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Location:
e32base.h
Link against: euser.lib
class CActiveScheduler : public CBase;
Controls the handling of asynchronous requests as represented by active objects.
An active scheduler is used to schedule the sequence in which active object request completion events are handled by a single event-handling thread.
An active scheduler can be instantiated and used directly if either:
the RunL() function of all of its active objects is guaranteed not to leave, or
each of its active objects implements a suitable RunError() function to provide suitable cleanup
If any of the active scheduler's active objects does not provide a RunError() function, then a CActiveScheduler derived class
must be defined and an implementation of the Error() function provided to perform the cleanup required.
There is one active scheduler per thread and the static functions provided by the class always refer to the current active scheduler.
CBase - Base class for all classes to be instantiated on the heap
CActiveScheduler - Controls the handling of asynchronous requests as represented by active objects
Defined in CActiveScheduler:
Add(), CActiveScheduler(), Current(), Error(), Extension_(), Halt(), Install(), Level(), OnStarting(), OnStopping(), Replace(), RunIfReady(), StackDepth(), Start(), Stop(), TLoopOwner, WaitForAnyRequest(), ~CActiveScheduler()
Inherited from CBase:
Delete(),
operator new()
IMPORT_C CActiveScheduler();
Constructs an active scheduler.
After construction, the scheduler should be installed.
IMPORT_C ~CActiveScheduler();
Frees resources prior to destruction.
Specifically, it removes all active objects from the active scheduler's list of active objects.
An active scheduler should only be destroyed when the top-level call to Start() has returned.
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static IMPORT_C void Install(CActiveScheduler *aScheduler);
Installs the specified active scheduler as the current active scheduler.
The installed active scheduler now handles events for this thread.
The current active scheduler can be uninstalled by passing a NULL pointer.
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static IMPORT_C CActiveScheduler *Current();
Gets a pointer to the currently installed active scheduler.
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static IMPORT_C void Add(CActive *aActive);
Adds the specified active object to the current active scheduler.
An active object can be removed from an active scheduler either by destroying the active object or by using its Deque() member function.
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static IMPORT_C void Start();
Starts a new wait loop under the control of the current active scheduler.
At least one active object, with an outstanding request, must be added to the scheduler before the wait loop is started, otherwise no events will occur and the thread will hang, or any events that do occur will be counted as stray signals, raising a panic.
While Start() is executing, user code runs only:
1. in the RunL() function of active objects known to the current active scheduler
2. in the RunError() function of an active object that leaves from its RunL()
3. in the current active scheduler’s Error() function, if an active object’s RunError() returns an error code.
Start() returns only when a corresponding Stop() or Halt() is issued.
Although this can be used to start a nested wait loop, this API is deprecated for that specific functionality, and a CActiveSchedulerWait object should be used instead.
(Note that a nested wait loop is used when the handling of a completed event in an active object requires the processing of further events from the other active objects before it can complete. This is a form of modal processing.)
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static IMPORT_C void Stop();
Stops the wait loop started by the most recent call to Start().
Typically, this is called by the RunL() of one of the scheduler’s active objects. When this RunL() finishes, the scheduler’s wait loop terminates, i.e. it does not wait for the completion of the next request.
It will not stop a wait loop started by a call to CActiveSchedulerWait::Start().
Stop() may also be called from Error().
Note that stopping a nested wait loop is deprecated using this functionality, use a CActiveSchedulerWait object instead.
static IMPORT_C TBool RunIfReady(TInt &aError, TInt aMinimumPriority);
Causes the RunL() function of at most one pending active object of priority aMinimumPriority or greater to be run.
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static IMPORT_C CActiveScheduler *Replace(CActiveScheduler *aNewActiveScheduler);
Allows the current active scheduler to be replaced, while retaining its active objects.
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virtual IMPORT_C void WaitForAnyRequest();
Wait for an asynchronous request to complete.
The default implementation just calls User::WaitForAnyRequest().
Derived classes can replace this. Typically, this would be done to implement code for maintaining an outstanding request;
this would be followed by a call to User::WaitForAnyRequest().
virtual IMPORT_C void Error(TInt aError) const;
Handles the result of a leave occurring in an active object’s RunL() function.
An active scheduler always invokes an active object’s RunL() function under a trap harness.
The default implementation must be replaced.
Any cleanup relevant to the possible causes of leaving should be performed. If Stop() or Halt() is called from within this function, the current wait loop terminates. This may be an appropriate response to catastrophic
error conditions.
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IMPORT_C void Halt(TInt aExitCode) const;
Unilaterally terminates the current scheduler loop.
This causes the current scheduler loop to stop, whether it was started using CActiveSchedulerWait::Start() or CActiveScheduler::Start(). It can also trigger a leave from Start() if an exit code is provided. If the current level has already been stopped, then this still records the exit code.
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IMPORT_C TInt StackDepth() const;
Gets the current number of nested wait loops.
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private: virtual IMPORT_C void OnStarting();
Dummy EXPORT for Binary Compatibility reasons. This method is never called.
private: virtual IMPORT_C void OnStopping();
Dummy EXPORT for Binary Compatibility reasons. This method is never called.
protected: virtual IMPORT_C TInt Extension_(TUint aExtensionId, TAny *&a0, TAny *a1);
Extension function
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protected: inline TInt Level() const;
Gets the scheduler's level of nestedness.
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typedef TLoop* CActiveScheduler::TLoopOwner;
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Copyright ©2008 Symbian Software Ltd. |
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