1 files changed, 54 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/Threading/TimeoutHelper.cs b/src/mscorlib/shared/System/Threading/TimeoutHelper.cs
new file mode 100644
index 0000000000..c66c9add92
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+++ b/src/mscorlib/shared/System/Threading/TimeoutHelper.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    /// <summary>
+    /// A helper class to capture a start time using Environment.TickCout as a time in milliseconds, also updates a given timeout bu subtracting the current time from
+    /// the start time
+    /// </summary>
+    internal static class TimeoutHelper
+    {
+        /// <summary>
+        /// Returns the Environment.TickCount as a start time in milliseconds as a uint, TickCount tools over from postive to negative every ~ 25 days
+        /// then ~25 days to back to positive again, uint is sued to ignore the sign and double the range to 50 days
+        /// </summary>
+        /// <returns></returns>
+        public static uint GetTime()
+        {
+            return (uint)Environment.TickCount;
+        }
+
+        /// <summary>
+        /// Helper function to measure and update the elapsed time
+        /// </summary>
+        /// <param name="startTime"> The first time (in milliseconds) observed when the wait started</param>
+        /// <param name="originalWaitMillisecondsTimeout">The orginal wait timeoutout in milliseconds</param>
+        /// <returns>The new wait time in milliseconds, -1 if the time expired</returns>
+        public static int UpdateTimeOut(uint startTime, int originalWaitMillisecondsTimeout)
+        {
+            // The function must be called in case the time out is not infinite
+            Debug.Assert(originalWaitMillisecondsTimeout != Timeout.Infinite);
+
+            uint elapsedMilliseconds = (GetTime() - startTime);
+
+            // Check the elapsed milliseconds is greater than max int because this property is uint
+            if (elapsedMilliseconds > int.MaxValue)
+            {
+                return 0;
+            }
+
+            // Subtract the elapsed time from the current wait time
+            int currentWaitTimeout = originalWaitMillisecondsTimeout - (int)elapsedMilliseconds; ;
+            if (currentWaitTimeout <= 0)
+            {
+                return 0;
+            }
+
+            return currentWaitTimeout;
+        }
+    }
+}