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Rework toggling the state of read notifier on buffered socket

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Read notifications on a buffered socket are enabled all the time while
the socket is connected unless the buffer size limit is reached. To
enable the read notifier again, the user needs to read the data or
enlarge the buffer with a setReadBufferSize() call.

According to that scenario, it's very likely that the socket will
toggle the state of notifier twice (on->off->on) in one notification
cycle. Also, use of the readyRead() signal with a queued connection
leads to the same problem.

This patch prevents this unnecessary toggling by:
- unconditionally setting the notifier's state in setReadBufferSize();
- deferring the notification disabling in canReadNotification()
  to the next notification cycle.

Change-Id: I29df32f12c9c80a325373af86963e924817f2167
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
This commit is contained in:
Alex Trotsenko 2016-03-19 14:34:21 +02:00 committed by Joerg Bornemann
parent 765eab5103
commit 13abbea788
1 changed files with 7 additions and 15 deletions
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22
src/network/socket/qabstractsocket.cpp
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@ -691,6 +691,7 @@ bool QAbstractSocketPrivate::canReadNotification()
if (isBuffered) {
// Return if there is no space in the buffer
if (readBufferMaxSize && buffer.size() >= readBufferMaxSize) {
socketEngine->setReadNotificationEnabled(false);
#if defined (QABSTRACTSOCKET_DEBUG)
qDebug("QAbstractSocketPrivate::canReadNotification() buffer is full");
#endif
@ -708,11 +709,6 @@ bool QAbstractSocketPrivate::canReadNotification()
return false;
}
newBytes = buffer.size() - newBytes;
// If read buffer is full, disable the read socket notifier.
if (readBufferMaxSize && buffer.size() == readBufferMaxSize) {
socketEngine->setReadNotificationEnabled(false);
}
}
// Only emit readyRead() if there is data available.
@ -728,10 +724,6 @@ bool QAbstractSocketPrivate::canReadNotification()
return true;
}
// turn the socket engine off if we've reached the buffer size limit
if (socketEngine && isBuffered)
socketEngine->setReadNotificationEnabled(readBufferMaxSize == 0 || readBufferMaxSize > q->bytesAvailable());
return true;
}
@ -2784,12 +2776,12 @@ void QAbstractSocket::setReadBufferSize(qint64 size)
if (d->readBufferMaxSize == size)
return;
d->readBufferMaxSize = size;
if (!d->emittedReadyRead && d->socketEngine) {
// ensure that the read notification is enabled if we've now got
// room in the read buffer
// but only if we're not inside canReadNotification -- that will take care on its own
if ((size == 0 || d->buffer.size() < size) && d->state == QAbstractSocket::ConnectedState) // Do not change the notifier unless we are connected.
d->socketEngine->setReadNotificationEnabled(true);
// Do not change the notifier unless we are connected.
if (d->socketEngine && d->state == QAbstractSocket::ConnectedState) {
// Ensure that the read notification is enabled if we've now got
// room in the read buffer.
d->socketEngine->setReadNotificationEnabled(size == 0 || d->buffer.size() < size);
}
}