Base the buffer size on the stream length

tests/ImageSharp.Tests/Image/ImageTests.Decode_Cancellation.cs

@@ -85,7 +85,7 @@ public partial class ImageTests
 
             Configuration configuration = Configuration.CreateDefaultInstance();
             configuration.FileSystem = new SingleStreamFileSystem((Stream)pausedStream);
-            configuration.StreamProcessingBufferSize = 256;
+            configuration.StreamProcessingBufferSize = (int)Math.Min(128, pausedStream.Length / 4);
 
             DecoderOptions options = new()
             {

tests/ImageSharp.Tests/TestUtilities/IPausedStream.cs

@@ -12,4 +12,6 @@ public interface IPausedStream : IDisposable
     public void Next();
 
     public void Release();
+
+    public long Length { get; }
 }

tests/ImageSharp.Tests/TestUtilities/PausedMemoryStream.cs

@@ -12,9 +12,9 @@ namespace SixLabors.ImageSharp.Tests.TestUtilities;
 /// </summary>
 public class PausedMemoryStream : MemoryStream, IPausedStream
 {
-    private readonly SemaphoreSlim semaphore = new SemaphoreSlim(0);
+    private readonly SemaphoreSlim semaphore = new(0);
 
-    private readonly CancellationTokenSource cancelationTokenSource = new CancellationTokenSource();
+    private readonly CancellationTokenSource cancelationTokenSource = new();
 
     private Action<Stream> onWaitingCallback;
 

tests/ImageSharp.Tests/TestUtilities/PausedStream.cs

@@ -7,9 +7,9 @@ namespace SixLabors.ImageSharp.Tests.TestUtilities;
 
 public class PausedStream : Stream, IPausedStream
 {
-    private readonly SemaphoreSlim semaphore = new SemaphoreSlim(0);
+    private readonly SemaphoreSlim semaphore = new(0);
 
-    private readonly CancellationTokenSource cancelationTokenSource = new CancellationTokenSource();
+    private readonly CancellationTokenSource cancelationTokenSource = new();
 
     private readonly Stream innerStream;
     private Action<Stream> onWaitingCallback;