1 files changed, 116 insertions, 0 deletions
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/DiagnosticCounter.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/DiagnosticCounter.cs
new file mode 100644
index 0000000000..ea4cb92612
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/DiagnosticCounter.cs
@@ -0,0 +1,116 @@
+// 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;
+using System.Diagnostics;
+using System.Collections;
+using System.Collections.Generic;
+using System.Text;
+using System.Threading;
+#if ES_BUILD_PCL
+    using System.Threading.Tasks;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// DiagnosticCounter is an abstract class that serves as the parent class for various Counter* classes, 
+    /// namely EventCounter, PollingCounter, IncrementingEventCounter, and IncrementingPollingCounter.
+    /// </summary>
+    public abstract class DiagnosticCounter : IDisposable
+    {
+        /// <summary>
+        /// All Counters live as long as the EventSource that they are attached to unless they are
+        /// explicitly Disposed.   
+        /// </summary>
+        /// <param name="name">The name.</param>
+        /// <param name="eventSource">The event source.</param>
+        public DiagnosticCounter(string name, EventSource eventSource)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(Name));
+            }
+
+            if (eventSource == null)
+            {
+                throw new ArgumentNullException(nameof(EventSource));
+            }
+
+            _group = CounterGroup.GetCounterGroup(eventSource);
+            _group.Add(this);
+            Name = name;
+            EventSource = eventSource;
+        }
+
+        /// <summary>
+        /// Removes the counter from set that the EventSource will report on.  After being disposed, this
+        /// counter will do nothing and its resource will be reclaimed if all references to it are removed.
+        /// If an EventCounter is not explicitly disposed it will be cleaned up automatically when the
+        /// EventSource it is attached to dies.  
+        /// </summary>
+        public void Dispose()
+        {
+            if (_group != null)
+            {
+                _group.Remove(this);
+                _group = null;
+            }
+        }
+
+        /// <summary>
+        /// Adds a key-value metadata to the EventCounter that will be included as a part of the payload
+        /// </summary>
+        public void AddMetadata(string key, string value)
+        {
+            lock (MyLock)
+            {
+                _metadata = _metadata ?? new Dictionary<string, string>();
+                _metadata.Add(key, value);
+            }
+        }
+
+        public string DisplayName { get; set; }
+
+        public string Name { get; }
+
+        public EventSource EventSource { get; }
+
+        #region private implementation
+
+        private CounterGroup _group;
+        private Dictionary<string, string> _metadata;
+
+        internal abstract void WritePayload(float intervalSec);
+
+        // arbitrarily we use name as the lock object.  
+        internal object MyLock { get { return Name; } }
+
+        internal void ReportOutOfBandMessage(string message)
+        {
+            EventSource.ReportOutOfBandMessage(message, true);
+        }
+
+        internal string GetMetadataString()
+        {
+            if (_metadata == null)
+            {
+                return "";
+            }
+
+            StringBuilder sb = new StringBuilder("");
+            foreach(KeyValuePair<string, string> kvPair in _metadata)
+            {
+                sb.Append($"{kvPair.Key}:{kvPair.Value},");
+            }
+            return sb.Length == 0 ? "" : sb.ToString(0, sb.Length - 1); // Get rid of the last ","
+        }
+
+        #endregion // private implementation
+    }
+}