diff --git a/StgSharp.Common/HighPerformance/Memory/TwoLayerSegregatedFitAllocator.cs b/StgSharp.Common/HighPerformance/Memory/TwoLayerSegregatedFitAllocator.cs
index 59a83c74..d1cc2ddf 100644
--- a/StgSharp.Common/HighPerformance/Memory/TwoLayerSegregatedFitAllocator.cs
+++ b/StgSharp.Common/HighPerformance/Memory/TwoLayerSegregatedFitAllocator.cs
@@ -2,8 +2,8 @@
 // -----------------------------------------------------------------------
 // file="TwoLayerSegregatedFitAllocator"
 // Project: StgSharp
-// AuthorGroup: Nitload
-// Copyright (c) Nitload. All rights reserved.
+// AuthorGroup: Nitload Space
+// Copyright (c) Nitload Space. All rights reserved.
 //     
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
@@ -31,6 +31,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Numerics;
+using System.Reflection.Metadata;
 using System.Runtime.InteropServices;
 using System.Text;
 using System.Threading.Tasks;
@@ -43,12 +44,13 @@ namespace StgSharp.HighPerformance.Memory
 
         private const ulong Mask48Bits = 0x0000FFFFFFFFFFFF;
 
-        private Metadata* _allocEnd;
         private readonly Metadata*[] _bucket;
         private readonly Metadata* _spareMemory;
         private readonly Action<nuint> _freeHandle;
         private bool disposedValue;
         private readonly int _align;
+
+        private int _allocEnd;
         private readonly Ptr64 _basePtr;
         private readonly ulong _maxAllocSize;
         private readonly ulong _totalSize;
@@ -58,8 +60,7 @@ namespace StgSharp.HighPerformance.Memory
                  int align,
                  ulong maxBlockSize,
                  Func<nuint, int, nuint> allocator,
-                 Action<nuint> freeHandle
-        )
+                 Action<nuint> freeHandle)
             : this(byteSize, align, maxBlockSize, (void*)allocator(byteSize, align), freeHandle) { }
 
         internal TwoLayerSegregatedFitAllocator(
@@ -67,8 +68,7 @@ namespace StgSharp.HighPerformance.Memory
                  int align,
                  ulong maxBlockSize,
                  void* externalPointer,
-                 Action<nuint> freeHandle
-        )
+                 Action<nuint> freeHandle)
         {
             _totalSize = byteSize;
             _basePtr = (Ptr64)(ulong)externalPointer;
@@ -77,7 +77,7 @@ namespace StgSharp.HighPerformance.Memory
             _bucket = new Metadata*[58 - BitOperations.LeadingZeroCount(_maxAllocSize)];
             _spareMemory = &((Metadata*)(ulong)(_basePtr + _totalSize))[-1];
             _freeHandle = freeHandle ?? (static_ => { });
-            _allocEnd = _spareMemory;
+            _allocEnd = 0;
 
             // init spare memory node
 
@@ -89,37 +89,23 @@ namespace StgSharp.HighPerformance.Memory
             _spareMemory->PreviousNear = 0;
         }
 
-        public TwoLayerSegregatedFitAllocator(
-               nuint byteSize
-        )
+        public TwoLayerSegregatedFitAllocator(nuint byteSize)
             : this(byteSize, 16, 32U * 1024U * 1024U, NativeMemory.AlignedAlloc(byteSize, 16),
                    ptr => NativeMemory.AlignedFree((void*)ptr)) { }
 
-        public TwoLayerSegregatedFitAllocator(
-               nuint byteSize,
-               uint maxBlockSize
-        )
+        public TwoLayerSegregatedFitAllocator(nuint byteSize, uint maxBlockSize)
             : this(byteSize, 16, maxBlockSize, NativeMemory.AlignedAlloc(byteSize, 16),
                    ptr => NativeMemory.AlignedFree((void*)ptr)) { }
 
