Add and use `Span`-from-`IntPtr` helper

src/BizHawk.Bizware.Audio/SDL2WavStream.cs

@@ -3,6 +3,7 @@ using System.IO;
 using System.Runtime.InteropServices;
 
 using BizHawk.Common;
+using BizHawk.Common.NumberExtensions;
 
 using static SDL2.SDL;
 
@@ -91,17 +92,19 @@ namespace BizHawk.Bizware.Audio
 		{
 		}
 
-		public unsafe int Read(Span<byte> buffer)
+		public int Read(Span<byte> buffer)
 		{
 			if (_wav == IntPtr.Zero)
 			{
 				throw new ObjectDisposedException(nameof(SDL2WavStream));
 			}
 
-			var count = (int)Math.Min(buffer.Length, _len - _pos);
+			uint count = Math.Min((uint) buffer.Length, _len - _pos);
-			new ReadOnlySpan<byte>((void*)((nint)_wav + _pos), count).CopyTo(buffer);
+			var countSigned = unchecked((int) count); // since `Span.Length` is at most `int.MaxValue`, so must `count` be
-			_pos += (uint)count;
+			// really, these fields should just be widened to whatever they're used as, which seems to be s64, and asserted to be in 0..<int.MaxValue
-			return count;
+			Util.UnsafeSpanFromPointer(ptr: _wav.Plus(_pos), length: countSigned).CopyTo(buffer);
+			_pos += count;
+			return countSigned;
 		}
 
 		public override int Read(byte[] buffer, int offset, int count)

src/BizHawk.Bizware.Graphics/D3D11/D3D11Pipeline.cs

@@ -2,6 +2,8 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Numerics;
 using System.Runtime.InteropServices;
+
+using BizHawk.Common;
 using BizHawk.Common.CollectionExtensions;
 using BizHawk.Common.StringExtensions;
 
@@ -303,11 +305,8 @@ namespace BizHawk.Bizware.Graphics
 				var mappedVb = Context.Map(VertexBuffer, MapMode.WriteDiscard);
 				try
 				{
-					unsafe
+					Util.UnsafeSpanFromPointer(ptr: data, length: count * VertexStride)
-					{
+						.CopyTo(Util.UnsafeSpanFromPointer(ptr: mappedVb.DataPointer, length: VertexBufferCount * VertexStride));
-						Buffer.MemoryCopy((void*)data, (void*)mappedVb.DataPointer,
-							VertexBufferCount * VertexStride, count * VertexStride);
-					}
 				}
 				finally
 				{
@@ -331,11 +330,8 @@ namespace BizHawk.Bizware.Graphics
 				var mappedIb = Context.Map(IndexBuffer, MapMode.WriteDiscard);
 				try
 				{
-					unsafe
+					Util.UnsafeSpanFromPointer(ptr: data, length: count * 2)
-					{
+						.CopyTo(Util.UnsafeSpanFromPointer(ptr: mappedIb.DataPointer, length: IndexBufferCount * 2));
-						Buffer.MemoryCopy((void*)data, (void*)mappedIb.DataPointer,
-							IndexBufferCount * 2, count * 2);
-					}
 				}
 				finally
 				{

src/BizHawk.Bizware.Graphics/D3D11/IGL_D3D11.cs

@@ -269,7 +269,7 @@ namespace BizHawk.Bizware.Graphics
 			Context.OMSetRenderTargets(_controlSwapChain.RTV);
 		}
 
