How to read Rotary encoder pulses?

[gazel]

Use QSocketNotifier on your /dev/button to be notified of changes in the button and only react when there actually is a change. There is no point in having a busy loop (and wasting cpu power and electricity) just for reading the button status.

Now i have tried both ways using processevents and Qsocketnotifier.
placing process events in a loop made the application heavy since CPU load
Qsocketnotifier works very good. now i have to check how fast the signals are caught.
here is the part for the code:

buttons_fd = ::open("/dev/buttons", 0);
        QSocketNotifier *sockerNotifier= new QSocketNotifier(buttons_fd,QSocketNotifier::Read,this);
        connect(sockerNotifier,SIGNAL(activated(int)),this,SLOT(notify()));

buttons_fd = ::open("/dev/buttons", 0);
        QSocketNotifier *sockerNotifier= new QSocketNotifier(buttons_fd,QSocketNotifier::Read,this);
        connect(sockerNotifier,SIGNAL(activated(int)),this,SLOT(notify()));

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thank you for your help