Nuclex.Support/Source/Tracking/ProgressionTracker.cs

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#region CPL License
/*
Nuclex Framework
Copyright (C) 2002-2007 Nuclex Development Labs
This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
IBM Common Public License for more details.
You should have received a copy of the IBM Common Public
License along with this library
*/
#endregion
using System;
using System.Collections.Generic;
using System.Threading;
namespace Nuclex.Support.Tracking {
/// <summary>Helps tracking the progress of one or more progressions</summary>
/// <remarks>
/// <para>
/// This is useful if you want to display a progress bar for multiple
/// progressions but can not guarantee that no additional progressions
/// will appear inmidst of execution.
/// </para>
/// <para>
/// This class does not implement the IProgression interface itself in
/// order to not violate the design principles of progressions which
/// guarantee that a progression will only finish once (whereas the
/// progression tracker might 'finish' any number of times).
/// </para>
/// </remarks>
public class ProgressionTracker : IDisposable {
#region class ProgressionMatcher
/// <summary>Matches a progression to a fully wrapped one</summary>
private class ProgressionMatcher {
/// <summary>
/// Initializes a new progression matcher that matches against
/// the specified progression
/// </summary>
/// <param name="toMatch">Progression to match against</param>
public ProgressionMatcher(Progression toMatch) {
this.toMatch = toMatch;
}
/// <summary>
/// Checks whether the provided progression matches the comparison
/// progression of the instance
/// </summary>
/// <param name="other">Progression to match to the comparison progression</param>
public bool Matches(ObservedWeightedProgression<Progression> other) {
return ReferenceEquals(other.WeightedProgression.Progression, this.toMatch);
}
/// <summary>Progression this instance compares against</summary>
private Progression toMatch;
}
#endregion // class ProgressionMatcher
/// <summary>Triggered when the idle state of the tracker changes</summary>
/// <remarks>
/// The tracker is idle when no progressions are being tracked in it. If you're
/// using this class to feed a progress bar, this would be the event to use for
/// showing or hiding the progress bar. The tracker starts off as idle because,
/// upon construction, its list of progressions will be empty.
/// </remarks>
public event EventHandler<IdleStateEventArgs> AsyncIdleStateChanged;
/// <summary>Triggered when the total progress has changed</summary>
public event EventHandler<ProgressUpdateEventArgs> AsyncProgressUpdated;
/// <summary>Initializes a new progression tracker</summary>
public ProgressionTracker() {
this.trackedProgressions = new List<ObservedWeightedProgression<Progression>>();
this.idle = true;
this.asyncEndedDelegate =
new ObservedWeightedProgression<Progression>.ReportDelegate(asyncEnded);
this.asyncProgressUpdatedDelegate =
new ObservedWeightedProgression<Progression>.ReportDelegate(asyncProgressUpdated);
}
/// <summary>Immediately releases all resources owned by the instance</summary>
public void Dispose() {
lock(this.trackedProgressions) {
// Get rid of all progression we're tracking. This unsubscribes the
// observers from the events of the progressions and stops us from
// being kept alive and receiving any further events if some of the
// tracked progressions are still executing.
for(int index = 0; index < this.trackedProgressions.Count; ++index)
this.trackedProgressions[index].Dispose();
this.trackedProgressions.Clear();
this.trackedProgressions = null;
} // lock
}
/// <summary>Begins tracking the specified progression</summary>
/// <param name="progression">Progression to be tracked</param>
public void Track(Progression progression) {
Track(progression, 1.0f);
}
/// <summary>Begins tracking the specified progression</summary>
/// <param name="progression">Progression to be tracked</param>
/// <param name="weight">Weight to assign to this progression</param>
public void Track(Progression progression, float weight) {
// Add the new progression into the tracking list. This has to be done
// inside a lock to prevent issues with the progressUpdate callback, which could
// access the totalWeight field before it has been updated to reflect the
// new progression added to the collection.
lock(this.trackedProgressions) {
this.trackedProgressions.Add(
new ObservedWeightedProgression<Progression>(
new WeightedProgression<Progression>(progression, weight),
this.asyncProgressUpdatedDelegate,
this.asyncEndedDelegate
)
);
// This can be done after we registered the wrapper to our delegates because
// any incoming progress updates will be stopped from the danger of a
// division-by-zero from the potentially still zeroed totalWeight by the lock.
this.totalWeight += weight;
// If this is the first progression to be added to the list, tell our
// owner that we're idle no longer!
if(this.trackedProgressions.Count == 1)
OnAsyncIdleStateChanged(false);
} // lock
// All done, the total progress is different now, so force a recalculation and
// send out the AsyncProgressUpdated event.
recalculateProgress();
}
/// <summary>Stops tracking the specified progression</summary>
/// <param name="progression">Progression to stop tracking of</param>
public void Untrack(Progression progression) {
lock(this.trackedProgressions) {
// Locate the object to be untracked in our collection
int removeIndex = this.trackedProgressions.FindIndex(
new Predicate<ObservedWeightedProgression<Progression>>(
new ProgressionMatcher(progression).Matches
)
);
if(removeIndex == -1)
throw new InvalidOperationException("Item is not being tracked");
// Remove and dispose the progression the user wants to untrack
{
ObservedWeightedProgression<Progression> wrappedProgression =
this.trackedProgressions[removeIndex];
this.trackedProgressions.RemoveAt(removeIndex);
wrappedProgression.Dispose();
}
// If the list is empty, then we're back in the idle state
if(this.trackedProgressions.Count == 0) {
this.totalWeight = 0.0f;
// Report that we're idle now!
