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Viewing changes to contrib/ICSharpCode.NRefactory/Utils/LazyInit.cs

  • Committer: Package Import Robot
  • Author(s): Jo Shields
  • Date: 2013-05-12 09:46:03 UTC
  • mto: This revision was merged to the branch mainline in revision 29.
  • Revision ID: package-import@ubuntu.com-20130512094603-mad323bzcxvmcam0
Tags: upstream-4.0.5+dfsg
Import upstream version 4.0.5+dfsg

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contrib/ICSharpCode.NRefactory/Utils/LazyInit.cs
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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
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// 
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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// software and associated documentation files (the "Software"), to deal in the Software
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// without restriction, including without limitation the rights to use, copy, modify, merge,
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// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
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// to whom the Software is furnished to do so, subject to the following conditions:
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// 
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// The above copyright notice and this permission notice shall be included in all copies or
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// substantial portions of the Software.
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// 
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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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 System.Threading;
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using ICSharpCode.NRefactory.TypeSystem;
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namespace ICSharpCode.NRefactory.Utils
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{
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        public static class LazyInit
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        {
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                public static T VolatileRead<T>(ref T location) where T : class
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                {
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                        #if NET45
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                        return Volatile.Read(ref location);
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                        #else
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                        T result = location;
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                        Thread.MemoryBarrier();
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                        return result;
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                        #endif
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                }
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                /// <summary>
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                /// Atomatically performs the following operation:
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                /// - If target is null: stores newValue in target and returns newValue.
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                /// - If target is not null: returns target.
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                /// </summary>
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                public static T GetOrSet<T>(ref T target, T newValue) where T : class
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                {
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                        T oldValue = Interlocked.CompareExchange(ref target, newValue, null);
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                        return oldValue ?? newValue;
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                }
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        }
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}