ln.types/threads/Pool.cs

using System;
using System.Threading;
using System.Collections.Generic;
using System.Linq;
using ln.logging;

namespace ln.types.threads
{
    public enum PoolThreadState { READY, WORKING, EXITED }

    public class Pool : IDisposable
    {
        public PoolThread[] PoolThreads
        {
            get
            {
                lock (poolThreads)
                {
                    return poolThreads.ToArray();
                }
            }
        }
        public int CurrentPoolSize
        {
            get
            {
                lock (poolThreads) { return poolThreads.Count; }
            }
            set
            {
                TargetPoolSize = value;
            }
        }
        public int TargetPoolSize { get; set; }

        public PoolThreadState[] ThreadStates
        {
            get
            {
                lock (poolThreads)
                {
                    return poolThreads.Select((x) => x.State).ToArray();
                }
            }
        }

        public int NumQueuedJobs => queuedJobs.Count;

        public PoolJob[] CurrentPoolJobs
        {
            get
            {
                lock (poolThreads)
                {
                    return poolThreads.Select((t) => t.CurrentJob).Where((j) => j != null).ToArray();
                }
            }
        }
        public PoolJob[] QueuedJobs
        {
            get
            {
                lock (queuedJobs)
                {
                    return queuedJobs.ToArray();
                }
            }
        }

        private List<PoolThread> poolThreads = new List<PoolThread>();
        private Queue<PoolJob> queuedJobs = new Queue<PoolJob>();

        private bool stopping;
        private int releaseThreads = 0;

        private Thread supervisorThread;

        public Pool()
        {
            SetPoolSize(4);
        }

        public Pool(int numThreads)
        {
            SetPoolSize(numThreads);
        }

        public void Close()
        {
            lock (queuedJobs)
            {
                stopping = true;
                foreach (PoolJob job in queuedJobs)
                {
                    job.RequestAbort();
                    job.ForceFail();
                }
                queuedJobs.Clear();
            }

            TargetPoolSize = 0;

            int waitFor = AmIPoolThread() ? 1 : 0;
            while (CurrentPoolSize > waitFor)
            {
                Thread.Sleep(250);
            }

            stopping = false;
        }

        public void Abort()
        {
            foreach (PoolJob job in CurrentPoolJobs)
            {
                job.RequestAbort();
            }
        }

        private PoolThread FindWaitingThread()
        {
            lock (queuedJobs)
            {
                foreach (PoolThread poolThread in poolThreads)
                    if (poolThread.State == PoolThreadState.READY)
                        return poolThread;
            }
            return null;
        }

        private bool AmIPoolThread()
        {
            Thread thread = Thread.CurrentThread;

            lock (poolThreads)
            {
                foreach (PoolThread poolThread in poolThreads)
                {
                    if (thread.Equals(poolThread.Thread))
                        return true;
                }
            }

            return false;
        }

        public void SetPoolSize(int poolSize)
        {
            TargetPoolSize = poolSize;
            if ((CurrentPoolSize == 0) && (TargetPoolSize > 0))
            {
                new PoolThread(this);
                new Thread(() => Supervisor()).Start();
            }
        }

        public void Enqueue(JobDelegate job)
        {
            Enqueue((poolJob) => job());
        }

        public PoolJob Enqueue(ExtendedJobDelegate extendedJobDelegate)
        {
            return Enqueue(extendedJobDelegate, "N/A");
        }
        public PoolJob Enqueue(ExtendedJobDelegate extendedJobDelegate,string jobName)
        {
            PoolJob poolJob = new PoolJob(jobName, extendedJobDelegate);

            Enqueue(poolJob);

            return poolJob;
        }
        public bool Enqueue(PoolJob poolJob)
        {
            if (stopping)
                throw new OperationCanceledException("Thread Pool to be shut down");

            lock (queuedJobs)
            {
                if (queuedJobs.Contains(poolJob) || CurrentPoolJobs.Contains(poolJob))
                    return false;

                queuedJobs.Enqueue(poolJob);
                Monitor.Pulse(queuedJobs);
            }

            return true;
        }

        private PoolJob Dequeue()
        {
            lock (queuedJobs)
            {
                if (queuedJobs.Count == 0)
                {
                    Monitor.Wait(queuedJobs);
                }

                if (releaseThreads > 0)
                {
                    releaseThreads--;
                    throw new TimeoutException();
                }

                if (queuedJobs.Count == 0)
                    return null;

                return queuedJobs.Dequeue();
            }
        }

        private void Supervisor()
        {
            supervisorThread = Thread.CurrentThread;

            lock (supervisorThread)
            {

                while (CurrentPoolSize > 0)
                {
                    Monitor.Wait(supervisorThread, 1000);

                    while (CurrentPoolSize != TargetPoolSize)
                    {
                        if (CurrentPoolSize - TargetPoolSize > 0)
                        {
                            lock (queuedJobs)
                            {
                                releaseThreads = CurrentPoolSize - TargetPoolSize;
                            }

                            if (CurrentPoolSize - TargetPoolSize > 0)
                            {
                                lock (queuedJobs)
                                {
                                    Monitor.PulseAll(queuedJobs);
                                }
                            }
                        }
                        else if (CurrentPoolSize - TargetPoolSize < 0)
                        {
                            for (int n = CurrentPoolSize; n < TargetPoolSize; n++)
                                new PoolThread(this);
                        }
                    }
                }
            }
            supervisorThread = null;
        }




        public class PoolThread
        {
            public Pool Pool { get; }
            public Thread Thread { get; }
            public PoolThreadState State { get; private set; }

            public PoolJob CurrentJob { get; private set; }

            private bool exitCalled { get; set; }

            public PoolThread(Pool pool)
            {
                State = PoolThreadState.WORKING;
                Pool = pool;
                Thread = new Thread(thread);

                lock (Pool.poolThreads)
                {
                    Pool.poolThreads.Add(this);
                }

                WaitStarted();
            }

            private void WaitStarted()
            {
                lock (this)
                {
                    Thread.Start();
                    Monitor.Wait(this, 5000);
                }
            }

            private void thread()
            {
                lock (this)
                {
                    Monitor.Pulse(this);
                }

                State = PoolThreadState.READY;

                while (!exitCalled)
                {
                    PoolJob poolJob = null;
                    try
                    {
                        poolJob = Pool.Dequeue();
                    } catch (TimeoutException)
                    {
                        break;
                    }

                    if (Pool.poolThreads.Count > 4)
                    {
                        Logging.Log(LogLevel.DEBUGDETAIL, "--");
                    }

                    if (poolJob != null)
                    {
                        State = PoolThreadState.WORKING;
                        CurrentJob = poolJob;
                        CurrentJob.Run(Pool);
                        CurrentJob = null;
                        State = PoolThreadState.READY;
                    }
                }

                State = PoolThreadState.EXITED;
                lock (Pool.poolThreads)
                {
                    Pool.poolThreads.Remove(this);
                }
             }

            public void Exit()
            {
                lock (this)
                {
                    exitCalled = true;
                }
            }
        }

        public void Dispose()
        {
            Close();
        }
    }
}