switch root namespace name to NITLOAD

src/Nitload.Common/HighPerformance/Memory/SlabAllocator.SequencialConcurrent.cs

@@ -0,0 +1,160 @@
+// -----------------------------------------------------------------------------
+// file="SlabAllocator.SequencialConcurrent"
+// Project: StgSharp
+// Copyright (c) Nitload.
+// SPDX-License-Identifier: MIT
+// -----------------------------------------------------------------------------
+
+using Nitload.Threading;
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace Nitload.Common.HighPerformance.Memory
+{
+    public sealed unsafe class ConcurrentSequentialSlabAllocator<T> : SlabAllocator<T>
+        where T : unmanaged
+    {
+
+        private T* _buffer;
+
+        private bool _disposed;
+
+        private readonly BufferExpansionLock _lock = new();
+        private readonly ConcurrentBufferStack<nuint> _stack;
+        private readonly int _elementSize;
+        private nuint _highestAllocated;
+        private ulong _capacity;
+
+        public ConcurrentSequentialSlabAllocator(
+               nuint initialCapacity
+        )
+        {
+            _elementSize = Unsafe.SizeOf<T>();
+            _capacity = initialCapacity;
+            _highestAllocated = 0;
+
+            _buffer = (T*)NativeMemory.Alloc(((nuint)_capacity) * ((nuint)_elementSize));
+            int initCount = _capacity switch
+            {
+                <= 4 => 4,
+                > 64 => 64,
+                _ => ((int)_capacity) / 4
+            };
+            // Callback fill instead of scratch span + CreateConcurrent: avoids
+            // the stackalloc and the copy, and sidesteps the CS0411 inference
+            // gap. Safe without locking — not yet published to other threads.
+            //
+            // Note this variant stores *indices*, not addresses, so the buffer
+            // argument is unused here; it is kept to match the shared
+            // SpanAction<T, nuint> shape.
+            _stack = new(initCount);
+            _stack.FillRange(init, 0);
+            _highestAllocated += (nuint)initCount;
+
+            static void init(
+                        Span<nuint> arr,
+                        nuint _
+            )
+            {
+                for (int i = 0; i < arr.Length; i++) {
+                    arr[i] = (nuint)i;
+                }
+            }
+        }
+
+        internal T* BasePointer => _buffer;
+
+        public override nuint Allocate()
+        {
+            if (_stack.TryPop(out nuint index)) {
+                return index;
+            }
+            while (true)
+            {
+                index = Volatile.Read(ref _highestAllocated);
+                _lock.EnterMetaDataRead();
+                try
+                {
+                    if (index >= _capacity)
+                    {
+                        _lock.ExitMetaDataRead();
+                        _lock.EnterExpansionProcess();
+                        try
+                        {
+                            _capacity = Volatile.Read(ref _capacity) * 2;
+                            nuint newSize = ((nuint)_capacity) * ((nuint)_elementSize);
+                            _lock.EnterBufferCopy();
+                            try
+                            {
+                                _buffer = (T*)NativeMemory.Realloc(_buffer, newSize);
+                            }
+                            finally
+                            {
+                                _lock.ExitBufferCopy();
+                            }
+                        }
+                        finally
+                        {
+                            _lock.ExitExpansionProcess();
+                        }
+                    }
+                    _ = Interlocked.Increment(ref Unsafe.As<nuint, ulong>(ref _highestAllocated));
+                    return index;
+                }
+                finally
+                {
+                    if (_lock.IsThreadReadingMetaData) {
+                        _lock.ExitMetaDataRead();
+                    }
+                }
+            }
+        }
+
+        public override void Dispose()
+        {
+            if (_disposed) {
+                return;
+            }
+            _disposed = true;
+            _stack.Dispose();
+            NativeMemory.Free(_buffer);
+            _lock.Dispose();
+            GC.SuppressFinalize(this);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override void EnterBufferReading()
+        {
+            _lock.EnterBufferRead();
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override void ExitBufferReading()
+        {
+            _lock.ExitBufferRead();
+        }
+
+        public override void Free(
+                             nuint index
+        )
+        {
+            _stack.Push(index);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override SlabAllocationHandle<T> ReadAllocation()
+        {
+            EnterBufferReading();
+            return new SlabAllocationHandle<T>(this, true);
+        }
+
+        ~ConcurrentSequentialSlabAllocator()
+        {
+            Dispose();
+        }
+
+    }
+}