-		private unsafe void UpdateConstantBuffers()
+		private void UpdateConstantBuffers()
 		{
 			for (var i = 0; i < ID3D11DeviceContext.CommonShaderConstantBufferSlotCount; i++)
 			{
@@ -282,7 +282,8 @@ namespace BizHawk.Bizware.Graphics
 				if (pb.VSBufferDirty)
 				{
 					var vsCb = Context.Map(CurPipeline.VSConstantBuffers[i], MapMode.WriteDiscard);
-					Buffer.MemoryCopy((void*)pb.VSPendingBuffer, (void*)vsCb.DataPointer, pb.VSBufferSize, pb.VSBufferSize);
+					Util.UnsafeSpanFromPointer(ptr: pb.VSPendingBuffer, length: pb.VSBufferSize)
+						.CopyTo(Util.UnsafeSpanFromPointer(ptr: vsCb.DataPointer, length: pb.VSBufferSize));
 					Context.Unmap(CurPipeline.VSConstantBuffers[i]);
 					pb.VSBufferDirty = false;
 				}
@@ -290,7 +291,8 @@ namespace BizHawk.Bizware.Graphics
 				if (pb.PSBufferDirty)
 				{
 					var psCb = Context.Map(CurPipeline.PSConstantBuffers[i], MapMode.WriteDiscard);
-					Buffer.MemoryCopy((void*)pb.PSPendingBuffer, (void*)psCb.DataPointer, pb.PSBufferSize, pb.PSBufferSize);
+					Util.UnsafeSpanFromPointer(ptr: pb.PSPendingBuffer, length: pb.PSBufferSize)
+						.CopyTo(Util.UnsafeSpanFromPointer(ptr: psCb.DataPointer, length: pb.PSBufferSize));
 					Context.Unmap(CurPipeline.PSConstantBuffers[i]);
 					pb.PSBufferDirty = false;
 				}

src/BizHawk.Bizware.Graphics/OpenGL/OpenGLPipeline.cs

@@ -4,6 +4,7 @@ using System.Numerics;
 
 using Silk.NET.OpenGL;
 
+using BizHawk.Common;
 using BizHawk.Common.CollectionExtensions;
 
 namespace BizHawk.Bizware.Graphics
@@ -209,10 +210,9 @@ namespace BizHawk.Bizware.Graphics
 			GL.DeleteBuffer(VBO);
 		}
 
-		public unsafe void SetVertexData(IntPtr data, int count)
+		public void SetVertexData(IntPtr data, int count)
 		{
-			var vertexes = new ReadOnlySpan<byte>((void*)data, count * VertexStride);
+			ReadOnlySpan<byte> vertexes = Util.UnsafeSpanFromPointer(ptr: data, length: count * VertexStride);
-
 			// BufferData reallocs and BufferSubData doesn't, so only use the former if we need to grow the buffer
 			if (vertexes.Length > VertexBufferLen)
 			{
@@ -225,10 +225,9 @@ namespace BizHawk.Bizware.Graphics
 			}
 		}
 
-		public unsafe void SetIndexData(IntPtr data, int count)
+		public void SetIndexData(IntPtr data, int count)
 		{
-			var indexes = new ReadOnlySpan<byte>((void*)data, count * 2);
+			ReadOnlySpan<byte> indexes = Util.UnsafeSpanFromPointer(ptr: data, length: count * 2);
-
 			if (indexes.Length > IndexBufferLen)
 			{
 				GL.BufferData(GLEnum.ElementArrayBuffer, indexes, GLEnum.DynamicDraw);

src/BizHawk.Bizware.Graphics/Renderers/ImGui2DRenderer.cs

@@ -8,6 +8,7 @@ using System.Runtime.InteropServices;
 
 using ImGuiNET;
 
+using BizHawk.Common;
 using BizHawk.Common.CollectionExtensions;
 
 using SDGraphics = System.Drawing.Graphics;
@@ -91,10 +92,10 @@ namespace BizHawk.Bizware.Graphics
 			_imGuiDrawList = IntPtr.Zero;
 		}
 
-		private unsafe void ClearStringOutput()
+		private void ClearStringOutput()
 		{
 			var bmpData = _stringOutput.LockBits(new(0, 0, _stringOutput.Width, _stringOutput.Height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
-			new Span<byte>((void*)bmpData.Scan0, bmpData.Stride * bmpData.Height).Clear();
+			Util.UnsafeSpanFromPointer(ptr: bmpData.Scan0, length: bmpData.Stride * bmpData.Height).Clear();
 			_stringOutput.UnlockBits(bmpData);
 		}
 

src/BizHawk.Common/Extensions/NumberExtensions.cs

@@ -121,6 +121,17 @@ namespace BizHawk.Common.NumberExtensions
 			return val;
 		}
 
