffer)
         return bytesRead;
     }
 
+    /// <inheritdoc/>
+    public override void WriteByte(byte value)
+    {
+        this.EnsureNotDisposed();
+        MemoryMarshal.Write(this.singleByteBuffer, ref value);
+        this.Write(this.singleByteBuffer, 0, 1);
+    }
+
     /// <inheritdoc/>
     public override void Write(byte[] buffer, int offset, int count)
     {
@@ -309,7 +317,7 @@ public byte[] ToArray()
         byte[] copy = new byte[this.length];
 
         this.Position = 0;
-        this.Read(copy, 0, copy.Length);
+        _ = this.Read(copy, 0, copy.Length);
         this.Position = position;
         return copy;
     }