RtlUIntPtrMult - NtDoc

#ifndef _NTINTSAFE_H_INCLUDED_
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM | WINAPI_PARTITION_GAMES)
//
// UINT_PTR multiplication
//
#ifdef _WIN64

#define RtlUIntPtrMult     RtlULongLongMult

#endif
#endif
#endif
View code on GitHub

#ifndef _NTINTSAFE_H_INCLUDED_
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM | WINAPI_PARTITION_GAMES)
//
// UINT_PTR multiplication
//
#ifdef _WIN64
// ...
#else

_Must_inspect_result_
__inline
NTSTATUS
RtlUIntPtrMult(
    _In_ UINT_PTR uMultiplicand,
    _In_ UINT_PTR uMultiplier,
    _Out_ _Deref_out_range_(==, uMultiplicand * uMultiplier) UINT_PTR* puResult)
{
    ULONGLONG ull64Result = UInt32x32To64(uMultiplicand, uMultiplier);

    return RtlULongLongToUIntPtr(ull64Result, puResult);
}

#endif
#endif
#endif
View code on GitHub