96 lines
4.6 KiB
C#
96 lines
4.6 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="ActivityIdHelper.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//------------------------------------------------------------------------------
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namespace System.Web.Util {
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using System;
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using System.Diagnostics.Tracing;
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using System.Runtime.CompilerServices;
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using System.Threading;
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internal sealed class ActivityIdHelper {
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private delegate Guid GetCurrentDelegate();
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private delegate void SetAndDestroyDelegate(Guid activityId);
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private delegate void SetAndPreserveDelegate(Guid activityId, out Guid oldActivityThatWillContinue);
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// Note to callers: this field can be null.
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internal static readonly ActivityIdHelper Instance = GetSingleton();
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private static readonly Guid _baseGuid = Guid.NewGuid();
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private static long _counter;
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private readonly GetCurrentDelegate _getCurrentDel;
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private readonly SetAndDestroyDelegate _setAndDestroyDel;
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private readonly SetAndPreserveDelegate _setAndPreserveDel;
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// use the factory to create an instance of this type
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private ActivityIdHelper(GetCurrentDelegate getCurrentDel, SetAndDestroyDelegate setAndDestroyDel, SetAndPreserveDelegate setAndPreserveDel) {
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_getCurrentDel = getCurrentDel;
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_setAndDestroyDel = setAndDestroyDel;
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_setAndPreserveDel = setAndPreserveDel;
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}
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// Gets the current thread's activity ID.
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public Guid CurrentThreadActivityId {
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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get { return _getCurrentDel(); }
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}
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private static ActivityIdHelper GetSingleton() {
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try {
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// The mscorlib APIs we depend on weren't added until Blue, so we can't
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// take a direct dependency. Need to light up instead.
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var getCurrentDel = (GetCurrentDelegate)Delegate.CreateDelegate(
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typeof(GetCurrentDelegate), typeof(EventSource), "get_CurrentThreadActivityId", ignoreCase: false, throwOnBindFailure: false);
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var setAndDestroyDel = (SetAndDestroyDelegate)Delegate.CreateDelegate(
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typeof(SetAndDestroyDelegate), typeof(EventSource), "SetCurrentThreadActivityId", ignoreCase: false, throwOnBindFailure: false);
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var setAndPreserveDel = (SetAndPreserveDelegate)Delegate.CreateDelegate(
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typeof(SetAndPreserveDelegate), typeof(EventSource), "SetCurrentThreadActivityId", ignoreCase: false, throwOnBindFailure: false);
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if (getCurrentDel != null && setAndDestroyDel != null && setAndPreserveDel != null) {
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return new ActivityIdHelper(getCurrentDel, setAndDestroyDel, setAndPreserveDel);
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}
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}
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catch {
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// exceptions are not fatal; we just won't be able to call the new APIs
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}
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return null;
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}
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// Disposes of the thread's existing activity ID, then sets the new activity ID on this thread.
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public void SetCurrentThreadActivityId(Guid activityId) {
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_setAndDestroyDel(activityId);
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}
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// Suspends (but does not dispose of) the thread's existing activity ID, then sets a new activity ID on this thread.
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public void SetCurrentThreadActivityId(Guid activityId, out Guid oldActivityThatWillContinue) {
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_setAndPreserveDel(activityId, out oldActivityThatWillContinue);
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}
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// !! SECURITY WARNING !!
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// The GUIDs created by this method are predictable and should be used ONLY for tracing.
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// Any other use (such as leaking them to the user) constitutes information disclosure.
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//
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// This is a perf-sensitive method since it could potentially be called many times per
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// request. Guid.NewGuid() is slow since it eventually calls CAPI, and we did actually
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// see it show up as a bottleneck when developing MVC 2. The below implementation has
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// measurably better performance characteristics than calling the other Guid ctors.
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static unsafe Guid UnsafeCreateNewActivityId() {
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Guid guidCopy = _baseGuid;
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*(long*)(&guidCopy) ^= Interlocked.Increment(ref _counter); // operate on the copy, not the original
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return guidCopy;
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}
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}
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}
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