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StgSharp.Common/HighPerformance/Memory/BufferStack.cs

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+//-----------------------------------------------------------------------
+// -----------------------------------------------------------------------
+// file="BufferStack.cs"
+// Project: StgSharp
+// 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 in the Software without restriction, 
+// including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, 
+// and to permit persons to whom the Software is furnished to do so, 
+// subject to the following conditions:
+//     
+// The above copyright notice and 
+// this permission notice shall be included in all copies 
+// or substantial portions of the Software.
+//     
+// THE SOFTWARE IS PROVIDED “AS IS”, 
+// WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
+// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
+// ARISING FROM, OUT OF OR IN CONNECTION WITH 
+// THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//     
+// -----------------------------------------------------------------------
+// -----------------------------------------------------------------------
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace StgSharp.HighPerformance.Memory
+{
+    [CollectionBuilder(typeof(BufferStackBuilder), nameof(BufferStackBuilder.Create))]
+    public unsafe class BufferStack<T> : IDisposable where T: unmanaged
+    {
+
+        private byte* _buffer;
+        private ulong _count;
+
+        public BufferStack(int capacity)
+        {
+            if (capacity <= 0) {
+                throw new ArgumentOutOfRangeException(nameof(capacity));
+            }
+
+            AllocateBuffer(capacity);
+        }
+
+        public int Count
+        {
+[MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => (int)_count;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Clear()
+        {
+            ((Header*)_buffer)->Top = 0;
+            _count = 0;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Dispose()
+        {
+            Marshal.FreeHGlobal((nint)_buffer);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public T Pop()
+        {
+            Header* header = (Header*)_buffer;
+            if (header->Top == 0) {
+                throw new InvalidOperationException("Stack underflow");
+            }
+
+            header->Top--;
+            _count--;
+            T* dataStart = (T*)(_buffer + sizeof(Header));
+            return dataStart[header->Top];
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Push(T item)
+        {
+            Header* header = (Header*)_buffer;
+            if (header->Top >= header->Capacity) {
+                Expand();
+            }
+
+            T* dataStart = (T*)(_buffer + sizeof(Header));
+            dataStart[header->Top] = item;
+            header->Top++;
+            _count++;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool TryPop(out T value)
+        {
+            Header* header = (Header*)_buffer;
+            if (header->Top == 0)
+            {
+                value = default;
+                return false;
+            }
+            header->Top--;
+            _count--;
+            T* dataStart = (T*)(_buffer + sizeof(Header));
+            value = dataStart[header->Top];
+            return true;
+        }
+
+        // Internal method for efficient bulk initialization
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal unsafe void InitializeFromSpan(ReadOnlySpan<T> span)
+        {
+            if (span.IsEmpty) {
+                return;
+            }
+
+            Header* header = (Header*)_buffer;
+            T* dataStart = (T*)(_buffer + sizeof(Header));
+
+            fixed (T* sourcePtr = span) {
+                Buffer.MemoryCopy(sourcePtr, dataStart, 
+                    header->Capacity * (nuint)sizeof(T), 
+                    (nuint)span.Length * (nuint)sizeof(T));
+            }
+
+            header->Top = (nuint)span.Length;
+            _count = (ulong)span.Length;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void AllocateBuffer(int capacity)
+        {
+            nuint size = (nuint)sizeof(Header) + ((nuint)capacity * (nuint)sizeof(T));
+            _buffer = (byte*)NativeMemory.Alloc(size);
+            Header* header = (Header*)_buffer;
+            header->Top = 0;
+            header->Capacity = (nuint)capacity;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void Expand()
+        {
+            Header* header = (Header*)_buffer;
+            nuint newCap = header->Capacity * 2;
+            nuint newSize = (nuint)sizeof(Header) + newCap * (nuint)sizeof(T);
+            _buffer = (byte*)NativeMemory.Realloc(_buffer, newSize);
+            header = (Header*)_buffer;
+            header->Capacity = newCap;
+        }
+
+        private struct Header
+        {
+
+            public nuint Capacity;
+            public nuint Top;
+
+        }
+
+    }
+}