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using System;
using System.Threading;
namespace LearnMeAThing.Utilities
{
/// <summary>
/// An object representing some number of jobs waiting to be completed.
///
/// Once WaitForCompletion() returns, references to this object should be
/// dropped as it may be handed out by it's associated JobRunner again.
/// </summary>
sealed class JobsCompletionToken
{
private readonly object Lock;
private int ActiveJobs;
private readonly IJob[] AssociatedJobs;
private readonly JobRunner Owner;
/// <summary>
/// Returns true if all the associated jobs
/// of this completion token have completed
/// </summary>
internal bool IsComplete
{
get
{
for(var i = 0; i < ActiveJobs; i++)
{
var job = AssociatedJobs[i];
if (!job.IsComplete) return false;
}
return true;
}
}
internal JobsCompletionToken(JobRunner owner, int maximumJobs)
{
Lock = new object();
Owner = owner;
AssociatedJobs = new IJob[maximumJobs];
ActiveJobs = 0;
}
/// <summary>
/// Make this completion token ready for use again
/// </summary>
internal void Reset()
{
ActiveJobs = 0;
Array.Clear(AssociatedJobs, 0, AssociatedJobs.Length);
}
/// <summary>
/// Attach a job to this token.
///
/// This does not start the job, it just makes
/// it's completion a condition for WaitForCompletion()'s
/// return.
/// </summary>
internal void AddJob(IJob job)
{
// just ignore it
if (job == null) return;
if (ActiveJobs == AssociatedJobs.Length) throw new InvalidOperationException($"Tried to add a job to a full {nameof(JobsCompletionToken)}");
AssociatedJobs[ActiveJobs] = job;
ActiveJobs++;
}
/// <summary>
/// Called to indicate that a single job has completed,
/// and that might indicate that the whole completion
/// token is now complete.
/// </summary>
internal void SignalJobCompleted()
{
lock (Lock)
{
Monitor.Pulse(Lock);
}
}
/// <summary>
/// Blocks until all the jobs associated with this runner are
/// complete.
/// </summary>
public void WaitForCompletion()
{
lock (Lock)
{
// kick everything off
// need to do this in the lock
// so there's no race to call
// SignalJobCompleted()
for(var i = 0; i < ActiveJobs; i++)
{
Owner.EnqueueJob(AssociatedJobs[i]);
}
Owner.WakeUpWorkerThreads();
while (!IsComplete)
{
Monitor.Wait(Lock);
}
}
Owner.ReturnCompletionToken(this);
}
}
}
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