OnAsyncIdleStateChanged(true);
} else {
// Rebuild the total weight from scratch. Subtracting the removed progression's
// weight would work, too, but might accumulate rounding errors making the sum
// drift slowly away from the actual value.
this.totalWeight = 0.0f;
for(int index = 0; index < this.trackedProgressions.Count; ++index)
this.totalWeight += this.trackedProgressions[index].WeightedProgression.Weight;
}
} // lock
}
/// <summary>Whether the tracker is currently idle</summary>
public bool Idle {
get { return this.idle; }
}
/// <summary>Current summed progress of the tracked progressions</summary>
public float Progress {
get { return this.progress; }
}
/// <summary>Fires the AsyncIdleStateChanged event</summary>
/// <param name="idle">New idle state to report</param>
protected virtual void OnAsyncIdleStateChanged(bool idle) {
this.idle = idle;
EventHandler<IdleStateEventArgs> copy = AsyncIdleStateChanged;
if(copy != null)
copy(this, new IdleStateEventArgs(idle));
}
/// <summary>Fires the AsyncProgressUpdated event</summary>
/// <param name="progress">New progress to report</param>
protected virtual void OnAsyncProgressUpdated(float progress) {
this.progress = progress;
EventHandler<ProgressUpdateEventArgs> copy = AsyncProgressUpdated;
if(copy != null)
copy(this, new ProgressUpdateEventArgs(progress));
}
/// <summary>Recalculates the total progress of the tracker</summary>
private void recalculateProgress() {
float totalProgress = 0.0f;
// Lock the progression to avoid trouble when someone tries to remove one
// of our tracked progressions while we're just processing a progress update
lock(this.trackedProgressions) {
// This is a safety measure. In theory, even after all progressions have
// ended and collection of tracked progressions is cleared, a waiting
// thread might deliver another progress update causing this method to
// be entered. In this case, the right thing is to do nothing at all.
if(this.totalWeight == 0.0f)
return;
// Sum up the total progress
for(int index = 0; index < this.trackedProgressions.Count; ++index) {
float weight = this.trackedProgressions[index].WeightedProgression.Weight;
totalProgress += this.trackedProgressions[index].Progress * weight;
}
// This also needs to be in the lock to guarantee that the totalWeight is
// the one for the number of progressions we just summed -- by design,
// the total weight always has to be updated at the same time as the collection.
totalProgress /= this.totalWeight;
}
// Finally, trigger the event
OnAsyncProgressUpdated(totalProgress);
}
/// <summary>Called when one of the tracked progressions has ended</summary>
private void asyncEnded() {
lock(this.trackedProgressions) {
// If any progressions in the list are still going, keep the entire list.
// This behavior is intentional in order to prevent the tracker's progress from
// jumping back repeatedly when multiple tracked progressions come to an end.
for(int index = 0; index < this.trackedProgressions.Count; ++index)
if(!this.trackedProgressions[index].WeightedProgression.Progression.Ended)
return;
// All progressions have finished, get rid of the wrappers and disconnect
// their events.
for(int index = 0; index < this.trackedProgressions.Count; ++index)
this.trackedProgressions[index].Dispose();
this.trackedProgressions.Clear();
this.totalWeight = 0.0f;
// Notify our owner that we're idle now.
OnAsyncIdleStateChanged(true);
}
}
/// <summary>Called when one of the tracked progression has achieved progress</summary>
private void asyncProgressUpdated() {
recalculateProgress();
}
/// <summary>Total weight of all progressions being tracked</summary>
private volatile float totalWeight;
/// <summary>Progressions being tracked by this tracker</summary>
private List<ObservedWeightedProgression<Progression>> trackedProgressions;
/// <summary>Delegate for the asyncEnded() method</summary>
private ObservedWeightedProgression<Progression>.ReportDelegate asyncEndedDelegate;
/// <summary>Delegate for the asyncProgressUpdated() method</summary>
private ObservedWeightedProgression<Progression>.ReportDelegate asyncProgressUpdatedDelegate;
/// <summary>Whether the tracker is currently idle</summary>
private bool idle;
/// <summary>Current summed progress of the tracked progressions</summary>
private float progress;
}
} // namespace Nuclex.Support.Tracking