Added UnsafeMultiHashMap

Misaki.HighPerformance.LowLevel/FunctionPointer.cs

@@ -0,0 +1,40 @@
+using System.Runtime.InteropServices;
+
+namespace Misaki.HighPerformance.LowLevel;
+
+/// <summary>
+/// A structure that encapsulates a function pointer and provides methods to convert between
+/// </summary>
+/// <remarks>
+/// This structure used marshalling to convert between function pointers and delegates, which is not ideal for high-performance scenarios.
+/// Use this only when necessary, and prefer using <c>delegate* unmanaged</c> for better performance.
+/// </remarks>
+/// <typeparam name="T">The delegate type that the function pointer represents.</typeparam>
+public readonly struct FunctionPointer<T>
+    where T : Delegate
+{
+    private readonly nint _ptr;
+
+    /// <summary>
+    /// Gets the native function pointer associated with this function pointer instance.
+    /// </summary>
+    public readonly nint Pointer => _ptr;
+
+    /// <summary>
+    /// Gets the delegate instance associated with the specified function pointer.
+    /// </summary>
+    /// <remarks>This property uses <see
+    /// cref="Marshal.GetDelegateForFunctionPointer{TDelegate}"/> to convert the function
+    /// pointer to a delegate. Ensure that the function pointer is valid and compatible with the delegate type
+    /// <typeparamref name="T"/>.</remarks>
+    public T Delegate => Marshal.GetDelegateForFunctionPointer<T>(_ptr);
+
+    /// <summary>
+    /// Creates a new instance of this function pointer with the following native pointer.
+    /// </summary>
+    /// <param name="ptr"></param>
+    public FunctionPointer(T func)
+    {
+        _ptr = Marshal.GetFunctionPointerForDelegate<T>(func);
+    }
+}