From cb75b7c244ca63980c83d4139ce19cc08e791679 Mon Sep 17 00:00:00 2001
From: "H. Utku Maden" <utkumaden@hotmail.com>
Date: Mon, 18 Nov 2024 20:47:28 +0300
Subject: [PATCH] Made Callbacks a public field in StbiStreamWrapper.cs

---
 ReFuel.StbImage.csproj | 10 +++++-----
 StbImage.cs            | 26 ++++++++++++++------------
 StbiStreamWrapper.cs   | 23 +++++++----------------
 3 files changed, 26 insertions(+), 33 deletions(-)

diff --git a/ReFuel.StbImage.csproj b/ReFuel.StbImage.csproj
index 7026d6a..811403e 100644
--- a/ReFuel.StbImage.csproj
+++ b/ReFuel.StbImage.csproj
@@ -14,7 +14,7 @@
     <!-- Nuget Properties. -->
     <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
     <PackageId>ReFuel.StbImage</PackageId>
-    <Version>2.0.2-rc.1</Version>
+    <Version>2.1.0-rc.0</Version>
     <Authors>STBI Authors, H. Utku Maden</Authors>
     <Description>
       A C# wrapper for the ubiquitous stb_image.h and stb_image_write.h library.
@@ -26,10 +26,10 @@
     <RepositoryUrl>https://git.mixedup.dev/ReFuel/ReFuel.StbImage</RepositoryUrl>
     <RepositoryType>git</RepositoryType>
     <PackageTags>stb; stb_image; stbi; image; load; save; read; write</PackageTags>
-    <PackageReleaseNotes># 2.0.2
+    <PackageReleaseNotes># 2.1.0 (ABI BRAKING)
 * Fixed calling convention of unmanaged function pointers. (Thanks NogginBops!)
-* Allocating a GC handle to StbiStreamWrapper class and passing it as userdata into stbi in order to prevent
-  the object from being prematurely collected by the garbage collector when optimizations are enabled in Release mode.
+* Modified StbiStreamWrapper in order to fixed backing delegates of function pointers from being prematurely collected 
+  by release mode JIT and the GC. StbiStreamWrapper.Callbacks is now a readonly field. (ABI BREAKING)
 
 # 2.0.1
 * Enabled optimizations across the board for native and managed assemblies.
@@ -56,7 +56,7 @@
     <Content Include="runtimes/linux-arm64/native/*.so">
       <PackagePath>runtimes/linux-arm64/native/</PackagePath>
       <Pack>true</Pack>
-      <CopyToOutputDirectory>PreserveNewest/</CopyToOutputDirectory>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
     <Content Include="runtimes/linux-x64/native/*.so">
       <PackagePath>runtimes/linux-x64/native/</PackagePath>
diff --git a/StbImage.cs b/StbImage.cs
index fc57153..28a3f88 100644
--- a/StbImage.cs
+++ b/StbImage.cs
@@ -209,19 +209,19 @@ namespace ReFuel.Stb
         {
             int x, y, iFormat;
             StbiStreamWrapper wrapper = new StbiStreamWrapper(stream, true);
-            GCHandle gch = GCHandle.Alloc(wrapper, GCHandleType.Normal);
-            wrapper.CreateCallbacks(out stbi_io_callbacks cb);
             stream.Position = 0;
             IntPtr imagePtr;
-            if (asFloat)
+            fixed (stbi_io_callbacks* cb = &wrapper.Callbacks)
             {
-                imagePtr = (IntPtr)Stbi.loadf_from_callbacks(&cb, (void*)(IntPtr)gch, &x, &y, &iFormat, (int)format);
+                if (asFloat)
+                {
+                    imagePtr = (IntPtr)Stbi.loadf_from_callbacks(cb, null, &x, &y, &iFormat, (int)format);
+                }
+                else
+                {
+                    imagePtr = (IntPtr)Stbi.load_from_callbacks(cb, null, &x, &y, &iFormat, (int)format);
+                }
             }
-            else
-            {
-                imagePtr = (IntPtr)Stbi.load_from_callbacks(&cb, (void*)(IntPtr)gch, &x, &y, &iFormat, (int)format);
-            }
-            gch.Free();
 
             if (imagePtr != IntPtr.Zero)
             {
@@ -319,10 +319,12 @@ namespace ReFuel.Stb
         {
             int x, y, iFormat;
             StbiStreamWrapper wrapper = new StbiStreamWrapper(stream, true);
-            wrapper.CreateCallbacks(out stbi_io_callbacks cb);
-
+            int result;
             stream.Position = 0;
-            int result = Stbi.info_from_callbacks(&cb, null, &x, &y, &iFormat);
+            fixed (stbi_io_callbacks* cb = &wrapper.Callbacks)
+            {
+                result = Stbi.info_from_callbacks(cb, null, &x, &y, &iFormat);
+            }
 
             width = x;
             height = y;
diff --git a/StbiStreamWrapper.cs b/StbiStreamWrapper.cs
index 37b6ad1..482ab93 100644
--- a/StbiStreamWrapper.cs
+++ b/StbiStreamWrapper.cs
@@ -32,11 +32,12 @@ namespace ReFuel.Stb
     public unsafe delegate int StbiEofProc(void *userdata);
 
     /// <summary>
-    /// An easy to use stream wrapper for use with STBI image load functions.
+    /// An easy-to-use stream wrapper for use with STBI image load functions.
     /// </summary>
     public unsafe class StbiStreamWrapper : IDisposable
     {
-        private readonly stbi_io_callbacks _callbacks;
+        public readonly stbi_io_callbacks Callbacks;
+
         private readonly Stream _stream;
         private readonly bool _keepOpen;
         private bool _isDisposed;
@@ -45,8 +46,6 @@ namespace ReFuel.Stb
         private StbiSkipProc _skipCb;
         private StbiEofProc _eofCb;
 
-        public ref readonly stbi_io_callbacks Callbacks => ref _callbacks;
-
         public StbiStreamWrapper(Stream stream, bool keepOpen = false)
         {
             if (stream == null) throw new ArgumentNullException(nameof(stream));
@@ -58,18 +57,10 @@ namespace ReFuel.Stb
             _skipCb = SkipCb;
             _eofCb = EofCb;
 
-            _callbacks = default;
-            _callbacks.read = Marshal.GetFunctionPointerForDelegate<StbiReadProc>(_readCb);
-            _callbacks.skip = Marshal.GetFunctionPointerForDelegate<StbiSkipProc>(_skipCb);
-            _callbacks.eof = Marshal.GetFunctionPointerForDelegate<StbiEofProc>(_eofCb);
-        }
-
-        public void CreateCallbacks(out stbi_io_callbacks cb)
-        {
-            cb = default;
-            cb.read = Marshal.GetFunctionPointerForDelegate<StbiReadProc>(_readCb);
-            cb.skip = Marshal.GetFunctionPointerForDelegate<StbiSkipProc>(_skipCb);
-            cb.eof = Marshal.GetFunctionPointerForDelegate<StbiEofProc>(_eofCb);
+            Callbacks = default;
+            Callbacks.read = Marshal.GetFunctionPointerForDelegate<StbiReadProc>(_readCb);
+            Callbacks.skip = Marshal.GetFunctionPointerForDelegate<StbiSkipProc>(_skipCb);
+            Callbacks.eof = Marshal.GetFunctionPointerForDelegate<StbiEofProc>(_eofCb);
         }
 
         private int ReadCb(void *userdata, byte* buffer, int count)