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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
using System.Threading.Tasks;
namespace System.Diagnostics.Tracing
{
/// <summary>Simple event listener than invokes a callback for each event received.</summary>
internal sealed class TestEventListener : EventListener
{
private readonly string _targetSourceName;
private readonly Guid _targetSourceGuid;
private readonly EventLevel _level;
private readonly double? _eventCounterInterval;
private Action<EventWrittenEventArgs> _eventWritten;
private List<EventSource> _tmpEventSourceList = new List<EventSource>();
public TestEventListener(string targetSourceName, EventLevel level, double? eventCounterInterval = null)
{
// Store the arguments
_targetSourceName = targetSourceName;
_level = level;
_eventCounterInterval = eventCounterInterval;
LoadSourceList();
}
public TestEventListener(Guid targetSourceGuid, EventLevel level, double? eventCounterInterval = null)
{
// Store the arguments
_targetSourceGuid = targetSourceGuid;
_level = level;
_eventCounterInterval = eventCounterInterval;
LoadSourceList();
}
private void LoadSourceList()
{
// The base constructor, which is called before this constructor,
// will invoke the virtual OnEventSourceCreated method for each
// existing EventSource, which means OnEventSourceCreated will be
// called before _targetSourceGuid and _level have been set. As such,
// we store a temporary list that just exists from the moment this instance
// is created (instance field initializers run before the base constructor)
// and until we finish construction... in that window, OnEventSourceCreated
// will store the sources into the list rather than try to enable them directly,
// and then here we can enumerate that list, then clear it out.
List<EventSource> sources;
lock (_tmpEventSourceList)
{
sources = _tmpEventSourceList;
_tmpEventSourceList = null;
}
foreach (EventSource source in sources)
{
EnableSourceIfMatch(source);
}
}
protected override void OnEventSourceCreated(EventSource eventSource)
{
List<EventSource> tmp = _tmpEventSourceList;
if (tmp != null)
{
lock (tmp)
{
if (_tmpEventSourceList != null)
{
_tmpEventSourceList.Add(eventSource);
return;
}
}
}
EnableSourceIfMatch(eventSource);
}
private void EnableSourceIfMatch(EventSource source)
{
if (source.Name.Equals(_targetSourceName) ||
source.Guid.Equals(_targetSourceGuid))
{
if (_eventCounterInterval != null)
{
var args = new Dictionary<string, string> { { "EventCounterIntervalSec", _eventCounterInterval?.ToString() } };
EnableEvents(source, _level, EventKeywords.All, args);
}
else
{
EnableEvents(source, _level);
}
}
}
public void RunWithCallback(Action<EventWrittenEventArgs> handler, Action body)
{
_eventWritten = handler;
try { body(); }
finally { _eventWritten = null; }
}
public async Task RunWithCallbackAsync(Action<EventWrittenEventArgs> handler, Func<Task> body)
{
_eventWritten = handler;
try { await body().ConfigureAwait(false); }
finally { _eventWritten = null; }
}
protected override void OnEventWritten(EventWrittenEventArgs eventData)
{
_eventWritten?.Invoke(eventData);
}
}
}
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