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		public static IntPtr Plus(this IntPtr p, int offset)
+			=> p + offset;
+
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		public static IntPtr Plus(this IntPtr p, uint offset)
+		{
+			var half = unchecked((int) offset >> 1);
+			return p + half + unchecked((int) (offset - half));
+		}
+
 		public static void RotateRightU8(ref byte b, int shift)
 		{
 			byte temp = b;

src/BizHawk.Common/Util.cs

@@ -4,9 +4,7 @@ using System.IO;
 using System.IO.Compression;
 using System.Linq;
 using System.Reflection;
-#if NETCOREAPP3_0_OR_GREATER
 using System.Runtime.CompilerServices;
-#endif
 using System.Threading;
 
 namespace BizHawk.Common
@@ -381,6 +379,31 @@ namespace BizHawk.Common
 			}
 		}
 
+		/// <summary>creates span over <paramref name="length"/> octets starting at <paramref name="ptr"/></summary>
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		public static Span<byte> UnsafeSpanFromPointer(IntPtr ptr, int length)
+		{
+			unsafe
+			{
+				return new(pointer: ptr.ToPointer(), length: length);
+			}
+		}
+
+		/// <summary>
+		/// creates span over <paramref name="count"/><c> * sizeof(</c><typeparamref name="T"/><c>)</c> octets
+		/// starting at <paramref name="ptr"/>
+		/// </summary>
+		/// <remarks>uses native endianness</remarks>
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		public static Span<T> UnsafeSpanFromPointer<T>(IntPtr ptr, int count)
+			where T : unmanaged
+		{
+			unsafe
+			{
+				return new(pointer: ptr.ToPointer(), length: count * sizeof(T));
+			}
+		}
+
 		public static void WriteByteBuffer(this BinaryWriter bw, byte[]? data)
 		{
 			if (data == null)

src/BizHawk.Emulation.Cores/Waterbox/NymaCore.Settings.cs

@@ -1,7 +1,8 @@
 using System.Collections.Generic;
 using System.Linq;
-using System.Runtime.InteropServices;
 using System.Text;
+
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using NymaTypes;
 
@@ -214,7 +215,7 @@ namespace BizHawk.Emulation.Cores.Waterbox
 			return val;
 		}
 
-		private unsafe void SettingsQuery(string name, IntPtr dest)
+		private void SettingsQuery(string name, IntPtr dest)
 		{
 			var val = SettingsQuery(name);
 			var bytes = val is null ? Array.Empty<byte>() : Encoding.UTF8.GetBytes(val);
@@ -222,9 +223,9 @@ namespace BizHawk.Emulation.Cores.Waterbox
 			{
 				throw new InvalidOperationException($"Value {val} for setting {name} was too long");
 			}
-
+			var dstSpan = Util.UnsafeSpanFromPointer(ptr: dest, length: 256);
-			new Span<byte>((void*)dest, 256).Clear();
+			dstSpan.Clear();
-			Marshal.Copy(bytes, 0, dest, bytes.Length);
+			bytes.CopyTo(dstSpan);
 		}
 
 		private LibNymaCore.FrontendSettingQuery _settingsQueryDelegate;

src/BizHawk.Emulation.Cores/Waterbox/WaterboxHost.cs

@@ -99,12 +99,12 @@ namespace BizHawk.Emulation.Cores.Waterbox
 				_handle = GCHandle.Alloc(this, GCHandleType.Weak);
 			}
 
-			public unsafe IntPtr Read(IntPtr data, UIntPtr size)
+			public IntPtr Read(IntPtr data, UIntPtr size)
 			{
+				var count = checked((int) size);
 				try
 				{
-					var count = (int)size;
+					var n = _backingSpanStream.Read(Util.UnsafeSpanFromPointer(ptr: data, length: count));
-					var n = _backingSpanStream.Read(new((void*)data, count));
 					return Z.SS(n);
 				}
 				catch
@@ -113,12 +113,12 @@ namespace BizHawk.Emulation.Cores.Waterbox
 				}
 			}
 
-			public unsafe int Write(IntPtr data, UIntPtr size)
+			public int Write(IntPtr data, UIntPtr size)
 			{
+				var count = checked((int) size);
 				try
 				{
-					var count = (int)size;
+					_backingSpanStream.Write(Util.UnsafeSpanFromPointer(ptr: data, length: count));
-					_backingSpanStream.Write(new((void*)data, count));
 					return 0;
 				}
 				catch