我正在开发一种测试工具,用于从PC并行端口生成波形.此工具旨在生成任何波形图案,定时精度为ms,因此我使用Lua脚本定义波形图案,当用户单击[开始]按钮时,GUI启动新的QThread以运行脚本.
> pwrite：将数据写入并行端口.
> msleep：等待某个ms(使用nanosleep()实现)
> print：覆盖Lua默认打印功能,此功能会将消息附加到一个QTextEdit小部件.
当调用pwrite时,写入的数据存储在全局变量中,然后以20ms的间隔更新GUI以更新GUI上的并行端口数据. (这20ms间隔刷新不是一个好的设计,但我还没弄清楚如何在数据改变时使用信号进行GUI更新).
该工具现在基本上是功能性的.波形输出没有问题,但并行端口数据更新有一些问题：
当Lua调用msleep时,GUI线程停止,并行端口数据仅在msleep结束后更新.
所以我的问题是：
>如何实现sleep方法,以便它不会阻止GUI线程更新？
>如何实现pwrite,以便GUI在写入数据发生变化时可以接收信号来更新并行端口数据？
程序GUI如下链接：
相关代码：
/* common.cpp file */
int L_MSleep(lua_State* l)
{
int milisec=0;
struct timespec req={0,0};
time_t sec;
milisec=luaL_optint(l,1,0); // obtain parameter
if (milisec==0)
return 0;
sec=(int)(milisec/1000);
milisec=milisec-(sec*1000);
req.tv_sec=sec;
req.tv_nsec=milisec*1000000L;
while(nanosleep(&req,&req)==-1)
continue;
return 1;
}
/* LuaRunner.cpp file */
LuaRunner::LuaRunner(QObject *parent) :
QThread(parent)
{
runlua = false;
}
void LuaRunner::run()
{
QString err = "";
runlua = true;
LUA_RunScript(this->ff,err);
runlua = false;
if(err != "")
{
emit errorMessage(err);
}
}
int LuaRunner::LUA_RunScript(QString ff,QString &err)
{
L = lua_open();
luaL_openlibs(L);
if (luaL_loadfile(L,ff.toAscii()) || lua_pcall(L,0))
{
err = QString(lua_tostring(L,-1));
return -1;
}
lua_register(L,"ssleep",L_SSleep);
lua_register(L,"msleep",L_MSleep);
lua_register(L,"pwrite",L_PortWrite);
lua_register(L,"print",L_Log);
lua_getglobal(L,"dotest");
if (!lua_isfunction(L,-1))
{
err = QString("Test function(dotest) should be a function");
return -1;
}
if(lua_pcall(L,-1));
return -1;
}
lua_close(L);
return 0;
}
解决方法
您正确地在专用线程中运行Lua脚本.这是正确的方法 – 差不多.每次要运行脚本时都要重新启动线程.那是错的.您还从LUA线程访问GUI线程中的数据,而不进行任何同步.这不好. Qt以信号和插槽之间的排队连接的形式提供了一种出色的机制.当signal-slot调用通过线程边界时,参数将被包装在QEvent中并异步传递给目标QObject.在每个线程中,事件传递是序列化的,因此您不必担心数据损坏等.
这是应该如何做的：
// LUAObject.h
#include <QObject>
class LUAObject : public QObject
{
Q_OBJECT
public:
LUAObject(QObject * parent = 0);
public slots:
void setScript(const QString &);
void runScript();
void stop();
signals:
void hasError(const QString &);
void finished();
void hasParallelData(int);
void hasMessage(const QString &);
private:
QString script;
bool stop;
}
// LUAObject.cpp
// whatever Lua includes you need etc
LUAObject::LUAObject(QObject* p) : QObject(p)
{}
void LUAObject::stop() { stopped = true; }
void LUAObject::setScript(const QString & scr)
{ script = scr; }
int L_PWrite(lua_State* l)
{
int data = luaL_optint(l,-1);
if (data != -1) {
// access the parallel port HERE,NOT in the GUI thread!
emit hasParallelData(luaL_optint(l,0));
}
return 0;
}
// returns a bool - true means we are stopped and should exit
int L_MSleep(lua_State* l)
{
int ms = luaL_optint(l,-1);
if (ms == -1) return 0;
QApplication::processEvents(QEventLoop::WaitForMoreEvents,ms);
lua_pushBoolean(l,stopped); // event processing would run the stop() slot call
return 1;
}
int L_SSleep(lua_State* l)
{
int secs = luaL_optint(l,-1);
if (secs == -1) return 0;
QApplication::processEvents(QEventLoop::WaitForMoreEvents,secs*1000);
lua_pushBoolean(l,stopped); // event processing would run the stop() slot call
return 1;
}
int L_Log(lua_State* l)
{
const char * msg = luaL_optstring(l,0);
if (!msg) return 0;
emit hasMessage(msg);
return 0;
}
class Lua // RAII
{
public:
explicit Lua(lua_state * l) : L(l) {}
~Lua() { lua_close(L); }
operator lua_state*() const { return L; }
private:
lua_state * L;
Q_DISABLE_COPY(LUA)
};
LUAObject::runScript()
{
stopped = false;
Lua L(lua_open());
luaL_openlibs(L);
if (luaL_loadbuffer(L,script.toAscii().constData(),script.length(),"script") || lua_pcall(L,0))
{
emit hasError(lua_tostring(L,-1));
return;
}
lua_register(L,L_SSleep);
lua_register(L,L_MSleep);
lua_register(L,L_PWrite);
lua_register(L,L_Log);
lua_getglobal(L,"dotest");
if (!lua_isfunction(L,-1))
{
emit hasError("Test function(dotest) should be a function");
return;
}
if(lua_pcall(L,0))
{
emit hasError(lua_tostring(L,-1));
return;
}
emit finished();
}
// main.cpp
#include <QApplication>
#include <QMetaMethod>
#include "LUAObject.h"
...
int main(int argc,char** argv)
{
QApplication(argc,argv);
MainWindow window;
...
QThread thread;
LUAObject lua;
thread.start(QThread::TimeCriticalPriority);
lua.moveToThread(&thread);
...
// NOTE: you can ONLY connect to LUAObject slots,you CANNOT call them
// directly since it runs in a separate thread!
connect(&window,SIGNAL(startClicked()),&lua,SLOT(runScript());
connect(&lua,SIGNAL(hasError(QString)),&window,SLOT(luaError(QString)));
...
window.show();
int rc = qApp->exec();
QMetaObject::invokeMethod(&lua,SLOT(stop())); // cross-thread slot invocation
thread.exit();
thread.wait();
return rc;
}
我将UI的实现留给您的想象力.请注意,它是未经测试的代码.它可能会让我知道的所有东西都爆炸.
