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#include "multithreading.h"
#include <wx/utils.h>
//#include "windows.h"
//MessageBox(0, "hi", "", 0);
/*choreography:
------------- ---------------
|main thread| |worker thread|
------------- ---------------
1. Instantiation (Constructor)
-------------------------------
create thread
enter waiting state
2. waitUntilReady
-------------------------------
wait until thread is ready
3. Call execute
-------------------------------
send signal to start
start processing
update UI while thread works
finish processing
wait until main thread is ready to receive signal
receive signal
enter waiting state
4. Termination (Destructor)
-------------------------------
wait until thread is in wait state
set exit flag
signal thread to continue (and exit)
*/
class WorkerThread : public wxThread
{
friend class UpdateWhileExecuting;
public:
WorkerThread(UpdateWhileExecuting* handler) :
readyToBeginProcessing(),
beginProcessing(readyToBeginProcessing),
threadIsInitialized(false),
threadExitIsRequested(false),
threadHandler(handler)
{ }
~WorkerThread() {}
ExitCode Entry()
{
readyToBeginProcessing.Lock(); //this lock needs to be called IN the thread => calling it from constructor(Main thread) would be useless
sharedData.Enter();
threadIsInitialized = true;
sharedData.Leave();
while (true)
{
beginProcessing.Wait();
//no mutex needed in this context
if (threadExitIsRequested)
return 0;
//actual (long running) work is done in this method
threadHandler->longRunner();
threadHandler->readyToReceiveResult.Lock();
threadHandler->receivingResult.Signal(); // kind of a double notice that work is completed
threadHandler->workDone = true; // workaround for wxCondition bug (wxWidgets v2.8.9, signal might geht lost)
threadHandler->readyToReceiveResult.Unlock();
}
return 0;
}
private:
wxMutex readyToBeginProcessing;
wxCondition beginProcessing;
//shared data
wxCriticalSection sharedData;
bool threadIsInitialized;
bool threadExitIsRequested;
UpdateWhileExecuting* threadHandler;
};
UpdateWhileExecuting::UpdateWhileExecuting() :
readyToReceiveResult(),
receivingResult(readyToReceiveResult),
workDone(false)
{
//mutex needs to be initially locked for condition receivingResult to work properly
readyToReceiveResult.Lock();
theWorkerThread = new WorkerThread(this);
theWorkerThread->Create();
theWorkerThread->Run();
//wait until the thread has locked readyToBeginProcessing
bool threadInitialized = false;
while (!threadInitialized)
{
theWorkerThread->sharedData.Enter();
threadInitialized = theWorkerThread->threadIsInitialized;
theWorkerThread->sharedData.Leave();
wxMilliSleep(5);
} //-> it's not nice, but works and is no issue
}
UpdateWhileExecuting::~UpdateWhileExecuting()
{
//wait until thread is ready, then start and exit immediately
readyToReceiveResult.Unlock(); //avoid possible deadlock, when thread might be waiting to send the signal
theWorkerThread->readyToBeginProcessing.Lock();
//set flag to exit thread
theWorkerThread->threadExitIsRequested = true;
theWorkerThread->beginProcessing.Signal();
theWorkerThread->readyToBeginProcessing.Unlock();
//theWorkerThread deletes itself!
}
void UpdateWhileExecuting::waitUntilReady()
{
readyToReceiveResult.Unlock(); //avoid possible deadlock, when thread might be waiting to send the signal (if abort was pressed)
theWorkerThread->readyToBeginProcessing.Lock();
workDone = false; //no mutex needed here (worker thread that changes this variable is in waiting state)
}
// /|\ \|/ must be called directly after each other
void UpdateWhileExecuting::execute(StatusUpdater* statusUpdater)
{
readyToReceiveResult.Lock();
theWorkerThread->beginProcessing.Signal();
theWorkerThread->readyToBeginProcessing.Unlock();
while (receivingResult.WaitTimeout(UI_UPDATE_INTERVAL) == wxCOND_TIMEOUT)
{
statusUpdater->triggerUI_Refresh(true); //ATTENTION: Exception "AbortThisProcess" may be thrown here!!!
if (workDone == true) //workaround for a bug in wxWidgets v2.8.9 class wxCondition: signals might get lost
break; //no mutex for workDone needed here: it is changed only when maintread is in WaitTimeout()
}
}
|
