Minimize number of system calls at opening

Currently, the method QSP::open() several times calls the system
functions to get/set of DCB/termios structures for each parameter.
It is not rational and should be minimized as possible, in ideally
to once executed.

Change-Id: If1f308176a82f3c8896fc648bf656f089e099f3f
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>

1 files changed, 104 insertions, 68 deletions

diff --git a/src/serialport/qserialport_win.cpp b/src/serialport/qserialport_win.cpp
index 7cbb81d4..f4f8317b 100644
--- a/src/serialport/qserialport_win.cpp
+++ b/src/serialport/qserialport_win.cpp
@@ -81,6 +81,94 @@
 
 QT_BEGIN_NAMESPACE
 
+static inline void qt_set_common_props(DCB *dcb)
+{
+    dcb->fBinary = TRUE;
+    dcb->fAbortOnError = FALSE;
+    dcb->fNull = FALSE;
+    dcb->fErrorChar = FALSE;
+
+    if (dcb->fDtrControl == DTR_CONTROL_HANDSHAKE)
+        dcb->fDtrControl = DTR_CONTROL_DISABLE;
+}
+
+static inline void qt_set_baudrate(DCB *dcb, qint32 baudrate)
+{
+    dcb->BaudRate = baudrate;
+}
+
+static inline void qt_set_databits(DCB *dcb, QSerialPort::DataBits databits)
+{
+    dcb->ByteSize = databits;
+}
+
+static inline void qt_set_parity(DCB *dcb, QSerialPort::Parity parity)
+{
+    dcb->fParity = TRUE;
+    switch (parity) {
+    case QSerialPort::NoParity:
+        dcb->Parity = NOPARITY;
+        dcb->fParity = FALSE;
+        break;
+    case QSerialPort::OddParity:
+        dcb->Parity = ODDPARITY;
+        break;
+    case QSerialPort::EvenParity:
+        dcb->Parity = EVENPARITY;
+        break;
+    case QSerialPort::MarkParity:
+        dcb->Parity = MARKPARITY;
+        break;
+    case QSerialPort::SpaceParity:
+        dcb->Parity = SPACEPARITY;
+        break;
+    default:
+        dcb->Parity = NOPARITY;
+        dcb->fParity = FALSE;
+        break;
+    }
+}
+
+static inline void qt_set_stopbits(DCB *dcb, QSerialPort::StopBits stopbits)
+{
+    switch (stopbits) {
+    case QSerialPort::OneStop:
+        dcb->StopBits = ONESTOPBIT;
+        break;
+    case QSerialPort::OneAndHalfStop:
+        dcb->StopBits = ONE5STOPBITS;
+        break;
+    case QSerialPort::TwoStop:
+        dcb->StopBits = TWOSTOPBITS;
+        break;
+    default:
+        dcb->StopBits = ONESTOPBIT;
+        break;
+    }
+}
+
+static inline void qt_set_flowcontrol(DCB *dcb, QSerialPort::FlowControl flowcontrol)
+{
+    dcb->fInX = FALSE;
+    dcb->fOutX = FALSE;
+    dcb->fOutxCtsFlow = FALSE;
+    dcb->fRtsControl = RTS_CONTROL_DISABLE;
+    switch (flowcontrol) {
+    case QSerialPort::NoFlowControl:
+        break;
+    case QSerialPort::SoftwareControl:
+        dcb->fInX = TRUE;
+        dcb->fOutX = TRUE;
+        break;
+    case QSerialPort::HardwareControl:
+        dcb->fOutxCtsFlow = TRUE;
+        dcb->fRtsControl = RTS_CONTROL_HANDSHAKE;
+        break;
+    default:
+        break;
+    }
+}
+
 bool QSerialPortPrivate::open(QIODevice::OpenMode mode)
 {
     DWORD desiredAccess = 0;
@@ -319,7 +407,8 @@ bool QSerialPortPrivate::setBaudRate(qint32 baudRate, QSerialPort::Directions di
     if (!getDcb(&dcb))
         return false;
 
-    dcb.BaudRate = baudRate;
+    qt_set_baudrate(&dcb, baudRate);
+
     return setDcb(&dcb);
 }
 
