From e48f4127e55276125136f17cffb70dc5ffb38fa3 Mon Sep 17 00:00:00 2001
From: Jeremy Pritts <49847914+ds5678@users.noreply.github.com>
Date: Sat, 29 Jun 2024 11:53:51 -0400
Subject: [PATCH] `Il2CppStructArray<T>.AsSpan()` (#129)

---
 .../Il2CppInterop.Runtime.csproj              |  2 +
 .../InteropTypes/Arrays/Il2CppStructArray.cs  | 47 +++++++++++--------
 2 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/Il2CppInterop.Runtime/Il2CppInterop.Runtime.csproj b/Il2CppInterop.Runtime/Il2CppInterop.Runtime.csproj
index 0766a12b..0815e6b0 100644
--- a/Il2CppInterop.Runtime/Il2CppInterop.Runtime.csproj
+++ b/Il2CppInterop.Runtime/Il2CppInterop.Runtime.csproj
@@ -10,6 +10,8 @@
     <Configurations>Debug;Release</Configurations>
     <Platforms>AnyCPU</Platforms>
     <ImplicitUsings>false</ImplicitUsings>
+    <LangVersion>Latest</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/Il2CppInterop.Runtime/InteropTypes/Arrays/Il2CppStructArray.cs b/Il2CppInterop.Runtime/InteropTypes/Arrays/Il2CppStructArray.cs
index 7553eaee..d1e5b07f 100644
--- a/Il2CppInterop.Runtime/InteropTypes/Arrays/Il2CppStructArray.cs
+++ b/Il2CppInterop.Runtime/InteropTypes/Arrays/Il2CppStructArray.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Il2CppInterop.Runtime.InteropTypes.Arrays;
 
@@ -9,6 +10,11 @@ static Il2CppStructArray()
         StaticCtorBody(typeof(Il2CppStructArray<T>));
     }
 
+    /// <summary>
+    /// The pointer to the first element in the array.
+    /// </summary>
+    private IntPtr ArrayStartPointer => IntPtr.Add(Pointer, 4 * IntPtr.Size);
+
     public Il2CppStructArray(IntPtr nativeObject) : base(nativeObject)
     {
     }
@@ -19,37 +25,38 @@ public Il2CppStructArray(long size) : base(AllocateArray(size))
 
     public Il2CppStructArray(T[] arr) : base(AllocateArray(arr.Length))
     {
-        for (var i = 0; i < arr.Length; i++)
-            this[i] = arr[i];
+        arr.CopyTo(this);
     }
 
-    public override unsafe T this[int index]
+    public override T this[int index]
     {
-        get
-        {
-            if (index < 0 || index >= Length)
-                throw new ArgumentOutOfRangeException(nameof(index),
-                    "Array index may not be negative or above length of the array");
-            var arrayStartPointer = IntPtr.Add(Pointer, 4 * IntPtr.Size);
-            return ((T*)arrayStartPointer.ToPointer())[index];
-        }
-        set
-        {
-            if (index < 0 || index >= Length)
-                throw new ArgumentOutOfRangeException(nameof(index),
-                    "Array index may not be negative or above length of the array");
-            var arrayStartPointer = IntPtr.Add(Pointer, 4 * IntPtr.Size);
-            ((T*)arrayStartPointer.ToPointer())[index] = value;
-        }
+        get => AsSpan()[index];
+        set => AsSpan()[index] = value;
     }
 
-    public static implicit operator Il2CppStructArray<T>(T[] arr)
+    public unsafe Span<T> AsSpan()
+    {
+        return new Span<T>(ArrayStartPointer.ToPointer(), Length);
+    }
+
+    [return: NotNullIfNotNull(nameof(arr))]
+    public static implicit operator Il2CppStructArray<T>?(T[]? arr)
     {
         if (arr == null) return null;
 
         return new Il2CppStructArray<T>(arr);
     }
 
+    public static implicit operator Span<T>(Il2CppStructArray<T>? il2CppArray)
+    {
+        return il2CppArray is not null ? il2CppArray.AsSpan() : default;
+    }
+
+    public static implicit operator ReadOnlySpan<T>(Il2CppStructArray<T>? il2CppArray)
+    {
+        return il2CppArray is not null ? il2CppArray.AsSpan() : default;
+    }
+
     private static IntPtr AllocateArray(long size)
     {
         if (size < 0)