Added UnsafeMultiHashMap

Misaki.HighPerformance.LowLevel/Buffer/Stack.cs

@@ -0,0 +1,223 @@
+using System.Runtime.CompilerServices;
+
+namespace Misaki.HighPerformance.LowLevel.Buffer;
+
+public unsafe partial struct Stack
+{
+    private static void** s_pStackBuffers = null;
+    private static int s_stackCount = 0;
+    private static int s_stackCapacity = 0;
+    private static readonly SpinLock s_locker = new SpinLock(false);
+
+    public static void DisposeAll()
+    {
+        if (s_pStackBuffers == null)
+        {
+            return;
+        }
+
+        for (var i = 0; i < s_stackCount; i++)
+        {
+            Free(s_pStackBuffers[i]);
+        }
+    }
+}
+
+/// <summary>
+/// Provides a stack-based memory allocator for unmanaged memory, enabling fast allocation and deallocation of memory
+/// blocks within a preallocated buffer.
+/// </summary>
+/// <remarks>This is not a thread-safe implementation.</remarks>
+public unsafe partial struct Stack : IDisposable
+{
+    private const nuint _DEFAULT_SIZE = 1024 * 1024; // 1MB
+
+    public readonly ref struct Scope : IDisposable
+    {
+        private readonly Stack* _allocator;
+        private readonly AllocationHandle _handle;
+        private readonly nuint _originalOffset;
+
+        public readonly AllocationHandle AllocationHandle => _handle;
+
+        internal Scope(Stack* allocator, AllocationHandle handle)
+        {
+            _allocator = allocator;
+            _handle = handle;
+            _originalOffset = allocator->_offset;
+            _allocator->_activeScopeCount++;
+        }
+
+        public void Dispose()
+        {
+            if (_allocator != null)
+            {
+                _allocator->_offset = _allocator->_offset > _originalOffset ? _originalOffset : _allocator->_offset;
+                _allocator->_activeScopeCount--;
+            }
+        }
+    }
+
+    private byte* _buffer;
+    private nuint _size;
+    private nuint _offset;
+    private uint _activeScopeCount;
+
+    internal readonly byte* Buffer => _buffer;
+
+    public nuint Offset
+    {
+        readonly get => _offset;
+        internal set => _offset = value;
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the StackAllocator class with a buffer of the specified size.
+    /// </summary>
+    /// <param name="size">The size, in bytes, of the memory buffer to allocate for stack-based allocations. Must be greater than zero.</param>
+    public Stack(nuint size)
+    {
+        if (size == 0)
+        {
+            throw new ArgumentException("Size must be greater than zero.", nameof(size));
+        }
+
+        Init(size);
+    }
+
+    private void Init(nuint size)
+    {
+        if (_buffer != null)
+        {
+            Free(_buffer);
+        }
+
+        _buffer = (byte*)Malloc(size);
+        _size = size;
+        _offset = 0;
+        _activeScopeCount = 0;
+
+        var token = false;
+        try
+        {
+            s_locker.Enter(ref token);
+            if (s_pStackBuffers == null)
+            {
+                s_pStackBuffers = (void**)Malloc((nuint)sizeof(void*) * 4u);
+                s_stackCapacity = 4;
+            }
+
+            if (s_stackCount >= s_stackCapacity)
+            {
+                var pOld = s_pStackBuffers;
+                var newCapacity = s_stackCapacity * 2;
+                var pNew = (void**)Realloc(pOld, (nuint)sizeof(void*) * (nuint)newCapacity);
+
+                s_pStackBuffers = pNew;
+                s_stackCapacity = newCapacity;
+            }
+
+            s_pStackBuffers[s_stackCount] = _buffer;
+            s_stackCount++;
+        }
+        finally
+        {
+            if (token)
+            {
+                s_locker.Exit();
+            }
+        }
+
+    }
+
+    private readonly void ThrowIfNoScope()
+    {
+        if (_activeScopeCount == 0)
+        {
+            throw new InvalidOperationException("Allocations can only be made within an active memory scope.");
+        }
+    }
+
+    private void EnsureInitialize()
+    {
+        if (_buffer == null || _size == 0)
+        {
+            Init(_DEFAULT_SIZE);
+        }
+    }
+
+    /// <summary>
+    /// Creates a new scope instance associated with the current stack context.
+    /// </summary>
+    /// <remarks>
+    /// The instance of <see cref="Stack"/> must be pinned or allocated on the native heap to ensure that the pointer remains valid for the lifetime of the scope.
+    /// </remarks>
+    /// <returns>A <see cref="Scope"/> object that represents a scope tied to this stack.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public Scope CreateScope(AllocationHandle handle)
+    {
+        EnsureInitialize();
+        return new Scope((Stack*)Unsafe.AsPointer(ref this), handle);
+    }
+
+    /// <summary>
+    /// Allocates a block of memory of the specified size and alignment from the buffer.
+    /// </summary>
+    /// <param name="size">The number of bytes to allocate. Must be greater than zero and less than or equal to the remaining buffer size.</param>
+    /// <param name="alignment">The alignment, in bytes, for the allocated memory block. Must be a power of two and greater than zero.</param>
+    /// <param name="allocationOption">An option specifying additional allocation behavior, such as whether the allocated memory should be cleared. The
+    /// default is <see cref="AllocationOption.None"/>.</param>
+    /// <returns>A pointer to the beginning of the allocated memory block if successful; otherwise, <see langword="null"/> if
+    /// there is insufficient space in the buffer.</returns>
+    public void* Allocate(nuint size, nuint alignment, AllocationOption allocationOption = AllocationOption.None)
+    {
+        ThrowIfNoScope();
+
+        if (size == 0)
+        {
+            return null;
+        }
+
+        if ((alignment & (alignment - 1)) != 0)
+        {
+            throw new ArgumentException("Alignment must be a power of two.", nameof(alignment));
+        }
+
+        var alignedOffset = (_offset + alignment - 1) & ~(alignment - 1);
+
+        var newOffset = alignedOffset + size;
+
+        if (newOffset > _size)
+        {
+            throw new OutOfMemoryException("Insufficient memory in stack allocator.");
+        }
+
+        var ptr = _buffer + alignedOffset;
+
+        _offset = newOffset;
+
+        if (allocationOption.HasFlag(AllocationOption.Clear))
+        {
+            MemClear(ptr, size);
+        }
+
+        return ptr;
+    }
+
+    /// <summary>
+    /// Resets the internal offset to its initial position.
+    /// </summary>
+    public void Reset()
+    {
+        _offset = 0;
+    }
+
+    public void Dispose()
+    {
+        Free(_buffer);
+
+        _buffer = null;
+        _size = 0;
+        _offset = 0;
+    }
+}