Regina Calculation Engine
Public Member Functions | List of all members
regina::NProgressTracker Class Reference

Manages progress tracking and cancellation polling for long operations. More...

#include <progress/nprogresstracker.h>

Public Member Functions

 NProgressTracker ()
 Creates a new progress tracker. More...
 
bool isFinished () const
 Queries whether the writing thread has finished all processing. More...
 
bool percentChanged () const
 Queries whether the percentage progress has changed since the last call to percentChanged(). More...
 
bool descriptionChanged () const
 Queries whether the stage description has changed since the last call to descriptionChanged(). More...
 
double percent () const
 Returns the percentage progress through the entire operation. More...
 
std::string description () const
 Returns the human-readable description of the current stage. More...
 
void cancel ()
 Indicates to the writing thread that the user wishes to cancel the operation. More...
 
void newStage (const char *desc, double weight=1)
 Used by the writing thread to indicate that it has moved on to a new stage of processing. More...
 
bool isCancelled () const
 Queries whether the reading thread has made a request for the writing thread to cancel the operation; in other words, whether cancel() has been called. More...
 
bool setPercent (double percent)
 Used by the writing thread to indicate the level of progress through the current stage. More...
 
void setFinished ()
 Used by the writing thread to indicate that it has finished all processing. More...
 

Detailed Description

Manages progress tracking and cancellation polling for long operations.

A typical progress tracker is simultaneously used by a writing thread, which is performing the long calculations, and a reading thread, which displays progress updates to the user and/or takes cancellation requests from the user.

Progress works through a series of stages. Each stage has a text description, as well as a percentage progress that rises from 0 to 100 as the stage progresses. Each stage also has a fractional weight (between 0 and 1 inclusive), and the percentage progress of the entire calculation is taken to be the weighted sum of the progress of the individual stages. The weights of all stages should sum to 1.

The life cycle of an NProgressTracker is as follows.

It is imperative that the writing thread does not access the tracker after calling setFinished(), and it is imperative that the reading thread does not destroy the tracker until after isFinished() returns true. In particular, even if the reading thread has called cancel(), it must still wait upon isFinished() before destroying the tracker. Until isFinished() returns true, there is no guarantee that the writing thread has detected and honoured the cancellation request.

Constructor & Destructor Documentation

regina::NProgressTracker::NProgressTracker ( )
inline

Creates a new progress tracker.

This sets a sensible state description (which declares that the operation is initialising), and marks the current progress as zero percent complete.

This is typically called by the reading thread.

Member Function Documentation

void regina::NProgressTracker::cancel ( )
inline

Indicates to the writing thread that the user wishes to cancel the operation.

The writing thread might not detect and/or respond to this request immediately (or indeed ever), and so the reading thread should continue to wait until isFinished() returns true before it cleans up and destroys this progress tracker.

This is typically called by the reading thread.

std::string regina::NProgressTracker::description ( ) const
inline

Returns the human-readable description of the current stage.

This is typically called by the reading thread.

Returns
the current stage description.
bool regina::NProgressTracker::descriptionChanged ( ) const
inline

Queries whether the stage description has changed since the last call to descriptionChanged().

If this is the first time descriptionChanged() is called, the result will be true.

This is typically called by the reading thread.

Returns
true if and only if the stage description has changed.
bool regina::NProgressTracker::isCancelled ( ) const
inline

Queries whether the reading thread has made a request for the writing thread to cancel the operation; in other words, whether cancel() has been called.

This is typically called by the writing thread.

Returns
true if and only if a cancellation request has been made.
bool regina::NProgressTracker::isFinished ( ) const
inline

Queries whether the writing thread has finished all processing.

This will eventually return true regardless of whether the processing finished naturally or was cancelled by the reading thread.

This is typically called by the reading thread.

Returns
true if and only if the writing thread has finished all processing.
void regina::NProgressTracker::newStage ( const char *  desc,
double  weight = 1 
)
inline

Used by the writing thread to indicate that it has moved on to a new stage of processing.

The percentage progress through the current stage will automatically be set to 100.

This is typically called by the writing thread.

Parameters
desca human-readable description of the new stage. Typically this begins with a capital and does not include a final period (full stop).
weightthe relative weight of this stage as a fraction of the entire operation. This weight must be between 0 and 1 inclusive, and the weights of all stages must sum to 1 in total.
double regina::NProgressTracker::percent ( ) const
inline

Returns the percentage progress through the entire operation.

This combines the progress through the current stage with all previous stages, taking into account the relative weights that the writing thread has passed to newStage().

This is typically called by the reading thread.

Returns
the current percentage progress.
bool regina::NProgressTracker::percentChanged ( ) const
inline

Queries whether the percentage progress has changed since the last call to percentChanged().

If this is the first time percentChanged() is called, the result will be true.

This is typically called by the reading thread.

Returns
true if and only if the percentage progress has changed.
void regina::NProgressTracker::setFinished ( )
inline

Used by the writing thread to indicate that it has finished all processing.

The percentage progress through both the current stage and the entire operation will automatically be set to 100, and the stage description will be updated to indicate that the operation is finished.

This is typically called by the writing thread.

bool regina::NProgressTracker::setPercent ( double  percent)
inline

Used by the writing thread to indicate the level of progress through the current stage.

Unlike percent(), which measures progress in the context of the entire operation, this routine takes a percentage that is strictly relative to the current stage (i.e., the stage most recently declared through a call to newStage()). When the stage begins, setPercent() would typically be given a figure close to 0; when the stage is finished, setPercent() would typically be given a figure close to 100.

There is no actual need to call setPercent(0) at the beginning of the stage or setPercent(100) at the end of the stage, since other routines (such as the constructor, newStage() and setFinished()) will take care of this for you.

This is typically called by the writing thread.

Parameters
percentthe percentage progress through this stage, as a number between 0 and 100 inclusive.
Returns
true if there has been no cancellation request, or false if cancel() has been called (typically by the reading thread).

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

Copyright © 1999-2014, The Regina development team
This software is released under the GNU General Public License, with some additional permissions; see the source code for details.
For further information, or to submit a bug or other problem, please contact Ben Burton (bab@debian.org).