Fixed calling engine functions from scripts

- Removed mono references in generator
- Implemented StringView type in C#

ScriptCore/Native/StringView.cs

@@ -0,0 +1,73 @@
+using GlitchyEngine.Core;
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace GlitchyEngine.Native;
+
+[DebuggerDisplay("{ToString(),raw}")]
+[StructLayout(LayoutKind.Sequential, Pack = 0)]
+[EngineClass("System.StringView")]
+internal unsafe struct StringView
+{
+    public byte* Utf8Ptr;
+    public long Length;
+
+    public StringView()
+    {
+        Utf8Ptr = null;
+        Length = 0;
+    }
+
+    public StringView(byte* utf8Ptr, long length)
+    {
+        Utf8Ptr = utf8Ptr;
+        Length = length;
+    }
+
+    public override string? ToString()
+    {
+        if (Utf8Ptr == null)
+            return null;
+
+        if (Length == 0)
+            return string.Empty;
+
+        if (Length is < 0 or > int.MaxValue)
+        {
+            throw new InvalidOperationException($"String length is invalid: {Length}.");
+        }
+
+        return Encoding.UTF8.GetString(Utf8Ptr, (int)Length);
+    }
+
+    /// <summary>
+    /// Creates a String<see cref="StringView"/>View that can be passed to native code. This method allocates native memory that must be freed using
+    /// <see cref="NativeMemory.Free"/>.
+    /// </summary>
+    /// <param name="s">The string to convert.</param>
+    /// <returns>The <see cref="StringView"/> pointing to the native memory containing the UTF8-text; or null, if <see cref="s"/> was null.</returns>
+    /// <remarks>
+    /// The allocated string is guaranteed to have a null terminator.
+    /// The null terminator is not counted into the length of the resulting <see cref="StringView"/>.
+    /// </remarks>
+    public static StringView FromManagedString(string? s)
+    {
+        if (s == null)
+            return new StringView();
+
+        int maxByteCount = Encoding.UTF8.GetMaxByteCount(s.Length);
+
+        byte* pointer = (byte*)NativeMemory.Alloc((nuint) checked (maxByteCount + 1));
+        int bytes = Encoding.UTF8.GetBytes((ReadOnlySpan<char>) s, new Span<byte>(pointer, maxByteCount));
+        pointer[bytes] = (byte) 0;
+
+        return new StringView(pointer, bytes);
+    }
+
+    public static void FreeNativeMemory(StringView s)
+    {
+        NativeMemory.Free(s.Utf8Ptr);
+    }
+}