--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Implab/Parallels/DispatchPool.cs	Fri Nov 08 01:27:04 2013 +0400
@@ -0,0 +1,238 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Diagnostics;
+
+namespace Implab.Parallels {
+    public abstract class DispatchPool<TUnit> : IDisposable {
+        readonly int m_minThreads;
+        readonly int m_maxThreads;
+        int m_runningThreads = 0;
+        int m_maxRunningThreads = 0;
+        int m_suspended = 0;
+        int m_exitRequired = 0;
+        AutoResetEvent m_hasTasks = new AutoResetEvent(false);
+
+        protected DispatchPool(int min, int max) {
+            if (min < 0)
+                throw new ArgumentOutOfRangeException("min");
+            if (max <= 0)
+                throw new ArgumentOutOfRangeException("max");
+
+            if (min > max)
+                min = max;
+            m_minThreads = min;
+            m_maxThreads = max;
+        }
+
+        protected DispatchPool(int threads)
+            : this(threads, threads) {
+        }
+
+        protected DispatchPool() {
+            int maxThreads, maxCP;
+            ThreadPool.GetMaxThreads(out maxThreads, out maxCP);
+
+            m_minThreads = 0;
+            m_maxThreads = maxThreads;
+        }
+
+        protected void InitPool() {
+            for (int i = 0; i < m_minThreads; i++)
+                StartWorker();
+        }
+
+        public int ThreadCount {
+            get {
+                return m_runningThreads;
+            }
+        }
+
+        public int MaxRunningThreads {
+            get {
+                return m_maxRunningThreads;
+            }
+        }
+
+        protected bool IsDisposed {
+            get {
+                return m_exitRequired != 0;
+            }
+        }
+
+        protected abstract bool TryDequeue(out TUnit unit);
+
+        protected virtual bool ExtendPool() {
+            if (m_suspended > 0) {
+                m_hasTasks.Set();
+                return true;
+            } else
+                return StartWorker();
+        }
+
+        /// <summary>
+        /// Запускает либо новый поток, если раньше не было ни одного потока, либо устанавливает событие пробуждение одного спящего потока
+        /// </summary>
+        protected void WakePool() {
+            m_hasTasks.Set(); // wake sleeping thread;
+
+            if (AllocateThreadSlot(1)) {
+                var worker = new Thread(this.Worker);
+                worker.IsBackground = true;
+                worker.Start();
+            }
+        }
+
+        protected virtual void Suspend() {
+            m_hasTasks.WaitOne();
+        }
+
+        #region thread slots traits
+
+        bool AllocateThreadSlot() {
+            int current;
+            // use spins to allocate slot for the new thread
+            do {
+                current = m_runningThreads;
+                if (current >= m_maxThreads || m_exitRequired != 0)
+                    // no more slots left or the pool has been disposed
+                    return false;
+            } while (current != Interlocked.CompareExchange(ref m_runningThreads, current + 1, current));
+
+            UpdateMaxThreads(current + 1);
+
+            return true;
+        }
+
+        bool AllocateThreadSlot(int desired) {
+            if (desired - 1 != Interlocked.CompareExchange(ref m_runningThreads, desired, desired - 1))
+                return false;
+
+            UpdateMaxThreads(desired);
+
+            return true;
+        }
+
+        bool ReleaseThreadSlot(out bool last) {
+            last = false;
+            int current;
+            // use spins to release slot for the new thread
+            do {
+                current = m_runningThreads;
+                if (current <= m_minThreads && m_exitRequired == 0)
+                    // the thread is reserved
+                    return false;
+            } while (current != Interlocked.CompareExchange(ref m_runningThreads, current - 1, current));
+
+            last = (current == 1);
+
+            return true;
+        }
+
+        /// <summary>
+        /// releases thread slot unconditionally, used during cleanup
+        /// </summary>
+        /// <returns>true - no more threads left</returns>
+        bool ReleaseThreadSlotAnyway() {
+            var left = Interlocked.Decrement(ref m_runningThreads);
+            return left == 0;
+        }
+
+        void UpdateMaxThreads(int count) {
+            int max;
+            do {
+                max = m_maxRunningThreads;
+                if (max >= count)
+                    break;
+            } while(max != Interlocked.CompareExchange(ref m_maxRunningThreads, count, max));
+        }
+
+        #endregion
+
+        bool StartWorker() {
+            if (AllocateThreadSlot()) {
+                // slot successfully allocated
+                var worker = new Thread(this.Worker);
+                worker.IsBackground = true;
+                worker.Start();
+
+                return true;
+            } else {
+                return false;
+            }
+        }
+
+        bool FetchTask(out TUnit unit) {
+            do {
+                // exit if requested
+                if (m_exitRequired != 0) {
+                    // release the thread slot
+                    if (ReleaseThreadSlotAnyway()) // it was the last worker
+                        m_hasTasks.Dispose();
+                    else
+                        m_hasTasks.Set(); // wake next worker
+                    unit = default(TUnit);
+                    return false;
+                }
+
+                // fetch task
+                if (TryDequeue(out unit)) {
+                    ExtendPool();
+                    return true;
+                }
+
+                //no tasks left, exit if the thread is no longer needed
+                bool last;
+                if (ReleaseThreadSlot(out last)) {
+                    if (last && m_hasTasks.WaitOne(0)) {
+                        if (AllocateThreadSlot(1))
+                            continue; // spin again...
+                        else
+                            // we failed to reallocate slot for this thread
+                            // therefore we need to release the event
+                            m_hasTasks.Set(); 
+                    }
+
+                    return false;
+                }
+
+                // entering suspend state
+                Interlocked.Increment(ref m_suspended);
+                // keep this thread and wait                
+                Suspend();
+                Interlocked.Decrement(ref m_suspended);
+            } while (true);
+        }
+
+        protected abstract void InvokeUnit(TUnit unit);
+
+        void Worker() {
+            TUnit unit;
+            while (FetchTask(out unit))
+                InvokeUnit(unit);
+        }
+
+        protected virtual void Dispose(bool disposing) {
+            if (disposing) {
+                if (m_exitRequired == 0) {
+                    if (Interlocked.CompareExchange(ref m_exitRequired, 1, 0) != 0)
+                        return;
+
+                    // wake sleeping threads
+                    m_hasTasks.Set();
+                    GC.SuppressFinalize(this);
+                }
+            }
+        }
+
+        public void Dispose() {
+            Dispose(true);
+        }
+
+        ~DispatchPool() {
+            Dispose(false);
+        }
+    }
+}