让我们使用QStateMachine
让这变得简单。让我们回想一下您希望这样的代码是什么样子的:
Serial->write("boot", 1000);
Serial->waitForKeyword("boot successful");
Serial->sendFile("image.dat");
让我们把它放在一个类中,该类对于程序员可能处于的每个状态都有显式的状态成员。我们还将有动作生成器send
, expect
等等,将给定的操作附加到状态。
// https://github.com/KubaO/stackoverflown/tree/master/questions/comm-commands-32486198
#include <QtWidgets>
#include <private/qringbuffer_p.h>
#include <type_traits>
[...]
class Programmer : public StatefulObject {
Q_OBJECT
AppPipe m_port { nullptr, QIODevice::ReadWrite, this };
State s_boot { &m_mach, "s_boot" },
s_send { &m_mach, "s_send" };
FinalState s_ok { &m_mach, "s_ok" },
s_failed { &m_mach, "s_failed" };
public:
Programmer(QObject * parent = 0) : StatefulObject(parent) {
connectSignals();
m_mach.setInitialState(&s_boot);
send (&s_boot, &m_port, "boot\n");
expect(&s_boot, &m_port, "boot successful", &s_send, 1000, &s_failed);
send (&s_send, &m_port, ":HULLOTHERE\n:00000001FF\n");
expect(&s_send, &m_port, "load successful", &s_ok, 1000, &s_failed);
}
AppPipe & pipe() { return m_port; }
};
对于程序员来说,这是功能齐全、完整的代码!完全异步、非阻塞,并且它还可以处理超时。
可以拥有即时生成状态的基础设施,这样您就不必手动创建所有状态。如果您有明确的状态,代码会小得多,恕我直言,更容易理解。只有对于具有 50-100 多个状态的复杂通信协议,摆脱显式命名状态才有意义。
The AppPipe
是一个简单的进程内双向管道,可以用作真实串行端口的替代品:
// See http://stackoverflow.com/a/32317276/1329652
/// A simple point-to-point intra-process pipe. The other endpoint can live in any
/// thread.
class AppPipe : public QIODevice {
[...]
};
The StatefulObject
拥有一个状态机,一些用于监视状态机进度的基本信号,以及connectSignals
用于连接信号与状态的方法:
class StatefulObject : public QObject {
Q_OBJECT
Q_PROPERTY (bool running READ isRunning NOTIFY runningChanged)
protected:
QStateMachine m_mach { this };
StatefulObject(QObject * parent = 0) : QObject(parent) {}
void connectSignals() {
connect(&m_mach, &QStateMachine::runningChanged, this, &StatefulObject::runningChanged);
for (auto state : m_mach.findChildren<QAbstractState*>())
QObject::connect(state, &QState::entered, this, [this, state]{
emit stateChanged(state->objectName());
});
}
public:
Q_SLOT void start() { m_mach.start(); }
Q_SIGNAL void runningChanged(bool);
Q_SIGNAL void stateChanged(const QString &);
bool isRunning() const { return m_mach.isRunning(); }
};
The State
and FinalState
是 Qt 3 风格的简单命名状态包装器。它们允许我们一次性声明状态并为其命名。
template <class S> struct NamedState : S {
NamedState(QState * parent, const char * name) : S(parent) {
this->setObjectName(QLatin1String(name));
}
};
typedef NamedState<QState> State;
typedef NamedState<QFinalState> FinalState;
动作生成器也非常简单。动作生成器的含义是“当进入给定状态时做某事”。要执行操作的状态始终作为第一个参数给出。第二个和后续参数特定于给定操作。有时,一个动作可能也需要一个目标状态,例如如果成功或失败。
void send(QAbstractState * src, QIODevice * dev, const QByteArray & data) {
QObject::connect(src, &QState::entered, dev, [dev, data]{
dev->write(data);
});
}
QTimer * delay(QState * src, int ms, QAbstractState * dst) {
auto timer = new QTimer(src);
timer->setSingleShot(true);
timer->setInterval(ms);
QObject::connect(src, &QState::entered, timer, static_cast<void (QTimer::*)()>(&QTimer::start));
QObject::connect(src, &QState::exited, timer, &QTimer::stop);
src->addTransition(timer, SIGNAL(timeout()), dst);
return timer;
}
void expect(QState * src, QIODevice * dev, const QByteArray & data, QAbstractState * dst,
int timeout = 0, QAbstractState * dstTimeout = nullptr)
{
addTransition(src, dst, dev, SIGNAL(readyRead()), [dev, data]{
return hasLine(dev, data);
});
if (timeout) delay(src, timeout, dstTimeout);
}
The hasLine
测试只是检查可以从给定针的设备读取的所有行。这对于这个简单的通信协议来说效果很好。如果您的通信更加复杂,您将需要更复杂的机器。即使您找到了针,也有必要阅读所有行。那是因为这个测试是从readyRead
信号,并且在该信号中您必须读取满足所选标准的所有数据。这里,标准是数据形成一条完整的线。
static bool hasLine(QIODevice * dev, const QByteArray & needle) {
auto result = false;
while (dev->canReadLine()) {
auto line = dev->readLine();
if (line.contains(needle)) result = true;
}
return result;
}
使用默认 API 向状态添加受保护的转换有点麻烦,因此我们将对其进行包装以使其更易于使用,并保持上面的操作生成器的可读性:
template <typename F>
class GuardedSignalTransition : public QSignalTransition {
F m_guard;
protected:
bool eventTest(QEvent * ev) Q_DECL_OVERRIDE {
