RtlStringCchPrintfExA - NtDoc

#ifndef _NTSTRSAFE_H_INCLUDED_
#ifndef NTSTRSAFE_LIB_IMPL
#ifndef _M_CEE_PURE
#ifndef NTSTRSAFE_NO_CCH_FUNCTIONS

NTSTRSAFEDDI
    RtlStringCchPrintfExA(
            _Out_writes_(cchDest) _Always_(_Post_z_) NTSTRSAFE_PSTR pszDest,
            _In_ size_t cchDest,
            _Outptr_opt_result_buffer_(*pcchRemaining) NTSTRSAFE_PSTR* ppszDestEnd,
            _Out_opt_ size_t* pcchRemaining,
            _In_ DWORD dwFlags,
            _In_ _Printf_format_string_ NTSTRSAFE_PCSTR pszFormat,
            ...)
{
    NTSTATUS status;

    status = RtlStringExValidateDestA(pszDest, cchDest, NTSTRSAFE_MAX_CCH, dwFlags);

    if (NT_SUCCESS(status))
    {
        NTSTRSAFE_PSTR pszDestEnd = pszDest;
        size_t cchRemaining = cchDest;

        status = RtlStringExValidateSrcA(&pszFormat, NULL, NTSTRSAFE_MAX_CCH, dwFlags);

        if (NT_SUCCESS(status))
        {
            if (dwFlags & (~STRSAFE_VALID_FLAGS))
            {
                status = STATUS_INVALID_PARAMETER;

                if (cchDest != 0)
                {
                    *pszDest = '\0';
                }
            }
            else if (cchDest == 0)
            {
                // only fail if there was actually a non-empty format string
                if (*pszFormat != '\0')
                {
                    if (pszDest == NULL)
                    {
                        status = STATUS_INVALID_PARAMETER;
                    }
                    else
                    {
                        status = STATUS_BUFFER_OVERFLOW;
                    }
                }
            }
            else
            {
                size_t cchNewDestLength = 0;
                va_list argList;

                va_start(argList, pszFormat);

                status = RtlStringVPrintfWorkerA(pszDest,
                        cchDest,
                        &cchNewDestLength,
                        pszFormat,
                        argList);

                va_end(argList);

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

                if (NT_SUCCESS(status)                           &&
                        (dwFlags & STRSAFE_FILL_BEHIND_NULL)    &&
                        (cchRemaining > 1))
                {
                    size_t cbRemaining;

                    // safe to multiply cchRemaining * sizeof(char) since cchRemaining < NTSTRSAFE_MAX_CCH and sizeof(char) is 1
                    cbRemaining = cchRemaining * sizeof(char);

                    // handle the STRSAFE_FILL_BEHIND_NULL flag
                    RtlStringExHandleFillBehindNullA(pszDestEnd, cbRemaining, dwFlags);
                }
            }
        }
        else
        {
            if (cchDest != 0)
            {
                *pszDest = '\0';
            }
        }

        if (!NT_SUCCESS(status)                                                                              &&
                (dwFlags & (STRSAFE_NO_TRUNCATION | STRSAFE_FILL_ON_FAILURE | STRSAFE_NULL_ON_FAILURE)) &&
                (cchDest != 0))
        {
            size_t cbDest;

            // safe to multiply cchDest * sizeof(char) since cchDest < NTSTRSAFE_MAX_CCH and sizeof(char) is 1
            cbDest = cchDest * sizeof(char);

            // handle the STRSAFE_FILL_ON_FAILURE, STRSAFE_NULL_ON_FAILURE, and STRSAFE_NO_TRUNCATION flags
            RtlStringExHandleOtherFlagsA(pszDest,
                    cbDest,
                    0,
                    &pszDestEnd,
                    &cchRemaining,
                    dwFlags);
        }

        if (NT_SUCCESS(status) || (status == STATUS_BUFFER_OVERFLOW))
        {
            if (ppszDestEnd)
            {
                *ppszDestEnd = pszDestEnd;
            }

            if (pcchRemaining)
            {
                *pcchRemaining = cchRemaining;
            }
        }
    }
    else if (cchDest > 0)
    {
        *pszDest = '\0';
    }

    return status;
}

#endif
#endif
#endif
#endif
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