-        public TwoLayerSegregatedFitAllocator(
-               nuint byteSize,
-               int align
-        )
+        public TwoLayerSegregatedFitAllocator(nuint byteSize, int align)
             : this(byteSize, align, 32U * 1024U * 1024U, NativeMemory.AlignedAlloc(byteSize, 16),
                    ptr => NativeMemory.AlignedFree((void*)ptr)) { }
 
-        public TwoLayerSegregatedFitAllocator(
-               nuint byteSize,
-               int align,
-               nuint maxBlockSize
-        )
+        public TwoLayerSegregatedFitAllocator(nuint byteSize, int align, nuint maxBlockSize)
             : this(byteSize, align, maxBlockSize, NativeMemory.AlignedAlloc(byteSize, 16),
                    ptr => NativeMemory.AlignedFree((void*)ptr)) { }
 
-        public Handle Alloc(
-                      nuint size
-        )
+        public Handle Alloc(nuint size)
         {
             ulong allocSize = nuint.Max(64, (~64U) & (size + 63));
             if (allocSize > _maxAllocSize) {
@@ -136,11 +122,11 @@ namespace StgSharp.HighPerformance.Memory
                     break;
                 }
             }
-            if (entry is null)
-            {
-                // alloc new from spare
+            if (entry is null && !TryGetNewMetadata(allocSize, out entry)) {
+                throw new OverflowException("No available ");
             }
             ulong remain = entry->Size - allocSize;
+
             throw new NotImplementedException();
         }
 
@@ -150,16 +136,12 @@ namespace StgSharp.HighPerformance.Memory
             GC.SuppressFinalize(this);
         }
 
-        public void Free(
-                    Handle handle
-        )
+        public void Free(Handle handle)
         {
             throw new NotImplementedException();
         }
 
-        protected virtual void Dispose(
-                               bool disposing
-        )
+        protected virtual void Dispose(bool disposing)
         {
             if (!disposedValue)
             {
@@ -171,12 +153,49 @@ namespace StgSharp.HighPerformance.Memory
             }
         }
 
+        private bool TryGetNewMetadata(ulong size, out Metadata* meta)
+        {
+            int idx = _spareMemory->NextLevel;
+            if (idx != 0)
+            {
+                meta = &_spareMemory[-idx];
+                _spareMemory->NextLevel = meta->NextLevel;
+                return true;
+            }
+            ulong spareSize = _spareMemory->Size;
+            if (spareSize < 32UL + size)
+            {
+                meta = null;
+                return false;
+            }
+            _allocEnd++;
+            meta = &_spareMemory[-_allocEnd];
+            spareSize -= 32UL - size;
+            _spareMemory->Size = spareSize;
+            _spareMemory->Position += size;
+            meta->Size = size;
+            return true;
+        }
+
         [StructLayout(LayoutKind.Sequential)]
-        public struct Handle
+        public readonly struct Handle
         {
 
-            internal readonly Metadata* Meta;
+            internal readonly Metadata* _meta;
             public readonly void* Pointer;
+            public readonly Ptr64 Size;
+
+            internal Handle(Metadata* meta, Ptr64 baseAddress)
+            {
+                _meta = meta;
+                Pointer = (void*)(ulong)(meta->Position + baseAddress);
+                Size = meta->Size;
+            }
+
+            [Obsolete("You should not create instance from default. Alloc from allocator please")]
+            public Handle() { }
+
+            public ref byte this[int offset] => ref ((byte*)Pointer)[offset];
 
         }
 
@@ -207,6 +226,12 @@ namespace StgSharp.HighPerformance.Memory
                 set => SizeMask = (SizeMask & ~Mask48Bits) | ((ulong)value & Mask48Bits);
             }
 
+            public Ptr64 SizeForSpare
+            {
+                get => SizeMask;
+                set => SizeMask = value;
+            }
+
             public static uint SizeOf { get; } = (uint)Unsafe.SizeOf<Metadata>();
 
         }