[Interest] Parsing data from serialport

[Konstantin Shegunov]

On Thu, Apr 4, 2019 at 5:46 PM Jérôme Godbout <godboutj at amotus.ca> wrote:

> It relief the main thread from read data all the time and keep a good
> reactivity. The dedicated thread try to read and can wait until something
> come along and once it found something that can be parsed, it emit his own
> signal that the main thread only have to handle into normal slot (will be
> queued, since it's not the same thread).
>
> But yeah, you can have the main thread do it and process the readyRead(),
> you main thread will perform the read and parsing. if you have any CRC and
> other things, this might be bad for application reactivity, depending on
> the amount of data flowing.
>
> -----Original Message-----
> From: Interest <interest-bounces at qt-project.org> On Behalf Of Paolo
> Angelelli
> Sent: April 4, 2019 10:19 AM
> To: interest at qt-project.org
> Subject: Re: [Interest] Parsing data from serialport
>
> What is the advantage of having such a continuous reading loop in a
> separate thread?
>
> I mean it as opposed to reacting to the readyRead() signal, and having a
> while(canReadLine()) { ... } in the reacting slot.
>

I think the point is that there's little reason to poll the serial port if
you can react to the event. Exactly what you'd do if you had a network
socket. Qt already does the heavy lifting for you, so you only need to
react to the signal and read as much as you want/need. Basically:

    QSerialPort * port;
    QObject::connect(port, &QIODevice::readyRead, port, [port] () -> void  {
        while (port->canReadLine())  {
            QByteArray data = port->readLine();
            // emit with data as argument and do the parsing
        }
    });

Whether you have the port in another thread or not is irrelevant in this
case, either can work fine (unlike your while-sleep loop).
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