RtlStringCbLengthW - NtDoc

#ifndef _NTSTRSAFE_H_INCLUDED_
#ifndef NTSTRSAFE_LIB_IMPL
#ifndef NTSTRSAFE_NO_CB_FUNCTIONS

_Must_inspect_result_
NTSTRSAFEDDI
    RtlStringCbLengthW(
            _In_reads_or_z_(cbMax / sizeof(wchar_t)) STRSAFE_PCNZWCH psz,
            _In_ _In_range_(1, NTSTRSAFE_MAX_CCH * sizeof(wchar_t)) size_t cbMax,
            _Out_opt_ _Deref_out_range_(<, cbMax - 1) size_t* pcbLength)
{
    NTSTATUS status;
    size_t cchMax = cbMax / sizeof(wchar_t);
    size_t cchLength = 0;

    if ((psz == NULL) || (cchMax > NTSTRSAFE_MAX_CCH))
    {
        status = STATUS_INVALID_PARAMETER;
    }
    else
    {
        status = RtlStringLengthWorkerW(psz, cchMax, &cchLength);
    }

    if (pcbLength)
    {
        if (NT_SUCCESS(status))
        {
            // safe to multiply cchLength * sizeof(wchar_t) since cchLength < NTSTRSAFE_MAX_CCH and sizeof(wchar_t) is 2
            *pcbLength = cchLength * sizeof(wchar_t);
        }
        else
        {
            *pcbLength = 0;
        }
    }

    return status;
}

#endif
#endif
#endif
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