1 files changed, 76 insertions, 0 deletions

diff --git a/src/dtf/WixToolset.Dtf.Compression.Cab/HandleManager.cs b/src/dtf/WixToolset.Dtf.Compression.Cab/HandleManager.cs
new file mode 100644
index 00000000..aad9a317
--- /dev/null
+++ b/src/dtf/WixToolset.Dtf.Compression.Cab/HandleManager.cs
@@ -0,0 +1,76 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Dtf.Compression.Cab
+{
+    using System;
+    using System.Collections.Generic;
+
+    /// <summary>
+    /// Generic class for managing allocations of integer handles
+    /// for objects of a certain type.
+    /// </summary>
+    /// <typeparam name="T">The type of objects the handles refer to.</typeparam>
+    internal sealed class HandleManager<T> where T : class
+    {
+        /// <summary>
+        /// Auto-resizing list of objects for which handles have been allocated.
+        /// Each handle is just an index into this list. When a handle is freed,
+        /// the list item at that index is set to null.
+        /// </summary>
+        private List<T> handles;
+
+        /// <summary>
+        /// Creates a new HandleManager instance.
+        /// </summary>
+        public HandleManager()
+        {
+            this.handles = new List<T>();
+        }
+
+        /// <summary>
+        /// Gets the object of a handle, or null if the handle is invalid.
+        /// </summary>
+        /// <param name="handle">The integer handle previously allocated
+        /// for the desired object.</param>
+        /// <returns>The object for which the handle was allocated.</returns>
+        public T this[int handle]
+        {
+            get
+            {
+                if (handle > 0 && handle <= this.handles.Count)
+                {
+                    return this.handles[handle - 1];
+                }
+                else
+                {
+                    return null;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Allocates a new handle for an object.
+        /// </summary>
+        /// <param name="obj">Object that the handle will refer to.</param>
+        /// <returns>New handle that can be later used to retrieve the object.</returns>
+        public int AllocHandle(T obj)
+        {
+            this.handles.Add(obj);
+            int handle = this.handles.Count;
+            return handle;
+        }
+
+        /// <summary>
+        /// Frees a handle that was previously allocated. Afterward the handle
+        /// will be invalid and the object it referred to can no longer retrieved.
+        /// </summary>
+        /// <param name="handle">Handle to be freed.</param>
+        public void FreeHandle(int handle)
+        {
+            if (handle > 0 && handle <= this.handles.Count)
+            {
+                this.handles[handle - 1] = null;
+            }
+        }
+    }
+}