HoistedLocals.cs source code in C# .NET

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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / Microsoft / Scripting / Compiler / HoistedLocals.cs / 1305376 / HoistedLocals.cs

                            /* **************************************************************************** 
 *
 * Copyright (c) Microsoft Corporation.
 *
 * This source code is subject to terms and conditions of the Microsoft Public License. A 
 * copy of the license can be found in the License.html file at the root of this distribution. If
 * you cannot locate the  Microsoft Public License, please send an email to 
 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 
 * by the terms of the Microsoft Public License.
 * 
 * You must not remove this notice, or any other, from this software.
 *
 *
 * ***************************************************************************/ 

using System.Collections.Generic; 
using System.Collections.ObjectModel; 
using System.Runtime.CompilerServices;
using System.Dynamic.Utils; 

namespace System.Linq.Expressions.Compiler {

    // Suppose we have something like: 
    //
    //    (string s)=>()=>s. 
    // 
    // We wish to generate the outer as:
    // 
    //      Func OuterMethod(Closure closure, string s)
    //      {
    //          object[] locals = new object[1];
    //          locals[0] = new StrongBox(); 
    //          ((StrongBox)locals[0]).Value = s;
    //          return ((DynamicMethod)closure.Constants[0]).CreateDelegate(typeof(Func), new Closure(null, locals)); 
    //      } 
    //
    // ... and the inner as: 
    //
    //      string InnerMethod(Closure closure)
    //      {
    //          object[] locals = closure.Locals; 
    //          return ((StrongBox)locals[0]).Value;
    //      } 
    // 
    // This class tracks that "s" was hoisted into a closure, as the 0th
    // element in the array 
    //
    /// 
    /// Stores information about locals and arguments that are hoisted into
    /// the closure array because they're referenced in an inner lambda. 
    ///
    /// This class is sometimes emitted as a runtime constant for internal 
    /// use to hoist variables/parameters in quoted expressions 
    ///
    /// Invariant: this class stores no mutable state 
    /// 
    internal sealed class HoistedLocals {

        // The parent locals, if any 
        internal readonly HoistedLocals Parent;
 
        // A mapping of hoisted variables to their indexes in the array 
        internal readonly ReadOnlyDictionary Indexes;
 
        // The variables, in the order they appear in the array
        internal readonly ReadOnlyCollection Variables;

        // A virtual variable for accessing this locals array 
        internal readonly ParameterExpression SelfVariable;
 
        internal HoistedLocals(HoistedLocals parent, ReadOnlyCollection vars) { 

            if (parent != null) { 
                // Add the parent locals array as the 0th element in the array
                vars = new TrueReadOnlyCollection(vars.AddFirst(parent.SelfVariable));
            }
 
            Dictionary indexes = new Dictionary(vars.Count);
            for (int i = 0; i < vars.Count; i++) { 
                indexes.Add(vars[i], i); 
            }
 
            SelfVariable = Expression.Variable(typeof(object[]), null);
            Parent = parent;
            Variables = vars;
            Indexes = new ReadOnlyDictionary(indexes); 
        }
 
        internal ParameterExpression ParentVariable { 
            get { return Parent != null ? Parent.SelfVariable : null; }
        } 

        internal static object[] GetParent(object[] locals) {
            return ((StrongBox)locals[0]).Value;
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
                        

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