From kde-devel  Fri Sep 19 06:31:43 2008
From: Thiago Macieira <thiago () kde ! org>
Date: Fri, 19 Sep 2008 06:31:43 +0000
To: kde-devel
Subject: Re: How to move large data inside a protocol over tcp using Qt/KDE?
Message-Id: <200809190831.43347.thiago () kde ! org>
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Matthew Woehlke wrote:
>Probably Qt polls the socket for you as part of the event loop, hence
>the readyRead signal. Assuming Qt supports non-blocking sockets (which
>it *really* should), you just keep trying to read until you get less
>bytes back than you asked for. Normally you take the little buffers and
>use them to progressively fill a larger buffer until you have an entire
>"message". At that point, you deal with the message, do a memmove to
>shift the buffer contents back to the beginning, and repeat until you
>have reason to stop.

That's how it works.

The sockets are non-blocking, always. And when the function doing the=20
reading (QAbstractSocketPrivate::canReadNotification()) is called, it=20
will read until it gets a -1 EWOULDBLOCK. When it gets that, it emits=20
readyRead().

So readyRead() is emitted once there's data to be read. Unlike a socket=20
polling, if you don't read the data, you won't be reminded again. The=20
signal emits again only when more data arrives.

=2D-=20
=A0 Thiago Macieira =A0- =A0thiago (AT) macieira.info - thiago (AT) kde.org
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