/* ****************************************************************************
*
* 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.
*
*
* ***************************************************************************/
#if CLR2
using Microsoft.Scripting.Ast;
#else
using System.Linq.Expressions;
#endif
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Dynamic.Utils;
using System.Runtime.CompilerServices;
namespace System.Dynamic{
/// <summary>
/// Represents a set of binding restrictions on the <see cref="DynamicMetaObject"/>under which the dynamic binding is valid.
/// </summary>
#if !SILVERLIGHT
[DebuggerTypeProxy(typeof(BindingRestrictionsProxy)), DebuggerDisplay("{DebugView}")]
#endif
public abstract class BindingRestrictions {
/// <summary>
/// Represents an empty set of binding restrictions. This field is read only.
/// </summary>
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes")]
public static readonly BindingRestrictions Empty = new CustomRestriction(Expression.Constant(true));
private const int TypeRestrictionHash = 0x10000000;
private const int InstanceRestrictionHash = 0x20000000;
private const int CustomRestrictionHash = 0x40000000;
private BindingRestrictions() {
}
// Overridden by specialized subclasses
internal abstract Expression GetExpression();
/// <summary>
/// Merges the set of binding restrictions with the current binding restrictions.
/// </summary>
/// <param name="restrictions">The set of restrictions with which to merge the current binding restrictions.</param>
/// <returns>The new set of binding restrictions.</returns>
public BindingRestrictions Merge(BindingRestrictions restrictions) {
ContractUtils.RequiresNotNull(restrictions, "restrictions");
if (this == Empty) {
return restrictions;
}
if (restrictions == Empty) {
return this;
}
return new MergedRestriction(this, restrictions);
}
/// <summary>
/// Creates the binding restriction that check the expression for runtime type identity.
/// </summary>
/// <param name="expression">The expression to test.</param>
/// <param name="type">The exact type to test.</param>
/// <returns>The new binding restrictions.</returns>
public static BindingRestrictions GetTypeRestriction(Expression expression, Type type) {
ContractUtils.RequiresNotNull(expression, "expression");
ContractUtils.RequiresNotNull(type, "type");
return new TypeRestriction(expression, type);
}
/// <summary>
/// The method takes a DynamicMetaObject, and returns an instance restriction for testing null if the object
/// holds a null value, otherwise returns a type restriction.
/// </summary>
internal static BindingRestrictions GetTypeRestriction(DynamicMetaObject obj) {
if (obj.Value == null && obj.HasValue) {
return BindingRestrictions.GetInstanceRestriction(obj.Expression, null);
} else {
return BindingRestrictions.GetTypeRestriction(obj.Expression, obj.LimitType);
}
}
/// <summary>
/// Creates the binding restriction that checks the expression for object instance identity.
/// </summary>
/// <param name="expression">The expression to test.</param>
/// <param name="instance">The exact object instance to test.</param>
/// <returns>The new binding restrictions.</returns>
public static BindingRestrictions GetInstanceRestriction(Expression expression, object instance) {
ContractUtils.RequiresNotNull(expression, "expression");
return new InstanceRestriction(expression, instance);
}
/// <summary>
/// Creates the binding restriction that checks the expression for arbitrary immutable properties.
/// </summary>
/// <param name="expression">The expression expression the restrictions.</param>
/// <returns>The new binding restrictions.</returns>
/// <remarks>
/// By convention, the general restrictions created by this method must only test
/// immutable object properties.
/// </remarks>
public static BindingRestrictions GetExpressionRestriction(Expression expression) {
ContractUtils.RequiresNotNull(expression, "expression");
ContractUtils.Requires(expression.Type == typeof(bool), "expression");
return new CustomRestriction(expression);
}
/// <summary>
/// Combines binding restrictions from the list of <see cref="DynamicMetaObject"/> instances into one set of restrictions.
/// </summary>
/// <param name="contributingObjects">The list of <see cref="DynamicMetaObject"/> instances from which to combine restrictions.</param>
/// <returns>The new set of binding restrictions.</returns>
public static BindingRestrictions Combine(IList<DynamicMetaObject> contributingObjects) {
BindingRestrictions res = BindingRestrictions.Empty;
if (contributingObjects != null) {
foreach (DynamicMetaObject mo in contributingObjects) {
if (mo != null) {
res = res.Merge(mo.Restrictions);
}
}
}
return res;
}
/// <summary>
/// Builds a balanced tree of AndAlso nodes.
/// We do this so the compiler won't stack overflow if we have many
/// restrictions.
