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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using Implab.Parallels;
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namespace Implab.Diagnostics {
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public class TraceRegistry {
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class Subscription : IDisposable {
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readonly WeakReference<TraceRegistry> m_registry;
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readonly Action<object> m_unsubscribe;
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public Subscription(TraceRegistry registry) {
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m_registry = new WeakReference<TraceRegistry>(registry);
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}
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public void Dispose() {
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TraceRegistry t;
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if (m_registry.TryGetTarget(out t))
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t.RemoveSubscription(this);
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}
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}
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public static TraceRegistry Global { get; } = new TraceRegistry();
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readonly object m_lock = new object();
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readonly Dictionary<object, Action<TraceChannel>> m_subscriptions = new Dictionary<object, Action<TraceChannel>>();
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readonly SimpleAsyncQueue<TraceChannel> m_channels = new SimpleAsyncQueue<TraceChannel>();
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internal void Register(TraceChannel channel) {
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// notifications can run in parallel
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Action<TraceChannel>[] handlers = null;
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lock(m_lock) {
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m_channels.Enqueue(channel);
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if (m_subscriptions.Count > 0) {
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handlers = new Action<TraceChannel>[m_subscriptions.Count];
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m_subscriptions.Values.CopyTo(handlers, 0);
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}
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}
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if (handlers != null)
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foreach(var h in handlers)
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h(channel);
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}
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/// <summary>
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/// Subscribes the specified handler to notifications about new trace
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/// channels
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/// </summary>
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/// <param name="handler"></param>
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/// <returns></returns>
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public IDisposable Subscribe(Action<TraceChannel> handler, bool existing) {
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Safe.ArgumentNotNull(handler, nameof(handler));
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var cookie = new Subscription(this);
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IEnumerable<TraceChannel> snap;
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// lock to ensure that no new channels will be added
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// while the subscription is added
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lock(m_lock) {
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m_subscriptions.Add(cookie, handler);
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snap = m_channels.Snapshot();
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}
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// announce previously declared channels if required
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if (existing) {
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foreach(var c in snap)
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handler(c);
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}
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// return the subscription
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return cookie;
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}
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void RemoveSubscription(object cookie) {
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lock(m_lock)
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m_subscriptions.Remove(cookie);
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}
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}
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}
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