RtlIntToULong - NtDoc

#ifndef _NTINTSAFE_H_INCLUDED_
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM | WINAPI_PARTITION_GAMES)

//
// INT -> ULONG conversion
//
_Must_inspect_result_
__inline
NTSTATUS
RtlIntToULong(
    _In_ INT iOperand,
    _Out_ _Deref_out_range_(==, iOperand) ULONG* pulResult)
{
    NTSTATUS status;

    if (iOperand >= 0)
    {
        *pulResult = (ULONG)iOperand;
        status = STATUS_SUCCESS;
    }
    else
    {
        *pulResult = ULONG_ERROR;
        status = STATUS_INTEGER_OVERFLOW;
    }

    return status;
}

#endif
#endif
View code on GitHub