FX::QThreadPool Class Reference

#include <QThread.h>

List of all members.

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Detailed Description

Provides a pool of worker threads.

Thread pools are an old & common invention used to work around the cost of creating and destroying a thread. They permit you to gain all the advantages of multi-threaded programming to a fine-grained level without many of the costs. Thus, they are ideal for when you regularly have small tasks to be carried out in parallel with the main execution.

Typically to send a job to a thread pool costs barely more than waking a sleeping thread. If there are no threads available (ie; they're all processing a job), the job enters a FIFO queue which is emptied as fast as the worker threads get through them. You furthermore can delay the execution of a job for an arbitrary number of milliseconds - thus a timed call dispatcher comes for free with this class.

Jobs can be waited upon for completion & cancelled. FX::FXProcess provides a process-wide thread pool which is created upon first-use - certain functionality such as the filing system monitor (FX::FXFSMonitor) use the process thread pool to run checks as well as dispatch notifications of changes.

Usage:

FXProcess::threadPool().dispatch(Generic::BindFuncN(obj, method, pars));

Cancelling jobs with cancel() can get tricky. If it's a simple case of cancelling it before it has run, all is good and Cancelled is returned. If the job is already running, you can optionally have cancel() wait until it's returned but in either case WasRunning is returned (if the job completed, the functor is deleted as usual). Be aware that if your job reschedules itself, cancel() when returning WasRunning won't actually have cancelled the job and you'll need to call it again. Suggested code is as follows:

while(QThreadPool::WasRunning==threadpool.cancel(job));

Definition at line 1228 of file QThread.h.

Public Types
typedef void *	handle
typedef Generic::Functor< Generic::TL::create< bool, QThreadPool *, handle, DispatchUpcallType >::value >	DispatchUpcallSpec
	PreDispatch
	PostDispatch
	CancelledPreDispatch
	NotFound
	Cancelled
	WasRunning
enum	DispatchUpcallType { PreDispatch, PostDispatch, CancelledPreDispatch }
enum	CancelledState { NotFound, Cancelled, WasRunning }
Public Member Functions
	QThreadPool (FXuint total=FXProcess::noOfProcessors(), bool dynamic=false)
	~QThreadPool ()
FXuint	total () const throw ()
FXuint	maximum () const throw ()
FXuint	free () const throw ()
void	setTotal (FXuint newno)
bool	dynamic () const throw ()
void	setDynamic (bool v)
handle	dispatch (FXAutoPtr< Generic::BoundFunctorV > code, FXuint delay=0, DispatchUpcallSpec *upcallv=0)
CancelledState	cancel (handle code, bool wait=true)
bool	reset (handle code, FXuint delay)
bool	wait (handle code, FXuint period=FXINFINITE)

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The documentation for this class was generated from the following file:

• QThread.h

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(C) 2002-2009 Niall Douglas. Some parts (C) to assorted authors.