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Archived:Change a synchronous Symbian C++ method to act like an asynchronous one

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==See also==
 
==See also==
[[Using CActiveSchedulerWait]]
+
[[Archived:Using CActiveSchedulerWait]]
  
[[Change asynchronous method into synchronous]]
+
[[Archived:Changing asynchronous method to synchronous in Symbian C++]]

Latest revision as of 03:30, 29 June 2012

Archived.pngArchived: This article is archived because it is not considered relevant for third-party developers creating commercial solutions today. If you think this article is still relevant, let us know by adding the template {{ReviewForRemovalFromArchive|user=~~~~|write your reason here}}.

Article Metadata
Tested with
Devices(s): Nokia N95
Compatibility
Platform(s): S60 3rd Edition, MR
S60 3rd Edition (initial release)
Article
Keywords: CActiveSchedulerWait, CActive, TRequestStatus
Created: tepaa (27 May 2008)
Last edited: hamishwillee (29 Jun 2012)

Contents

[edit] Overview

This code snippet shows how to modify a synchronous method to behave like an asynchronous method.

There are two different methods:

  • void LongRunningTaskL(TInt& aResult) is a synchronous method that acts like an asynchronous one but returns when the task has been completed.
  • void LongRunningTaskL(MMySynchronousTaskDone* aObserver) is a synchronous method that acts like an asynchronous method. Note that the method returns right after it has been started and notifies of task completion via MMySynchronousTaskDone.

[edit] MMP file

The following capabilities and libraries are required:

CAPABILITY None
LIBRARY euser.lib

[edit] Header

#include <e32base.h>
 
class MMySynchronousTaskDone
{
public:
virtual void TaskDone(TInt aRet) = 0;
};
 
class CMySynchronousClass : public CActive
{
enum EState
{
EIdle = 0,
EStarted,
ERunningTask1,
ERunningTask2,
ERunningTask3,
EEnd
};
 
public:
static CMySynchronousClass* NewL();
virtual ~CMySynchronousClass();
 
public:
// Synchronous method that acts like an asynchronous one
// but returns when task completed.
void LongRunningTaskL(TInt& aResult);
 
// Synchronous method that acts like an asynchronous one
// note that the method returns right after it has been started
// and notifies of task completion via MMySynchronousTaskDone
void LongRunningTaskL(MMySynchronousTaskDone* aObserver);
 
private: // From CActive
void RunL();
TInt RunError(TInt aError);
void DoCancel();
 
private:
CMySynchronousClass();
void ConstructL();
void GiveTimeToOthers();
void DoLongRunningTask();
 
private:
EState iRunningState;
CActiveSchedulerWait* iSchedulerWait;
TInt iSomeLongRunningTask;
MMySynchronousTaskDone* iObserver;
};

[edit] Source

CMySynchronousClass* CMySynchronousClass::NewL()
{
CMySynchronousClass* self = new (ELeave) CMySynchronousClass();
CleanupStack::PushL( self );
self->ConstructL();
CleanupStack::Pop();
return self;
}
 
CMySynchronousClass::CMySynchronousClass():CActive(EPriorityStandard)
{
}
 
void CMySynchronousClass::ConstructL()
{
CActiveScheduler::Add(this);
iSchedulerWait = new (ELeave) CActiveSchedulerWait();
}
 
CMySynchronousClass::~CMySynchronousClass()
{
Cancel();
delete iSchedulerWait;
}
 
// This method returns after synchronous task completion
void CMySynchronousClass::LongRunningTaskL(TInt& aResult)
{
if (iRunningState == EIdle)
{
iSomeLongRunningTask = 0;
iRunningState = EStarted;
 
GiveTimeToOthers();
iSchedulerWait->Start();
 
// Continues here after CActiveSchedulerWait::AsyncComplete() is called
if (iStatus.Int() != KErrNone)
{
User::Leave(iStatus.Int());
}
aResult = iSomeLongRunningTask;
}
else
{
User::Leave(KErrNotReady);
}
}
 
// This method returns right after the synchronous task is started
void CMySynchronousClass::LongRunningTaskL(MMySynchronousTaskDone* aObserver)
{
if (iRunningState == EIdle)
{
iObserver = aObserver;
iSomeLongRunningTask = 0;
iRunningState = EStarted;
GiveTimeToOthers();
}
else
{
User::Leave(KErrNotReady);
}
 
}
 
void CMySynchronousClass::DoLongRunningTask()
{
// TODO: Here is a synchronous method call.
// Try to split call in small parts.
iSomeLongRunningTask++;
}
 
void CMySynchronousClass::GiveTimeToOthers()
{
TRequestStatus* status = &iStatus;
User::RequestComplete( status, KErrNone );
SetActive();
}
 
void CMySynchronousClass::RunL()
{
switch (iRunningState)
{
case EIdle:
{
break;
}
case EStarted:
{
iRunningState = ERunningTask1;
// TODO: Call synchronous method
DoLongRunningTask();
 
GiveTimeToOthers();
break;
}
case ERunningTask1:
{
iRunningState = ERunningTask2;
// TODO: Call synchronous method
DoLongRunningTask();
 
GiveTimeToOthers();
break;
}
case ERunningTask2:
{
iRunningState = ERunningTask3;
// TODO: Call synchronous method
DoLongRunningTask();
 
GiveTimeToOthers();
break;
}
case ERunningTask3:
{
iRunningState = EEnd;
// TODO: Do some end processing if needed
 
GiveTimeToOthers();
break;
}
case EEnd:
{
// Done
iRunningState = EIdle;
if (iObserver)
{
iObserver->TaskDone(iSomeLongRunningTask);
}
if (iSchedulerWait->IsStarted())
{
iSchedulerWait->AsyncStop();
}
break;
}
default:
{
if (iSchedulerWait->IsStarted())
{
iSchedulerWait->AsyncStop();
}
break;
}
};
}
 
TInt CMySynchronousClass::RunError(TInt aError)
{
if (iObserver)
{
iObserver->TaskDone(aError);
}
return KErrNone;
}
 
void CMySynchronousClass::DoCancel()
{
if (iObserver)
{
iObserver->TaskDone(KErrCancel);
}
if (iSchedulerWait->IsStarted())
{
iSchedulerWait->AsyncStop();
}
}

[edit] Postconditions

The synchronous method acts like an asynchronous one.

[edit] See also

Archived:Using CActiveSchedulerWait

Archived:Changing asynchronous method to synchronous in Symbian C++

This page was last modified on 29 June 2012, at 03:30.
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