Use QWinOverlappedIoNotifier instead of QWinEventNotifier

The reasons of this change are following:

1) Implementation of QEventDispatcherWin32 has restrictions to
maximum quantity of QWinEvenNotifier instances in one thread.

Method QEventDispatcherWin32::registerEventNotifier() registers
the [MAXIMUM_WAIT_OBJECTS - 2] numbers of notifiers only. Where
the MAXIMUM_WAIT_OBJECTS that is equal to 64, since it is a part
of "Multiple-object Wait Functions" API:

http://msdn.microsoft.com/en-us/library/windows/desktop/ms687069%28v=vs.85%29.aspx

2) There is need to have three instances of QWinEventNotifier to
watch I/O events of each serial port.

It has limits to the maximum number of used serial ports and it
is [(MAXIMUM_WAIT_OBJECTS - 2) / 3] = 20 for the one thread.

3) Attempting to move or to resize a window of GUI application
lead to suspending of I/O events from serial port.

A long suspension can lead to overflowing of FIFO of device, so
the data can be lost.

All these shortcomings are resolved with QWinOverlappedIoNotifier,
which uses the "I/O Completion Ports" API:

http://msdn.microsoft.com/en-us/library/windows/desktop/aa365198%28v=vs.85%29.aspx

Tested on Windows 8 with the virtual (com0com), on-board and
the USB (PL2303) serial ports.

Task-number: QTBUG-34946
Change-Id: I879d939f86c8dcde0fe21a8d6267e81152822aa4
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>

1 files changed, 9 insertions, 14 deletions

diff --git a/src/serialport/qserialport_p.h b/src/serialport/qserialport_p.h
index 43a4f20..a62c3c5 100644
--- a/src/serialport/qserialport_p.h
+++ b/src/serialport/qserialport_p.h
@@ -101,7 +101,7 @@ QT_BEGIN_NAMESPACE
 #endif
 
 class QThread;
-class QWinEventNotifier;
+class QWinOverlappedIoNotifier;
 class QTimer;
 class QSocketNotifier;
 
@@ -148,7 +148,7 @@ public:
     bool setFlowControl(QSerialPort::FlowControl flowControl);
     bool setDataErrorPolicy(QSerialPort::DataErrorPolicy policy);
 
-    QSerialPort::SerialPortError decodeSystemError() const;
+    QSerialPort::SerialPortError decodeSystemError(int systemErrorCode = -1) const;
 
     qint64 bytesToWrite() const;
     qint64 writeData(const char *data, qint64 maxSize);
@@ -205,25 +205,22 @@ public:
     bool initialize();
     bool updateDcb();
     bool updateCommTimeouts();
-    qint64 handleOverlappedResult(int direction, OVERLAPPED &overlapped);
+    qint64 overlappedResult(OVERLAPPED *overlapped);
     void handleLineStatusErrors();
-    bool waitAnyEvent(int msecs, bool *timedOut, HANDLE *triggeredEvent);
+    OVERLAPPED *waitForNotified(int msecs);
 
-    bool _q_completeAsyncCommunication();
-    bool _q_completeAsyncRead();
-    bool _q_completeAsyncWrite();
+    bool completeAsyncCommunication(qint64 bytesTransferred);
+    bool completeAsyncRead(qint64 bytesTransferred);
+    bool completeAsyncWrite(qint64 bytesTransferred);
 
     bool startAsyncCommunication();
     bool startAsyncRead();
     bool _q_startAsyncWrite();
+    void _q_notified(DWORD numberOfBytes, DWORD errorCode, OVERLAPPED *overlapped);
 
     bool emulateErrorPolicy();
     void emitReadyRead();
 
-    bool setCommunicationNotificationEnabled(bool enable);
-    bool setReadNotificationEnabled(bool enable);
-    bool setWriteNotificationEnabled(bool enable);
-
     DCB currentDcb;
     DCB restoredDcb;
     COMMTIMEOUTS currentCommTimeouts;
@@ -234,9 +231,7 @@ public:
     bool readyReadEmitted;
     bool writeStarted;
     bool readStarted;
-    QWinEventNotifier *communicationNotifier;
-    QWinEventNotifier *readCompletionNotifier;
-    QWinEventNotifier *writeCompletionNotifier;
+    QWinOverlappedIoNotifier *notifier;
     QTimer *startAsyncWriteTimer;
     OVERLAPPED communicationOverlapped;
     OVERLAPPED readCompletionOverlapped;