Custom single thread job example

IJobSingle.cs

[JobProducerType(typeof(JobCustomSingleExtensions.JobCustomSingleStruct<>))]
public interface IJobCustomSingle
{
    void Execute();
}

public static class JobCustomSingleExtensions
{
    public static void EarlyJobInit<T>() where T : struct, IJobCustomSingle
    {
        JobCustomSingleStruct<T>.Initialize();
    }
    
    private static IntPtr GetReflectionData<T>() where T : struct, IJobCustomSingle
    {
        JobCustomSingleStruct<T>.Initialize();
        return JobCustomSingleStruct<T>.jobReflectionData.Data;
    }
    
    public static unsafe JobHandle Schedule<TJob>(this TJob jobData, JobHandle dependsOn = default)
        where TJob : struct, IJobCustomSingle
    {
        var fullData = new JobCustomSingleStruct<TJob>
        {
            JobData = jobData
        };
            
        var scheduleParams = new JobsUtility.JobScheduleParameters(UnsafeUtility.AddressOf(ref fullData),
            GetReflectionData<TJob>(), dependsOn, ScheduleMode.Single);
            
        return JobsUtility.Schedule(ref scheduleParams);
    }
    
    public static unsafe JobHandle ScheduleByRef<TJob>(this ref TJob jobData, JobHandle dependsOn = default)
        where TJob : struct, IJobCustomSingle
    {
        var fullData = new JobCustomSingleStruct<TJob>
        {
            JobData = jobData
        };
            
        var scheduleParams = new JobsUtility.JobScheduleParameters(UnsafeUtility.AddressOf(ref fullData),
            GetReflectionData<TJob>(), dependsOn, ScheduleMode.Single);
            
        return JobsUtility.Schedule(ref scheduleParams);
    }
    
    [StructLayout(LayoutKind.Sequential)]
    internal struct JobCustomSingleStruct<TJob>
        where TJob : struct, IJobCustomSingle
    {
        public TJob JobData;
        internal static readonly SharedStatic<IntPtr> jobReflectionData =
            SharedStatic<IntPtr>.GetOrCreate<JobCustomSingleStruct<TJob>>();
            
        [BurstDiscard]
        internal static void Initialize()
        {
            if (jobReflectionData.Data == IntPtr.Zero)
            {
                jobReflectionData.Data = JobsUtility.CreateJobReflectionData(typeof(JobCustomSingleStruct<TJob>),
                    typeof(TJob), (ExecuteJobFunction)Execute);
            }
        }
            
        private delegate void ExecuteJobFunction(ref JobCustomSingleStruct<TJob> fullData, IntPtr additionalPtr,
            IntPtr bufferRangePatchData,
            ref JobRanges ranges, int jobIndex);
            
        public static void Execute(ref JobCustomSingleStruct<TJob> fullData, IntPtr additionalPtr, IntPtr bufferRangePatchData,
            ref JobRanges ranges, int jobIndex)
        {
            fullData.JobData.Execute();
        }
    }
}