@@ -329,7 +418,8 @@ bool QSerialPortPrivate::setDataBits(QSerialPort::DataBits dataBits)
     if (!getDcb(&dcb))
         return false;
 
-    dcb.ByteSize = dataBits;
+    qt_set_databits(&dcb, dataBits);
+
     return setDcb(&dcb);
 }
 
@@ -339,29 +429,8 @@ bool QSerialPortPrivate::setParity(QSerialPort::Parity parity)
     if (!getDcb(&dcb))
         return false;
 
-    dcb.fParity = TRUE;
-    switch (parity) {
-    case QSerialPort::NoParity:
-        dcb.Parity = NOPARITY;
-        dcb.fParity = FALSE;
-        break;
-    case QSerialPort::OddParity:
-        dcb.Parity = ODDPARITY;
-        break;
-    case QSerialPort::EvenParity:
-        dcb.Parity = EVENPARITY;
-        break;
-    case QSerialPort::MarkParity:
-        dcb.Parity = MARKPARITY;
-        break;
-    case QSerialPort::SpaceParity:
-        dcb.Parity = SPACEPARITY;
-        break;
-    default:
-        dcb.Parity = NOPARITY;
-        dcb.fParity = FALSE;
-        break;
-    }
+    qt_set_parity(&dcb, parity);
+
     return setDcb(&dcb);
 }
 
@@ -371,20 +440,8 @@ bool QSerialPortPrivate::setStopBits(QSerialPort::StopBits stopBits)
     if (!getDcb(&dcb))
         return false;
 
-    switch (stopBits) {
-    case QSerialPort::OneStop:
-        dcb.StopBits = ONESTOPBIT;
-        break;
-    case QSerialPort::OneAndHalfStop:
-        dcb.StopBits = ONE5STOPBITS;
-        break;
-    case QSerialPort::TwoStop:
-        dcb.StopBits = TWOSTOPBITS;
-        break;
-    default:
-        dcb.StopBits = ONESTOPBIT;
-        break;
-    }
+    qt_set_stopbits(&dcb, stopBits);
+
     return setDcb(&dcb);
 }
 
@@ -394,24 +451,8 @@ bool QSerialPortPrivate::setFlowControl(QSerialPort::FlowControl flowControl)
     if (!getDcb(&dcb))
         return false;
 
-    dcb.fInX = FALSE;
-    dcb.fOutX = FALSE;
-    dcb.fOutxCtsFlow = FALSE;
-    dcb.fRtsControl = RTS_CONTROL_DISABLE;
-    switch (flowControl) {
-    case QSerialPort::NoFlowControl:
-        break;
-    case QSerialPort::SoftwareControl:
-        dcb.fInX = TRUE;
-        dcb.fOutX = TRUE;
-        break;
-    case QSerialPort::HardwareControl:
-        dcb.fOutxCtsFlow = TRUE;
-        dcb.fRtsControl = RTS_CONTROL_HANDSHAKE;
-        break;
-    default:
-        break;
-    }
+    qt_set_flowcontrol(&dcb, flowControl);
+
     return setDcb(&dcb);
 }
 
@@ -623,17 +664,12 @@ inline bool QSerialPortPrivate::initialize()
 
     restoredDcb = dcb;
 
-    dcb.fBinary = TRUE;
-    dcb.fInX = FALSE;
-    dcb.fOutX = FALSE;
-    dcb.fAbortOnError = FALSE;
-    dcb.fNull = FALSE;
-    dcb.fErrorChar = FALSE;
-
-    if (dcb.fDtrControl == DTR_CONTROL_HANDSHAKE)
-        dcb.fDtrControl = DTR_CONTROL_DISABLE;
-
-    dcb.BaudRate = inputBaudRate;
+    qt_set_common_props(&dcb);
+    qt_set_baudrate(&dcb, inputBaudRate);
+    qt_set_databits(&dcb, dataBits);
+    qt_set_parity(&dcb, parity);
+    qt_set_stopbits(&dcb, stopBits);
+    qt_set_flowcontrol(&dcb, flowControl);
 
     if (!setDcb(&dcb))
         return false;