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/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Apache License, Version 2.0. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Apache License, Version 2.0, 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 Apache License, Version 2.0.
*
* 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;
#if !FEATURE_CORE_DLR
namespace Microsoft.Scripting.Ast.Compiler {
#else
namespace System.Linq.Expressions.Compiler {
#endif
// Suppose we have something like:
//
// (string s)=>()=>s.
//
// We wish to generate the outer as:
//
// Func<string> OuterMethod(Closure closure, string s)
// {
// object[] locals = new object[1];
// locals[0] = new StrongBox<string>();
// ((StrongBox<string>)locals[0]).Value = s;
// return ((DynamicMethod)closure.Constants[0]).CreateDelegate(typeof(Func<string>), new Closure(null, locals));
// }
//
// ... and the inner as:
//
// string InnerMethod(Closure closure)
// {
// object[] locals = closure.Locals;
// return ((StrongBox<string>)locals[0]).Value;
// }
//
// This class tracks that "s" was hoisted into a closure, as the 0th
// element in the array
//
/// <summary>
/// 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
/// </summary>
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 System.Dynamic.Utils.ReadOnlyDictionary<Expression, int> Indexes;
// The variables, in the order they appear in the array
internal readonly ReadOnlyCollection<ParameterExpression> Variables;
// A virtual variable for accessing this locals array
internal readonly ParameterExpression SelfVariable;
internal HoistedLocals(HoistedLocals parent, ReadOnlyCollection<ParameterExpression> vars) {
if (parent != null) {
// Add the parent locals array as the 0th element in the array
vars = new TrueReadOnlyCollection<ParameterExpression>(vars.AddFirst(parent.SelfVariable));
}
Dictionary<Expression, int> indexes = new Dictionary<Expression, int>(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 System.Dynamic.Utils.ReadOnlyDictionary<Expression, int>(indexes);
}
internal ParameterExpression ParentVariable {
get { return Parent != null ? Parent.SelfVariable : null; }
}
internal static object[] GetParent(object[] locals) {
return ((StrongBox<object[]>)locals[0]).Value;
}
}
}
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