/// </summary>
private sealed class TestBuilder {
private readonly Set<BindingRestrictions> _unique = new Set<BindingRestrictions>();
private readonly Stack<AndNode> _tests = new Stack<AndNode>();
private struct AndNode {
internal int Depth;
internal Expression Node;
}
internal void Append(BindingRestrictions restrictions) {
if (_unique.Contains(restrictions)) {
return;
}
_unique.Add(restrictions);
Push(restrictions.GetExpression(), 0);
}
internal Expression ToExpression() {
Expression result = _tests.Pop().Node;
while (_tests.Count > 0) {
result = Expression.AndAlso(_tests.Pop().Node, result);
}
return result;
}
private void Push(Expression node, int depth) {
while (_tests.Count > 0 && _tests.Peek().Depth == depth) {
node = Expression.AndAlso(_tests.Pop().Node, node);
depth++;
}
_tests.Push(new AndNode { Node = node, Depth = depth });
}
}
/// <summary>
/// Creates the <see cref="Expression"/> representing the binding restrictions.
/// </summary>
/// <returns>The expression tree representing the restrictions.</returns>
public Expression ToExpression() {
// We could optimize this better, e.g. common subexpression elimination
// But for now, it's good enough.
if (this == Empty) {
return Expression.Constant(true);
}
var testBuilder = new TestBuilder();
// Visit the tree, left to right.
// Use an explicit stack so we don't stack overflow.
//
// Left-most node is on top of the stack, so we always expand the
// left most node each iteration.
var stack = new Stack<BindingRestrictions>();
stack.Push(this);
do {
var top = stack.Pop();
var m = top as MergedRestriction;
if (m != null) {
stack.Push(m.Right);
stack.Push(m.Left);
} else {
testBuilder.Append(top);
}
} while (stack.Count > 0);
return testBuilder.ToExpression();
}
private sealed class MergedRestriction : BindingRestrictions {
internal readonly BindingRestrictions Left;
internal readonly BindingRestrictions Right;
internal MergedRestriction(BindingRestrictions left, BindingRestrictions right) {
Left = left;
Right = right;
}
internal override Expression GetExpression() {
throw ContractUtils.Unreachable;
}
}
private sealed class CustomRestriction : BindingRestrictions {
private readonly Expression _expression;
internal CustomRestriction(Expression expression) {
_expression = expression;
}
public override bool Equals(object obj) {
var other = obj as CustomRestriction;
return other != null && other._expression == _expression;
}
public override int GetHashCode() {
return CustomRestrictionHash ^ _expression.GetHashCode();
}
internal override Expression GetExpression() {
return _expression;
}
}
private sealed class TypeRestriction : BindingRestrictions {
private readonly Expression _expression;
private readonly Type _type;
internal TypeRestriction(Expression parameter, Type type) {
_expression = parameter;
_type = type;
}
public override bool Equals(object obj) {
var other = obj as TypeRestriction;
return other != null && TypeUtils.AreEquivalent(other._type, _type) && other._expression == _expression;
}
public override int GetHashCode() {
return TypeRestrictionHash ^ _expression.GetHashCode() ^ _type.GetHashCode();
}
internal override Expression GetExpression() {
return Expression.TypeEqual(_expression, _type);
}
}
private sealed class InstanceRestriction : BindingRestrictions {
private readonly Expression _expression;
private readonly object _instance;
internal InstanceRestriction(Expression parameter, object instance) {
_expression = parameter;
_instance = instance;
}
public override bool Equals(object obj) {
var other = obj as InstanceRestriction;
return other != null && other._instance == _instance && other._expression == _expression;
}
public override int GetHashCode() {
return InstanceRestrictionHash ^ RuntimeHelpers.GetHashCode(_instance) ^ _expression.GetHashCode();
}
internal override Expression GetExpression() {
if (_instance == null) {
return Expression.Equal(
Expression.Convert(_expression, typeof(object)),
Expression.Constant(null)
);
}
ParameterExpression temp = Expression.Parameter(typeof(object), null);
return Expression.Block(
new[] { temp },
Expression.Assign(
temp,
Expression.Property(
Expression.Constant(new WeakReference(_instance)),
typeof(WeakReference).GetProperty("Target")
)
),
Expression.AndAlso(
//check that WeekReference was not collected.
Expression.NotEqual(temp, Expression.Constant(null)),
Expression.Equal(
Expression.Convert(_expression, typeof(object)),
temp
)
)
);
}
}
private string DebugView {
get { return ToExpression().ToString(); }
}
private sealed class BindingRestrictionsProxy {
private readonly BindingRestrictions _node;
public BindingRestrictionsProxy(BindingRestrictions node) {
_node = node;
}
public bool IsEmpty {
get { return _node == Empty; }
}
public Expression Test {
get { return _node.ToExpression(); }
}
public BindingRestrictions[] Restrictions {
get {
var restrictions = new List<BindingRestrictions>();
// Visit the tree, left to right
//
// Left-most node is on top of the stack, so we always expand the
// left most node each iteration.
var stack = new Stack<BindingRestrictions>();
stack.Push(_node);
do {
var top = stack.Pop();
var m = top as MergedRestriction;
if (m != null) {
stack.Push(m.Right);
stack.Push(m.Left);
} else {
restrictions.Add(top);
}
} while (stack.Count > 0);
return restrictions.ToArray();
}
}
public override string ToString() {
// To prevent fxcop warning about this field
return _node.DebugView;
}
}
}
}
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