chore: import upstream snapshot with attribution

Common/Interfaces/IBusyCollection.cs

@@ -0,0 +1,76 @@
+/*
+ * QUANTCONNECT.COM - Democratizing Finance, Empowering Individuals.
+ * Lean Algorithmic Trading Engine v2.0. Copyright 2014 QuantConnect Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+*/
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace QuantConnect.Interfaces
+{
+    /// <summary>
+    /// Interface used to handle items being processed and communicate busy state
+    /// </summary>
+    /// <typeparam name="T">The item type being processed</typeparam>
+    public interface IBusyCollection<T> : IDisposable
+    {
+        /// <summary>
+        /// Gets a wait handle that can be used to wait until this instance is done
+        /// processing all of it's item
+        /// </summary>
+        WaitHandle WaitHandle { get; }
+
+        /// <summary>
+        /// Gets the number of items held within this collection
+        /// </summary>
+        int Count { get; }
+
+        /// <summary>
+        /// Returns true if processing, false otherwise
+        /// </summary>
+        bool IsBusy { get; }
+
+        /// <summary>
+        /// Adds the items to this collection
+        /// </summary>
+        /// <param name="item">The item to be added</param>
+        void Add(T item);
+
+        /// <summary>
+        /// Adds the items to this collection
+        /// </summary>
+        /// <param name="item">The item to be added</param>
+        /// <param name="cancellationToken">A cancellation token to observer</param>
+        void Add(T item, CancellationToken cancellationToken);
+
+        /// <summary>
+        /// Marks the collection as not accepting any more additions
+        /// </summary>
+        void CompleteAdding();
+
+        /// <summary>
+        /// Provides a consuming enumerable for items in this collection.
+        /// </summary>
+        /// <returns>An enumerable that removes and returns items from the collection</returns>
+        IEnumerable<T> GetConsumingEnumerable();
+
+        /// <summary>
+        /// Provides a consuming enumerable for items in this collection.
+        /// </summary>
+        /// <param name="cancellationToken">A cancellation token to observer</param>
+        /// <returns>An enumerable that removes and returns items from the collection</returns>
+        IEnumerable<T> GetConsumingEnumerable(CancellationToken cancellationToken);
+    }
+}