UnityECS/LocalPackages/com.nimin.lowlevel/Runtime/StructUtility.cs

using Unity.Collections.LowLevel.Unsafe;

namespace GameCore.LowLevel
{
    public static class StructUtility
    {
        public static int OffsetOf<T, F>()
            where T : struct
            where F : struct
        {
            var fields = typeof(T).GetFields();
            foreach (var f in fields)
            {
                if (f.DeclaringType == typeof(F))
                    return UnsafeUtility.GetFieldOffset(f);
            }

            return -1;
        }
    }
}