return QSignalTransition::eventTest(ev) && m_guard();
}
public:
GuardedSignalTransition(const QObject * sender, const char * signal, F && guard) :
QSignalTransition(sender, signal), m_guard(std::move(guard)) {}
GuardedSignalTransition(const QObject * sender, const char * signal, const F & guard) :
QSignalTransition(sender, signal), m_guard(guard) {}
};
template <typename F> static GuardedSignalTransition<F> *
addTransition(QState * src, QAbstractState *target,
const QObject * sender, const char * signal, F && guard) {
auto t = new GuardedSignalTransition<typename std::decay<F>::type>
(sender, signal, std::forward<F>(guard));
t->setTargetState(target);
src->addTransition(t);
return t;
}
就是这样 - 如果您有一个真正的设备,这就是您所需要的。由于我没有您的设备,我将创建另一个StatefulObject
模拟假定的设备行为:
class Device : public StatefulObject {
Q_OBJECT
AppPipe m_dev { nullptr, QIODevice::ReadWrite, this };
State s_init { &m_mach, "s_init" },
s_booting { &m_mach, "s_booting" },
s_firmware { &m_mach, "s_firmware" };
FinalState s_loaded { &m_mach, "s_loaded" };
public:
Device(QObject * parent = 0) : StatefulObject(parent) {
connectSignals();
m_mach.setInitialState(&s_init);
expect(&s_init, &m_dev, "boot", &s_booting);
delay (&s_booting, 500, &s_firmware);
send (&s_firmware, &m_dev, "boot successful\n");
expect(&s_firmware, &m_dev, ":00000001FF", &s_loaded);
send (&s_loaded, &m_dev, "load successful\n");
}
Q_SLOT void stop() { m_mach.stop(); }
AppPipe & pipe() { return m_dev; }
};
现在让我们把这一切都很好地可视化。我们将有一个带有文本浏览器的窗口,显示通信内容。下面是启动/停止编程器或设备的按钮,以及指示模拟设备和编程器状态的标签:
int main(int argc, char ** argv) {
using Q = QObject;
QApplication app{argc, argv};
Device dev;
Programmer prog;
QWidget w;
QGridLayout grid{&w};
QTextBrowser comms;
QPushButton devStart{"Start Device"}, devStop{"Stop Device"},
progStart{"Start Programmer"};
QLabel devState, progState;
grid.addWidget(&comms, 0, 0, 1, 3);
grid.addWidget(&devState, 1, 0, 1, 2);
grid.addWidget(&progState, 1, 2);
grid.addWidget(&devStart, 2, 0);
grid.addWidget(&devStop, 2, 1);
grid.addWidget(&progStart, 2, 2);
devStop.setDisabled(true);
w.show();
我们将连接设备和程序员的AppPipe
s。我们还将可视化程序员发送和接收的内容:
dev.pipe().addOther(&prog.pipe());
prog.pipe().addOther(&dev.pipe());
Q::connect(&prog.pipe(), &AppPipe::hasOutgoing, &comms, [&](const QByteArray & data){
comms.append(formatData(">", "blue", data));
});
Q::connect(&prog.pipe(), &AppPipe::hasIncoming, &comms, [&](const QByteArray & data){
comms.append(formatData("<", "green", data));
});
最后,我们将连接按钮和标签:
Q::connect(&devStart, &QPushButton::clicked, &dev, &Device::start);
Q::connect(&devStop, &QPushButton::clicked, &dev, &Device::stop);
Q::connect(&dev, &Device::runningChanged, &devStart, &QPushButton::setDisabled);
Q::connect(&dev, &Device::runningChanged, &devStop, &QPushButton::setEnabled);
Q::connect(&dev, &Device::stateChanged, &devState, &QLabel::setText);
Q::connect(&progStart, &QPushButton::clicked, &prog, &Programmer::start);
Q::connect(&prog, &Programmer::runningChanged, &progStart, &QPushButton::setDisabled);
Q::connect(&prog, &Programmer::stateChanged, &progState, &QLabel::setText);
return app.exec();
}
#include "main.moc"
The Programmer
and Device
可以存在于任何线程中。我将它们留在主线程中,因为没有理由将它们移出,但是您可以将它们放入专用线程中,或者将它们放入自己的线程中,或者放入与其他对象共享的线程中,等等。它是完全透明的,因为AppPipe
支持跨线程通信。如果QSerialPort
被用来代替AppPipe
。重要的是每个实例QIODevice
仅从一个线程使用。其他一切都是通过信号/槽连接发生的。
例如。如果你想要Programmer
要生活在专用线程中,您需要在以下位置添加以下内容main
:
// fix QThread brokenness
struct Thread : QThread { ~Thread() { quit(); wait(); } };
Thread progThread;
prog.moveToThread(&progThread);
progThread.start();
一个小助手格式化数据以使其更易于阅读:
static QString formatData(const char * prefix, const char * color, const QByteArray & data) {
auto text = QString::fromLatin1(data).toHtmlEscaped();
if (text.endsWith('\n')) text.truncate(text.size() - 1);
text.replace(QLatin1Char('\n'), QString::fromLatin1("<br/>%1 ").arg(QLatin1String(prefix)));
return QString::fromLatin1("<font color=\"%1\">%2 %3</font><br/>")
.arg(QLatin1String(color)).arg(QLatin1String(prefix)).arg(text);
}