1 files changed, 239 insertions, 0 deletions

diff --git a/ThirdParty/SmartThreadPool/PriorityQueue.cs b/ThirdParty/SmartThreadPool/PriorityQueue.cs
new file mode 100644
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+++ b/ThirdParty/SmartThreadPool/PriorityQueue.cs
@@ -0,0 +1,239 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace Amib.Threading.Internal
+{
+    #region PriorityQueue class
+
+    /// <summary>
+    /// PriorityQueue class
+    /// This class is not thread safe because we use external lock
+    /// </summary>
+    public sealed class PriorityQueue : IEnumerable
+    {
+        #region Private members
+
+        /// <summary>
+        /// The number of queues, there is one for each type of priority
+        /// </summary>
+        private const int _queuesCount = WorkItemPriority.Highest-WorkItemPriority.Lowest+1;
+
+        /// <summary>
+        /// Work items queues. There is one for each type of priority
+        /// </summary>
+        private readonly LinkedList<IHasWorkItemPriority>[] _queues = new LinkedList<IHasWorkItemPriority>[_queuesCount];
+
+        /// <summary>
+        /// The total number of work items within the queues
+        /// </summary>
+        private int _workItemsCount;
+
+        /// <summary>
+        /// Use with IEnumerable interface
+        /// </summary>
+        private int _version;
+
+        #endregion
+
+        #region Contructor
+
+        public PriorityQueue()
+        {
+            for(int i = 0; i < _queues.Length; ++i)
+            {
+                _queues[i] = new LinkedList<IHasWorkItemPriority>();
+            }
+        }
+
+        #endregion
+
+        #region Methods
+
+        /// <summary>
+        /// Enqueue a work item.
+        /// </summary>
+        /// <param name="workItem">A work item</param>
+        public void Enqueue(IHasWorkItemPriority workItem)
+        {
+            Debug.Assert(null != workItem);
+
+            int queueIndex = _queuesCount-(int)workItem.WorkItemPriority-1;
+            Debug.Assert(queueIndex >= 0);
+            Debug.Assert(queueIndex < _queuesCount);
+
+            _queues[queueIndex].AddLast(workItem);
+            ++_workItemsCount;
+            ++_version;
+        }
+
+        /// <summary>
+        /// Dequeque a work item.
+        /// </summary>
+        /// <returns>Returns the next work item</returns>
+        public IHasWorkItemPriority Dequeue()
+        {
+            IHasWorkItemPriority workItem = null;
+
+            if(_workItemsCount > 0)
+            {
+                int queueIndex = GetNextNonEmptyQueue(-1);
+                Debug.Assert(queueIndex >= 0);
+                workItem = _queues[queueIndex].First.Value;
+                _queues[queueIndex].RemoveFirst();
+                Debug.Assert(null != workItem);
+                --_workItemsCount;
+                ++_version;
+            }
+
+            return workItem;
+        }
+
+        /// <summary>
+        /// Find the next non empty queue starting at queue queueIndex+1
+        /// </summary>
+        /// <param name="queueIndex">The index-1 to start from</param>
+        /// <returns>
+        /// The index of the next non empty queue or -1 if all the queues are empty
+        /// </returns>
+        private int GetNextNonEmptyQueue(int queueIndex)
+        {
+            for(int i = queueIndex+1; i < _queuesCount; ++i)
+            {
+                if(_queues[i].Count > 0)
+                {
+                    return i;
+                }
+            }
+            return -1;
+        }
+
+        /// <summary>
+        /// The number of work items
+        /// </summary>
+        public int Count
+        {
+            get
+            {
+                return _workItemsCount;
+            }
+        }
+
+        /// <summary>
+        /// Clear all the work items
+        /// </summary>
+        public void Clear()
+        {
+            if (_workItemsCount > 0)
+            {
+                foreach(LinkedList<IHasWorkItemPriority> queue in _queues)
+                {
+                    queue.Clear();
+                }
+                _workItemsCount = 0;
+                ++_version;
+            }
+        }
+
+        #endregion
+
+        #region IEnumerable Members
+
+        /// <summary>
+        /// Returns an enumerator to iterate over the work items
+        /// </summary>
+        /// <returns>Returns an enumerator</returns>
+        public IEnumerator GetEnumerator()
+        {
+            return new PriorityQueueEnumerator(this);
+        }
+
+        #endregion
+
+        #region PriorityQueueEnumerator
+
+        /// <summary>
+        /// The class the implements the enumerator
+        /// </summary>
+        private class PriorityQueueEnumerator : IEnumerator
+        {
+            private readonly PriorityQueue _priorityQueue;
+            private int _version;
+            private int _queueIndex;
+            private IEnumerator _enumerator;
+
+            public PriorityQueueEnumerator(PriorityQueue priorityQueue)
+            {
+                _priorityQueue = priorityQueue;
+                _version = _priorityQueue._version;
+                _queueIndex = _priorityQueue.GetNextNonEmptyQueue(-1);
+                if (_queueIndex >= 0)
+                {
+                    _enumerator = _priorityQueue._queues[_queueIndex].GetEnumerator();
+                }
+                else
+                {
+                    _enumerator = null;
+                }
+            }
+
+            #region IEnumerator Members
+
+            public void Reset()
+            {
+                _version = _priorityQueue._version;
+                _queueIndex = _priorityQueue.GetNextNonEmptyQueue(-1);
+                if (_queueIndex >= 0)
+                {
+                    _enumerator = _priorityQueue._queues[_queueIndex].GetEnumerator();
+                }
+                else
+                {
+                    _enumerator = null;
+                }
+            }
+
+            public object Current
+            {
+                get
+                {
+                    Debug.Assert(null != _enumerator);
+                    return _enumerator.Current;
+                }
+            }
+
+            public bool MoveNext()
+            {
+                if (null == _enumerator)
+                {
+                    return false;
+                }
+
+                if(_version != _priorityQueue._version)
+                {
+                    throw new InvalidOperationException("The collection has been modified");
+
+                }
+                if (!_enumerator.MoveNext())
+                {
+                    _queueIndex = _priorityQueue.GetNextNonEmptyQueue(_queueIndex);
+                    if(-1 == _queueIndex)
+                    {
+                        return false;
+                    }
+                    _enumerator = _priorityQueue._queues[_queueIndex].GetEnumerator();
+                    _enumerator.MoveNext();
+                    return true;
+                }
+                return true;
+            }
+
+            #endregion
+        }
+
+        #endregion
+    }
+
+    #endregion
+}