feat: execute full-repo remaining parity closure plan

src/NATS.Server/IO/AdaptiveReadBuffer.cs

@@ -0,0 +1,19 @@
+namespace NATS.Server.IO;
+
+public sealed class AdaptiveReadBuffer
+{
+    private int _target = 4096;
+
+    public int CurrentSize => Math.Clamp(_target, 512, 64 * 1024);
+
+    public void RecordRead(int bytesRead)
+    {
+        if (bytesRead <= 0)
+            return;
+
+        if (bytesRead >= _target)
+            _target = Math.Min(_target * 2, 64 * 1024);
+        else if (bytesRead < _target / 4)
+            _target = Math.Max(_target / 2, 512);
+    }
+}

src/NATS.Server/IO/OutboundBufferPool.cs

@@ -0,0 +1,15 @@
+using System.Buffers;
+
+namespace NATS.Server.IO;
+
+public sealed class OutboundBufferPool
+{
+    public IMemoryOwner<byte> Rent(int size)
+    {
+        if (size <= 512)
+            return MemoryPool<byte>.Shared.Rent(512);
+        if (size <= 4096)
+            return MemoryPool<byte>.Shared.Rent(4096);
+        return MemoryPool<byte>.Shared.Rent(64 * 1024);
+    }
+}