{

public static int RefCountOffset { get; } = GetRefCountOffset();

public static int ObjectHeadOffset => RefCountOffset;

internal static void Initialize(Version version)

{

string offsetsClassSuffix = string.Format(CultureInfo.InvariantCulture,

"{0}{1}", version.Major, version.Minor);

var thisAssembly = Assembly.GetExecutingAssembly();

const string nativeTypeOffsetClassName = "Python.Runtime.NativeTypeOffset";

string className = "Python.Runtime.TypeOffset" + offsetsClassSuffix;

Type nativeOffsetsClass = thisAssembly.GetType(nativeTypeOffsetClassName, throwOnError: false);

Type typeOffsetsClass =

// Try platform native offsets first. It is only present when generated by setup.py

nativeOffsetsClass ?? thisAssembly.GetType(className, throwOnError: false);

if (typeOffsetsClass is null)

{

var types = thisAssembly.GetTypes().Select(type => type.Name).Where(name => name.StartsWith("TypeOffset"));

string message = $"Searching for {className}, found {string.Join(",", types)}.";

throw new NotSupportedException($"Python ABI v{version} is not supported: {message}");

}

var typeOffsets = (ITypeOffsets)Activator.CreateInstance(typeOffsetsClass);

TypeOffset.Use(typeOffsets, nativeOffsetsClass == null ? ObjectHeadOffset : 0);

}

static unsafe int GetRefCountOffset()

{

using var tempObject = Runtime.PyList_New(0);

IntPtr* tempPtr = (IntPtr*)tempObject.DangerousGetAddress();

int offset = 0;

while(tempPtr[offset] != (IntPtr)1)

{

offset++;

if (offset > 100)

throw new InvalidProgramException("PyObject_HEAD could not be found withing reasonable distance from the start of PyObject");

}

return offset * IntPtr.Size;

}