RtlUnicodeStringCbCopyStringNEx - NtDoc

#ifndef _NTSTRSAFE_H_INCLUDED_
#ifndef NTSTRSAFE_LIB_IMPL
#ifndef NTSTRSAFE_NO_UNICODE_STRING_FUNCTIONS
#ifndef NTSTRSAFE_NO_CB_FUNCTIONS

NTSTRSAFEDDI
RtlUnicodeStringCbCopyStringNEx(
        _Inout_ PUNICODE_STRING DestinationString,
        _In_ NTSTRSAFE_PCWSTR pszSrc,
        _In_ size_t cbToCopy,
        _Out_opt_ PUNICODE_STRING RemainingString,
        _In_ DWORD dwFlags)
{
    NTSTATUS status;
    wchar_t* pszDest;
    size_t cchDest;

    status = RtlUnicodeStringValidateDestWorker(DestinationString,
            &pszDest,
            &cchDest,
            NULL,
            NTSTRSAFE_UNICODE_STRING_MAX_CCH,
            dwFlags);

    if (NT_SUCCESS(status))
    {
        wchar_t* pszDestEnd = pszDest;
        size_t cchRemaining = cchDest;
        size_t cchNewDestLength = 0;
        size_t cchToCopy = cbToCopy / sizeof(wchar_t);

        status = RtlStringExValidateSrcW(&pszSrc, &cchToCopy, NTSTRSAFE_UNICODE_STRING_MAX_CCH, dwFlags);

        if (NT_SUCCESS(status))
        {
            if (dwFlags & (~STRSAFE_UNICODE_STRING_VALID_FLAGS))
            {
                status = STATUS_INVALID_PARAMETER;
            }
            else if (cchDest == 0)
            {
                // only fail if there was actually src data to copy
                if ((cchToCopy != 0) && (*pszSrc != L'\0'))
                {
                    if (pszDest == NULL)
                    {
                        status = STATUS_INVALID_PARAMETER;
                    }
                    else
                    {
                        status = STATUS_BUFFER_OVERFLOW;
                    }
                }
            }
            else
            {
                status = RtlWideCharArrayCopyStringWorker(pszDest,
                        cchDest,
                        &cchNewDestLength,
                        pszSrc,
                        cchToCopy);

                pszDestEnd = pszDest + cchNewDestLength;
                cchRemaining = cchDest - cchNewDestLength;

                if (NT_SUCCESS(status)              &&
                        (dwFlags & STRSAFE_FILL_BEHIND) &&
                        (cchRemaining != 0))
                {
                    // handle the STRSAFE_FILL_BEHIND flag
                    RtlUnicodeStringExHandleFill(pszDestEnd, cchRemaining, dwFlags);
                }
            }
        }

        if (!NT_SUCCESS(status)                                                                                      &&
                (dwFlags & (STRSAFE_NO_TRUNCATION | STRSAFE_FILL_ON_FAILURE | STRSAFE_ZERO_LENGTH_ON_FAILURE))  &&
                (cchDest != 0))
        {
            // handle the STRSAFE_NO_TRUNCATION, STRSAFE_FILL_ON_FAILURE, and STRSAFE_ZERO_LENGTH_ON_FAILURE flags
            RtlUnicodeStringExHandleOtherFlags(pszDest,
                    cchDest,
                    0,
                    &cchNewDestLength,
                    &pszDestEnd,
                    &cchRemaining,
                    dwFlags);
        }

        if (DestinationString)
        {
            // safe to multiply cchNewDestLength * sizeof(wchar_t) since cchDest < NTSTRSAFE_UNICODE_STRING_MAX_CCH and sizeof(wchar_t) is 2
            DestinationString->Length = (USHORT)(cchNewDestLength * sizeof(wchar_t));
        }

        if (NT_SUCCESS(status) || (status == STATUS_BUFFER_OVERFLOW))
        {
            if (RemainingString)
            {
                RemainingString->Length = 0;
                // safe to multiply cchRemaining * sizeof(wchar_t) since cchRemaining < NTSTRSAFE_UNICODE_STRING_MAX_CCH and sizeof(wchar_t) is 2
                RemainingString->MaximumLength = (USHORT)(cchRemaining * sizeof(wchar_t));
                RemainingString->Buffer = pszDestEnd;
            }
        }
    }

    return status;
}

#endif
#endif
#endif
#endif
View code on GitHub